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• Development of Peptide-Based Probes for Molecular Imaging of the Postsynaptic Density in the Brain. Fernandes, Eduardo F. A.; Palner, Mikael; Raval, Nakul Ravi; Jeppesen, Troels E.; Danková, Daniela; Bærentzen, Simone L.; Werner, Christian; Eilts, Janna; Maric, Hans M.; Doose, Sören; Aripaka, Sanjay Sagar; Kaalund, Sanne Simone; Aznar, Susana; Kjaer, Andreas; Schlosser, Andreas; Haugaard-Kedström, Linda M.; Knudsen, Gitte M.; Herth, Matthias M.; Stro̷mgaard Kristian. In J. Med. Chem., 67(14), S. 11975–11988. American Chemical Society, 2024.
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  The postsynaptic density (PSD) comprises numerous scaffolding proteins, receptors, and signaling molecules that coordinate synaptic transmission in the brain. Postsynaptic density protein 95 (PSD-95) is a master scaffold protein within the PSD and one of its most abundant proteins and therefore constitutes a very attractive biomarker of PSD function and its pathological changes. Here, we exploit a high-affinity inhibitor of PSD-95, AVLX-144, as a template for developing probes for molecular imaging of the PSD. AVLX-144-based probes were labeled with the radioisotopes fluorine-18 and tritium, as well as a fluorescent tag. Tracer binding showed saturable, displaceable, and uneven distribution in rat brain slices, proving effective in quantitative autoradiography and cell imaging studies. Notably, we observed diminished tracer binding in human post-mortem Parkinson’s disease (PD) brain slices, suggesting postsynaptic impairment in PD. We thus offer a suite of translational probes for visualizing and understanding PSD-related pathologies.

  @article{fernandes2024development, abstract = {The postsynaptic density (PSD) comprises numerous scaffolding proteins, receptors, and signaling molecules that coordinate synaptic transmission in the brain. Postsynaptic density protein 95 (PSD-95) is a master scaffold protein within the PSD and one of its most abundant proteins and therefore constitutes a very attractive biomarker of PSD function and its pathological changes. Here, we exploit a high-affinity inhibitor of PSD-95, AVLX-144, as a template for developing probes for molecular imaging of the PSD. AVLX-144-based probes were labeled with the radioisotopes fluorine-18 and tritium, as well as a fluorescent tag. Tracer binding showed saturable, displaceable, and uneven distribution in rat brain slices, proving effective in quantitative autoradiography and cell imaging studies. Notably, we observed diminished tracer binding in human post-mortem Parkinson’s disease (PD) brain slices, suggesting postsynaptic impairment in PD. We thus offer a suite of translational probes for visualizing and understanding PSD-related pathologies.}, author = {Fernandes, Eduardo F. A. and Palner, Mikael and Raval, Nakul Ravi and Jeppesen, Troels E. and Danková, Daniela and Bærentzen, Simone L. and Werner, Christian and Eilts, Janna and Maric, Hans M. and Doose, Sören and Aripaka, Sanjay Sagar and Kaalund, Sanne Simone and Aznar, Susana and Kjaer, Andreas and Schlosser, Andreas and Haugaard-Kedström, Linda M. and Knudsen, Gitte M. and Herth, Matthias M. and Stro̷mgaard, Kristian}, booktitle = {Journal of Medicinal Chemistry}, journal = {J. Med. Chem.}, keywords = {maric}, month = {07}, number = 14, pages = {11975–11988}, publisher = {American Chemical Society}, title = {Development of Peptide-Based Probes for Molecular Imaging of the Postsynaptic Density in the Brain}, volume = 67, year = 2024 }

  %0 Journal Article %1 fernandes2024development %A Fernandes, Eduardo F. A. %A Palner, Mikael %A Raval, Nakul Ravi %A Jeppesen, Troels E. %A Danková, Daniela %A Bærentzen, Simone L. %A Werner, Christian %A Eilts, Janna %A Maric, Hans M. %A Doose, Sören %A Aripaka, Sanjay Sagar %A Kaalund, Sanne Simone %A Aznar, Susana %A Kjaer, Andreas %A Schlosser, Andreas %A Haugaard-Kedström, Linda M. %A Knudsen, Gitte M. %A Herth, Matthias M. %A Stro̷mgaard, Kristian %B Journal of Medicinal Chemistry %D 2024 %I American Chemical Society %J J. Med. Chem. %N 14 %P 11975--11988 %R 10.1021/acs.jmedchem.4c00615 %T Development of Peptide-Based Probes for Molecular Imaging of the Postsynaptic Density in the Brain %U https://doi.org/10.1021/acs.jmedchem.4c00615 %V 67 %X The postsynaptic density (PSD) comprises numerous scaffolding proteins, receptors, and signaling molecules that coordinate synaptic transmission in the brain. Postsynaptic density protein 95 (PSD-95) is a master scaffold protein within the PSD and one of its most abundant proteins and therefore constitutes a very attractive biomarker of PSD function and its pathological changes. Here, we exploit a high-affinity inhibitor of PSD-95, AVLX-144, as a template for developing probes for molecular imaging of the PSD. AVLX-144-based probes were labeled with the radioisotopes fluorine-18 and tritium, as well as a fluorescent tag. Tracer binding showed saturable, displaceable, and uneven distribution in rat brain slices, proving effective in quantitative autoradiography and cell imaging studies. Notably, we observed diminished tracer binding in human post-mortem Parkinson’s disease (PD) brain slices, suggesting postsynaptic impairment in PD. We thus offer a suite of translational probes for visualizing and understanding PSD-related pathologies.
• The neuropeptide pigment-dispersing factor signals independently of Bruchpilot-labelled active zones in daily remodelled terminals of Drosophila clock neurons. Hofbauer, Benedikt; Zandawala, Meet; Reinhard, Nils; Rieger, Dirk; Werner, Christian; Evers, Jan Felix; Wegener, Christian. In European Journal of Neuroscience, 59(10), S. 2665–2685. John Wiley & Sons, Ltd, 2024.
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  The small ventrolateral neurons (sLNvs) are key components of the central clock in the Drosophila brain. They signal via the neuropeptide pigment-dispersing factor (PDF) to align the molecular clockwork of different central clock neurons and to modulate downstream circuits. The dorsal terminals of the sLNvs undergo daily morphological changes that affect presynaptic sites organised by the active zone protein Bruchpilot (BRP), a homolog of mammalian ELKS proteins. However, the role of these presynaptic sites for PDF release is ill-defined. Here, we combined expansion microscopy with labelling of active zones by endogenously tagged BRP to examine the spatial correlation between PDF-containing dense-core vesicles and BRP-labelled active zones. We found that the number of BRP-labelled puncta in the sLNv terminals was similar while their density differed between Zeitgeber time (ZT) 2 and 14. The relative distance between BRP- and PDF-labelled puncta was increased in the morning, around the reported time of PDF release. Spontaneous dense-core vesicle release profiles of sLNvs in a publicly available ssTEM dataset (FAFB) consistently lacked spatial correlation to BRP-organised active zones. RNAi-mediated downregulation of brp and other active zone proteins expressed by the sLNvs did not affect PDF-dependent locomotor rhythmicity. In contrast, down-regulation of genes encoding proteins of the canonical vesicle release machinery, the dense-core vesicle-related protein CADPS, as well as PDF impaired locomotor rhythmicity. Taken together, our study suggests that PDF release from the sLNvs is independent of BRP-organised active zones, while BRP may be redistributed to active zones in a time-dependent manner.

  @article{hofbauer2024neuropeptide, abstract = {The small ventrolateral neurons (sLNvs) are key components of the central clock in the Drosophila brain. They signal via the neuropeptide pigment-dispersing factor (PDF) to align the molecular clockwork of different central clock neurons and to modulate downstream circuits. The dorsal terminals of the sLNvs undergo daily morphological changes that affect presynaptic sites organised by the active zone protein Bruchpilot (BRP), a homolog of mammalian ELKS proteins. However, the role of these presynaptic sites for PDF release is ill-defined. Here, we combined expansion microscopy with labelling of active zones by endogenously tagged BRP to examine the spatial correlation between PDF-containing dense-core vesicles and BRP-labelled active zones. We found that the number of BRP-labelled puncta in the sLNv terminals was similar while their density differed between Zeitgeber time (ZT) 2 and 14. The relative distance between BRP- and PDF-labelled puncta was increased in the morning, around the reported time of PDF release. Spontaneous dense-core vesicle release profiles of sLNvs in a publicly available ssTEM dataset (FAFB) consistently lacked spatial correlation to BRP-organised active zones. RNAi-mediated downregulation of brp and other active zone proteins expressed by the sLNvs did not affect PDF-dependent locomotor rhythmicity. In contrast, down-regulation of genes encoding proteins of the canonical vesicle release machinery, the dense-core vesicle-related protein CADPS, as well as PDF impaired locomotor rhythmicity. Taken together, our study suggests that PDF release from the sLNvs is independent of BRP-organised active zones, while BRP may be redistributed to active zones in a time-dependent manner.}, author = {Hofbauer, Benedikt and Zandawala, Meet and Reinhard, Nils and Rieger, Dirk and Werner, Christian and Evers, Jan Felix and Wegener, Christian}, booktitle = {European Journal of Neuroscience}, journal = {European Journal of Neuroscience}, keywords = {werner}, month = {05}, number = 10, pages = {2665–2685}, publisher = {John Wiley & Sons, Ltd}, title = {The neuropeptide pigment-dispersing factor signals independently of Bruchpilot-labelled active zones in daily remodelled terminals of Drosophila clock neurons}, volume = 59, year = 2024 }

  %0 Journal Article %1 hofbauer2024neuropeptide %A Hofbauer, Benedikt %A Zandawala, Meet %A Reinhard, Nils %A Rieger, Dirk %A Werner, Christian %A Evers, Jan Felix %A Wegener, Christian %B European Journal of Neuroscience %D 2024 %I John Wiley & Sons, Ltd %J European Journal of Neuroscience %N 10 %P 2665--2685 %R https://doi.org/10.1111/ejn.16294 %T The neuropeptide pigment-dispersing factor signals independently of Bruchpilot-labelled active zones in daily remodelled terminals of Drosophila clock neurons %U https://doi.org/10.1111/ejn.16294 %V 59 %X The small ventrolateral neurons (sLNvs) are key components of the central clock in the Drosophila brain. They signal via the neuropeptide pigment-dispersing factor (PDF) to align the molecular clockwork of different central clock neurons and to modulate downstream circuits. The dorsal terminals of the sLNvs undergo daily morphological changes that affect presynaptic sites organised by the active zone protein Bruchpilot (BRP), a homolog of mammalian ELKS proteins. However, the role of these presynaptic sites for PDF release is ill-defined. Here, we combined expansion microscopy with labelling of active zones by endogenously tagged BRP to examine the spatial correlation between PDF-containing dense-core vesicles and BRP-labelled active zones. We found that the number of BRP-labelled puncta in the sLNv terminals was similar while their density differed between Zeitgeber time (ZT) 2 and 14. The relative distance between BRP- and PDF-labelled puncta was increased in the morning, around the reported time of PDF release. Spontaneous dense-core vesicle release profiles of sLNvs in a publicly available ssTEM dataset (FAFB) consistently lacked spatial correlation to BRP-organised active zones. RNAi-mediated downregulation of brp and other active zone proteins expressed by the sLNvs did not affect PDF-dependent locomotor rhythmicity. In contrast, down-regulation of genes encoding proteins of the canonical vesicle release machinery, the dense-core vesicle-related protein CADPS, as well as PDF impaired locomotor rhythmicity. Taken together, our study suggests that PDF release from the sLNvs is independent of BRP-organised active zones, while BRP may be redistributed to active zones in a time-dependent manner.
• LGI1 Autoantibodies Enhance Synaptic Transmission by Presynaptic Kv1 Loss and Increased Action Potential Broadening. Ritzau-Jost, Andreas; Gsell, Felix; Sell, Josefine; Sachs, Stefan; Montanaro, Jacqueline; Kirmann, Toni; Maaß, Sebastian; Irani, Sarosh R.; Werner, Christian; Geis, Christian; Sauer, Markus; Shigemoto, Ryuichi; Hallermann, Stefan. In Neurology Neuroimmunology & Neuroinflammation, 11(5), S. e200284-. Wolters Kluwer, 2024.
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  Background and Objectives: Autoantibodies against the protein leucine-rich glioma inactivated 1 (LGI1) cause the most common subtype of autoimmune encephalitis with predominant involvement of the limbic system, associated with seizures and memory deficits. LGI1 and its receptor ADAM22 are part of a transsynaptic protein complex that includes several proteins involved in presynaptic neurotransmitter release and postsynaptic glutamate sensing. Autoantibodies against LGI1 increase excitatory synaptic strength, but studies that genetically disrupt the LGI1-ADAM22 complex report a reduction in postsynaptic glutamate receptor-mediated responses. Thus, the mechanisms underlying the increased synaptic strength induced by LGI1 autoantibodies remain elusive, and the contributions of presynaptic molecules to the LGI1-transsynaptic complex remain unclear. We therefore investigated the presynaptic mechanisms that mediate autoantibody-induced synaptic strengthening. Methods: We studied the effects of patient-derived purified polyclonal LGI1 autoantibodies on synaptic structure and function by combining direct patch-clamp recordings from presynaptic boutons and somata of hippocampal neurons with super-resolution light and electron microscopy of hippocampal cultures and brain slices. We also identified the protein domain mediating the presynaptic effect using domain-specific patient-derived monoclonal antibodies. Results: LGI1 autoantibodies dose-dependently increased short-term depression during high-frequency transmission, consistent with increased release probability. The increased neurotransmission was not related to presynaptic calcium channels because presynaptic Cav2.1 channel density, calcium current amplitude, and calcium channel gating were unaffected by LGI1 autoantibodies. By contrast, application of LGI1 autoantibodies homogeneously reduced Kv1.1 and Kv1.2 channel density on the surface of presynaptic boutons. Direct presynaptic patch-clamp recordings revealed that LGI1 autoantibodies cause a pronounced broadening of the presynaptic action potential. Domain-specific effects of LGI1 autoantibodies were analyzed at the neuronal soma. Somatic action potential broadening was induced by polyclonal LGI1 autoantibodies and patient-derived monoclonal autoantibodies targeting the epitempin domain, but not the leucin-rich repeat domain. Discussion Our results indicate that LGI1 autoantibodies reduce the density of both Kv1.1 and Kv1.2 on presynaptic boutons, without actions on calcium channel density or function, thereby broadening the presynaptic action potential and increasing neurotransmitter release. This study provides a molecular explanation for the neuronal hyperactivity observed in patients with LGI1 autoantibodies.

  @article{ritzaujostautoantibodies, abstract = {Background and Objectives: Autoantibodies against the protein leucine-rich glioma inactivated 1 (LGI1) cause the most common subtype of autoimmune encephalitis with predominant involvement of the limbic system, associated with seizures and memory deficits. LGI1 and its receptor ADAM22 are part of a transsynaptic protein complex that includes several proteins involved in presynaptic neurotransmitter release and postsynaptic glutamate sensing. Autoantibodies against LGI1 increase excitatory synaptic strength, but studies that genetically disrupt the LGI1-ADAM22 complex report a reduction in postsynaptic glutamate receptor-mediated responses. Thus, the mechanisms underlying the increased synaptic strength induced by LGI1 autoantibodies remain elusive, and the contributions of presynaptic molecules to the LGI1-transsynaptic complex remain unclear. We therefore investigated the presynaptic mechanisms that mediate autoantibody-induced synaptic strengthening. Methods: We studied the effects of patient-derived purified polyclonal LGI1 autoantibodies on synaptic structure and function by combining direct patch-clamp recordings from presynaptic boutons and somata of hippocampal neurons with super-resolution light and electron microscopy of hippocampal cultures and brain slices. We also identified the protein domain mediating the presynaptic effect using domain-specific patient-derived monoclonal antibodies. Results: LGI1 autoantibodies dose-dependently increased short-term depression during high-frequency transmission, consistent with increased release probability. The increased neurotransmission was not related to presynaptic calcium channels because presynaptic Cav2.1 channel density, calcium current amplitude, and calcium channel gating were unaffected by LGI1 autoantibodies. By contrast, application of LGI1 autoantibodies homogeneously reduced Kv1.1 and Kv1.2 channel density on the surface of presynaptic boutons. Direct presynaptic patch-clamp recordings revealed that LGI1 autoantibodies cause a pronounced broadening of the presynaptic action potential. Domain-specific effects of LGI1 autoantibodies were analyzed at the neuronal soma. Somatic action potential broadening was induced by polyclonal LGI1 autoantibodies and patient-derived monoclonal autoantibodies targeting the epitempin domain, but not the leucin-rich repeat domain. Discussion Our results indicate that LGI1 autoantibodies reduce the density of both Kv1.1 and Kv1.2 on presynaptic boutons, without actions on calcium channel density or function, thereby broadening the presynaptic action potential and increasing neurotransmitter release. This study provides a molecular explanation for the neuronal hyperactivity observed in patients with LGI1 autoantibodies.}, author = {Ritzau-Jost, Andreas and Gsell, Felix and Sell, Josefine and Sachs, Stefan and Montanaro, Jacqueline and Kirmann, Toni and Maaß, Sebastian and Irani, Sarosh R. and Werner, Christian and Geis, Christian and Sauer, Markus and Shigemoto, Ryuichi and Hallermann, Stefan}, booktitle = {Neurology Neuroimmunology & Neuroinflammation}, journal = {Neurology Neuroimmunology & Neuroinflammation}, keywords = {home}, number = 5, pages = {e200284–}, publisher = {Wolters Kluwer}, title = {LGI1 Autoantibodies Enhance Synaptic Transmission by Presynaptic Kv1 Loss and Increased Action Potential Broadening}, volume = 11, year = 2024 }

  %0 Journal Article %1 ritzaujostautoantibodies %A Ritzau-Jost, Andreas %A Gsell, Felix %A Sell, Josefine %A Sachs, Stefan %A Montanaro, Jacqueline %A Kirmann, Toni %A Maaß, Sebastian %A Irani, Sarosh R. %A Werner, Christian %A Geis, Christian %A Sauer, Markus %A Shigemoto, Ryuichi %A Hallermann, Stefan %B Neurology Neuroimmunology & Neuroinflammation %D 2024 %I Wolters Kluwer %J Neurology Neuroimmunology & Neuroinflammation %N 5 %P e200284-- %R 10.1212/NXI.0000000000200284 %T LGI1 Autoantibodies Enhance Synaptic Transmission by Presynaptic Kv1 Loss and Increased Action Potential Broadening %U https://doi.org/10.1212/NXI.0000000000200284 %V 11 %X Background and Objectives: Autoantibodies against the protein leucine-rich glioma inactivated 1 (LGI1) cause the most common subtype of autoimmune encephalitis with predominant involvement of the limbic system, associated with seizures and memory deficits. LGI1 and its receptor ADAM22 are part of a transsynaptic protein complex that includes several proteins involved in presynaptic neurotransmitter release and postsynaptic glutamate sensing. Autoantibodies against LGI1 increase excitatory synaptic strength, but studies that genetically disrupt the LGI1-ADAM22 complex report a reduction in postsynaptic glutamate receptor-mediated responses. Thus, the mechanisms underlying the increased synaptic strength induced by LGI1 autoantibodies remain elusive, and the contributions of presynaptic molecules to the LGI1-transsynaptic complex remain unclear. We therefore investigated the presynaptic mechanisms that mediate autoantibody-induced synaptic strengthening. Methods: We studied the effects of patient-derived purified polyclonal LGI1 autoantibodies on synaptic structure and function by combining direct patch-clamp recordings from presynaptic boutons and somata of hippocampal neurons with super-resolution light and electron microscopy of hippocampal cultures and brain slices. We also identified the protein domain mediating the presynaptic effect using domain-specific patient-derived monoclonal antibodies. Results: LGI1 autoantibodies dose-dependently increased short-term depression during high-frequency transmission, consistent with increased release probability. The increased neurotransmission was not related to presynaptic calcium channels because presynaptic Cav2.1 channel density, calcium current amplitude, and calcium channel gating were unaffected by LGI1 autoantibodies. By contrast, application of LGI1 autoantibodies homogeneously reduced Kv1.1 and Kv1.2 channel density on the surface of presynaptic boutons. Direct presynaptic patch-clamp recordings revealed that LGI1 autoantibodies cause a pronounced broadening of the presynaptic action potential. Domain-specific effects of LGI1 autoantibodies were analyzed at the neuronal soma. Somatic action potential broadening was induced by polyclonal LGI1 autoantibodies and patient-derived monoclonal autoantibodies targeting the epitempin domain, but not the leucin-rich repeat domain. Discussion Our results indicate that LGI1 autoantibodies reduce the density of both Kv1.1 and Kv1.2 on presynaptic boutons, without actions on calcium channel density or function, thereby broadening the presynaptic action potential and increasing neurotransmitter release. This study provides a molecular explanation for the neuronal hyperactivity observed in patients with LGI1 autoantibodies.
• Visualizing the trans-synaptic arrangement of synaptic proteins by expansion microscopy. Sachs, Stefan; Reinhard, Sebastian; Eilts, Janna; Sauer, Markus; Werner, Christian. In Frontiers in Cellular Neuroscience, 18. 2024.
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  High fidelity synaptic neurotransmission in the millisecond range is provided by a defined structural arrangement of synaptic proteins. At the presynapse multi-epitope scaffolding proteins are organized spatially at release sites to guarantee optimal binding of neurotransmitters at receptor clusters. The organization of pre- and postsynaptic proteins in trans-synaptic nanocolumns would thus intuitively support efficient information transfer at the synapse. Visualization of these protein-dense regions as well as the minute size of protein-packed synaptic clefts remains, however, challenging. To enable efficient labeling of these protein complexes, we developed post-gelation immunolabeling expansion microscopy combined with Airyscan super-resolution microscopy. Using ~8-fold expanded samples, Airyscan enables multicolor fluorescence imaging with 20–40 nm spatial resolution. Post-immunolabeling of decrowded (expanded) samples provides increased labeling efficiency and allows the visualization of trans-synaptic nanocolumns. Our approach is ideally suited to investigate the pathological impact on nanocolumn arrangement e.g., in limbic encephalitis with autoantibodies targeting trans-synaptic leucine-rich glioma inactivated 1 protein (LGI1).

  @article{sachs2024visualizing, abstract = {High fidelity synaptic neurotransmission in the millisecond range is provided by a defined structural arrangement of synaptic proteins. At the presynapse multi-epitope scaffolding proteins are organized spatially at release sites to guarantee optimal binding of neurotransmitters at receptor clusters. The organization of pre- and postsynaptic proteins in trans-synaptic nanocolumns would thus intuitively support efficient information transfer at the synapse. Visualization of these protein-dense regions as well as the minute size of protein-packed synaptic clefts remains, however, challenging. To enable efficient labeling of these protein complexes, we developed post-gelation immunolabeling expansion microscopy combined with Airyscan super-resolution microscopy. Using  8-fold expanded samples, Airyscan enables multicolor fluorescence imaging with 20–40 nm spatial resolution. Post-immunolabeling of decrowded (expanded) samples provides increased labeling efficiency and allows the visualization of trans-synaptic nanocolumns. Our approach is ideally suited to investigate the pathological impact on nanocolumn arrangement e.g., in limbic encephalitis with autoantibodies targeting trans-synaptic leucine-rich glioma inactivated 1 protein (LGI1).}, author = {Sachs, Stefan and Reinhard, Sebastian and Eilts, Janna and Sauer, Markus and Werner, Christian}, journal = {Frontiers in Cellular Neuroscience}, keywords = {werner}, title = {Visualizing the trans-synaptic arrangement of synaptic proteins by expansion microscopy}, volume = 18, year = 2024 }

  %0 Journal Article %1 sachs2024visualizing %A Sachs, Stefan %A Reinhard, Sebastian %A Eilts, Janna %A Sauer, Markus %A Werner, Christian %D 2024 %J Frontiers in Cellular Neuroscience %T Visualizing the trans-synaptic arrangement of synaptic proteins by expansion microscopy %U https://www.frontiersin.org/journals/cellular-neuroscience/articles/10.3389/fncel.2024.1328726 %V 18 %X High fidelity synaptic neurotransmission in the millisecond range is provided by a defined structural arrangement of synaptic proteins. At the presynapse multi-epitope scaffolding proteins are organized spatially at release sites to guarantee optimal binding of neurotransmitters at receptor clusters. The organization of pre- and postsynaptic proteins in trans-synaptic nanocolumns would thus intuitively support efficient information transfer at the synapse. Visualization of these protein-dense regions as well as the minute size of protein-packed synaptic clefts remains, however, challenging. To enable efficient labeling of these protein complexes, we developed post-gelation immunolabeling expansion microscopy combined with Airyscan super-resolution microscopy. Using ~8-fold expanded samples, Airyscan enables multicolor fluorescence imaging with 20–40 nm spatial resolution. Post-immunolabeling of decrowded (expanded) samples provides increased labeling efficiency and allows the visualization of trans-synaptic nanocolumns. Our approach is ideally suited to investigate the pathological impact on nanocolumn arrangement e.g., in limbic encephalitis with autoantibodies targeting trans-synaptic leucine-rich glioma inactivated 1 protein (LGI1).

• Enhanced synaptic protein visualization by multicolor super-resolution expansion microscopy. Eilts, Janna; Reinhard, Sebastian; Michetschläger, Nikolas; Werner, Christian; Sauer, Markus. In Neurophotonics, 10(4), S. 044412-. 2023.
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  SignificanceUnderstanding the organization of biomolecules into complexes and their dynamics is crucial for comprehending cellular functions and dysfunctions, particularly in neuronal networks connected by synapses. In the last two decades, various powerful super-resolution (SR) microscopy techniques have been developed that produced stunning images of synapses and their molecular organization. However, current SR microscopy methods do not permit multicolor fluorescence imaging with 20 to 30 nm spatial resolution.AimWe developed a method that enables 4-color fluorescence imaging of synaptic proteins in neurons with 20 to 30 nm lateral resolution.ApproachWe used post-expansion immunolabeling of eightfold expanded hippocampal neurons in combination with Airyscan and structured illumination microscopy (SIM).ResultsWe demonstrate that post-expansion immunolabeling of approximately eightfold expanded hippocampal neurons enables efficient labeling of synaptic proteins in crowded compartments with minimal linkage error and enables in combination with Airyscan and SIM four-color three-dimensional fluorescence imaging with 20 to 30 nm lateral resolution. Using immunolabeling of Synaptobrevin 2 as an efficient marker of the vesicle pool allowed us to identify individual synaptic vesicles colocalized with Rab3-interacting molecule 1 and 2 (RIM1/2), a marker of pre-synaptic fusion sites.ConclusionsOur optimized expansion microscopy approach improves the visualization and location of pre- and post-synaptic proteins and can thus provide invaluable insights into the spatial organization of proteins at synapses.

  @article{eilts2023enhanced, abstract = {SignificanceUnderstanding the organization of biomolecules into complexes and their dynamics is crucial for comprehending cellular functions and dysfunctions, particularly in neuronal networks connected by synapses. In the last two decades, various powerful super-resolution (SR) microscopy techniques have been developed that produced stunning images of synapses and their molecular organization. However, current SR microscopy methods do not permit multicolor fluorescence imaging with 20 to 30 nm spatial resolution.AimWe developed a method that enables 4-color fluorescence imaging of synaptic proteins in neurons with 20 to 30 nm lateral resolution.ApproachWe used post-expansion immunolabeling of eightfold expanded hippocampal neurons in combination with Airyscan and structured illumination microscopy (SIM).ResultsWe demonstrate that post-expansion immunolabeling of approximately eightfold expanded hippocampal neurons enables efficient labeling of synaptic proteins in crowded compartments with minimal linkage error and enables in combination with Airyscan and SIM four-color three-dimensional fluorescence imaging with 20 to 30 nm lateral resolution. Using immunolabeling of Synaptobrevin 2 as an efficient marker of the vesicle pool allowed us to identify individual synaptic vesicles colocalized with Rab3-interacting molecule 1 and 2 (RIM1/2), a marker of pre-synaptic fusion sites.ConclusionsOur optimized expansion microscopy approach improves the visualization and location of pre- and post-synaptic proteins and can thus provide invaluable insights into the spatial organization of proteins at synapses.}, author = {Eilts, Janna and Reinhard, Sebastian and Michetschläger, Nikolas and Werner, Christian and Sauer, Markus}, booktitle = {Neurophotonics}, journal = {Neurophotonics}, keywords = {werner}, month = 10, number = 4, pages = {044412–}, title = {Enhanced synaptic protein visualization by multicolor super-resolution expansion microscopy}, volume = 10, year = 2023 }

  %0 Journal Article %1 eilts2023enhanced %A Eilts, Janna %A Reinhard, Sebastian %A Michetschläger, Nikolas %A Werner, Christian %A Sauer, Markus %B Neurophotonics %D 2023 %J Neurophotonics %N 4 %P 044412-- %R 10.1117/1.NPh.10.4.044412 %T Enhanced synaptic protein visualization by multicolor super-resolution expansion microscopy %U https://doi.org/10.1117/1.NPh.10.4.044412 %V 10 %X SignificanceUnderstanding the organization of biomolecules into complexes and their dynamics is crucial for comprehending cellular functions and dysfunctions, particularly in neuronal networks connected by synapses. In the last two decades, various powerful super-resolution (SR) microscopy techniques have been developed that produced stunning images of synapses and their molecular organization. However, current SR microscopy methods do not permit multicolor fluorescence imaging with 20 to 30 nm spatial resolution.AimWe developed a method that enables 4-color fluorescence imaging of synaptic proteins in neurons with 20 to 30 nm lateral resolution.ApproachWe used post-expansion immunolabeling of eightfold expanded hippocampal neurons in combination with Airyscan and structured illumination microscopy (SIM).ResultsWe demonstrate that post-expansion immunolabeling of approximately eightfold expanded hippocampal neurons enables efficient labeling of synaptic proteins in crowded compartments with minimal linkage error and enables in combination with Airyscan and SIM four-color three-dimensional fluorescence imaging with 20 to 30 nm lateral resolution. Using immunolabeling of Synaptobrevin 2 as an efficient marker of the vesicle pool allowed us to identify individual synaptic vesicles colocalized with Rab3-interacting molecule 1 and 2 (RIM1/2), a marker of pre-synaptic fusion sites.ConclusionsOur optimized expansion microscopy approach improves the visualization and location of pre- and post-synaptic proteins and can thus provide invaluable insights into the spatial organization of proteins at synapses.
• Filamin A organizes γ‑aminobutyric acid type B receptors at the plasma membrane. Jobin, Marie-Lise; Siddig, Sana; Koszegi, Zsombor; Lanoiselée, Yann; Khayenko, Vladimir; Sungkaworn, Titiwat; Werner, Christian; Seier, Kerstin; Misigaiski, Christin; Mantovani, Giovanna; Sauer, Markus; Maric, Hans M.; Calebiro, Davide. In Nature Communications, 14(1), S. 34-. 2023.
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  The γ-aminobutyric acid type B (GABAB) receptor is a prototypical family C G protein-coupled receptor (GPCR) that plays a key role in the regulation of synaptic transmission. Although growing evidence suggests that GPCR signaling in neurons might be highly organized in time and space, limited information is available about the mechanisms controlling the nanoscale organization of GABAB receptors and other GPCRs on the neuronal plasma membrane. Using a combination of biochemical assays in vitro, single-particle tracking, and super-resolution microscopy, we provide evidence that the spatial organization and diffusion of GABAB receptors on the plasma membrane are governed by dynamic interactions with filamin A, which tethers the receptors to sub-cortical actin filaments. We further show that GABAB receptors are located together with filamin A in small nanodomains in hippocampal neurons. These interactions are mediated by the first intracellular loop of the GABAB1 subunit and modulate the kinetics of Gαi protein activation in response to GABA stimulation.

  @article{jobin2023filamin, abstract = {The γ-aminobutyric acid type B (GABAB) receptor is a prototypical family C G protein-coupled receptor (GPCR) that plays a key role in the regulation of synaptic transmission. Although growing evidence suggests that GPCR signaling in neurons might be highly organized in time and space, limited information is available about the mechanisms controlling the nanoscale organization of GABAB receptors and other GPCRs on the neuronal plasma membrane. Using a combination of biochemical assays in vitro, single-particle tracking, and super-resolution microscopy, we provide evidence that the spatial organization and diffusion of GABAB receptors on the plasma membrane are governed by dynamic interactions with filamin A, which tethers the receptors to sub-cortical actin filaments. We further show that GABAB receptors are located together with filamin A in small nanodomains in hippocampal neurons. These interactions are mediated by the first intracellular loop of the GABAB1 subunit and modulate the kinetics of Gαi protein activation in response to GABA stimulation.}, author = {Jobin, Marie-Lise and Siddig, Sana and Koszegi, Zsombor and Lanoiselée, Yann and Khayenko, Vladimir and Sungkaworn, Titiwat and Werner, Christian and Seier, Kerstin and Misigaiski, Christin and Mantovani, Giovanna and Sauer, Markus and Maric, Hans M. and Calebiro, Davide}, journal = {Nature Communications}, keywords = {werner}, number = 1, pages = {34–}, title = {Filamin A organizes γ‑aminobutyric acid type B receptors at the plasma membrane}, volume = 14, year = 2023 }

  %0 Journal Article %1 jobin2023filamin %A Jobin, Marie-Lise %A Siddig, Sana %A Koszegi, Zsombor %A Lanoiselée, Yann %A Khayenko, Vladimir %A Sungkaworn, Titiwat %A Werner, Christian %A Seier, Kerstin %A Misigaiski, Christin %A Mantovani, Giovanna %A Sauer, Markus %A Maric, Hans M. %A Calebiro, Davide %D 2023 %J Nature Communications %N 1 %P 34-- %R 10.1038/s41467-022-35708-1 %T Filamin A organizes γ‑aminobutyric acid type B receptors at the plasma membrane %U https://doi.org/10.1038/s41467-022-35708-1 %V 14 %X The γ-aminobutyric acid type B (GABAB) receptor is a prototypical family C G protein-coupled receptor (GPCR) that plays a key role in the regulation of synaptic transmission. Although growing evidence suggests that GPCR signaling in neurons might be highly organized in time and space, limited information is available about the mechanisms controlling the nanoscale organization of GABAB receptors and other GPCRs on the neuronal plasma membrane. Using a combination of biochemical assays in vitro, single-particle tracking, and super-resolution microscopy, we provide evidence that the spatial organization and diffusion of GABAB receptors on the plasma membrane are governed by dynamic interactions with filamin A, which tethers the receptors to sub-cortical actin filaments. We further show that GABAB receptors are located together with filamin A in small nanodomains in hippocampal neurons. These interactions are mediated by the first intracellular loop of the GABAB1 subunit and modulate the kinetics of Gαi protein activation in response to GABA stimulation.
• Expansion microscopy in honeybee brains for high-resolution neuroanatomical analyses in social insects. Kraft, Nadine; Muenz, Thomas S.; Reinhard, Sebastian; Werner, Christian; Sauer, Markus; Groh, Claudia; Rössler, Wolfgang. In Cell and Tissue Research, 393(3), S. 489–506. 2023.
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  The diffraction limit of light microscopy poses a problem that is frequently faced in structural analyses of social insect brains. With the introduction of expansion microscopy (ExM), a tool became available to overcome this limitation by isotropic physical expansion of preserved specimens. Our analyses focus on synaptic microcircuits (microglomeruli, MG) in the mushroom body (MB) of social insects, high-order brain centers for sensory integration, learning, and memory. MG undergo significant structural reorganizations with age, sensory experience, and during long-term memory formation. However, the changes in subcellular architecture involved in this plasticity have only partially been accessed yet. Using the western honeybee Apis mellifera as an experimental model, we established ExM for the first time in a social insect species and applied it to investigate plasticity in synaptic microcircuits within MG of the MB calyces. Using combinations of antibody staining and neuronal tracing, we demonstrate that this technique enables quantitative and qualitative analyses of structural neuronal plasticity at high resolution in a social insect brain.

  @article{kraft2023expansion, abstract = {The diffraction limit of light microscopy poses a problem that is frequently faced in structural analyses of social insect brains. With the introduction of expansion microscopy (ExM), a tool became available to overcome this limitation by isotropic physical expansion of preserved specimens. Our analyses focus on synaptic microcircuits (microglomeruli, MG) in the mushroom body (MB) of social insects, high-order brain centers for sensory integration, learning, and memory. MG undergo significant structural reorganizations with age, sensory experience, and during long-term memory formation. However, the changes in subcellular architecture involved in this plasticity have only partially been accessed yet. Using the western honeybee Apis mellifera as an experimental model, we established ExM for the first time in a social insect species and applied it to investigate plasticity in synaptic microcircuits within MG of the MB calyces. Using combinations of antibody staining and neuronal tracing, we demonstrate that this technique enables quantitative and qualitative analyses of structural neuronal plasticity at high resolution in a social insect brain.}, author = {Kraft, Nadine and Muenz, Thomas S. and Reinhard, Sebastian and Werner, Christian and Sauer, Markus and Groh, Claudia and Rössler, Wolfgang}, journal = {Cell and Tissue Research}, keywords = {werner}, number = 3, pages = {489–506}, title = {Expansion microscopy in honeybee brains for high-resolution neuroanatomical analyses in social insects}, volume = 393, year = 2023 }

  %0 Journal Article %1 kraft2023expansion %A Kraft, Nadine %A Muenz, Thomas S. %A Reinhard, Sebastian %A Werner, Christian %A Sauer, Markus %A Groh, Claudia %A Rössler, Wolfgang %D 2023 %J Cell and Tissue Research %N 3 %P 489--506 %R 10.1007/s00441-023-03803-4 %T Expansion microscopy in honeybee brains for high-resolution neuroanatomical analyses in social insects %U https://doi.org/10.1007/s00441-023-03803-4 %V 393 %X The diffraction limit of light microscopy poses a problem that is frequently faced in structural analyses of social insect brains. With the introduction of expansion microscopy (ExM), a tool became available to overcome this limitation by isotropic physical expansion of preserved specimens. Our analyses focus on synaptic microcircuits (microglomeruli, MG) in the mushroom body (MB) of social insects, high-order brain centers for sensory integration, learning, and memory. MG undergo significant structural reorganizations with age, sensory experience, and during long-term memory formation. However, the changes in subcellular architecture involved in this plasticity have only partially been accessed yet. Using the western honeybee Apis mellifera as an experimental model, we established ExM for the first time in a social insect species and applied it to investigate plasticity in synaptic microcircuits within MG of the MB calyces. Using combinations of antibody staining and neuronal tracing, we demonstrate that this technique enables quantitative and qualitative analyses of structural neuronal plasticity at high resolution in a social insect brain.

• Recombinant pro-CTSD (cathepsin D) enhances SNCA/α-Synuclein degradation in α-Synucleinopathy models. Prieto Huarcaya, Susy; Drobny, Alice; Marques, André R. A.; Di Spiezio, Alessandro; Dobert, Jan Philipp; Balta, Denise; Werner, Christian; Rizo, Tania; Gallwitz, Lisa; Bub, Simon; Stojkovska, Iva; Belur, Nandkishore R.; Fogh, Jens; Mazzulli, Joseph R; Xiang, Wei; Fulzele, Amitkumar; Dejung, Mario; Sauer, Markus; Winner, Beate; Rose-John, Stefan; Arnold, Philipp; Saftig, Paul; Zunke, Friederike. In Autophagy, 18(5), S. 1127–1151. Taylor & Francis, 2022.
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  Parkinson disease (PD) is a neurodegenerative disorder characterized by the abnormal intracellular accumulation of SNCA/α-synuclein. While the exact mechanisms underlying SNCA pathology are not fully understood, increasing evidence suggests the involvement of autophagy as well as lysosomal deficiencies. Because CTSD (cathepsin D) has been proposed to be the major lysosomal protease involved in SNCA degradation, its deficiency has been linked to the presence of insoluble SNCA conformers in the brain of mice and humans as well as to the transcellular transmission of SNCA aggregates. We here postulate that SNCA degradation can be enhanced by the application of the recombinant human proform of CTSD (rHsCTSD). Our results reveal that rHsCTSD is efficiently endocytosed by neuronal cells, correctly targeted to lysosomes and matured to an enzymatically active protease. In dopaminergic neurons derived from induced pluripotent stem cells (iPSC) of PD patients harboring the A53T mutation within the SNCA gene, we confirm the reduction of insoluble SNCA after treatment with rHsCTSD. Moreover, we demonstrate a decrease of pathological SNCA conformers in the brain and within primary neurons of a ctsd-deficient mouse model after dosing with rHsCTSD. Boosting lysosomal CTSD activity not only enhanced SNCA clearance in human and murine neurons as well as tissue, but also restored endo-lysosome and autophagy function. Our findings indicate that CTSD is critical for SNCA clearance and function. Thus, enzyme replacement strategies utilizing CTSD may also be of therapeutic interest for the treatment of PD and other synucleinopathies aiming to decrease the SNCA burden. Abbreviations: aa: amino acid; SNCA/α-synuclein: synuclein alpha; APP: amyloid beta precursor protein; BBB: blood brain barrier; BF: basal forebrain; CBB: Coomassie Brilliant Blue; CLN: neuronal ceroid lipofuscinosis; CNL10: neuronal ceroid lipofuscinosis type 10; Corr.: corrected; CTSD: cathepsin D; CTSB: cathepsin B; DA: dopaminergic; DA-iPSn: induced pluripotent stem cell-derived dopaminergic neurons; dox: doxycycline; ERT: enzyme replacement therapy; Fx: fornix, GBA/?-glucocerebrosidase: glucosylceramidase beta; h: hour; HC: hippocampus; HT: hypothalamus; i.c.: intracranially; IF: immunofluorescence; iPSC: induced pluripotent stem cell; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LSDs: lysosomal storage disorders; MAPT: microtubule associated protein tau; M6P: mannose-6-phosphate; M6PR: mannose-6-phosphate receptor; MB: midbrain; mCTSD: mature form of CTSD; neurofil.: neurofilament; PD: Parkinson disease; proCTSD: proform of CTSD; PRNP: prion protein; RFU: relative fluorescence units; rHsCTSD: recombinant human proCTSD; SAPC: Saposin C; SIM: structured illumination microscopy; T-insol: Triton-insoluble; T-sol: Triton-soluble; TEM: transmission electron microscopy, TH: tyrosine hydroxylase; Thal: thalamus

  @article{prietohuarcaya2022recombinant, abstract = {Parkinson disease (PD) is a neurodegenerative disorder characterized by the abnormal intracellular accumulation of SNCA/α-synuclein. While the exact mechanisms underlying SNCA pathology are not fully understood, increasing evidence suggests the involvement of autophagy as well as lysosomal deficiencies. Because CTSD (cathepsin D) has been proposed to be the major lysosomal protease involved in SNCA degradation, its deficiency has been linked to the presence of insoluble SNCA conformers in the brain of mice and humans as well as to the transcellular transmission of SNCA aggregates. We here postulate that SNCA degradation can be enhanced by the application of the recombinant human proform of CTSD (rHsCTSD). Our results reveal that rHsCTSD is efficiently endocytosed by neuronal cells, correctly targeted to lysosomes and matured to an enzymatically active protease. In dopaminergic neurons derived from induced pluripotent stem cells (iPSC) of PD patients harboring the A53T mutation within the SNCA gene, we confirm the reduction of insoluble SNCA after treatment with rHsCTSD. Moreover, we demonstrate a decrease of pathological SNCA conformers in the brain and within primary neurons of a ctsd-deficient mouse model after dosing with rHsCTSD. Boosting lysosomal CTSD activity not only enhanced SNCA clearance in human and murine neurons as well as tissue, but also restored endo-lysosome and autophagy function. Our findings indicate that CTSD is critical for SNCA clearance and function. Thus, enzyme replacement strategies utilizing CTSD may also be of therapeutic interest for the treatment of PD and other synucleinopathies aiming to decrease the SNCA burden. Abbreviations: aa: amino acid; SNCA/α-synuclein: synuclein alpha; APP: amyloid beta precursor protein; BBB: blood brain barrier; BF: basal forebrain; CBB: Coomassie Brilliant Blue; CLN: neuronal ceroid lipofuscinosis; CNL10: neuronal ceroid lipofuscinosis type 10; Corr.: corrected; CTSD: cathepsin D; CTSB: cathepsin B; DA: dopaminergic; DA-iPSn: induced pluripotent stem cell-derived dopaminergic neurons; dox: doxycycline; ERT: enzyme replacement therapy; Fx: fornix, GBA/?-glucocerebrosidase: glucosylceramidase beta; h: hour; HC: hippocampus; HT: hypothalamus; i.c.: intracranially; IF: immunofluorescence; iPSC: induced pluripotent stem cell; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LSDs: lysosomal storage disorders; MAPT: microtubule associated protein tau; M6P: mannose-6-phosphate; M6PR: mannose-6-phosphate receptor; MB: midbrain; mCTSD: mature form of CTSD; neurofil.: neurofilament; PD: Parkinson disease; proCTSD: proform of CTSD; PRNP: prion protein; RFU: relative fluorescence units; rHsCTSD: recombinant human proCTSD; SAPC: Saposin C; SIM: structured illumination microscopy; T-insol: Triton-insoluble; T-sol: Triton-soluble; TEM: transmission electron microscopy, TH: tyrosine hydroxylase; Thal: thalamus}, author = {Prieto Huarcaya, Susy and Drobny, Alice and Marques, André R. A. and Di Spiezio, Alessandro and Dobert, Jan Philipp and Balta, Denise and Werner, Christian and Rizo, Tania and Gallwitz, Lisa and Bub, Simon and Stojkovska, Iva and Belur, Nandkishore R. and Fogh, Jens and Mazzulli, Joseph R and Xiang, Wei and Fulzele, Amitkumar and Dejung, Mario and Sauer, Markus and Winner, Beate and Rose-John, Stefan and Arnold, Philipp and Saftig, Paul and Zunke, Friederike}, booktitle = {Autophagy}, journal = {Autophagy}, keywords = {werner}, month = {05}, number = 5, pages = {1127–1151}, publisher = {Taylor & Francis}, title = {Recombinant pro-CTSD (cathepsin D) enhances SNCA/α-Synuclein degradation in α-Synucleinopathy models}, volume = 18, year = 2022 }

  %0 Journal Article %1 prietohuarcaya2022recombinant %A Prieto Huarcaya, Susy %A Drobny, Alice %A Marques, André R. A. %A Di Spiezio, Alessandro %A Dobert, Jan Philipp %A Balta, Denise %A Werner, Christian %A Rizo, Tania %A Gallwitz, Lisa %A Bub, Simon %A Stojkovska, Iva %A Belur, Nandkishore R. %A Fogh, Jens %A Mazzulli, Joseph R %A Xiang, Wei %A Fulzele, Amitkumar %A Dejung, Mario %A Sauer, Markus %A Winner, Beate %A Rose-John, Stefan %A Arnold, Philipp %A Saftig, Paul %A Zunke, Friederike %B Autophagy %D 2022 %I Taylor & Francis %J Autophagy %N 5 %P 1127--1151 %R 10.1080/15548627.2022.2045534 %T Recombinant pro-CTSD (cathepsin D) enhances SNCA/α-Synuclein degradation in α-Synucleinopathy models %U https://doi.org/10.1080/15548627.2022.2045534 %V 18 %X Parkinson disease (PD) is a neurodegenerative disorder characterized by the abnormal intracellular accumulation of SNCA/α-synuclein. While the exact mechanisms underlying SNCA pathology are not fully understood, increasing evidence suggests the involvement of autophagy as well as lysosomal deficiencies. Because CTSD (cathepsin D) has been proposed to be the major lysosomal protease involved in SNCA degradation, its deficiency has been linked to the presence of insoluble SNCA conformers in the brain of mice and humans as well as to the transcellular transmission of SNCA aggregates. We here postulate that SNCA degradation can be enhanced by the application of the recombinant human proform of CTSD (rHsCTSD). Our results reveal that rHsCTSD is efficiently endocytosed by neuronal cells, correctly targeted to lysosomes and matured to an enzymatically active protease. In dopaminergic neurons derived from induced pluripotent stem cells (iPSC) of PD patients harboring the A53T mutation within the SNCA gene, we confirm the reduction of insoluble SNCA after treatment with rHsCTSD. Moreover, we demonstrate a decrease of pathological SNCA conformers in the brain and within primary neurons of a ctsd-deficient mouse model after dosing with rHsCTSD. Boosting lysosomal CTSD activity not only enhanced SNCA clearance in human and murine neurons as well as tissue, but also restored endo-lysosome and autophagy function. Our findings indicate that CTSD is critical for SNCA clearance and function. Thus, enzyme replacement strategies utilizing CTSD may also be of therapeutic interest for the treatment of PD and other synucleinopathies aiming to decrease the SNCA burden. Abbreviations: aa: amino acid; SNCA/α-synuclein: synuclein alpha; APP: amyloid beta precursor protein; BBB: blood brain barrier; BF: basal forebrain; CBB: Coomassie Brilliant Blue; CLN: neuronal ceroid lipofuscinosis; CNL10: neuronal ceroid lipofuscinosis type 10; Corr.: corrected; CTSD: cathepsin D; CTSB: cathepsin B; DA: dopaminergic; DA-iPSn: induced pluripotent stem cell-derived dopaminergic neurons; dox: doxycycline; ERT: enzyme replacement therapy; Fx: fornix, GBA/?-glucocerebrosidase: glucosylceramidase beta; h: hour; HC: hippocampus; HT: hypothalamus; i.c.: intracranially; IF: immunofluorescence; iPSC: induced pluripotent stem cell; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LSDs: lysosomal storage disorders; MAPT: microtubule associated protein tau; M6P: mannose-6-phosphate; M6PR: mannose-6-phosphate receptor; MB: midbrain; mCTSD: mature form of CTSD; neurofil.: neurofilament; PD: Parkinson disease; proCTSD: proform of CTSD; PRNP: prion protein; RFU: relative fluorescence units; rHsCTSD: recombinant human proCTSD; SAPC: Saposin C; SIM: structured illumination microscopy; T-insol: Triton-insoluble; T-sol: Triton-soluble; TEM: transmission electron microscopy, TH: tyrosine hydroxylase; Thal: thalamus
• Nanoscopic dopamine transporter distribution and conformation are inversely regulated by excitatory drive and D2 autoreceptor activity. Lycas, Matthew D.; Ejdrup, Aske L.; Sørensen, Andreas T.; Haahr, Nicolai O.; Jørgensen, Søren H.; Guthrie, Daryl A.; Støier, Jonatan F.; Werner, Christian; Newman, Amy Hauck; Sauer, Markus; Herborg, Freja; Gether, Ulrik. In Cell Reports, 40(13), S. 111431-. 2022.
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  The nanoscopic organization and regulation of individual molecular components in presynaptic varicosities of neurons releasing modulatory volume neurotransmitters like dopamine (DA) remain largely elusive. Here we show, by application of several super-resolution microscopy techniques to cultured neurons and mouse striatal slices, that the DA transporter (DAT), a key protein in varicosities of dopaminergic neurons, exists in the membrane in dynamic equilibrium between an inward-facing nanodomain-localized and outward-facing unclustered configuration. The balance between these configurations is inversely regulated by excitatory drive and DA D2 autoreceptor activation in a manner dependent on Ca2+ influx via N-type voltage-gated Ca2+ channels. The DAT nanodomains contain tens of transporters molecules and overlap with nanodomains of PIP2 (phosphatidylinositol-4,5-bisphosphate) but show little overlap with D2 autoreceptor, syntaxin-1, and clathrin nanodomains. The data reveal a mechanism for rapid alterations of nanoscopic DAT distribution and show a striking link of this to the conformational state of the transporter.

  @article{lycas2022nanoscopic, abstract = {The nanoscopic organization and regulation of individual molecular components in presynaptic varicosities of neurons releasing modulatory volume neurotransmitters like dopamine (DA) remain largely elusive. Here we show, by application of several super-resolution microscopy techniques to cultured neurons and mouse striatal slices, that the DA transporter (DAT), a key protein in varicosities of dopaminergic neurons, exists in the membrane in dynamic equilibrium between an inward-facing nanodomain-localized and outward-facing unclustered configuration. The balance between these configurations is inversely regulated by excitatory drive and DA D2 autoreceptor activation in a manner dependent on Ca2+ influx via N-type voltage-gated Ca2+ channels. The DAT nanodomains contain tens of transporters molecules and overlap with nanodomains of PIP2 (phosphatidylinositol-4,5-bisphosphate) but show little overlap with D2 autoreceptor, syntaxin-1, and clathrin nanodomains. The data reveal a mechanism for rapid alterations of nanoscopic DAT distribution and show a striking link of this to the conformational state of the transporter.}, author = {Lycas, Matthew D. and Ejdrup, Aske L. and Sørensen, Andreas T. and Haahr, Nicolai O. and Jørgensen, Søren H. and Guthrie, Daryl A. and Støier, Jonatan F. and Werner, Christian and Newman, Amy Hauck and Sauer, Markus and Herborg, Freja and Gether, Ulrik}, journal = {Cell Reports}, keywords = {werner}, number = 13, pages = {111431–}, title = {Nanoscopic dopamine transporter distribution and conformation are inversely regulated by excitatory drive and D2 autoreceptor activity}, volume = 40, year = 2022 }

  %0 Journal Article %1 lycas2022nanoscopic %A Lycas, Matthew D. %A Ejdrup, Aske L. %A Sørensen, Andreas T. %A Haahr, Nicolai O. %A Jørgensen, Søren H. %A Guthrie, Daryl A. %A Støier, Jonatan F. %A Werner, Christian %A Newman, Amy Hauck %A Sauer, Markus %A Herborg, Freja %A Gether, Ulrik %D 2022 %J Cell Reports %N 13 %P 111431-- %R https://doi.org/10.1016/j.celrep.2022.111431 %T Nanoscopic dopamine transporter distribution and conformation are inversely regulated by excitatory drive and D2 autoreceptor activity %U https://www.sciencedirect.com/science/article/pii/S2211124722012724 %V 40 %X The nanoscopic organization and regulation of individual molecular components in presynaptic varicosities of neurons releasing modulatory volume neurotransmitters like dopamine (DA) remain largely elusive. Here we show, by application of several super-resolution microscopy techniques to cultured neurons and mouse striatal slices, that the DA transporter (DAT), a key protein in varicosities of dopaminergic neurons, exists in the membrane in dynamic equilibrium between an inward-facing nanodomain-localized and outward-facing unclustered configuration. The balance between these configurations is inversely regulated by excitatory drive and DA D2 autoreceptor activation in a manner dependent on Ca2+ influx via N-type voltage-gated Ca2+ channels. The DAT nanodomains contain tens of transporters molecules and overlap with nanodomains of PIP2 (phosphatidylinositol-4,5-bisphosphate) but show little overlap with D2 autoreceptor, syntaxin-1, and clathrin nanodomains. The data reveal a mechanism for rapid alterations of nanoscopic DAT distribution and show a striking link of this to the conformational state of the transporter.

• Anti–contactin-1 Antibodies Affect Surface Expression and Sodium Currents in Dorsal Root Ganglia. Grüner, Julia; Stengel, Helena; Werner, Christian; Appeltshauser, Luise; Sommer, Claudia; Villmann, Carmen; Doppler, Kathrin. In Neurology Neuroimmunology & Neuroinflammation, 8(5), S. e1056-. Wolters Kluwer, 2021.
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  Background and Objectives: As autoantibodies to contactin-1 from patients with chronic inflammatory demyelinating polyradiculoneuropathy not only bind to the paranodes where they are supposed to cause conduction failure but also bind to other neuronal cell types, we aimed to investigate the effect of anti–contactin-1 autoantibodies on contactin-1 surface expression in cerebellar granule neurons, dorsal root ganglion neurons, and contactin-1–transfected human embryonic kidney 293 cells. Methods: Immunocytochemistry including structured illumination microscopy and immunoblotting was used to determine expression levels of contactin-1 and/or sodium channels after long-term exposure to autoantibodies from 3 seropositive patients. For functional analysis of sodium channels, whole-cell recordings of sodium currents were performed on dorsal root ganglion neurons incubated with anti–contactin-1 autoantibodies. Results: We found a reduction in contactin-1 expression levels on dorsal root ganglion neurons, cerebellar granule neurons, and contactin-1–transfected human embryonic kidney 293 cells and decreased dorsal root ganglion sodium currents after long-term exposure to anti–contactin-1 autoantibodies. Sodium channel density did not decrease. Discussion: Our results demonstrate a direct effect of anti–contactin-1 autoantibodies on the surface expression of contactin-1 and sodium currents in dorsal root ganglion neurons. This may be the pathophysiologic correlate of sensory ataxia reported in these patients.

  @article{gruneranticontactin1, abstract = {Background and Objectives: As autoantibodies to contactin-1 from patients with chronic inflammatory demyelinating polyradiculoneuropathy not only bind to the paranodes where they are supposed to cause conduction failure but also bind to other neuronal cell types, we aimed to investigate the effect of anti–contactin-1 autoantibodies on contactin-1 surface expression in cerebellar granule neurons, dorsal root ganglion neurons, and contactin-1–transfected human embryonic kidney 293 cells. Methods: Immunocytochemistry including structured illumination microscopy and immunoblotting was used to determine expression levels of contactin-1 and/or sodium channels after long-term exposure to autoantibodies from 3 seropositive patients. For functional analysis of sodium channels, whole-cell recordings of sodium currents were performed on dorsal root ganglion neurons incubated with anti–contactin-1 autoantibodies. Results: We found a reduction in contactin-1 expression levels on dorsal root ganglion neurons, cerebellar granule neurons, and contactin-1–transfected human embryonic kidney 293 cells and decreased dorsal root ganglion sodium currents after long-term exposure to anti–contactin-1 autoantibodies. Sodium channel density did not decrease. Discussion: Our results demonstrate a direct effect of anti–contactin-1 autoantibodies on the surface expression of contactin-1 and sodium currents in dorsal root ganglion neurons. This may be the pathophysiologic correlate of sensory ataxia reported in these patients.}, author = {Grüner, Julia and Stengel, Helena and Werner, Christian and Appeltshauser, Luise and Sommer, Claudia and Villmann, Carmen and Doppler, Kathrin}, booktitle = {Neurology Neuroimmunology & Neuroinflammation}, journal = {Neurology Neuroimmunology & Neuroinflammation}, keywords = {werner}, number = 5, pages = {e1056–}, publisher = {Wolters Kluwer}, title = {Anti–contactin-1 Antibodies Affect Surface Expression and Sodium Currents in Dorsal Root Ganglia}, volume = 8, year = 2021 }

  %0 Journal Article %1 gruneranticontactin1 %A Grüner, Julia %A Stengel, Helena %A Werner, Christian %A Appeltshauser, Luise %A Sommer, Claudia %A Villmann, Carmen %A Doppler, Kathrin %B Neurology Neuroimmunology & Neuroinflammation %D 2021 %I Wolters Kluwer %J Neurology Neuroimmunology & Neuroinflammation %N 5 %P e1056-- %R 10.1212/NXI.0000000000001056 %T Anti–contactin-1 Antibodies Affect Surface Expression and Sodium Currents in Dorsal Root Ganglia %U https://doi.org/10.1212/NXI.0000000000001056 %V 8 %X Background and Objectives: As autoantibodies to contactin-1 from patients with chronic inflammatory demyelinating polyradiculoneuropathy not only bind to the paranodes where they are supposed to cause conduction failure but also bind to other neuronal cell types, we aimed to investigate the effect of anti–contactin-1 autoantibodies on contactin-1 surface expression in cerebellar granule neurons, dorsal root ganglion neurons, and contactin-1–transfected human embryonic kidney 293 cells. Methods: Immunocytochemistry including structured illumination microscopy and immunoblotting was used to determine expression levels of contactin-1 and/or sodium channels after long-term exposure to autoantibodies from 3 seropositive patients. For functional analysis of sodium channels, whole-cell recordings of sodium currents were performed on dorsal root ganglion neurons incubated with anti–contactin-1 autoantibodies. Results: We found a reduction in contactin-1 expression levels on dorsal root ganglion neurons, cerebellar granule neurons, and contactin-1–transfected human embryonic kidney 293 cells and decreased dorsal root ganglion sodium currents after long-term exposure to anti–contactin-1 autoantibodies. Sodium channel density did not decrease. Discussion: Our results demonstrate a direct effect of anti–contactin-1 autoantibodies on the surface expression of contactin-1 and sodium currents in dorsal root ganglion neurons. This may be the pathophysiologic correlate of sensory ataxia reported in these patients.
• Genetic Code Expansion and Click-Chemistry Labeling to Visualize GABA-A Receptors by Super-Resolution Microscopy. Kuhlemann, Alexander; Beliu, Gerti; Janzen, Dieter; Petrini, Enrica Maria; Taban, Danush; Helmerich, Dominic A.; Doose, Sören; Bruno, Martina; Barberis, Andrea; Villmann, Carmen; Sauer, Markus; Werner, Christian. In Frontiers in Synaptic Neuroscience, 13. 2021.
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  Fluorescence labeling of difficult to access protein sites, e.g., in confined compartments, requires small fluorescent labels that can be covalently tethered at well-defined positions with high efficiency. Here, we report site-specific labeling of the extracellular domain of γ-aminobutyric acid type A (GABA-A) receptor subunits by genetic code expansion (GCE) with unnatural amino acids (ncAA) combined with bioorthogonal click-chemistry labeling with tetrazine dyes in HEK-293-T cells and primary cultured neurons. After optimization of GABA-A receptor expression and labeling efficiency, most effective variants were selected for super-resolution microscopy and functionality testing by whole-cell patch clamp. Our results show that GCE with ncAA and bioorthogonal click labeling with small tetrazine dyes represents a versatile method for highly efficient site-specific fluorescence labeling of proteins in a crowded environment, e.g., extracellular protein domains in confined compartments such as the synaptic cleft.

  @article{kuhlemann2021genetic, abstract = {Fluorescence labeling of difficult to access protein sites, e.g., in confined compartments, requires small fluorescent labels that can be covalently tethered at well-defined positions with high efficiency. Here, we report site-specific labeling of the extracellular domain of γ-aminobutyric acid type A (GABA-A) receptor subunits by genetic code expansion (GCE) with unnatural amino acids (ncAA) combined with bioorthogonal click-chemistry labeling with tetrazine dyes in HEK-293-T cells and primary cultured neurons. After optimization of GABA-A receptor expression and labeling efficiency, most effective variants were selected for super-resolution microscopy and functionality testing by whole-cell patch clamp. Our results show that GCE with ncAA and bioorthogonal click labeling with small tetrazine dyes represents a versatile method for highly efficient site-specific fluorescence labeling of proteins in a crowded environment, e.g., extracellular protein domains in confined compartments such as the synaptic cleft.}, author = {Kuhlemann, Alexander and Beliu, Gerti and Janzen, Dieter and Petrini, Enrica Maria and Taban, Danush and Helmerich, Dominic A. and Doose, Sören and Bruno, Martina and Barberis, Andrea and Villmann, Carmen and Sauer, Markus and Werner, Christian}, journal = {Frontiers in Synaptic Neuroscience}, keywords = {werner}, title = {Genetic Code Expansion and Click-Chemistry Labeling to Visualize GABA-A Receptors by Super-Resolution Microscopy}, volume = 13, year = 2021 }

  %0 Journal Article %1 kuhlemann2021genetic %A Kuhlemann, Alexander %A Beliu, Gerti %A Janzen, Dieter %A Petrini, Enrica Maria %A Taban, Danush %A Helmerich, Dominic A. %A Doose, Sören %A Bruno, Martina %A Barberis, Andrea %A Villmann, Carmen %A Sauer, Markus %A Werner, Christian %D 2021 %J Frontiers in Synaptic Neuroscience %T Genetic Code Expansion and Click-Chemistry Labeling to Visualize GABA-A Receptors by Super-Resolution Microscopy %U https://www.frontiersin.org/journals/synaptic-neuroscience/articles/10.3389/fnsyn.2021.727406 %V 13 %X Fluorescence labeling of difficult to access protein sites, e.g., in confined compartments, requires small fluorescent labels that can be covalently tethered at well-defined positions with high efficiency. Here, we report site-specific labeling of the extracellular domain of γ-aminobutyric acid type A (GABA-A) receptor subunits by genetic code expansion (GCE) with unnatural amino acids (ncAA) combined with bioorthogonal click-chemistry labeling with tetrazine dyes in HEK-293-T cells and primary cultured neurons. After optimization of GABA-A receptor expression and labeling efficiency, most effective variants were selected for super-resolution microscopy and functionality testing by whole-cell patch clamp. Our results show that GCE with ncAA and bioorthogonal click labeling with small tetrazine dyes represents a versatile method for highly efficient site-specific fluorescence labeling of proteins in a crowded environment, e.g., extracellular protein domains in confined compartments such as the synaptic cleft.
• Super-resolving Microscopy in Neuroscience. Werner, Christian; Sauer, Markus; Geis, Christian. In Chem. Rev., 121(19), S. 11971–12015. American Chemical Society, 2021.
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  Fluorescence imaging techniques play a pivotal role in our understanding of the nervous system. The emergence of various super-resolution microscopy methods and specialized fluorescent probes enables direct insight into neuronal structure and protein arrangements in cellular subcompartments with so far unmatched resolution. Super-resolving visualization techniques in neurons unveil a novel understanding of cytoskeletal composition, distribution, motility, and signaling of membrane proteins, subsynaptic structure and function, and neuron–glia interaction. Well-defined molecular targets in autoimmune and neurodegenerative disease models provide excellent starting points for in-depth investigation of disease pathophysiology using novel and innovative imaging methodology. Application of super-resolution microscopy in human brain samples and for testing clinical biomarkers is still in its infancy but opens new opportunities for translational research in neurology and neuroscience. In this review, we describe how super-resolving microscopy has improved our understanding of neuronal and brain function and dysfunction in the last two decades.

  @article{werner2021superresolving, abstract = {Fluorescence imaging techniques play a pivotal role in our understanding of the nervous system. The emergence of various super-resolution microscopy methods and specialized fluorescent probes enables direct insight into neuronal structure and protein arrangements in cellular subcompartments with so far unmatched resolution. Super-resolving visualization techniques in neurons unveil a novel understanding of cytoskeletal composition, distribution, motility, and signaling of membrane proteins, subsynaptic structure and function, and neuron–glia interaction. Well-defined molecular targets in autoimmune and neurodegenerative disease models provide excellent starting points for in-depth investigation of disease pathophysiology using novel and innovative imaging methodology. Application of super-resolution microscopy in human brain samples and for testing clinical biomarkers is still in its infancy but opens new opportunities for translational research in neurology and neuroscience. In this review, we describe how super-resolving microscopy has improved our understanding of neuronal and brain function and dysfunction in the last two decades.}, author = {Werner, Christian and Sauer, Markus and Geis, Christian}, booktitle = {Chemical Reviews}, journal = {Chem. Rev.}, keywords = {werner}, month = 10, number = 19, pages = {11971–12015}, publisher = {American Chemical Society}, title = {Super-resolving Microscopy in Neuroscience}, volume = 121, year = 2021 }

  %0 Journal Article %1 werner2021superresolving %A Werner, Christian %A Sauer, Markus %A Geis, Christian %B Chemical Reviews %D 2021 %I American Chemical Society %J Chem. Rev. %N 19 %P 11971--12015 %R 10.1021/acs.chemrev.0c01174 %T Super-resolving Microscopy in Neuroscience %U https://doi.org/10.1021/acs.chemrev.0c01174 %V 121 %X Fluorescence imaging techniques play a pivotal role in our understanding of the nervous system. The emergence of various super-resolution microscopy methods and specialized fluorescent probes enables direct insight into neuronal structure and protein arrangements in cellular subcompartments with so far unmatched resolution. Super-resolving visualization techniques in neurons unveil a novel understanding of cytoskeletal composition, distribution, motility, and signaling of membrane proteins, subsynaptic structure and function, and neuron–glia interaction. Well-defined molecular targets in autoimmune and neurodegenerative disease models provide excellent starting points for in-depth investigation of disease pathophysiology using novel and innovative imaging methodology. Application of super-resolution microscopy in human brain samples and for testing clinical biomarkers is still in its infancy but opens new opportunities for translational research in neurology and neuroscience. In this review, we describe how super-resolving microscopy has improved our understanding of neuronal and brain function and dysfunction in the last two decades.

• Super-resolution imaging reveals the nanoscale organization of metabotropic glutamate receptors at presynaptic active zones. Siddig, Sana; Aufmkolk, Sarah; Doose, Sören; Jobin, Marie-Lise; Werner, Christian; Sauer, Markus; Calebiro, Davide. In Sci Adv, 6(16), S. eaay7193-. 2020.
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  G protein–coupled receptors (GPCRs) play a fundamental role in the modulation of synaptic transmission. A pivotal example is provided by the metabotropic glutamate receptor type 4 (mGluR4), which inhibits glutamate release at presynaptic active zones (AZs). However, how GPCRs are organized within AZs to regulate neurotransmission remains largely unknown. Here, we applied two-color super-resolution imaging by direct stochastic optical reconstruction microscopy (dSTORM) to investigate the nanoscale organization of mGluR4 at parallel fiber AZs in the mouse cerebellum. We find an inhomogeneous distribution, with multiple nanodomains inside AZs, each containing, on average, one to two mGluR4 subunits. Within these nanodomains, mGluR4s are often localized in close proximity to voltage-dependent CaV2.1 channels and Munc-18-1, which are both essential for neurotransmitter release. These findings provide previously unknown insights into the molecular organization of GPCRs at AZs, suggesting a likely implication of a close association between mGluR4 and the secretory machinery in modulating synaptic transmission.

  @article{siddig2020superresolution, abstract = {G protein–coupled receptors (GPCRs) play a fundamental role in the modulation of synaptic transmission. A pivotal example is provided by the metabotropic glutamate receptor type 4 (mGluR4), which inhibits glutamate release at presynaptic active zones (AZs). However, how GPCRs are organized within AZs to regulate neurotransmission remains largely unknown. Here, we applied two-color super-resolution imaging by direct stochastic optical reconstruction microscopy (dSTORM) to investigate the nanoscale organization of mGluR4 at parallel fiber AZs in the mouse cerebellum. We find an inhomogeneous distribution, with multiple nanodomains inside AZs, each containing, on average, one to two mGluR4 subunits. Within these nanodomains, mGluR4s are often localized in close proximity to voltage-dependent CaV2.1 channels and Munc-18-1, which are both essential for neurotransmitter release. These findings provide previously unknown insights into the molecular organization of GPCRs at AZs, suggesting a likely implication of a close association between mGluR4 and the secretory machinery in modulating synaptic transmission.}, author = {Siddig, Sana and Aufmkolk, Sarah and Doose, Sören and Jobin, Marie-Lise and Werner, Christian and Sauer, Markus and Calebiro, Davide}, journal = {Sci Adv}, keywords = {home}, month = {04}, number = 16, pages = {eaay7193–}, title = {Super-resolution imaging reveals the nanoscale organization of metabotropic glutamate receptors at presynaptic active zones}, volume = 6, year = 2020 }

  %0 Journal Article %1 siddig2020superresolution %A Siddig, Sana %A Aufmkolk, Sarah %A Doose, Sören %A Jobin, Marie-Lise %A Werner, Christian %A Sauer, Markus %A Calebiro, Davide %D 2020 %J Sci Adv %N 16 %P eaay7193-- %R 10.1126/sciadv.aay7193 %T Super-resolution imaging reveals the nanoscale organization of metabotropic glutamate receptors at presynaptic active zones %U http://advances.sciencemag.org/content/6/16/eaay7193.abstract %V 6 %X G protein–coupled receptors (GPCRs) play a fundamental role in the modulation of synaptic transmission. A pivotal example is provided by the metabotropic glutamate receptor type 4 (mGluR4), which inhibits glutamate release at presynaptic active zones (AZs). However, how GPCRs are organized within AZs to regulate neurotransmission remains largely unknown. Here, we applied two-color super-resolution imaging by direct stochastic optical reconstruction microscopy (dSTORM) to investigate the nanoscale organization of mGluR4 at parallel fiber AZs in the mouse cerebellum. We find an inhomogeneous distribution, with multiple nanodomains inside AZs, each containing, on average, one to two mGluR4 subunits. Within these nanodomains, mGluR4s are often localized in close proximity to voltage-dependent CaV2.1 channels and Munc-18-1, which are both essential for neurotransmitter release. These findings provide previously unknown insights into the molecular organization of GPCRs at AZs, suggesting a likely implication of a close association between mGluR4 and the secretory machinery in modulating synaptic transmission.

• Anti-CNTN1 IgG3 induces acute conduction block and motor deficits in a passive transfer rat model. Doppler, Kathrin; Schuster, Yasmin; Appeltshauser, Luise; Biko, Lydia; Villmann, Carmen; Weishaupt, Andreas; Werner, Christian; Sommer, Claudia. In Journal of Neuroinflammation, 16(1), S. 73-. 2019.
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  Autoantibodies against the paranodal protein contactin-1 have recently been described in patients with severe acute-onset autoimmune neuropathies and mainly belong to the IgG4 subclass that does not activate complement. IgG3 anti-contactin-1 autoantibodies are rare, but have been detected during the acute onset of disease in some cases. There is evidence that anti-contactin-1 prevents adhesive interaction, and chronic exposure to anti-contactin-1 IgG4 leads to structural changes at the nodes accompanied by neuropathic symptoms. However, the pathomechanism of acute onset of disease and the pathogenic role of IgG3 anti-contactin-1 is largely unknown.

  @article{doppler2019anticntn1, abstract = {Autoantibodies against the paranodal protein contactin-1 have recently been described in patients with severe acute-onset autoimmune neuropathies and mainly belong to the IgG4 subclass that does not activate complement. IgG3 anti-contactin-1 autoantibodies are rare, but have been detected during the acute onset of disease in some cases. There is evidence that anti-contactin-1 prevents adhesive interaction, and chronic exposure to anti-contactin-1 IgG4 leads to structural changes at the nodes accompanied by neuropathic symptoms. However, the pathomechanism of acute onset of disease and the pathogenic role of IgG3 anti-contactin-1 is largely unknown.}, author = {Doppler, Kathrin and Schuster, Yasmin and Appeltshauser, Luise and Biko, Lydia and Villmann, Carmen and Weishaupt, Andreas and Werner, Christian and Sommer, Claudia}, journal = {Journal of Neuroinflammation}, keywords = {werner}, number = 1, pages = {73–}, title = {Anti-CNTN1 IgG3 induces acute conduction block and motor deficits in a passive transfer rat model}, volume = 16, year = 2019 }

  %0 Journal Article %1 doppler2019anticntn1 %A Doppler, Kathrin %A Schuster, Yasmin %A Appeltshauser, Luise %A Biko, Lydia %A Villmann, Carmen %A Weishaupt, Andreas %A Werner, Christian %A Sommer, Claudia %D 2019 %J Journal of Neuroinflammation %N 1 %P 73-- %R 10.1186/s12974-019-1462-z %T Anti-CNTN1 IgG3 induces acute conduction block and motor deficits in a passive transfer rat model %U https://doi.org/10.1186/s12974-019-1462-z %V 16 %X Autoantibodies against the paranodal protein contactin-1 have recently been described in patients with severe acute-onset autoimmune neuropathies and mainly belong to the IgG4 subclass that does not activate complement. IgG3 anti-contactin-1 autoantibodies are rare, but have been detected during the acute onset of disease in some cases. There is evidence that anti-contactin-1 prevents adhesive interaction, and chronic exposure to anti-contactin-1 IgG4 leads to structural changes at the nodes accompanied by neuropathic symptoms. However, the pathomechanism of acute onset of disease and the pathogenic role of IgG3 anti-contactin-1 is largely unknown.

• Bioorthogonal Click Chemistry Enables Site-specific Fluorescence Labeling of Functional NMDA Receptors for Super-Resolution Imaging. Neubert, Franziska; Beliu, Gerti; Terpitz, Ulrich; Werner, Christian; Geis, Christian; Sauer, Markus; Doose, Sören. In Angewandte Chemie International Edition, 57(50), S. 16364–16369. John Wiley & Sons, Ltd, 2018.
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  Abstract Super-resolution microscopy requires small fluorescent labels. We report the application of genetic code expansion in combination with bioorthogonal click chemistry to label the NR1 domain of the NMDA receptor. We generated NR1 mutants incorporating an unnatural amino acid at various positions in order to attach small organic fluorophores such as Cy5-tetrazine site-specifically to the extracellular domain of the receptor. Mutants were optimized with regard to protein expression, labeling efficiency and receptor functionality as tested by fluorescence microscopy and whole-cell patch clamp. The results show that bioorthogonal click chemistry in combination with small organic dyes is superior to available immunocytochemistry protocols for receptor labeling in live and fixed cells and enables single-molecule sensitive super-resolution microscopy experiments.

  @article{neubert2018bioorthogonal, abstract = {Abstract Super-resolution microscopy requires small fluorescent labels. We report the application of genetic code expansion in combination with bioorthogonal click chemistry to label the NR1 domain of the NMDA receptor. We generated NR1 mutants incorporating an unnatural amino acid at various positions in order to attach small organic fluorophores such as Cy5-tetrazine site-specifically to the extracellular domain of the receptor. Mutants were optimized with regard to protein expression, labeling efficiency and receptor functionality as tested by fluorescence microscopy and whole-cell patch clamp. The results show that bioorthogonal click chemistry in combination with small organic dyes is superior to available immunocytochemistry protocols for receptor labeling in live and fixed cells and enables single-molecule sensitive super-resolution microscopy experiments.}, author = {Neubert, Franziska and Beliu, Gerti and Terpitz, Ulrich and Werner, Christian and Geis, Christian and Sauer, Markus and Doose, Sören}, booktitle = {Angewandte Chemie International Edition}, journal = {Angewandte Chemie International Edition}, keywords = {terpitz}, month = 10, number = 50, pages = {16364–16369}, publisher = {John Wiley & Sons, Ltd}, title = {Bioorthogonal Click Chemistry Enables Site-specific Fluorescence Labeling of Functional NMDA Receptors for Super-Resolution Imaging}, volume = 57, year = 2018 }

  %0 Journal Article %1 neubert2018bioorthogonal %A Neubert, Franziska %A Beliu, Gerti %A Terpitz, Ulrich %A Werner, Christian %A Geis, Christian %A Sauer, Markus %A Doose, Sören %B Angewandte Chemie International Edition %D 2018 %I John Wiley & Sons, Ltd %J Angewandte Chemie International Edition %N 50 %P 16364--16369 %R 10.1002/anie.201808951 %T Bioorthogonal Click Chemistry Enables Site-specific Fluorescence Labeling of Functional NMDA Receptors for Super-Resolution Imaging %U https://doi.org/10.1002/anie.201808951 %V 57 %X Abstract Super-resolution microscopy requires small fluorescent labels. We report the application of genetic code expansion in combination with bioorthogonal click chemistry to label the NR1 domain of the NMDA receptor. We generated NR1 mutants incorporating an unnatural amino acid at various positions in order to attach small organic fluorophores such as Cy5-tetrazine site-specifically to the extracellular domain of the receptor. Mutants were optimized with regard to protein expression, labeling efficiency and receptor functionality as tested by fluorescence microscopy and whole-cell patch clamp. The results show that bioorthogonal click chemistry in combination with small organic dyes is superior to available immunocytochemistry protocols for receptor labeling in live and fixed cells and enables single-molecule sensitive super-resolution microscopy experiments.
• Quantification of sweat gland innervation in patients with Fabry disease: A case-control study. Kokotis, Panagiotis; Üçeyler, Nurcan; Werner, Christian; Tsivgoulis, Georgios; Papanikola, Nektaria; Katsanos, Aristeidis H.; Karandreas, Nikos; Sommer, Claudia. In Journal of the Neurological Sciences, 390, S. 135–138. 2018.
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  Hypohidrosis and heat intolerance, frequently reported by men and women with Fabry disease (FD), is thought to be related not only to the deposition of globotriaosylceramide (Gb3) in eccrine sweat glands, but also to reduced sweat gland sympathetic innervation. Methods We performed a case-control study to compare the density of sweat gland innervation between patients with FD and healthy controls by examining lower leg skin punch biopsies. We used a standardized grid of circles superimposed upon the immunofluorescent specimen to create a simple pattern of circles over the sweat gland. Nerve fibers that crossed within the circles were manually counted (“crossed circles”). Nerve fibers that touched the edge of the circle but did not enter were spared (“uncrossed circles”). The percentage of crossed circles from all circles was determined. Results Biopsy specimens were available of 37 FD patients (median age 44 years, 19–67; n = 18 men) and 16 controls (median age 48 years, 24–83, n = 7 men). Totally there were 153 sweat glands from FD patients and 63 from controls, in which innervation was quantified. While mean sweat gland innervation per biopsy did not differ between the entire FD cohort and controls, data stratification for the reported sweating phenotype revealed a stepwise lower innervation in women with FD and hypohidrosis (n.s.) and anhidrosis (p < .05) compared to women reporting normal sweating. Conclusion Sweat gland innervation is reduced in women with FD and anhidrosis compared to female patients without sweating impairment. Loss of sweat gland innervation may play a role in FD associated anhidrosis, at least in women.

  @article{kokotis2018quantification, abstract = {Hypohidrosis and heat intolerance, frequently reported by men and women with Fabry disease (FD), is thought to be related not only to the deposition of globotriaosylceramide (Gb3) in eccrine sweat glands, but also to reduced sweat gland sympathetic innervation. Methods We performed a case-control study to compare the density of sweat gland innervation between patients with FD and healthy controls by examining lower leg skin punch biopsies. We used a standardized grid of circles superimposed upon the immunofluorescent specimen to create a simple pattern of circles over the sweat gland. Nerve fibers that crossed within the circles were manually counted (“crossed circles”). Nerve fibers that touched the edge of the circle but did not enter were spared (“uncrossed circles”). The percentage of crossed circles from all circles was determined. Results Biopsy specimens were available of 37 FD patients (median age 44 years, 19–67; n = 18 men) and 16 controls (median age 48 years, 24–83, n = 7 men). Totally there were 153 sweat glands from FD patients and 63 from controls, in which innervation was quantified. While mean sweat gland innervation per biopsy did not differ between the entire FD cohort and controls, data stratification for the reported sweating phenotype revealed a stepwise lower innervation in women with FD and hypohidrosis (n.s.) and anhidrosis (p < .05) compared to women reporting normal sweating. Conclusion Sweat gland innervation is reduced in women with FD and anhidrosis compared to female patients without sweating impairment. Loss of sweat gland innervation may play a role in FD associated anhidrosis, at least in women.}, author = {Kokotis, Panagiotis and Üçeyler, Nurcan and Werner, Christian and Tsivgoulis, Georgios and Papanikola, Nektaria and Katsanos, Aristeidis H. and Karandreas, Nikos and Sommer, Claudia}, journal = {Journal of the Neurological Sciences}, keywords = {werner}, pages = {135–138}, title = {Quantification of sweat gland innervation in patients with Fabry disease: A case-control study}, volume = 390, year = 2018 }

  %0 Journal Article %1 kokotis2018quantification %A Kokotis, Panagiotis %A Üçeyler, Nurcan %A Werner, Christian %A Tsivgoulis, Georgios %A Papanikola, Nektaria %A Katsanos, Aristeidis H. %A Karandreas, Nikos %A Sommer, Claudia %D 2018 %J Journal of the Neurological Sciences %P 135--138 %R https://doi.org/10.1016/j.jns.2018.04.035 %T Quantification of sweat gland innervation in patients with Fabry disease: A case-control study %U https://www.sciencedirect.com/science/article/pii/S0022510X18302041 %V 390 %X Hypohidrosis and heat intolerance, frequently reported by men and women with Fabry disease (FD), is thought to be related not only to the deposition of globotriaosylceramide (Gb3) in eccrine sweat glands, but also to reduced sweat gland sympathetic innervation. Methods We performed a case-control study to compare the density of sweat gland innervation between patients with FD and healthy controls by examining lower leg skin punch biopsies. We used a standardized grid of circles superimposed upon the immunofluorescent specimen to create a simple pattern of circles over the sweat gland. Nerve fibers that crossed within the circles were manually counted (“crossed circles”). Nerve fibers that touched the edge of the circle but did not enter were spared (“uncrossed circles”). The percentage of crossed circles from all circles was determined. Results Biopsy specimens were available of 37 FD patients (median age 44 years, 19–67; n = 18 men) and 16 controls (median age 48 years, 24–83, n = 7 men). Totally there were 153 sweat glands from FD patients and 63 from controls, in which innervation was quantified. While mean sweat gland innervation per biopsy did not differ between the entire FD cohort and controls, data stratification for the reported sweating phenotype revealed a stepwise lower innervation in women with FD and hypohidrosis (n.s.) and anhidrosis (p < .05) compared to women reporting normal sweating. Conclusion Sweat gland innervation is reduced in women with FD and anhidrosis compared to female patients without sweating impairment. Loss of sweat gland innervation may play a role in FD associated anhidrosis, at least in women.
• Human Autoantibodies against the AMPA Receptor Subunit GluA2 Induce Receptor Reorganization and Memory Dysfunction. Haselmann, Holger; Mannara, Francesco; Werner, Christian; Planagumà, Jesús; Miguez-Cabello, Federico; Schmidl, Lars; Grünewald, Benedikt; Petit-Pedrol, Mar; Kirmse, Knut; Classen, Joseph; Demir, Fatih; Klöcker, Nikolaj; Soto, David; Doose, Sören; Dalmau, Josep; Hallermann, Stefan; Geis, Christian. In Neuron, 100(1), S. 91–105.e9. 2018.
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  AMPA receptors are essential for fast excitatory transmission in the CNS. Autoantibodies to AMPA receptors have been identified in humans with autoimmune encephalitis and severe defects of hippocampal function. Here, combining electrophysiology and high-resolution imaging with neuronal culture preparations and passive-transfer models in wild-type and GluA1-knockout mice, we analyze how specific human autoantibodies against the AMPA receptor subunit GluA2 affect receptor function and composition, synaptic transmission, and plasticity. Anti-GluA2 antibodies induce receptor internalization and a reduction of synaptic GluA2-containing AMPARs followed by compensatory ryanodine receptor-dependent incorporation of synaptic non-GluA2 AMPARs. Furthermore, application of human pathogenic anti-GluA2 antibodies to mice impairs long-term synaptic plasticity in vitro and affects learning and memory in vivo. Our results identify a specific immune-neuronal rearrangement of AMPA receptor subunits, providing a framework to explain disease symptoms.

  @article{haselmann2018human, abstract = {AMPA receptors are essential for fast excitatory transmission in the CNS. Autoantibodies to AMPA receptors have been identified in humans with autoimmune encephalitis and severe defects of hippocampal function. Here, combining electrophysiology and high-resolution imaging with neuronal culture preparations and passive-transfer models in wild-type and GluA1-knockout mice, we analyze how specific human autoantibodies against the AMPA receptor subunit GluA2 affect receptor function and composition, synaptic transmission, and plasticity. Anti-GluA2 antibodies induce receptor internalization and a reduction of synaptic GluA2-containing AMPARs followed by compensatory ryanodine receptor-dependent incorporation of synaptic non-GluA2 AMPARs. Furthermore, application of human pathogenic anti-GluA2 antibodies to mice impairs long-term synaptic plasticity in vitro and affects learning and memory in vivo. Our results identify a specific immune-neuronal rearrangement of AMPA receptor subunits, providing a framework to explain disease symptoms.}, author = {Haselmann, Holger and Mannara, Francesco and Werner, Christian and Planagumà, Jesús and Miguez-Cabello, Federico and Schmidl, Lars and Grünewald, Benedikt and Petit-Pedrol, Mar and Kirmse, Knut and Classen, Joseph and Demir, Fatih and Klöcker, Nikolaj and Soto, David and Doose, Sören and Dalmau, Josep and Hallermann, Stefan and Geis, Christian}, journal = {Neuron}, keywords = {werner}, number = 1, pages = {91–105.e9}, title = {Human Autoantibodies against the AMPA Receptor Subunit GluA2 Induce Receptor Reorganization and Memory Dysfunction}, volume = 100, year = 2018 }

  %0 Journal Article %1 haselmann2018human %A Haselmann, Holger %A Mannara, Francesco %A Werner, Christian %A Planagumà, Jesús %A Miguez-Cabello, Federico %A Schmidl, Lars %A Grünewald, Benedikt %A Petit-Pedrol, Mar %A Kirmse, Knut %A Classen, Joseph %A Demir, Fatih %A Klöcker, Nikolaj %A Soto, David %A Doose, Sören %A Dalmau, Josep %A Hallermann, Stefan %A Geis, Christian %D 2018 %J Neuron %N 1 %P 91--105.e9 %R https://doi.org/10.1016/j.neuron.2018.07.048 %T Human Autoantibodies against the AMPA Receptor Subunit GluA2 Induce Receptor Reorganization and Memory Dysfunction %U http://www.sciencedirect.com/science/article/pii/S0896627318306469 %V 100 %X AMPA receptors are essential for fast excitatory transmission in the CNS. Autoantibodies to AMPA receptors have been identified in humans with autoimmune encephalitis and severe defects of hippocampal function. Here, combining electrophysiology and high-resolution imaging with neuronal culture preparations and passive-transfer models in wild-type and GluA1-knockout mice, we analyze how specific human autoantibodies against the AMPA receptor subunit GluA2 affect receptor function and composition, synaptic transmission, and plasticity. Anti-GluA2 antibodies induce receptor internalization and a reduction of synaptic GluA2-containing AMPARs followed by compensatory ryanodine receptor-dependent incorporation of synaptic non-GluA2 AMPARs. Furthermore, application of human pathogenic anti-GluA2 antibodies to mice impairs long-term synaptic plasticity in vitro and affects learning and memory in vivo. Our results identify a specific immune-neuronal rearrangement of AMPA receptor subunits, providing a framework to explain disease symptoms.

• Defective synaptic transmission causes disease signs in a mouse model of juvenile neuronal ceroid lipofuscinosis. Grünewald, Benedikt; Lange, Maren D; Werner, Christian; O’Leary, Aet; Weishaupt, Andreas; Popp, Sandy; Pearce, David A; Wiendl, Heinz; Reif, Andreas; Pape, Hans C; Toyka, Klaus V; Sommer, Claudia; Geis, Christian. In eLife, 6, C. Rosenmund (Hrsg.), S. e28685-. eLife Sciences Publications, Ltd, 2017.
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  Juvenile neuronal ceroid lipofuscinosis (JNCL or Batten disease) caused by mutations in the CLN3 gene is the most prevalent inherited neurodegenerative disease in childhood resulting in widespread central nervous system dysfunction and premature death. The consequences of CLN3 mutation on the progression of the disease, on neuronal transmission, and on central nervous network dysfunction are poorly understood. We used Cln3 knockout (Cln3Δex1-6) mice and found increased anxiety-related behavior and impaired aversive learning as well as markedly affected motor function including disordered coordination. Patch-clamp and loose-patch recordings revealed severely affected inhibitory and excitatory synaptic transmission in the amygdala, hippocampus, and cerebellar networks. Changes in presynaptic release properties may result from dysfunction of CLN3 protein. Furthermore, loss of calbindin, neuropeptide Y, parvalbumin, and GAD65-positive interneurons in central networks collectively support the hypothesis that degeneration of GABAergic interneurons may be the cause of supraspinal GABAergic disinhibition.

  @article{grunewald2017defective, abstract = {Juvenile neuronal ceroid lipofuscinosis (JNCL or Batten disease) caused by mutations in the CLN3 gene is the most prevalent inherited neurodegenerative disease in childhood resulting in widespread central nervous system dysfunction and premature death. The consequences of CLN3 mutation on the progression of the disease, on neuronal transmission, and on central nervous network dysfunction are poorly understood. We used Cln3 knockout (Cln3Δex1-6) mice and found increased anxiety-related behavior and impaired aversive learning as well as markedly affected motor function including disordered coordination. Patch-clamp and loose-patch recordings revealed severely affected inhibitory and excitatory synaptic transmission in the amygdala, hippocampus, and cerebellar networks. Changes in presynaptic release properties may result from dysfunction of CLN3 protein. Furthermore, loss of calbindin, neuropeptide Y, parvalbumin, and GAD65-positive interneurons in central networks collectively support the hypothesis that degeneration of GABAergic interneurons may be the cause of supraspinal GABAergic disinhibition.}, author = {Grünewald, Benedikt and Lange, Maren D and Werner, Christian and O'Leary, Aet and Weishaupt, Andreas and Popp, Sandy and Pearce, David A and Wiendl, Heinz and Reif, Andreas and Pape, Hans C and Toyka, Klaus V and Sommer, Claudia and Geis, Christian}, editor = {Rosenmund, Christian}, journal = {eLife}, keywords = {werner}, pages = {e28685–}, publisher = {eLife Sciences Publications, Ltd}, title = {Defective synaptic transmission causes disease signs in a mouse model of juvenile neuronal ceroid lipofuscinosis}, volume = 6, year = 2017 }

  %0 Journal Article %1 grunewald2017defective %A Grünewald, Benedikt %A Lange, Maren D %A Werner, Christian %A O'Leary, Aet %A Weishaupt, Andreas %A Popp, Sandy %A Pearce, David A %A Wiendl, Heinz %A Reif, Andreas %A Pape, Hans C %A Toyka, Klaus V %A Sommer, Claudia %A Geis, Christian %D 2017 %E Rosenmund, Christian %I eLife Sciences Publications, Ltd %J eLife %P e28685-- %R 10.7554/eLife.28685 %T Defective synaptic transmission causes disease signs in a mouse model of juvenile neuronal ceroid lipofuscinosis %U https://doi.org/10.7554/eLife.28685 %V 6 %X Juvenile neuronal ceroid lipofuscinosis (JNCL or Batten disease) caused by mutations in the CLN3 gene is the most prevalent inherited neurodegenerative disease in childhood resulting in widespread central nervous system dysfunction and premature death. The consequences of CLN3 mutation on the progression of the disease, on neuronal transmission, and on central nervous network dysfunction are poorly understood. We used Cln3 knockout (Cln3Δex1-6) mice and found increased anxiety-related behavior and impaired aversive learning as well as markedly affected motor function including disordered coordination. Patch-clamp and loose-patch recordings revealed severely affected inhibitory and excitatory synaptic transmission in the amygdala, hippocampus, and cerebellar networks. Changes in presynaptic release properties may result from dysfunction of CLN3 protein. Furthermore, loss of calbindin, neuropeptide Y, parvalbumin, and GAD65-positive interneurons in central networks collectively support the hypothesis that degeneration of GABAergic interneurons may be the cause of supraspinal GABAergic disinhibition.

• Human autoantibodies to amphiphysin induce defective presynaptic vesicle dynamics and composition. Werner, Christian; Pauli, Martin; Doose, Sören; Weishaupt, Andreas; Haselmann, Holger; Grünewald, Benedikt; Sauer, Markus; Heckmann, Manfred; Toyka, Klaus V.; Asan, Esther; Sommer, Claudia; Geis, Christian. In Brain, 139(2), S. 365–379. 2016.
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  See Irani (doi:10.1093/awv364) for a scientific commentary on this article. Stiff-person syndrome is the prototype of a central nervous system disorder with autoantibodies targeting presynaptic antigens. Patients with paraneoplastic stiff-person syndrome may harbour autoantibodies to the BAR (Bin/Amphiphysin/Rvs) domain protein amphiphysin, which target its SH3 domain. These patients have neurophysiological signs of compromised central inhibition and respond to symptomatic treatment with medication enhancing GABAergic transmission. High frequency neurotransmission as observed in tonic GABAergic interneurons relies on fast exocytosis of neurotransmitters based on compensatory endocytosis. As amphiphysin is involved in clathrin-mediated endocytosis, patient autoantibodies are supposed to interfere with this function, leading to disinhibition by reduction of GABAergic neurotransmission. We here investigated the effects of human anti-amphiphysin autoantibodies on structural components of presynaptic boutons ex vivo and in vitro using electron microscopy and super-resolution direct stochastic optical reconstruction microscopy. Ultrastructural analysis of spinal cord presynaptic boutons was performed after in vivo intrathecal passive transfer of affinity-purified human anti-amphiphysin autoantibodies in rats and revealed signs of markedly disabled clathrin-mediated endocytosis. This was unmasked at high synaptic activity and characterized by a reduction of the presynaptic vesicle pool, clathrin coated intermediates, and endosome-like structures. Super-resolution microscopy of inhibitory GABAergic presynaptic boutons in primary neurons revealed that specific human anti-amphiphysin immunoglobulin G induced an increase of the essential vesicular protein synaptobrevin 2 and a reduction of synaptobrevin 7. This constellation suggests depletion of resting pool vesicles and trapping of releasable pool vesicular proteins at the plasma membrane. Similar effects were found in amphiphysin-deficient neurons from knockout mice. Application of specific patient antibodies did not show additional effects. Blocking alternative pathways of clathrin-independent endocytosis with brefeldin A reversed the autoantibody induced effects on molecular vesicle composition. Endophilin as an interaction partner of amphiphysin showed reduced clustering within presynaptic terminals. Collectively, these results point towards an autoantibody-induced structural disorganization in GABAergic synapses with profound changes in presynaptic vesicle pools, activation of alternative endocytic pathways, and potentially compensatory rearrangement of proteins involved in clathrin-mediated endocytosis. Our findings provide novel insights into synaptic pathomechanisms in a prototypic antibody-mediated central nervous system disease, which may serve as a proof-of-principle example in this evolving group of autoimmune disorders associated with autoantibodies to synaptic antigens.

  @article{werner2016human, abstract = {See Irani (doi:10.1093/awv364) for a scientific commentary on this article. Stiff-person syndrome is the prototype of a central nervous system disorder with autoantibodies targeting presynaptic antigens. Patients with paraneoplastic stiff-person syndrome may harbour autoantibodies to the BAR (Bin/Amphiphysin/Rvs) domain protein amphiphysin, which target its SH3 domain. These patients have neurophysiological signs of compromised central inhibition and respond to symptomatic treatment with medication enhancing GABAergic transmission. High frequency neurotransmission as observed in tonic GABAergic interneurons relies on fast exocytosis of neurotransmitters based on compensatory endocytosis. As amphiphysin is involved in clathrin-mediated endocytosis, patient autoantibodies are supposed to interfere with this function, leading to disinhibition by reduction of GABAergic neurotransmission. We here investigated the effects of human anti-amphiphysin autoantibodies on structural components of presynaptic boutons ex vivo and in vitro using electron microscopy and super-resolution direct stochastic optical reconstruction microscopy. Ultrastructural analysis of spinal cord presynaptic boutons was performed after in vivo intrathecal passive transfer of affinity-purified human anti-amphiphysin autoantibodies in rats and revealed signs of markedly disabled clathrin-mediated endocytosis. This was unmasked at high synaptic activity and characterized by a reduction of the presynaptic vesicle pool, clathrin coated intermediates, and endosome-like structures. Super-resolution microscopy of inhibitory GABAergic presynaptic boutons in primary neurons revealed that specific human anti-amphiphysin immunoglobulin G induced an increase of the essential vesicular protein synaptobrevin 2 and a reduction of synaptobrevin 7. This constellation suggests depletion of resting pool vesicles and trapping of releasable pool vesicular proteins at the plasma membrane. Similar effects were found in amphiphysin-deficient neurons from knockout mice. Application of specific patient antibodies did not show additional effects. Blocking alternative pathways of clathrin-independent endocytosis with brefeldin A reversed the autoantibody induced effects on molecular vesicle composition. Endophilin as an interaction partner of amphiphysin showed reduced clustering within presynaptic terminals. Collectively, these results point towards an autoantibody-induced structural disorganization in GABAergic synapses with profound changes in presynaptic vesicle pools, activation of alternative endocytic pathways, and potentially compensatory rearrangement of proteins involved in clathrin-mediated endocytosis. Our findings provide novel insights into synaptic pathomechanisms in a prototypic antibody-mediated central nervous system disease, which may serve as a proof-of-principle example in this evolving group of autoimmune disorders associated with autoantibodies to synaptic antigens.}, author = {Werner, Christian and Pauli, Martin and Doose, Sören and Weishaupt, Andreas and Haselmann, Holger and Grünewald, Benedikt and Sauer, Markus and Heckmann, Manfred and Toyka, Klaus V. and Asan, Esther and Sommer, Claudia and Geis, Christian}, journal = {Brain}, keywords = {werner}, month = {02}, number = 2, pages = {365–379}, title = {Human autoantibodies to amphiphysin induce defective presynaptic vesicle dynamics and composition}, volume = 139, year = 2016 }

  %0 Journal Article %1 werner2016human %A Werner, Christian %A Pauli, Martin %A Doose, Sören %A Weishaupt, Andreas %A Haselmann, Holger %A Grünewald, Benedikt %A Sauer, Markus %A Heckmann, Manfred %A Toyka, Klaus V. %A Asan, Esther %A Sommer, Claudia %A Geis, Christian %D 2016 %J Brain %N 2 %P 365--379 %T Human autoantibodies to amphiphysin induce defective presynaptic vesicle dynamics and composition %U http://dx.doi.org/10.1093/brain/awv324 %V 139 %X See Irani (doi:10.1093/awv364) for a scientific commentary on this article. Stiff-person syndrome is the prototype of a central nervous system disorder with autoantibodies targeting presynaptic antigens. Patients with paraneoplastic stiff-person syndrome may harbour autoantibodies to the BAR (Bin/Amphiphysin/Rvs) domain protein amphiphysin, which target its SH3 domain. These patients have neurophysiological signs of compromised central inhibition and respond to symptomatic treatment with medication enhancing GABAergic transmission. High frequency neurotransmission as observed in tonic GABAergic interneurons relies on fast exocytosis of neurotransmitters based on compensatory endocytosis. As amphiphysin is involved in clathrin-mediated endocytosis, patient autoantibodies are supposed to interfere with this function, leading to disinhibition by reduction of GABAergic neurotransmission. We here investigated the effects of human anti-amphiphysin autoantibodies on structural components of presynaptic boutons ex vivo and in vitro using electron microscopy and super-resolution direct stochastic optical reconstruction microscopy. Ultrastructural analysis of spinal cord presynaptic boutons was performed after in vivo intrathecal passive transfer of affinity-purified human anti-amphiphysin autoantibodies in rats and revealed signs of markedly disabled clathrin-mediated endocytosis. This was unmasked at high synaptic activity and characterized by a reduction of the presynaptic vesicle pool, clathrin coated intermediates, and endosome-like structures. Super-resolution microscopy of inhibitory GABAergic presynaptic boutons in primary neurons revealed that specific human anti-amphiphysin immunoglobulin G induced an increase of the essential vesicular protein synaptobrevin 2 and a reduction of synaptobrevin 7. This constellation suggests depletion of resting pool vesicles and trapping of releasable pool vesicular proteins at the plasma membrane. Similar effects were found in amphiphysin-deficient neurons from knockout mice. Application of specific patient antibodies did not show additional effects. Blocking alternative pathways of clathrin-independent endocytosis with brefeldin A reversed the autoantibody induced effects on molecular vesicle composition. Endophilin as an interaction partner of amphiphysin showed reduced clustering within presynaptic terminals. Collectively, these results point towards an autoantibody-induced structural disorganization in GABAergic synapses with profound changes in presynaptic vesicle pools, activation of alternative endocytic pathways, and potentially compensatory rearrangement of proteins involved in clathrin-mediated endocytosis. Our findings provide novel insights into synaptic pathomechanisms in a prototypic antibody-mediated central nervous system disease, which may serve as a proof-of-principle example in this evolving group of autoimmune disorders associated with autoantibodies to synaptic antigens.

• Interactions of Human Autoantibodies with Hippocampal GABAergic Synaptic Transmission – Analyzing Antibody-Induced Effects ex vivo. Haselmann, Holger; Röpke, Luise; Werner, Christian; Kunze, Albrecht; Geis, Christian. In Frontiers in Neurology, 6. 2015.
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  Autoantibodies (aAB) to the presynaptic located enzyme glutamate decarboxylase 65 (GAD65) are a characteristic attribute for a variety of autoimmune diseases of the central nervous system including subtypes of limbic encephalitis, stiff person-syndrome, cerebellar ataxia, and Batten’s disease. Clinical signs of hyperexcitability and improvement of disease symptoms upon immunotherapy in some of these disorders suggest a possible pathogenic role of associated aAB. Recent experimental studies report inconsistent results regarding a direct pathogenic influence of anti-GAD65 aAB affecting inhibitory synaptic transmission in central GABAergic pathways. We here provide a method for direct evaluation of aAB-induced pathomechanisms in the intact hippocampal network. Purified patient IgG fractions containing aAB to GAD65 together with fixable lipophilic styryl dyes (FMdyes) are stereotactically injected into the hilus and the dentate gyrus in anesthetized mice. Twenty-four hours after intrahippocampal injection, acute hippocampal slices are prepared and transferred to a patch-clamp recording setup equipped with a fluorescence light source. Intraneural incorporated FMdyes show correct injection site for patch-clamp recording. Whole-cell patch-clamp recordings are performed from granule cells in the dentate gyrus and extracellular stimulation is applied in the border area of the dentate gyrus-hilus region to stimulate GABAergic afferents arising from parvalbumin positive basket cells. GABA-A receptor mediated inhibitory postsynaptic currents (IPSC) and miniature IPSC are recorded after blocking glutamatergic transmission. This approach allows investigation of potential aAB-induced effects on GABA-A receptor signaling ex vivo in an intact neuronal network. This offers several advantages compared to experimental procedures used in previous studies by in vitro AB preincubation of primary neurons or slice preparations. Furthermore, this method requires only small amounts of patient material that are often limited in rare diseases.

  @article{haselmann2015interactions, abstract = {Autoantibodies (aAB) to the presynaptic located enzyme glutamate decarboxylase 65 (GAD65) are a characteristic attribute for a variety of autoimmune diseases of the central nervous system including subtypes of limbic encephalitis, stiff person-syndrome, cerebellar ataxia, and Batten’s disease. Clinical signs of hyperexcitability and improvement of disease symptoms upon immunotherapy in some of these disorders suggest a possible pathogenic role of associated aAB. Recent experimental studies report inconsistent results regarding a direct pathogenic influence of anti-GAD65 aAB affecting inhibitory synaptic transmission in central GABAergic pathways. We here provide a method for direct evaluation of aAB-induced pathomechanisms in the intact hippocampal network. Purified patient IgG fractions containing aAB to GAD65 together with fixable lipophilic styryl dyes (FMdyes) are stereotactically injected into the hilus and the dentate gyrus in anesthetized mice. Twenty-four hours after intrahippocampal injection, acute hippocampal slices are prepared and transferred to a patch-clamp recording setup equipped with a fluorescence light source. Intraneural incorporated FMdyes show correct injection site for patch-clamp recording. Whole-cell patch-clamp recordings are performed from granule cells in the dentate gyrus and extracellular stimulation is applied in the border area of the dentate gyrus-hilus region to stimulate GABAergic afferents arising from parvalbumin positive basket cells. GABA-A receptor mediated inhibitory postsynaptic currents (IPSC) and miniature IPSC are recorded after blocking glutamatergic transmission. This approach allows investigation of potential aAB-induced effects on GABA-A receptor signaling ex vivo in an intact neuronal network. This offers several advantages compared to experimental procedures used in previous studies by in vitro AB preincubation of primary neurons or slice preparations. Furthermore, this method requires only small amounts of patient material that are often limited in rare diseases.}, author = {Haselmann, Holger and Röpke, Luise and Werner, Christian and Kunze, Albrecht and Geis, Christian}, journal = {Frontiers in Neurology}, keywords = {werner}, title = {Interactions of Human Autoantibodies with Hippocampal GABAergic Synaptic Transmission – Analyzing Antibody-Induced Effects ex vivo}, volume = 6, year = 2015 }

  %0 Journal Article %1 haselmann2015interactions %A Haselmann, Holger %A Röpke, Luise %A Werner, Christian %A Kunze, Albrecht %A Geis, Christian %D 2015 %J Frontiers in Neurology %T Interactions of Human Autoantibodies with Hippocampal GABAergic Synaptic Transmission – Analyzing Antibody-Induced Effects ex vivo %U https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2015.00136 %V 6 %X Autoantibodies (aAB) to the presynaptic located enzyme glutamate decarboxylase 65 (GAD65) are a characteristic attribute for a variety of autoimmune diseases of the central nervous system including subtypes of limbic encephalitis, stiff person-syndrome, cerebellar ataxia, and Batten’s disease. Clinical signs of hyperexcitability and improvement of disease symptoms upon immunotherapy in some of these disorders suggest a possible pathogenic role of associated aAB. Recent experimental studies report inconsistent results regarding a direct pathogenic influence of anti-GAD65 aAB affecting inhibitory synaptic transmission in central GABAergic pathways. We here provide a method for direct evaluation of aAB-induced pathomechanisms in the intact hippocampal network. Purified patient IgG fractions containing aAB to GAD65 together with fixable lipophilic styryl dyes (FMdyes) are stereotactically injected into the hilus and the dentate gyrus in anesthetized mice. Twenty-four hours after intrahippocampal injection, acute hippocampal slices are prepared and transferred to a patch-clamp recording setup equipped with a fluorescence light source. Intraneural incorporated FMdyes show correct injection site for patch-clamp recording. Whole-cell patch-clamp recordings are performed from granule cells in the dentate gyrus and extracellular stimulation is applied in the border area of the dentate gyrus-hilus region to stimulate GABAergic afferents arising from parvalbumin positive basket cells. GABA-A receptor mediated inhibitory postsynaptic currents (IPSC) and miniature IPSC are recorded after blocking glutamatergic transmission. This approach allows investigation of potential aAB-induced effects on GABA-A receptor signaling ex vivo in an intact neuronal network. This offers several advantages compared to experimental procedures used in previous studies by in vitro AB preincubation of primary neurons or slice preparations. Furthermore, this method requires only small amounts of patient material that are often limited in rare diseases.
• Stiff person-syndrome IgG affects presynaptic GABAergic release mechanisms. Werner, Christian; Haselmann, Holger; Weishaupt, Andreas; Toyka, Klaus V.; Sommer, Claudia; Geis, Christian. In Journal of Neural Transmission, 122(3), S. 357–362. 2015.
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  The majority of patients with stiff person-syndrome (SPS) are characterized by autoantibodies to glutamate decarboxylase 65 (GAD65). In previous passive-transfer studies, SPS immunoglobulin G (IgG) induced SPS core symptoms. We here provide evidence that SPS-IgG causes a higher frequency of spontaneous vesicle fusions. Sustained GABAergic transmission and presynaptic GABAergic vesicle pool size remained unchanged. Since these findings cannot be attributed to anti-GAD65 autoantibodies alone, we propose that additional autoantibodies with so far undefined antigen specificity might affect presynaptic release mechanisms.

  @article{werner2015stiff, abstract = {The majority of patients with stiff person-syndrome (SPS) are characterized by autoantibodies to glutamate decarboxylase 65 (GAD65). In previous passive-transfer studies, SPS immunoglobulin G (IgG) induced SPS core symptoms. We here provide evidence that SPS-IgG causes a higher frequency of spontaneous vesicle fusions. Sustained GABAergic transmission and presynaptic GABAergic vesicle pool size remained unchanged. Since these findings cannot be attributed to anti-GAD65 autoantibodies alone, we propose that additional autoantibodies with so far undefined antigen specificity might affect presynaptic release mechanisms.}, author = {Werner, Christian and Haselmann, Holger and Weishaupt, Andreas and Toyka, Klaus V. and Sommer, Claudia and Geis, Christian}, journal = {Journal of Neural Transmission}, keywords = {werner}, number = 3, pages = {357–362}, title = {Stiff person-syndrome IgG affects presynaptic GABAergic release mechanisms}, volume = 122, year = 2015 }

  %0 Journal Article %1 werner2015stiff %A Werner, Christian %A Haselmann, Holger %A Weishaupt, Andreas %A Toyka, Klaus V. %A Sommer, Claudia %A Geis, Christian %D 2015 %J Journal of Neural Transmission %N 3 %P 357--362 %R 10.1007/s00702-014-1268-1 %T Stiff person-syndrome IgG affects presynaptic GABAergic release mechanisms %U https://doi.org/10.1007/s00702-014-1268-1 %V 122 %X The majority of patients with stiff person-syndrome (SPS) are characterized by autoantibodies to glutamate decarboxylase 65 (GAD65). In previous passive-transfer studies, SPS immunoglobulin G (IgG) induced SPS core symptoms. We here provide evidence that SPS-IgG causes a higher frequency of spontaneous vesicle fusions. Sustained GABAergic transmission and presynaptic GABAergic vesicle pool size remained unchanged. Since these findings cannot be attributed to anti-GAD65 autoantibodies alone, we propose that additional autoantibodies with so far undefined antigen specificity might affect presynaptic release mechanisms.