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Thomas C Sudhof - One of the best experts on this subject based on the ideXlab platform.
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SPARCL1 Promotes Excitatory But Not Inhibitory Synapse Formation and Function Independent of Neurexins and Neuroligins.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2020Co-Authors: Kathlyn J. Gan, Thomas C SudhofAbstract:Emerging evidence supports roles for secreted extracellular matrix proteins in boosting synaptogenesis, synaptic transmission, and synaptic plasticity. SPARCL1 (a.k.a. Hevin), a secreted non-neuronal protein, was reported to increase synaptogenesis by simultaneously binding to presynaptic neurexin-1α and to postsynaptic Neuroligin-1B, thereby catalyzing formation of trans-synaptic neurexin/Neuroligin complexes. However, neurexins and Neuroligins do not themselves mediate synaptogenesis, raising the question of how SPARCL1 enhances synapse formation by binding to these molecules. Moreover, it remained unclear whether SPARCL1 acts on all synapses containing neurexins and Neuroligins or only on a subset of synapses, and whether it enhances synaptic transmission in addition to boosting synaptogenesis or induces silent synapses. To explore these questions, we examined the synaptic effects of SPARCL1 and their dependence on neurexins and Neuroligins. Using mixed neuronal and glial cultures from neonatal mouse cortex of both sexes, we show that SPARCL1 selectively increases excitatory but not inhibitory synapse numbers, enhances excitatory but not inhibitory synaptic transmission, and augments NMDA-receptor-mediated synaptic responses more than AMPAR-mediated synaptic responses. None of these effects were mediated by SPARCL1-binding to neurexins or Neuroligins. Neurons from triple neurexin-1/2/3 or from quadruple Neuroligin-1/2/3/4 conditional knockout mice that lacked all neurexins or all Neuroligins were fully responsive to SPARCL1. Taken together, our results reveal that SPARCL1 selectively boosts excitatory but not inhibitory synaptogenesis and synaptic transmission by a novel mechanism that is independent of neurexins and Neuroligins. SIGNIFICANCE STATEMENT: Emerging evidence supports roles for extracellular matrix proteins in boosting synapse formation and function. Previous studies demonstrated that SPARCL1, a secreted non-neuronal protein, promotes synapse formation in rodent and human neurons. However, it remained unclear whether SPARCL1 acts on all or on only a subset of synapses, induces functional or largely inactive synapses, and generates synapses by bridging presynaptic neurexins and postsynaptic Neuroligins. Here, we report that SPARCL1 selectively induces excitatory synapses, increases their efficacy, and enhances their NMDA receptor content. Moreover, using rigorous genetic manipulations, we show that SPARCL1 does not require neurexins and Neuroligins for its activity. Thus, SPARCL1 selectively boosts excitatory synaptogenesis and synaptic transmission by a novel mechanism that is independent of neurexins and Neuroligins.
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Neuroligin 1 signaling controls ltp and nmda receptors by distinct molecular pathways
Neuron, 2019Co-Authors: Xiaoting Wu, Ashley M Riley, William D Hale, Wade Morishita, Thomas C Sudhof, Robert C MalenkaAbstract:Summary Neuroligins, postsynaptic cell adhesion molecules that are linked to neuropsychiatric disorders, are extensively studied, but fundamental questions about their functions remain. Using in vivo replacement strategies in quadruple conditional knockout mice of all Neuroligins to avoid heterodimerization artifacts, we show, in hippocampal CA1 pyramidal neurons, that Neuroligin-1 performs two key functions in excitatory synapses by distinct molecular mechanisms. N-methyl-D-aspartate (NMDA) receptor-dependent LTP requires trans-synaptic binding of postsynaptic Neuroligin-1 to presynaptic β-neurexins but not the cytoplasmic sequences of Neuroligins. In contrast, postsynaptic NMDA receptor (NMDAR)-mediated responses involve a neurexin-independent mechanism that requires the Neuroligin-1 cytoplasmic sequences. Strikingly, deletion of Neuroligins blocked the spine expansion associated with LTP, as monitored by two-photon imaging; this block involved a mechanism identical to that of the role of Neuroligin-1 in NMDAR-dependent LTP. Our data suggest that Neuroligin-1 performs two mechanistically distinct signaling functions and that neurolign-1-mediated trans-synaptic cell adhesion signaling critically regulates LTP.
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Autism-associated Neuroligin-4 mutation selectively impairs glycinergic synaptic transmission in mouse brainstem synapses.
The Journal of experimental medicine, 2018Co-Authors: Bo Zhang, Nils Brose, W. Dylan Hale, Ozgun Gokce, Thomas C SudhofAbstract:In human patients, loss-of-function mutations of the postsynaptic cell-adhesion molecule Neuroligin-4 were repeatedly identified as monogenetic causes of autism. In mice, Neuroligin-4 deletions caused autism-related behavioral impairments and subtle changes in synaptic transmission, and Neuroligin-4 was found, at least in part, at glycinergic synapses. However, low expression levels precluded a comprehensive analysis of Neuroligin-4 localization, and overexpression of Neuroligin-4 puzzlingly impaired excitatory but not inhibitory synaptic function. As a result, the function of Neuroligin-4 remains unclear, as does its relation to other Neuroligins. To clarify these issues, we systematically examined the function of Neuroligin-4, focusing on excitatory and inhibitory inputs to defined projection neurons of the mouse brainstem as central model synapses. We show that loss of Neuroligin-4 causes a profound impairment of glycinergic but not glutamatergic synaptic transmission and a decrease in glycinergic synapse numbers. Thus, Neuroligin-4 is essential for the organization and/or maintenance of glycinergic synapses.
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developmental plasticity shapes synaptic phenotypes of autism associated Neuroligin 3 mutations in the calyx of held
Molecular Psychiatry, 2017Co-Authors: Bo Zhang, Ozgun Gokce, E Seigneur, P Wei, J Morgan, Thomas C SudhofAbstract:Neuroligins are postsynaptic cell-adhesion molecules that bind to presynaptic neurexins. Mutations in Neuroligin-3 predispose to autism, but how such mutations affect synaptic function remains incompletely understood. Here we systematically examined the effect of three autism-associated mutations, the Neuroligin-3 knockout, the R451C knockin, and the R704C knockin, on synaptic transmission in the calyx of Held, a central synapse ideally suited for high-resolution analyses of synaptic transmission. Surprisingly, germline knockout of Neuroligin-3 did not alter synaptic transmission, whereas the Neuroligin-3 R451C and R704C knockins decreased and increased, respectively, synaptic transmission. These puzzling results prompted us to ask whether Neuroligin-3 mutant phenotypes may be reshaped by developmental plasticity. Indeed, conditional knockout of Neuroligin-3 during late development produced a marked synaptic phenotype, whereas conditional knockout of Neuroligin-3 during early development caused no detectable effect, mimicking the germline knockout. In canvassing potentially redundant candidate genes, we identified developmentally early expression of another synaptic neurexin ligand, cerebellin-1. Strikingly, developmentally early conditional knockout of cerebellin-1 only modestly impaired synaptic transmission, whereas in contrast to the individual single knockouts, developmentally early conditional double knockout of both cerebellin-1 and Neuroligin-3 severely decreased synaptic transmission. Our data suggest an unanticipated mechanism of developmental compensation whereby cerebellin-1 and Neuroligin-3 functionally occlude each other during development of calyx synapses. Thus, although acute manipulations more likely reveal basic gene functions, developmental plasticity can be a major factor in shaping the overall phenotypes of genetic neuropsychiatric disorders.
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Unique versus Redundant Functions of Neuroligin Genes in Shaping Excitatory and Inhibitory Synapse Properties
The Journal of Neuroscience, 2017Co-Authors: Soham Chanda, W. Dylan Hale, Bo Zhang, Marius Wernig, Thomas C SudhofAbstract:Neuroligins are evolutionarily conserved postsynaptic cell adhesion molecules that interact with presynaptic neurexins. Neurons express multiple Neuroligin isoforms that are targeted to specific synapses, but their synaptic functions and mechanistic redundancy are not completely understood. Overexpression or RNAi-mediated knockdown of Neuroligins, respectively, causes a dramatic increase or decrease in synapse density, whereas genetic deletions of Neuroligins impair synapse function with only minor effects on synapse numbers, raising fundamental questions about the overall physiological role of Neuroligins. Here, we have systematically analyzed the effects of conditional genetic deletions of all major Neuroligin isoforms (i.e., NL1, NL2, and NL3), either individually or in combinations, in cultured mouse hippocampal and cortical neurons. We found that conditional genetic deletions of Neuroligins caused no change or only a small change in synapses numbers, but strongly impaired synapse function. This impairment was isoform specific, suggesting that Neuroligins are not functionally redundant. Sparse Neuroligin deletions produced phenotypes comparable to those of global deletions, indicating that Neuroligins function in a cell-autonomous manner. Mechanistically, Neuroligin deletions decreased the synaptic levels of neurotransmitter receptors and had no effect on presynaptic release probabilities. Overexpression of Neuroligin-1 in control or Neuroligin-deficient neurons increased synaptic transmission and synapse density but not spine numbers, suggesting that these effects reflect a gain-of-function mechanism; whereas overexpression of Neuroligin-3, which, like Neuroligin-1 is also targeted to excitatory synapses, had no comparable effect. Our data demonstrate that Neuroligins are required for the physiological organization of neurotransmitter receptors in postsynaptic specializations and suggest that they do not play a major role in synapse formation. SIGNIFICANCE STATEMENT Human Neuroligin genes have been associated with autism, but the cellular functions of different Neuroligins and their molecular mechanisms remain incompletely understood. Here, we performed comparative analyses in cultured mouse neurons of all major Neuroligin isoforms, either individually or in combinations, using conditional knockouts. We found that Neuroligin deletions did not affect synapse numbers but differentially impaired excitatory or inhibitory synaptic functions in an isoform-specific manner. These impairments were due, at least in part, to a decrease in synaptic distribution of neurotransmitter receptors upon deletion of Neuroligins. Conversely, the overexpression of Neuroligin-1 increased synapse numbers but not spine numbers. Our results suggest that various Neuroligin isoforms perform unique postsynaptic functions in organizing synapses but are not essential for synapse formation or maintenance.
Davide Comoletti - One of the best experts on this subject based on the ideXlab platform.
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Transcellular Neuroligin-2 interactions enhance insulin secretion and are integral to pancreatic β cell function.
The Journal of biological chemistry, 2012Co-Authors: Arthur T. Suckow, Davide Comoletti, Palmer Taylor, Meghan T Miller, Sonya Egodage, Charles Zhang, Ian R. Sweet, Steven D. ChesslerAbstract:Abstract Normal glucose-stimulated insulin secretion is dependent on interactions between neighboring β cells. Elucidation of the reasons why this cell-to-cell contact is essential will probably yield critical insights into β cell maturation and function. In the central nervous system, transcellular protein interactions (i.e. interactions between proteins on the surfaces of different cells) involving Neuroligins are key mediators of synaptic functional development. We previously demonstrated that β cells express Neuroligin-2 and that insulin secretion is affected by changes in Neuroligin-2 expression. Here we show that the effect of Neuroligin-2 on insulin secretion is mediated by transcellular interactions. Neuroligin-2 binds with nanomolar affinity to a partner on the β cell surface and contributes to the increased insulin secretion brought about by β cell-to-β cell contact. It does so in a manner seemingly independent of interactions with neurexin, a known binding partner. As in the synapse, transcellular Neuroligin-2 interactions enhance the functioning of the submembrane exocytic machinery. Also, as in the synapse, Neuroligin-2 clustering is important. Neuroligin-2 in soluble form, rather than presented on a cell surface, decreases insulin secretion by rat islets and MIN-6 cells, most likely by interfering with endogenous Neuroligin interactions. Prolonged contact with Neuroligin-2-expressing cells increases INS-1 β cell proliferation and insulin content. These results extend the known parallels between the synaptic and β cell secretory machineries to extracellular interactions. Neuroligin-2 interactions are one of the few transcellular protein interactions thus far identified that directly enhance insulin secretion. Together, these results indicate a significant role for transcellular Neuroligin-2 interactions in the establishment of β cell function.
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Structural insights into the exquisite selectivity of neurexin/Neuroligin synaptic interactions.
EMBO Journal, 2010Co-Authors: Philippe Leone, Géraldine Ferracci, Simon U Garcia, Sandrine Conrod, Yves Bourne, Davide Comoletti, Palmer Taylor, Pascale MarchotAbstract:The extracellular domains of Neuroligins and neurexins interact through Ca(2+) to form flexible trans-synaptic associations characterized by selectivity for Neuroligin or neurexin subtypes. This heterophilic interaction, essential for synaptic maturation and differentiation, is regulated by gene selection, alternative mRNA splicing and post-translational modifications. A new, 2.6 A-resolution crystal structure of a soluble neurexin-1beta-Neuroligin-4 (Nrx1beta-NL4) complex permits a detailed description of the Ca(2+)-coordinated interface and unveils concerted positional rearrangements of several residues of NL4, not observed in Neuroligin-1, associated with Nrx1beta binding. Surface plasmon resonance analysis of the binding of structure-guided Nrx1beta mutants towards NL4 and Neuroligin-1 shows that flexibility of the Nrx1beta-binding site in NL4 is reflected in a greater dissociation constant of the complex and higher sensitivity to ionic strength and pH variations. Analysis of Neuroligin mutants points to critical functions for two respective residues in Neuroligin-1 and Neuroligin-2 in governing the affinity of the complexes. Although Neuroligin-1 and Neuroligin-2 have pre-determined conformations that respectively promote and prevent Nrx1beta association, unique conformational reshaping of the NL4 surface is required to permit Nrx1beta association.
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Structural insights into the exquisite selectivity of neurexin/Neuroligin synaptic interactions.
The EMBO Journal, 2010Co-Authors: Philippe Leone, Géraldine Ferracci, Simon U Garcia, Sandrine Conrod, Yves Bourne, Davide Comoletti, Palmer Taylor, Pascale MarchotAbstract:The extracellular domains of Neuroligins and neurexins interact through Ca2+ to form flexible trans-synaptic associations characterized by selectivity for Neuroligin or neurexin subtypes. This heterophilic interaction, essential for synaptic maturation and differentiation, is regulated by gene selection, alternative mRNA splicing and post-translational modifications. A new, 2.6 A-resolution crystal structure of a soluble neurexin-1β–Neuroligin-4 (Nrx1β–NL4) complex permits a detailed description of the Ca2+-coordinated interface and unveils concerted positional rearrangements of several residues of NL4, not observed in Neuroligin-1, associated with Nrx1β binding. Surface plasmon resonance analysis of the binding of structure-guided Nrx1β mutants towards NL4 and Neuroligin-1 shows that flexibility of the Nrx1β-binding site in NL4 is reflected in a greater dissociation constant of the complex and higher sensitivity to ionic strength and pH variations. Analysis of Neuroligin mutants points to critical functions for two respective residues in Neuroligin-1 and Neuroligin-2 in governing the affinity of the complexes. Although Neuroligin-1 and Neuroligin-2 have pre-determined conformations that respectively promote and prevent Nrx1β association, unique conformational reshaping of the NL4 surface is required to permit Nrx1β association.
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Structure-function relationships of the alpha/beta-hydrolase fold domain of Neuroligin: A comparison with acetylcholinesterase.
Chem Biol Interact, 2010Co-Authors: Philippe Leone, Davide Comoletti, Yves Bourne, Palmer Taylor, Pascale MarchotAbstract:The Neuroligins are postsynaptic cell adhesion proteins whose extracellular domain belongs to the alpha/beta-hydrolase fold family of proteins, a family characterized through the enzyme acetylcholinesterase (AChE) and other enzymes with various substrate specificities. Neuroligin associations with the pre-synaptic neurexins participate in synapse maturation and maintenance. Alternative splicing of the Neuroligin and neurexin genes results in multiple isoforms and presumably regulation of activity, while mutations appear to be associated with autism spectrum disorders. The crystal structures of the extracellular, cell adhesion domain of three Neuroligins (NL1, NL2 and NL4) revealed features that distinguish the Neuroligins from their enzyme relatives and could not be predicted by homology modelling from an AChE template. The structures of NL1 and NL4 bound with a soluble beta-neurexin domain (Nrxbeta1) revealed the precise position and orientation of the bound Nrxbeta1 and the Ca(2+)-dependent interaction network at the complex interface. Herein we present an overview of the unbound and Nrxbeta1-bound Neuroligin structures and compare them with structures of AChEs with and without a bound fasciculin partner. This study exemplifies how an alpha/beta-hydrolase fold domain tailored for catalysis varies to acquire adhesion properties, and defines three surface regions with distinctive locations and properties for homologous or heterologous partner association.
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Characterization of the solution structure of a Neuroligin/β-neurexin complex
Chemico-Biological Interactions, 2008Co-Authors: Davide Comoletti, Palmer Taylor, Alexander Grishaev, Andrew E Whitten, Jill TrewhellaAbstract:Neuroligins are post-synaptic cell adhesion molecules that promote synaptic maturation and stabilization upon binding with pre-synaptic partners, the α- and β-neurexins. Using a combination of analytical ultracentrifugation, small angle X-ray, and neutron scattering, we have characterized the low-resolution three-dimensional structure of the extracellular domain of the Neuroligins, free in solution, and in complex with β-neurexin. The globular extracellular domain of the Neuroligins forms stable homodimers through a four-helix bundle typical of the cholinesterases and other members of the α/β-hydrolase fold family. The presence of the stalk region adds to the extracellular domain of Neuroligin-1 an elongated structure, suggesting a rod-like nature of the stalk domain. Sedimentation equilibrium coupled with solution scattering data of the β-neurexin/Neuroligin-1 complex indicated a 2:2 stoichiometry where two β-neurexin molecules bind to a Neuroligin-1 dimer. Deuteration of neurexin allowed us to collect neutron scattering data that, in combination with other biochemical techniques, provide a basis for optimizing the positioning of each component in a detailed computational model of the Neuroligin/neurexin complex. As several mutations of both neurexin and Neuroligin genes have been linked to autism spectrum disorders and mental retardation, these new structures provide an important framework for the study of altered structure and function of these synaptic proteins.
Palmer Taylor - One of the best experts on this subject based on the ideXlab platform.
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Transcellular Neuroligin-2 interactions enhance insulin secretion and are integral to pancreatic β cell function.
The Journal of biological chemistry, 2012Co-Authors: Arthur T. Suckow, Davide Comoletti, Palmer Taylor, Meghan T Miller, Sonya Egodage, Charles Zhang, Ian R. Sweet, Steven D. ChesslerAbstract:Abstract Normal glucose-stimulated insulin secretion is dependent on interactions between neighboring β cells. Elucidation of the reasons why this cell-to-cell contact is essential will probably yield critical insights into β cell maturation and function. In the central nervous system, transcellular protein interactions (i.e. interactions between proteins on the surfaces of different cells) involving Neuroligins are key mediators of synaptic functional development. We previously demonstrated that β cells express Neuroligin-2 and that insulin secretion is affected by changes in Neuroligin-2 expression. Here we show that the effect of Neuroligin-2 on insulin secretion is mediated by transcellular interactions. Neuroligin-2 binds with nanomolar affinity to a partner on the β cell surface and contributes to the increased insulin secretion brought about by β cell-to-β cell contact. It does so in a manner seemingly independent of interactions with neurexin, a known binding partner. As in the synapse, transcellular Neuroligin-2 interactions enhance the functioning of the submembrane exocytic machinery. Also, as in the synapse, Neuroligin-2 clustering is important. Neuroligin-2 in soluble form, rather than presented on a cell surface, decreases insulin secretion by rat islets and MIN-6 cells, most likely by interfering with endogenous Neuroligin interactions. Prolonged contact with Neuroligin-2-expressing cells increases INS-1 β cell proliferation and insulin content. These results extend the known parallels between the synaptic and β cell secretory machineries to extracellular interactions. Neuroligin-2 interactions are one of the few transcellular protein interactions thus far identified that directly enhance insulin secretion. Together, these results indicate a significant role for transcellular Neuroligin-2 interactions in the establishment of β cell function.
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Structural insights into the exquisite selectivity of neurexin/Neuroligin synaptic interactions.
EMBO Journal, 2010Co-Authors: Philippe Leone, Géraldine Ferracci, Simon U Garcia, Sandrine Conrod, Yves Bourne, Davide Comoletti, Palmer Taylor, Pascale MarchotAbstract:The extracellular domains of Neuroligins and neurexins interact through Ca(2+) to form flexible trans-synaptic associations characterized by selectivity for Neuroligin or neurexin subtypes. This heterophilic interaction, essential for synaptic maturation and differentiation, is regulated by gene selection, alternative mRNA splicing and post-translational modifications. A new, 2.6 A-resolution crystal structure of a soluble neurexin-1beta-Neuroligin-4 (Nrx1beta-NL4) complex permits a detailed description of the Ca(2+)-coordinated interface and unveils concerted positional rearrangements of several residues of NL4, not observed in Neuroligin-1, associated with Nrx1beta binding. Surface plasmon resonance analysis of the binding of structure-guided Nrx1beta mutants towards NL4 and Neuroligin-1 shows that flexibility of the Nrx1beta-binding site in NL4 is reflected in a greater dissociation constant of the complex and higher sensitivity to ionic strength and pH variations. Analysis of Neuroligin mutants points to critical functions for two respective residues in Neuroligin-1 and Neuroligin-2 in governing the affinity of the complexes. Although Neuroligin-1 and Neuroligin-2 have pre-determined conformations that respectively promote and prevent Nrx1beta association, unique conformational reshaping of the NL4 surface is required to permit Nrx1beta association.
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Structural insights into the exquisite selectivity of neurexin/Neuroligin synaptic interactions.
The EMBO Journal, 2010Co-Authors: Philippe Leone, Géraldine Ferracci, Simon U Garcia, Sandrine Conrod, Yves Bourne, Davide Comoletti, Palmer Taylor, Pascale MarchotAbstract:The extracellular domains of Neuroligins and neurexins interact through Ca2+ to form flexible trans-synaptic associations characterized by selectivity for Neuroligin or neurexin subtypes. This heterophilic interaction, essential for synaptic maturation and differentiation, is regulated by gene selection, alternative mRNA splicing and post-translational modifications. A new, 2.6 A-resolution crystal structure of a soluble neurexin-1β–Neuroligin-4 (Nrx1β–NL4) complex permits a detailed description of the Ca2+-coordinated interface and unveils concerted positional rearrangements of several residues of NL4, not observed in Neuroligin-1, associated with Nrx1β binding. Surface plasmon resonance analysis of the binding of structure-guided Nrx1β mutants towards NL4 and Neuroligin-1 shows that flexibility of the Nrx1β-binding site in NL4 is reflected in a greater dissociation constant of the complex and higher sensitivity to ionic strength and pH variations. Analysis of Neuroligin mutants points to critical functions for two respective residues in Neuroligin-1 and Neuroligin-2 in governing the affinity of the complexes. Although Neuroligin-1 and Neuroligin-2 have pre-determined conformations that respectively promote and prevent Nrx1β association, unique conformational reshaping of the NL4 surface is required to permit Nrx1β association.
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Structure-function relationships of the alpha/beta-hydrolase fold domain of Neuroligin: A comparison with acetylcholinesterase.
Chem Biol Interact, 2010Co-Authors: Philippe Leone, Davide Comoletti, Yves Bourne, Palmer Taylor, Pascale MarchotAbstract:The Neuroligins are postsynaptic cell adhesion proteins whose extracellular domain belongs to the alpha/beta-hydrolase fold family of proteins, a family characterized through the enzyme acetylcholinesterase (AChE) and other enzymes with various substrate specificities. Neuroligin associations with the pre-synaptic neurexins participate in synapse maturation and maintenance. Alternative splicing of the Neuroligin and neurexin genes results in multiple isoforms and presumably regulation of activity, while mutations appear to be associated with autism spectrum disorders. The crystal structures of the extracellular, cell adhesion domain of three Neuroligins (NL1, NL2 and NL4) revealed features that distinguish the Neuroligins from their enzyme relatives and could not be predicted by homology modelling from an AChE template. The structures of NL1 and NL4 bound with a soluble beta-neurexin domain (Nrxbeta1) revealed the precise position and orientation of the bound Nrxbeta1 and the Ca(2+)-dependent interaction network at the complex interface. Herein we present an overview of the unbound and Nrxbeta1-bound Neuroligin structures and compare them with structures of AChEs with and without a bound fasciculin partner. This study exemplifies how an alpha/beta-hydrolase fold domain tailored for catalysis varies to acquire adhesion properties, and defines three surface regions with distinctive locations and properties for homologous or heterologous partner association.
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Characterization of the solution structure of a Neuroligin/β-neurexin complex
Chemico-Biological Interactions, 2008Co-Authors: Davide Comoletti, Palmer Taylor, Alexander Grishaev, Andrew E Whitten, Jill TrewhellaAbstract:Neuroligins are post-synaptic cell adhesion molecules that promote synaptic maturation and stabilization upon binding with pre-synaptic partners, the α- and β-neurexins. Using a combination of analytical ultracentrifugation, small angle X-ray, and neutron scattering, we have characterized the low-resolution three-dimensional structure of the extracellular domain of the Neuroligins, free in solution, and in complex with β-neurexin. The globular extracellular domain of the Neuroligins forms stable homodimers through a four-helix bundle typical of the cholinesterases and other members of the α/β-hydrolase fold family. The presence of the stalk region adds to the extracellular domain of Neuroligin-1 an elongated structure, suggesting a rod-like nature of the stalk domain. Sedimentation equilibrium coupled with solution scattering data of the β-neurexin/Neuroligin-1 complex indicated a 2:2 stoichiometry where two β-neurexin molecules bind to a Neuroligin-1 dimer. Deuteration of neurexin allowed us to collect neutron scattering data that, in combination with other biochemical techniques, provide a basis for optimizing the positioning of each component in a detailed computational model of the Neuroligin/neurexin complex. As several mutations of both neurexin and Neuroligin genes have been linked to autism spectrum disorders and mental retardation, these new structures provide an important framework for the study of altered structure and function of these synaptic proteins.
Pascale Marchot - One of the best experts on this subject based on the ideXlab platform.
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A Triad of Crystals Sheds Light on MDGA Interference with Neuroligation
Neuron, 2017Co-Authors: Olivier Thoumine, Pascale MarchotAbstract:Neurexins and Neuroligins form trans-synaptic complexes that promote synapse development. In this issue of Neuron, Aricescu and colleagues (Elegheert et al., 2017) complement and strengthen two recent reports by the Kim and Rudenko teams (Kim et al., 2017; Gangwar et al., 2017) to dissect the molecular determinants by which MDGAs challenge the neurexin-Neuroligin partnership.
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The Neuroligins and Their Ligands: from Structure to Function at the Synapse
Journal of Molecular Neuroscience, 2014Co-Authors: Yves Bourne, Pascale MarchotAbstract:The Neuroligins are cell adhesion proteins whose extracellular domain belongs to the α/β-hydrolase fold family of proteins, mainly containing enzymes and exemplified by acetylcholinesterase. The ectodomain of postsynaptic Neuroligins interacts through a calcium ion with the ectodomain of presynaptic neurexins to form flexible trans-synaptic associations characterized by selectivity for Neuroligin or neurexin subtypes. This heterophilic interaction, essential for synaptic differentiation, maturation, and maintenance, is regulated by gene selection, alternative mRNA splicing, and posttranslational modifications. Mutations leading to deficiencies in the expression, folding, maturation, and binding properties of either partner are associated with autism spectrum disorders. The currently available structural and functional data illustrate how these two families of cell adhesion molecules bridge the synaptic cleft to participate in synapse plasticity and support its dynamic nature. Neuroligin partners distinct from the neurexins, and which may undergo either trans or cis interaction, have also been described, and tridimensional structures of some of them are available. Our study emphasizes the partnership versatility of the Neuroligin ectodomain associated with molecular flexibility and alternative binding sites, proposes homology models of the structurally non-characterized Neuroligin partners, and exemplifies the large structural variability at the surface of the α/β-hydrolase fold subunit. This study also provides new insights into possible surface binding sites associated with non-catalytic properties of the acetylcholinesterase subunit.
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Structural insights into the exquisite selectivity of neurexin/Neuroligin synaptic interactions.
EMBO Journal, 2010Co-Authors: Philippe Leone, Géraldine Ferracci, Simon U Garcia, Sandrine Conrod, Yves Bourne, Davide Comoletti, Palmer Taylor, Pascale MarchotAbstract:The extracellular domains of Neuroligins and neurexins interact through Ca(2+) to form flexible trans-synaptic associations characterized by selectivity for Neuroligin or neurexin subtypes. This heterophilic interaction, essential for synaptic maturation and differentiation, is regulated by gene selection, alternative mRNA splicing and post-translational modifications. A new, 2.6 A-resolution crystal structure of a soluble neurexin-1beta-Neuroligin-4 (Nrx1beta-NL4) complex permits a detailed description of the Ca(2+)-coordinated interface and unveils concerted positional rearrangements of several residues of NL4, not observed in Neuroligin-1, associated with Nrx1beta binding. Surface plasmon resonance analysis of the binding of structure-guided Nrx1beta mutants towards NL4 and Neuroligin-1 shows that flexibility of the Nrx1beta-binding site in NL4 is reflected in a greater dissociation constant of the complex and higher sensitivity to ionic strength and pH variations. Analysis of Neuroligin mutants points to critical functions for two respective residues in Neuroligin-1 and Neuroligin-2 in governing the affinity of the complexes. Although Neuroligin-1 and Neuroligin-2 have pre-determined conformations that respectively promote and prevent Nrx1beta association, unique conformational reshaping of the NL4 surface is required to permit Nrx1beta association.
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Structural insights into the exquisite selectivity of neurexin/Neuroligin synaptic interactions.
The EMBO Journal, 2010Co-Authors: Philippe Leone, Géraldine Ferracci, Simon U Garcia, Sandrine Conrod, Yves Bourne, Davide Comoletti, Palmer Taylor, Pascale MarchotAbstract:The extracellular domains of Neuroligins and neurexins interact through Ca2+ to form flexible trans-synaptic associations characterized by selectivity for Neuroligin or neurexin subtypes. This heterophilic interaction, essential for synaptic maturation and differentiation, is regulated by gene selection, alternative mRNA splicing and post-translational modifications. A new, 2.6 A-resolution crystal structure of a soluble neurexin-1β–Neuroligin-4 (Nrx1β–NL4) complex permits a detailed description of the Ca2+-coordinated interface and unveils concerted positional rearrangements of several residues of NL4, not observed in Neuroligin-1, associated with Nrx1β binding. Surface plasmon resonance analysis of the binding of structure-guided Nrx1β mutants towards NL4 and Neuroligin-1 shows that flexibility of the Nrx1β-binding site in NL4 is reflected in a greater dissociation constant of the complex and higher sensitivity to ionic strength and pH variations. Analysis of Neuroligin mutants points to critical functions for two respective residues in Neuroligin-1 and Neuroligin-2 in governing the affinity of the complexes. Although Neuroligin-1 and Neuroligin-2 have pre-determined conformations that respectively promote and prevent Nrx1β association, unique conformational reshaping of the NL4 surface is required to permit Nrx1β association.
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Structure-function relationships of the alpha/beta-hydrolase fold domain of Neuroligin: A comparison with acetylcholinesterase.
Chem Biol Interact, 2010Co-Authors: Philippe Leone, Davide Comoletti, Yves Bourne, Palmer Taylor, Pascale MarchotAbstract:The Neuroligins are postsynaptic cell adhesion proteins whose extracellular domain belongs to the alpha/beta-hydrolase fold family of proteins, a family characterized through the enzyme acetylcholinesterase (AChE) and other enzymes with various substrate specificities. Neuroligin associations with the pre-synaptic neurexins participate in synapse maturation and maintenance. Alternative splicing of the Neuroligin and neurexin genes results in multiple isoforms and presumably regulation of activity, while mutations appear to be associated with autism spectrum disorders. The crystal structures of the extracellular, cell adhesion domain of three Neuroligins (NL1, NL2 and NL4) revealed features that distinguish the Neuroligins from their enzyme relatives and could not be predicted by homology modelling from an AChE template. The structures of NL1 and NL4 bound with a soluble beta-neurexin domain (Nrxbeta1) revealed the precise position and orientation of the bound Nrxbeta1 and the Ca(2+)-dependent interaction network at the complex interface. Herein we present an overview of the unbound and Nrxbeta1-bound Neuroligin structures and compare them with structures of AChEs with and without a bound fasciculin partner. This study exemplifies how an alpha/beta-hydrolase fold domain tailored for catalysis varies to acquire adhesion properties, and defines three surface regions with distinctive locations and properties for homologous or heterologous partner association.
Antony A Boucard - One of the best experts on this subject based on the ideXlab platform.
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direct visualization of trans synaptic neurexin Neuroligin interactions during synapse formation
The Journal of Neuroscience, 2014Co-Authors: Theodoros Tsetsenis, Antony A Boucard, Demet Arac, Axel T Brunger, Thomas C SudhofAbstract:Neurexins and Neuroligins are synaptic cell-adhesion molecules that are essential for normal synapse specification and function and are thought to bind to each other trans-synaptically, but such interactions have not been demonstrated directly. Here, we generated neurexin-1β and Neuroligin-1 and Neuroligin-2 fusion proteins containing complementary “split” GFP fragments positioned such that binding of neurexin-1β to Neuroligin-1 or Neuroligin-2 allowed GFP reconstitution without dramatically changing their binding affinities. GFP fluorescence was only reconstituted from split-GFP-modified neurexin-1β and Neuroligin-1 if and after neurexin-1β bound to its Neuroligin partner; reassociation of the split-GFP components with each other did not mediate binding. Using trans-cellular reconstitution of GFP fluorescence from split-GFP-modified neurexin-1β and Neuroligins as an assay, we demonstrate that trans-synaptic neurexin/Neuroligin binding indeed occurred when mouse hippocampal neurons formed synapses onto non-neuronal COS-7 cells expressing Neuroligins or when mouse hippocampal neurons formed synapses with each other. This visualization of synapses by neurexin/Neuroligin binding prompted us to refer to this approach as “SynView.” Our data demonstrate that neurexin-1β forms a trans-synaptic complex with Neuroligin-1 and Neuroligin-2 and that this interaction can be used to label synapses in a specific fashion in vivo.
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Direct Visualization of Trans-Synaptic Neurexin–Neuroligin Interactions during Synapse Formation
The Journal of Neuroscience, 2014Co-Authors: Theodoros Tsetsenis, Antony A Boucard, Demet AracAbstract:Neurexins and Neuroligins are synaptic cell-adhesion molecules that are essential for normal synapse specification and function and are thought to bind to each other trans-synaptically, but such interactions have not been demonstrated directly. Here, we generated neurexin-1β and Neuroligin-1 and Neuroligin-2 fusion proteins containing complementary “split” GFP fragments positioned such that binding of neurexin-1β to Neuroligin-1 or Neuroligin-2 allowed GFP reconstitution without dramatically changing their binding affinities. GFP fluorescence was only reconstituted from split-GFP-modified neurexin-1β and Neuroligin-1 if and after neurexin-1β bound to its Neuroligin partner; reassociation of the split-GFP components with each other did not mediate binding. Using trans-cellular reconstitution of GFP fluorescence from split-GFP-modified neurexin-1β and Neuroligins as an assay, we demonstrate that trans-synaptic neurexin/Neuroligin binding indeed occurred when mouse hippocampal neurons formed synapses onto non-neuronal COS-7 cells expressing Neuroligins or when mouse hippocampal neurons formed synapses with each other. This visualization of synapses by neurexin/Neuroligin binding prompted us to refer to this approach as “SynView.” Our data demonstrate that neurexin-1β forms a trans-synaptic complex with Neuroligin-1 and Neuroligin-2 and that this interaction can be used to label synapses in a specific fashion in vivo.
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Neuroligin 1 performs neurexin dependent and neurexin independent functions in synapse validation
The EMBO Journal, 2009Co-Authors: Jaewon Ko, Antony A Boucard, Demet Arac, Axel T Brunger, Chen Zhang, Thomas C SudhofAbstract:Postsynaptic Neuroligins are thought to perform essential functions in synapse validation and synaptic transmission by binding to, and dimerizing, presynaptic α- and β-neurexins. To test this hypothesis, we examined the functional effects of Neuroligin-1 mutations that impair only α-neurexin binding, block both α- and β-neurexin binding, or abolish Neuroligin-1 dimerization. Abolishing α-neurexin binding abrogated Neuroligin-induced generation of neuronal synapses onto transfected non-neuronal cells in the so-called artificial synapse-formation assay, even though β-neurexin binding was retained. Thus, in this assay, Neuroligin-1 induces apparent synapse formation by binding to presynaptic α-neurexins. In transfected neurons, however, neither α- nor β-neurexin binding was essential for the ability of postsynaptic Neuroligin-1 to dramatically increase synapse density, suggesting a neurexin-independent mechanism of synapse formation. Moreover, Neuroligin-1 dimerization was not required for either the non-neuronal or the neuronal synapse-formation assay. Nevertheless, both α-neurexin binding and Neuroligin-1 dimerization were essential for the increase in apparent synapse size that is induced by Neuroligin-1 in transfected neurons. Thus, Neuroligin-1 performs diverse synaptic functions by mechanisms that include as essential components of α-neurexin binding and Neuroligin dimerization, but extend beyond these activities.
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Neuroligin‐1 performs neurexin‐dependent and neurexin‐independent functions in synapse validation
The EMBO Journal, 2009Co-Authors: Jaewon Ko, Antony A Boucard, Demet Arac, Axel T Brunger, Chen Zhang, Thomas C SudhofAbstract:Postsynaptic Neuroligins are thought to perform essential functions in synapse validation and synaptic transmission by binding to, and dimerizing, presynaptic α- and β-neurexins. To test this hypothesis, we examined the functional effects of Neuroligin-1 mutations that impair only α-neurexin binding, block both α- and β-neurexin binding, or abolish Neuroligin-1 dimerization. Abolishing α-neurexin binding abrogated Neuroligin-induced generation of neuronal synapses onto transfected non-neuronal cells in the so-called artificial synapse-formation assay, even though β-neurexin binding was retained. Thus, in this assay, Neuroligin-1 induces apparent synapse formation by binding to presynaptic α-neurexins. In transfected neurons, however, neither α- nor β-neurexin binding was essential for the ability of postsynaptic Neuroligin-1 to dramatically increase synapse density, suggesting a neurexin-independent mechanism of synapse formation. Moreover, Neuroligin-1 dimerization was not required for either the non-neuronal or the neuronal synapse-formation assay. Nevertheless, both α-neurexin binding and Neuroligin-1 dimerization were essential for the increase in apparent synapse size that is induced by Neuroligin-1 in transfected neurons. Thus, Neuroligin-1 performs diverse synaptic functions by mechanisms that include as essential components of α-neurexin binding and Neuroligin dimerization, but extend beyond these activities.
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structures of Neuroligin 1 and the Neuroligin 1 neurexin 1β complex reveal specific protein protein and protein ca2 interactions
Neuron, 2007Co-Authors: Antony A Boucard, Pavel Strop, Demet Arac, Evan W. Newell, Engin Ozkan, Thomas C SudhofAbstract:Summary Neurexins and Neuroligins provide trans -synaptic connectivity by the Ca 2+ -dependent interaction of their alternatively spliced extracellular domains. Neuroligins specify synapses in an activity-dependent manner, presumably by binding to neurexins. Here, we present the crystal structures of Neuroligin-1 in isolation and in complex with neurexin-1β. Neuroligin-1 forms a constitutive dimer, and two neurexin-1β monomers bind to two identical surfaces on the opposite faces of the Neuroligin-1 dimer to form a heterotetramer. The Neuroligin-1/neurexin-1β complex exhibits a nanomolar affinity and includes a large binding interface that contains bound Ca 2+ . Alternatively spliced sites in neurexin-1β and in Neuroligin-1 are positioned nearby the binding interface, explaining how they regulate the interaction. Structure-based mutations of Neuroligin-1 at the interface disrupt binding to neurexin-1β, but not the folding of Neuroligin-1 and confirm the validity of the binding interface of the Neuroligin-1/neurexin-1β complex. Our results provide molecular insights for understanding the role of cell-adhesion proteins in synapse function.