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Thomas C. Südhof - One of the best experts on this subject based on the ideXlab platform.
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glud1 is a signal transduction device disguised as an ionotropic receptor
Nature, 2021Co-Authors: Jinye Dai, Thomas C. Südhof, Christopher Patzke, Kif Liakathali, Erica SeigneurAbstract:Ionotropic glutamate delta receptors 1 (GluD1) and 2 (GluD2) exhibit the molecular architecture of postsynaptic ionotropic glutamate receptors, but assemble into trans-synaptic adhesion complexes by binding to secreted cerebellins that in turn interact with presynaptic Neurexins1–4. It is unclear whether Neurexin–cerebellin–GluD1/2 assemblies serve an adhesive synapse-formation function or mediate trans-synaptic signalling. Here we show in hippocampal synapses, that binding of presynaptic Neurexin–cerebellin complexes to postsynaptic GluD1 controls glutamate receptor activity without affecting synapse numbers. Specifically, Neurexin-1–cerebellin-2 and Neurexin-3–cerebellin-2 complexes differentially regulate NMDA (N-methyl-d-aspartate) receptors and AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors by activating distinct postsynaptic GluD1 effector signals. Of note, minimal GluD1 and GluD2 constructs containing only their N-terminal cerebellin-binding and C-terminal cytoplasmic domains, joined by an unrelated transmembrane region, fully control the levels of NMDA and AMPA receptors. The distinct signalling specificity of presynaptic Neurexin-1 and Neurexin-35,6 is encoded by their alternatively spliced splice site 4 sequences, whereas the regulatory functions of postsynaptic GluD1 are mediated by conserved cytoplasmic sequence motifs spanning 5–13 residues. Thus, GluDs are signalling molecules that regulate NMDA and AMPA receptors by an unexpected transduction mechanism that bypasses their ionotropic receptor architecture and directly converts extracellular Neurexin–cerebellin signals into postsynaptic receptor responses. The ionotropic glutamate delta receptors GluD1 and GluD2 form distinct Neurexin–cerebellin complexes that differentially regulate postsynaptic glutamate receptor activities.
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sparcl1 promotes excitatory but not inhibitory synapse formation and function independent of Neurexins and neuroligins
The Journal of Neuroscience, 2020Co-Authors: Kathlyn J Gan, Thomas C. SüdhofAbstract:Emerging evidence supports roles for secreted extracellular matrix proteins in boosting synaptogenesis, synaptic transmission, and synaptic plasticity. SPARCL1 (also known as 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 NMDAR-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 KO mice that lacked all Neurexins or all neuroligins were fully responsive to SPARCL1. 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 NMDAR 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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Neurexins cluster ca 2 channels within the presynaptic active zone
The EMBO Journal, 2020Co-Authors: Fujun Luo, Alessandra Sclip, Man Jiang, Thomas C. SüdhofAbstract:To achieve ultrafast neurotransmission, neurons assemble synapses with highly organized presynaptic and postsynaptic nanomachines that are aligned by synaptic adhesion molecules. How functional assembly of presynaptic active zones is controlled via trans-synaptic interactions remains unknown. Here, we conditionally deleted all three Neurexin adhesion molecules from presynaptic neurons of the calyx of Held in the mouse auditory system, a model synapse that allows precise biophysical analyses of synaptic properties. The pan-Neurexin deletion had no effect on synapse development or the basic release machinery, but dramatically impaired fast neurotransmitter release. The overall properties of presynaptic calcium ion channels appeared normal, as reflected by the similar characteristics of calcium currents recorded at the nerve terminals. However, the pan-Neurexin deletion significantly impaired the tight coupling of calcium influx to exocytosis, thereby suppressing neurotransmitter release. Furthermore, the pan-Neurexin deletion reduced the function of calcium-activated BK potassium channels, whose activation depends on their tight association with presynaptic calcium channels. Together, these results suggest that Neurexins perform a major function at the calyx synapse in coupling presynaptic calcium channels to release sites.
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structures of neurexophilin Neurexin complexes reveal a regulatory mechanism of alternative splicing
The EMBO Journal, 2019Co-Authors: Steven C Wilson, Thomas C. Südhof, Ian K White, Qiangjun Zhou, Richard A Pfuetzner, Ucheor B Choi, Axel T BrungerAbstract:Neurexins are presynaptic, cell-adhesion molecules that specify the functional properties of synapses via interactions with trans-synaptic ligands. Neurexins are extensively alternatively spliced at six canonical sites that regulate multifarious ligand interactions, but the structural mechanisms underlying alternative splicing-dependent Neurexin regulation are largely unknown. Here, we determined high-resolution structures of the complex of neurexophilin-1 and the second laminin/Neurexin/sex-hormone-binding globulin domain (LNS2) of Neurexin-1 and examined how alternative splicing at splice site #2 (SS2) regulates the complex. Our data reveal a unique, extensive, neurexophilin-Neurexin binding interface that extends the jelly-roll β-sandwich of LNS2 of Neurexin-1 into neurexophilin-1. The SS2A insert of LNS2 augments this interface, increasing the binding affinity of LNS2 for neurexophilin-1. Taken together, our data reveal an unexpected architecture of neurexophilin-Neurexin complexes that accounts for the modulation of binding by alternative splicing, which in turn regulates the competition of neurexophilin for Neurexin binding with other ligands.
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Synaptic Neurexin-1 assembles into dynamically regulated active zone nanoclusters
Journal of Cell Biology, 2019Co-Authors: Justin H. Trotter, Stephan Maxeiner, Theodoros Tsetsenis, Xiaowei Zhuang, Thomas C. SüdhofAbstract:Neurexins are well-characterized presynaptic cell adhesion molecules that engage multifarious postsynaptic ligands and organize diverse synapse properties. However, the precise synaptic localization of Neurexins remains enigmatic. Using super-resolution microscopy, we demonstrate that Neurexin-1 forms discrete nanoclusters at excitatory synapses, revealing a novel organizational feature of synaptic architecture. Synapses generally contain a single nanocluster that comprises more than four Neurexin-1 molecules and that also includes Neurexin-2 and/or Neurexin-3 isoforms. Moreover, we find that Neurexin-1 is physiologically cleaved by ADAM10 similar to its ligand neuroligin-1, with ∼4–6% of Neurexin-1 and ∼2–3% of neuroligin-1 present in the adult brain as soluble ectodomain proteins. Blocking ADAM10-mediated Neurexin-1 cleavage dramatically increased the synaptic Neurexin-1 content, thereby elevating the percentage of Homer1(+) excitatory synapses containing Neurexin-1 nanoclusters from 40–50% to ∼80%, and doubling the number of Neurexin-1 molecules per nanocluster. Taken together, our results reveal an unexpected nanodomain organization of synapses in which Neurexin-1 is assembled into discrete presynaptic nanoclusters that are dynamically regulated via ectodomain cleavage.
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 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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High Affinity Neurexin Binding to Cell Adhesion G-protein-coupled Receptor CIRL1/Latrophilin-1 Produces an Intercellular Adhesion Complex *
2013Co-Authors: Antony A BoucardAbstract:Background: Neurexins and CIRL/latrophilin-1 (CL1) are independent synaptic receptors for �-latrotoxin. Results: Neurexins and CL1 form a high affinity complex that mediates intercellular adhesion and is regulated by Neurexin alternative splicing. Conclusion: Thus, two independent �-latrotoxin receptors interact trans-cellularly to form a connection between neurons. Significance: The Neurexin-CL1 complex may be involved in trans-synaptic cell adhesion and mediate �-latrotoxin toxicity. The G-protein-coupled receptor CIRL1/latrophilin-1 (CL1) and the type-1 membrane proteins Neurexins represent distinct neuronal cell adhesion molecules that exhibit no similarities except for one common function: both proteins are receptors for �-latrotoxin, a component of black widow spider venom that induces massive neurotransmitter release at synapses. Unexpectedly, we have now identified a direct binding interaction between the extracellular domains of CL1 and Neurexins tha
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high affinity Neurexin binding to cell adhesion g protein coupled receptor cirl1 latrophilin 1 produces an intercellular adhesion complex
Journal of Biological Chemistry, 2012Co-Authors: Antony A Boucard, Thomas C. SüdhofAbstract:The G-protein-coupled receptor CIRL1/latrophilin-1 (CL1) and the type-1 membrane proteins Neurexins represent distinct neuronal cell adhesion molecules that exhibit no similarities except for one common function: both proteins are receptors for α-latrotoxin, a component of black widow spider venom that induces massive neurotransmitter release at synapses. Unexpectedly, we have now identified a direct binding interaction between the extracellular domains of CL1 and Neurexins that is regulated by alternative splicing of Neurexins at splice site 4 (SS4). Using saturation binding assays, we showed that Neurexins lacking an insert at SS4 bind to CL1 with nanomolar affinity, whereas Neurexins containing an insert at SS4 are unable to bind. CL1 competed for Neurexin binding with neuroligin-1, a well characterized Neurexin ligand. The extracellular sequences of CL1 contain five domains (lectin, olfactomedin-like, serine/threonine-rich, hormone-binding, and G-protein-coupled receptor autoproteolysis-inducing (GAIN) domains). Of these domains, the olfactomedin-like domain mediates Neurexin binding as shown by deletion mapping. Cell adhesion assays using cells expressing Neurexins and CL1 revealed that their interaction produces a stable intercellular adhesion complex, indicating that their interaction can be trans-cellular. Thus, our data suggest that CL1 constitutes a novel ligand for Neurexins that may be localized postsynaptically based on its well characterized interaction with intracellular SH3 and multiple ankyrin repeats adaptor proteins (SHANK) and could form a trans-synaptic complex with presynaptic Neurexins.
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neuroligin 1 performs Neurexin dependent and Neurexin independent functions in synapse validation
The EMBO Journal, 2009Co-Authors: Jaewon Ko, Demet Arac, Chen Zhang, Antony A BoucardAbstract: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, Engin Ozkan, Evan W. NewellAbstract: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.
Katsuhiko Tabuchi - One of the best experts on this subject based on the ideXlab platform.
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β Neurexins control neural circuits by regulating synaptic endocannabinoid signaling
Cell, 2015Co-Authors: Garret R Anderson, Csaba Foldy, Jason Aoto, Katsuhiko Tabuchi, Sung-jin Lee, Jason P Covy, Ada Xin Yee, Lu Chen, Robert C MalenkaAbstract:α- and β-Neurexins are presynaptic cell-adhesion molecules implicated in autism and schizophrenia. We find that, although β-Neurexins are expressed at much lower levels than α-Neurexins, conditional knockout of β-Neurexins with continued expression of α-Neurexins dramatically decreased neurotransmitter release at excitatory synapses in cultured cortical neurons. The β-Neurexin knockout phenotype was attenuated by CB1-receptor inhibition, which blocks presynaptic endocannabinoid signaling, or by 2-arachidonoylglycerol synthesis inhibition, which impairs postsynaptic endocannabinoid release. In synapses formed by CA1-region pyramidal neurons onto burst-firing subiculum neurons, presynaptic in vivo knockout of β-Neurexins aggravated endocannabinoid-mediated inhibition of synaptic transmission and blocked LTP; presynaptic CB1-receptor antagonists or postsynaptic 2-arachidonoylglycerol synthesis inhibition again reversed this block. Moreover, conditional knockout of β-Neurexins in CA1-region neurons impaired contextual fear memories. Thus, our data suggest that presynaptic β-Neurexins control synaptic strength in excitatory synapses by regulating postsynaptic 2-arachidonoylglycerol synthesis, revealing an unexpected role for β-Neurexins in the endocannabinoid-dependent regulation of neural circuits.
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distinct circuit dependent functions of presynaptic Neurexin 3 at gabaergic and glutamatergic synapses
Nature Neuroscience, 2015Co-Authors: Jason Aoto, Csaba Foldy, Katsuhiko Tabuchi, Silviana Maria Ciurea Ilcus, Thomas C. SüdhofAbstract:α- and β-Neurexins are presynaptic cell-adhesion molecules whose general importance for synaptic transmission is well documented. The specific functions of Neurexins, however, remain largely unknown because no conditional Neurexin knockouts are available and targeting all α- and β-Neurexins produced by a particular gene is challenging. Using newly generated constitutive and conditional knockout mice that target all Neurexin-3α and Neurexin-3β isoforms, we found that Neurexin-3 was differentially required for distinct synaptic functions in different brain regions. Specifically, we found that, in cultured neurons and acute slices of the hippocampus, extracellular sequences of presynaptic Neurexin-3 mediated trans-synaptic regulation of postsynaptic AMPA receptors. In cultured neurons and acute slices of the olfactory bulb, however, intracellular sequences of presynaptic Neurexin-3 were selectively required for GABA release. Thus, our data indicate that Neurexin-3 performs distinct essential pre- or postsynaptic functions in different brain regions by distinct mechanisms.
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presynaptic Neurexin 3 alternative splicing trans synaptically controls postsynaptic ampa receptor trafficking
Cell, 2013Co-Authors: Jason Aoto, David C Martinelli, Robert C Malenka, Katsuhiko TabuchiAbstract:Summary Neurexins are essential presynaptic cell adhesion molecules that are linked to schizophrenia and autism and are subject to extensive alternative splicing. Here, we used a genetic approach to test the physiological significance of Neurexin alternative splicing. We generated knockin mice in which alternatively spliced sequence #4 (SS4) of neuexin-3 is constitutively included but can be selectively excised by cre-recombination. SS4 of Neurexin-3 was chosen because it is highly regulated and controls Neurexin binding to neuroligins, LRRTMs, and other ligands. Unexpectedly, constitutive inclusion of SS4 in presynaptic Neurexin-3 decreased postsynaptic AMPA, but not NMDA receptor levels, and enhanced postsynaptic AMPA receptor endocytosis. Moreover, constitutive inclusion of SS4 in presynaptic Neurexin-3 abrogated postsynaptic AMPA receptor recruitment during NMDA receptor-dependent LTP. These phenotypes were fully rescued by constitutive excision of SS4 in Neurexin-3. Thus, alternative splicing of presynaptic Neurexin-3 controls postsynaptic AMPA receptor trafficking, revealing an unanticipated alternative splicing mechanism for trans -synaptic regulation of synaptic strength and long-term plasticity.
Palmer Taylor - One of the best experts on this subject based on the ideXlab platform.
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lrrtm2 interacts with Neurexin1 and regulates excitatory synapse formation
Neuron, 2009Co-Authors: Joris De Wit, Emily L Sylwestrak, Matthew L Osullivan, Stefanie Otto, Katie Tiglio, Jeffrey N Savas, Davide Comoletti, Palmer Taylor, Anirvan GhoshAbstract:Summary We identify the leucine-rich repeat transmembrane protein LRRTM2 as a key regulator of excitatory synapse development and function. LRRTM2 localizes to excitatory synapses in transfected hippocampal neurons, and shRNA-mediated knockdown of LRRTM2 leads to a decrease in excitatory synapses without affecting inhibitory synapses. LRRTM2 interacts with PSD-95 and regulates surface expression of AMPA receptors, and lentivirus-mediated knockdown of LRRTM2 in vivo decreases the strength of evoked excitatory synaptic currents. Structure-function studies indicate that LRRTM2 induces presynaptic differentiation via the extracellular LRR domain. We identify Neurexin1 as a receptor for LRRTM2 based on affinity chromatography. LRRTM2 binds to both Neurexin 1α and Neurexin 1β, and shRNA-mediated knockdown of Neurexin1 abrogates LRRTM2-induced presynaptic differentiation. These observations indicate that an LRRTM2-Neurexin1 interaction plays a critical role in regulating excitatory synapse development.
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structural analysis of the synaptic protein neuroligin and its β Neurexin complex determinants for folding and cell adhesion
Neuron, 2007Co-Authors: Igor P Fabrichny, Yves Bourne, Davide Comoletti, Palmer Taylor, Philippe Leone, Gerlind Sulzenbacher, Meghan T Miller, Pascale MarchotAbstract:The neuroligins are postsynaptic cell adhesion proteins whose associations with presynaptic Neurexins participate in synaptogenesis. Mutations in the neuroligin and Neurexin genes appear to be associated with autism and mental retardation. The crystal structure of a neuroligin reveals features not found in its catalytically active relatives, such as the fully hydrophobic interface forming the functional neuroligin dimer; the conformations of surface loops surrounding the vestigial active center; the location of determinants that are critical for folding and processing; and the absence of a macromolecular dipole and presence of an electronegative, hydrophilic surface for Neurexin binding. The structure of a beta-Neurexin-neuroligin complex reveals the precise orientation of the bound Neurexin and, despite a limited resolution, provides substantial information on the Ca2+-dependent interactions network involved in trans-synaptic Neurexin-neuroligin association. These structures exemplify how an alpha/beta-hydrolase fold varies in surface topography to confer adhesion properties and provide templates for analyzing abnormal processing or recognition events associated with autism.
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gene selection alternative splicing and post translational processing regulate neuroligin selectivity for β Neurexins
Biochemistry, 2006Co-Authors: Davide Comoletti, Antony A Boucard, Robyn E Flynn, Lori L Jennings, Borries Demeler, Virgil Schirf, Jianxin Shi, Helen R Newlin, Palmer TaylorAbstract:Neuroligins 1-4 are postsynaptic transmembrane proteins capable of initiating presynaptic maturation via interactions with beta-Neurexin. Both neuroligins and beta-Neurexins have alternatively spliced inserts in their extracellular domains. Using analytical ultracentrifugation, we determined that the extracellular domains of the neuroligins sediment as dimers, whereas the extracellular domains of the beta-Neurexins appear monomeric. Sedimentation velocity experiments of titrated stoichiometry ratios of beta-Neurexin and neuroligin suggested a 2:2 complex formation. The recognition properties of individual neuroligins toward beta-Neurexin-1 (NX1beta), along with the influence of their splice inserts, were explored by surface plasmon resonance and affinity chromatography. Different neuroligins display a range of NX1beta affinities spanning more than 2 orders of magnitude. Whereas splice insert 4 in beta-Neurexin appears to act only as a modulator of the neuroligin/beta-Neurexin association, splice insert B in neuroligin-1 (NL1) is the key element regulating the NL1/NX1beta binding. Our data indicate that gene selection, mRNA splicing, and post-translational modifications combine to give rise to a controlled neuroligin recognition code with a rank ordering of affinities for particular Neurexins that is conserved for the neuroligins across mammalian species.
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a splice code for trans synaptic cell adhesion mediated by binding of neuroligin 1 to α and β Neurexins
Neuron, 2005Co-Authors: Antony A Boucard, Alexander A Chubykin, Davide Comoletti, Palmer TaylorAbstract:Previous studies suggested that postsynaptic neuroligins form a trans-synaptic complex with presynaptic β-Neurexins, but not with presynaptic α-Neurexins. Unexpectedly, we now find that neuroligins also bind α-Neurexins and that α- and β-Neurexin binding by neuroligin 1 is regulated by alternative splicing of neuroligin 1 (at splice site B) and of Neurexins (at splice site 4). In neuroligin 1, splice site B is a master switch that determines α-Neurexin binding but leaves β-Neurexin binding largely unaffected, whereas alternative splicing of Neurexins modulates neuroligin binding. Moreover, neuroligin 1 splice variants with distinct Neurexin binding properties differentially regulate synaptogenesis: neuroligin 1 that binds only β-Neurexins potently stimulates synapse formation, whereas neuroligin 1 that binds to both α- and β-Neurexins more effectively promotes synapse expansion. These findings suggest that neuroligin binding to α- and β-Neurexins mediates trans-synaptic cell adhesion but has distinct effects on synapse formation, indicating that expression of different neuroligin and Neurexin isoforms specifies a trans-synaptic signaling code.
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the arg451cys neuroligin 3 mutation associated with autism reveals a defect in protein processing
The Journal of Neuroscience, 2004Co-Authors: Davide Comoletti, Robyn E Flynn, Lori L Jennings, Igor Tsigelny, Antonella De Jaco, Guido M Gaietta, Mark H Ellisman, Palmer TaylorAbstract:The neuroligins are a family of postsynaptic transmembrane proteins that associate with presynaptic partners, the β-Neurexins. Neurexins and neuroligins play a critical role in initiating formation and differentiation of synaptic junctions. A recent study reported that a mutation of neuroligin-3 ( NL3 ), an X-linked gene, was found in siblings with autistic spectrum disorder in which two affected brothers had a point mutation that substituted a Cys for Arg451. To characterize the mutation at the biochemical level, we analyzed expression and activity of the mutated protein. Mass spectrometry comparison of the disulfide bonding pattern between the native and the mutated proteins indicates the absence of aberrant disulfide bonding, suggesting that the secondary structure of the mutated protein is conserved. However, the mutation separately affects protein expression and activity. The Cys mutation causes defective neuroligin trafficking, leading to retention of the protein in the endoplasmic reticulum. This, in turn, decreases the delivery of NL3 to the cell surface. Also, the small fraction of protein that reaches the cell membrane lacks or has markedly diminished β-Neurexin-1 (NX1β) binding activity. Other substitutions for Arg451 allow for normal cellular expression but diminished affinity for NX1β. Our findings reveal a cellular phenotype and loss of function for a congenital mutation associated with autistic spectrum disorders.
Bernd Stahl - One of the best experts on this subject based on the ideXlab platform.
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genetic analysis of alpha latrotoxin receptors reveals functional interdependence of cirl latrophilin 1 and Neurexin 1 alpha
Journal of Biological Chemistry, 2002Co-Authors: Sönke Tobaben, Thomas C. Südhof, Bernd StahlAbstract:α-Latrotoxin triggers massive neurotransmitter release from nerve terminals by binding to at least two distinct presynaptic receptors, Neurexin 1α and CIRL1/latrophilin1 (CL1). We have now generated knockout (KO) mice that lack CL1 and analyzed them alone or in combination with Neurexin 1α KO mice. Mice lacking only CL1, or both CL1 and Neurexin 1α, were viable and fertile. Ca2+-independent binding of α-latrotoxin to brain membranes was impaired similarly in CL1 single and in CL1/Neurexin 1α double KO mice (∼75% decrease) but not in Neurexin 1α single KO mice. In contrast, Ca2+-dependent binding (∼2 times above Ca2+-independent binding) was altered in both CL1 (∼50% decrease) and Neurexin 1α single KO mice (∼25% decrease) and was decreased further in double KO mice (∼75% decrease). Synaptosomes lacking CL1 exhibited the same decrease in α-latrotoxin-stimulated glutamate release in the presence and absence of Ca2+(∼75%). In contrast, synaptosomes lacking Neurexin 1α exhibited only a small decrease in α-latrotoxin-triggered release in the absence of Ca2+ (∼20%) but a major decrease in the presence of Ca2+ (∼75%). Surprisingly, synaptosomes lacking both CL1 and Neurexin 1α displayed a relatively smaller decrease in α-latrotoxin-stimulated glutamate release than synaptosomes lacking only CL1 in the absence of Ca2+ (∼50versus ∼75%), but the same decrease in the presence of Ca2+ (∼75%). Our data suggest the following two major conclusions. 1) CL1 and Neurexin 1α together account for the majority (75%) of α-latrotoxin receptors in brain, with the remaining receptor activity possibly due to other CL and Neurexin isoforms, and 2) the two receptors act additively in binding α-latrotoxin but not in triggering release. Together these data suggest that the two receptors act autonomously in binding of α-latrotoxin but cooperatively in transducing the stimulation of neurotransmitter release by α-latrotoxin.
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genetic analysis of α latrotoxin receptors reveals functional interdependence of cirl latrophilin 1 and Neurexin 1α
Journal of Biological Chemistry, 2002Co-Authors: Sönke Tobaben, Bernd StahlAbstract:α-Latrotoxin triggers massive neurotransmitter release from nerve terminals by binding to at least two distinct presynaptic receptors, Neurexin 1α and CIRL1/latrophilin1 (CL1). We have now generated knockout (KO) mice that lack CL1 and analyzed them alone or in combination with Neurexin 1α KO mice. Mice lacking only CL1, or both CL1 and Neurexin 1α, were viable and fertile. Ca2+-independent binding of α-latrotoxin to brain membranes was impaired similarly in CL1 single and in CL1/Neurexin 1α double KO mice (∼75% decrease) but not in Neurexin 1α single KO mice. In contrast, Ca2+-dependent binding (∼2 times above Ca2+-independent binding) was altered in both CL1 (∼50% decrease) and Neurexin 1α single KO mice (∼25% decrease) and was decreased further in double KO mice (∼75% decrease). Synaptosomes lacking CL1 exhibited the same decrease in α-latrotoxin-stimulated glutamate release in the presence and absence of Ca2+(∼75%). In contrast, synaptosomes lacking Neurexin 1α exhibited only a small decrease in α-latrotoxin-triggered release in the absence of Ca2+ (∼20%) but a major decrease in the presence of Ca2+ (∼75%). Surprisingly, synaptosomes lacking both CL1 and Neurexin 1α displayed a relatively smaller decrease in α-latrotoxin-stimulated glutamate release than synaptosomes lacking only CL1 in the absence of Ca2+ (∼50versus ∼75%), but the same decrease in the presence of Ca2+ (∼75%). Our data suggest the following two major conclusions. 1) CL1 and Neurexin 1α together account for the majority (75%) of α-latrotoxin receptors in brain, with the remaining receptor activity possibly due to other CL and Neurexin isoforms, and 2) the two receptors act additively in binding α-latrotoxin but not in triggering release. Together these data suggest that the two receptors act autonomously in binding of α-latrotoxin but cooperatively in transducing the stimulation of neurotransmitter release by α-latrotoxin.
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Genetic analysis of alpha-latrotoxin receptors reveals functional interdependence of CIRL/latrophilin 1 and Neurexin 1 alpha
The Journal of biological chemistry, 2001Co-Authors: Sönke Tobaben, Bernd StahlAbstract:Abstract α-Latrotoxin triggers massive neurotransmitter release from nerve terminals by binding to at least two distinct presynaptic receptors, Neurexin 1α and CIRL1/latrophilin1 (CL1). We have now generated knockout (KO) mice that lack CL1 and analyzed them alone or in combination with Neurexin 1α KO mice. Mice lacking only CL1, or both CL1 and Neurexin 1α, were viable and fertile. Ca2+-independent binding of α-latrotoxin to brain membranes was impaired similarly in CL1 single and in CL1/Neurexin 1α double KO mice (∼75% decrease) but not in Neurexin 1α single KO mice. In contrast, Ca2+-dependent binding (∼2 times above Ca2+-independent binding) was altered in both CL1 (∼50% decrease) and Neurexin 1α single KO mice (∼25% decrease) and was decreased further in double KO mice (∼75% decrease). Synaptosomes lacking CL1 exhibited the same decrease in α-latrotoxin-stimulated glutamate release in the presence and absence of Ca2+(∼75%). In contrast, synaptosomes lacking Neurexin 1α exhibited only a small decrease in α-latrotoxin-triggered release in the absence of Ca2+ (∼20%) but a major decrease in the presence of Ca2+ (∼75%). Surprisingly, synaptosomes lacking both CL1 and Neurexin 1α displayed a relatively smaller decrease in α-latrotoxin-stimulated glutamate release than synaptosomes lacking only CL1 in the absence of Ca2+ (∼50versus ∼75%), but the same decrease in the presence of Ca2+ (∼75%). Our data suggest the following two major conclusions. 1) CL1 and Neurexin 1α together account for the majority (75%) of α-latrotoxin receptors in brain, with the remaining receptor activity possibly due to other CL and Neurexin isoforms, and 2) the two receptors act additively in binding α-latrotoxin but not in triggering release. Together these data suggest that the two receptors act autonomously in binding of α-latrotoxin but cooperatively in transducing the stimulation of neurotransmitter release by α-latrotoxin.