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Isoform- and ligand-specific modulation of the adhesion GPCR ADGRL3/Latrophilin3 by a synthetic binder. Nat Commun 2023; 14:635. [PMID: 36746957 PMCID: PMC9902482 DOI: 10.1038/s41467-023-36312-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 01/24/2023] [Indexed: 02/08/2023] Open
Abstract
Adhesion G protein-coupled receptors (aGPCRs) are cell-surface proteins with large extracellular regions that bind to multiple ligands to regulate key biological functions including neurodevelopment and organogenesis. Modulating a single function of a specific aGPCR isoform while affecting no other function and no other receptor is not trivial. Here, we engineered an antibody, termed LK30, that binds to the extracellular region of the aGPCR ADGRL3, and specifically acts as an agonist for ADGRL3 but not for its isoform, ADGRL1. The LK30/ADGRL3 complex structure revealed that the LK30 binding site on ADGRL3 overlaps with the binding site for an ADGRL3 ligand - teneurin. In cellular-adhesion assays, LK30 specifically broke the trans-cellular interaction of ADGRL3 with teneurin, but not with another ADGRL3 ligand - FLRT3. Our work provides proof of concept for the modulation of isoform- and ligand-specific aGPCR functions using unique tools, and thus establishes a foundation for the development of fine-tuned aGPCR-targeted therapeutics.
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2
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Chen M, Blum D, Engelhard L, Raunser S, Wagner R, Gatsogiannis C. Molecular architecture of black widow spider neurotoxins. Nat Commun 2021; 12:6956. [PMID: 34845192 PMCID: PMC8630228 DOI: 10.1038/s41467-021-26562-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 10/11/2021] [Indexed: 12/14/2022] Open
Abstract
Latrotoxins (LaTXs) are presynaptic pore-forming neurotoxins found in the venom of Latrodectus spiders. The venom contains a toxic cocktail of seven LaTXs, with one of them targeting vertebrates (α-latrotoxin (α-LTX)), five specialized on insects (α, β, γ, δ, ε- latroinsectotoxins (LITs), and one on crustaceans (α-latrocrustatoxin (α-LCT)). LaTXs bind to specific receptors on the surface of neuronal cells, inducing the release of neurotransmitters either by directly stimulating exocytosis or by forming Ca2+-conductive tetrameric pores in the membrane. Despite extensive studies in the past decades, a high-resolution structure of a LaTX is not yet available and the precise mechanism of LaTX action remains unclear. Here, we report cryoEM structures of the α-LCT monomer and the δ-LIT dimer. The structures reveal that LaTXs are organized in four domains. A C-terminal domain of ankyrin-like repeats shields a central membrane insertion domain of six parallel α-helices. Both domains are flexibly linked via an N-terminal α-helical domain and a small β-sheet domain. A comparison between the structures suggests that oligomerization involves major conformational changes in LaTXs with longer C-terminal domains. Based on our data we propose a cyclic mechanism of oligomerization, taking place prior membrane insertion. Both recombinant α-LCT and δ-LIT form channels in artificial membrane bilayers, that are stabilized by Ca2+ ions and allow calcium flux at negative membrane potentials. Our comparative analysis between α-LCT and δ-LIT provides first crucial insights towards understanding the molecular mechanism of the LaTX family. The venom of Latrodectus spiders contains seven Latrotoxins (LaTXs), among them α-latrocrustatoxin (LCT) and δ- latroinsectotoxins δ-LIT. LaTXs bind to specific receptors on the surface of neuronal cells and target the molecular exocytosis machinery. Here, the authors present the cryo-EM structure of the α-LCT monomer and the δ-LIT dimer, which reveal that LaTXs are organized in four domains and they discuss the potential oligomerisation mechanism that takes place before LaTXs membrane insertion. Both recombinant α-LCT and δ-LIT form channels in artificial membrane bilayers, that are stabilized by Ca2+ ions.
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Affiliation(s)
- Minghao Chen
- Institute for Medical Physics and Biophysics and Center for Soft Nanoscience, Westfälische Wilhelms Universität Münster, 48149, Münster, Germany.,Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227, Dortmund, Germany
| | - Daniel Blum
- MOLIFE Research Center, Jacobs University Bremen, 28759, Bremen, Germany
| | - Lena Engelhard
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227, Dortmund, Germany
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227, Dortmund, Germany
| | - Richard Wagner
- MOLIFE Research Center, Jacobs University Bremen, 28759, Bremen, Germany
| | - Christos Gatsogiannis
- Institute for Medical Physics and Biophysics and Center for Soft Nanoscience, Westfälische Wilhelms Universität Münster, 48149, Münster, Germany. .,Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227, Dortmund, Germany.
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3
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Li J, Xie Y, Cornelius S, Jiang X, Sando R, Kordon SP, Pan M, Leon K, Südhof TC, Zhao M, Araç D. Alternative splicing controls teneurin-latrophilin interaction and synapse specificity by a shape-shifting mechanism. Nat Commun 2020; 11:2140. [PMID: 32358586 PMCID: PMC7195488 DOI: 10.1038/s41467-020-16029-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 04/06/2020] [Indexed: 02/07/2023] Open
Abstract
The trans-synaptic interaction of the cell-adhesion molecules teneurins (TENs) with latrophilins (LPHNs/ADGRLs) promotes excitatory synapse formation when LPHNs simultaneously interact with FLRTs. Insertion of a short alternatively-spliced region within TENs abolishes the TEN-LPHN interaction and switches TEN function to specify inhibitory synapses. How alternative-splicing regulates TEN-LPHN interaction remains unclear. Here, we report the 2.9 Å resolution cryo-EM structure of the TEN2-LPHN3 complex, and describe the trimeric TEN2-LPHN3-FLRT3 complex. The structure reveals that the N-terminal lectin domain of LPHN3 binds to the TEN2 barrel at a site far away from the alternatively spliced region. Alternative-splicing regulates the TEN2-LPHN3 interaction by hindering access to the LPHN-binding surface rather than altering it. Strikingly, mutagenesis of the LPHN-binding surface of TEN2 abolishes the LPHN3 interaction and impairs excitatory but not inhibitory synapse formation. These results suggest that a multi-level coincident binding mechanism mediated by a cryptic adhesion complex between TENs and LPHNs regulates synapse specificity. The trans-synaptic interaction of the cell-adhesion molecules teneurins (TENs) with latrophilins (LPHNs) promotes excitatory synapse formation. Here authors report the high resolution cryo-EM structure of the TEN2-LPHN3 complex, describe the trimeric TEN2-LPHN3-FLRT3 complex and show how alternative-splicing regulates the TEN2-LPHN3 interaction.
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Affiliation(s)
- Jingxian Li
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.,Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, 60637, USA
| | - Yuan Xie
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA
| | - Shaleeka Cornelius
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, 94305, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Xian Jiang
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, 94305, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Richard Sando
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, 94305, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Szymon P Kordon
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.,Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, 60637, USA
| | - Man Pan
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA
| | - Katherine Leon
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.,Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, 60637, USA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, 94305, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Minglei Zhao
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.
| | - Demet Araç
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA. .,Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, 60637, USA.
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4
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Araç D, Li J. Teneurins and latrophilins: two giants meet at the synapse. Curr Opin Struct Biol 2019; 54:141-151. [PMID: 30952063 DOI: 10.1016/j.sbi.2019.01.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/10/2019] [Accepted: 01/22/2019] [Indexed: 12/19/2022]
Abstract
Teneurins and latrophilins are both conserved families of cell adhesion proteins that mediate cellular communication and play critical roles in embryonic and neural development. However, their mechanisms of action remain poorly understood. In the past several years, three-dimensional structures of teneurins and latrophilins have been reported at atomic resolutions and revealed distinct protein folds and unique structural features. In this review, we discuss these structures which, together with structure-guided biochemical and functional analyses, provide hints for the mechanisms of trans-cellular communication at the synapse and other cell-cell contact sites.
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Affiliation(s)
- Demet Araç
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, IL 60637, USA.
| | - Jingxian Li
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, IL 60637, USA
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5
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Nazarko O, Kibrom A, Winkler J, Leon K, Stoveken H, Salzman G, Merdas K, Lu Y, Narkhede P, Tall G, Prömel S, Araç D. A Comprehensive Mutagenesis Screen of the Adhesion GPCR Latrophilin-1/ADGRL1. iScience 2018; 3:264-278. [PMID: 30428326 PMCID: PMC6137404 DOI: 10.1016/j.isci.2018.04.019] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 04/16/2018] [Accepted: 04/24/2018] [Indexed: 11/15/2022] Open
Abstract
Adhesion G-protein-coupled receptors (aGPCRs) play critical roles in diverse cellular processes in neurobiology, development, immunity, and numerous diseases. The lack of molecular understanding of their activation mechanisms, especially with regard to the transmembrane domains, hampers further studies to facilitate aGPCR-targeted drug development. Latrophilin-1/ADGRL1 is a model aGPCR that regulates synapse formation and embryogenesis, and its mutations are associated with cancer and attention-deficit/hyperactivity disorder. Here, we established functional assays to monitor latrophilin-1 function and showed the activation of latrophilin-1 by its endogenous agonist peptide. Via a comprehensive mutagenesis screen, we identified transmembrane domain residues essential for latrophilin-1 basal activity and for agonist peptide response. Strikingly, a cancer-associated mutation exhibited increased basal activity and failed to rescue the embryonic developmental phenotype in transgenic worms. These results provide a mechanistic foundation for future aGPCR-targeted drug design.
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Affiliation(s)
- Olha Nazarko
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Amanuel Kibrom
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Jana Winkler
- Rudolf Schönheimer Institute of Biochemistry, Molecular Biochemistry, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany
| | - Katherine Leon
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Hannah Stoveken
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | - Gabriel Salzman
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Katarzyna Merdas
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Yue Lu
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Pradnya Narkhede
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Gregory Tall
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | - Simone Prömel
- Rudolf Schönheimer Institute of Biochemistry, Molecular Biochemistry, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany
| | - Demet Araç
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA.
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6
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Anderson GR, Maxeiner S, Sando R, Tsetsenis T, Malenka RC, Südhof TC. Postsynaptic adhesion GPCR latrophilin-2 mediates target recognition in entorhinal-hippocampal synapse assembly. J Cell Biol 2017; 216:3831-3846. [PMID: 28972101 PMCID: PMC5674891 DOI: 10.1083/jcb.201703042] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 07/24/2017] [Accepted: 08/17/2017] [Indexed: 12/15/2022] Open
Abstract
Synapse assembly likely requires postsynaptic target recognition by incoming presynaptic afferents. Using newly generated conditional knock-in and knockout mice, we show in this study that latrophilin-2 (Lphn2), a cell-adhesion G protein-coupled receptor and presumptive α-latrotoxin receptor, controls the numbers of a specific subset of synapses in CA1-region hippocampal neurons, suggesting that Lphn2 acts as a synaptic target-recognition molecule. In cultured hippocampal neurons, Lphn2 maintained synapse numbers via a postsynaptic instead of a presynaptic mechanism, which was surprising given its presumptive role as an α-latrotoxin receptor. In CA1-region neurons in vivo, Lphn2 was specifically targeted to dendritic spines in the stratum lacunosum-moleculare, which form synapses with presynaptic entorhinal cortex afferents. In this study, postsynaptic deletion of Lphn2 selectively decreased spine numbers and impaired synaptic inputs from entorhinal but not Schaffer-collateral afferents. Behaviorally, loss of Lphn2 from the CA1 region increased spatial memory retention but decreased learning of sequential spatial memory tasks. Thus, Lphn2 appears to control synapse numbers in the entorhinal cortex/CA1 region circuit by acting as a domain-specific postsynaptic target-recognition molecule.
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MESH Headings
- Animals
- Behavior, Animal
- CA1 Region, Hippocampal/metabolism
- CA1 Region, Hippocampal/pathology
- CA1 Region, Hippocampal/physiopathology
- Cells, Cultured
- Dendritic Spines/metabolism
- Dendritic Spines/pathology
- Entorhinal Cortex/metabolism
- Entorhinal Cortex/pathology
- Entorhinal Cortex/physiopathology
- Fear
- Genotype
- Maze Learning
- Memory
- Mice, Mutant Strains
- Motor Activity
- Neurons/metabolism
- Neurons/pathology
- Phenotype
- Presynaptic Terminals/metabolism
- Presynaptic Terminals/pathology
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Peptide/genetics
- Receptors, Peptide/metabolism
- Rotarod Performance Test
- Smell
- Synaptic Membranes/metabolism
- Synaptic Membranes/pathology
- Synaptic Potentials
- Time Factors
- Transfection
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Affiliation(s)
- Garret R Anderson
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA
- Department of Psychiatry and Behavioral Science, Nancy Pritzker Laboratory, Stanford University Medical School, Stanford, CA
| | - Stephan Maxeiner
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA
| | - Richard Sando
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA
| | - Theodoros Tsetsenis
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA
| | - Robert C Malenka
- Department of Psychiatry and Behavioral Science, Nancy Pritzker Laboratory, Stanford University Medical School, Stanford, CA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University Medical School, Stanford, CA
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7
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Stoveken HM, Bahr LL, Anders MW, Wojtovich AP, Smrcka AV, Tall GG. Dihydromunduletone Is a Small-Molecule Selective Adhesion G Protein-Coupled Receptor Antagonist. Mol Pharmacol 2016; 90:214-24. [PMID: 27338081 DOI: 10.1124/mol.116.104828] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 06/10/2016] [Indexed: 12/21/2022] Open
Abstract
Adhesion G protein-coupled receptors (aGPCRs) have emerging roles in development and tissue maintenance and is the most prevalent GPCR subclass mutated in human cancers, but to date, no drugs have been developed to target them in any disease. aGPCR extracellular domains contain a conserved subdomain that mediates self-cleavage proximal to the start of the 7-transmembrane domain (7TM). The two receptor protomers, extracellular domain and amino terminal fragment (NTF), and the 7TM or C-terminal fragment remain noncovalently bound at the plasma membrane in a low-activity state. We recently demonstrated that NTF dissociation liberates the 7TM N-terminal stalk, which acts as a tethered-peptide agonist permitting receptor-dependent heterotrimeric G protein activation. In many cases, natural aGPCR ligands are extracellular matrix proteins that dissociate the NTF to reveal the tethered agonist. Given the perceived difficulty in modifying extracellular matrix proteins to create aGPCR probes, we developed a serum response element (SRE)-luciferase-based screening approach to identify GPR56/ADGRG1 small-molecule inhibitors. A 2000-compound library comprising known drugs and natural products was screened for GPR56-dependent SRE activation inhibitors that did not inhibit constitutively active Gα13-dependent SRE activation. Dihydromunduletone (DHM), a rotenoid derivative, was validated using cell-free aGPCR/heterotrimeric G protein guanosine 5'-3-O-(thio)triphosphate binding reconstitution assays. DHM inhibited GPR56 and GPR114/ADGRG5, which have similar tethered agonists, but not the aGPCR GPR110/ADGRF1, M3 muscarinic acetylcholine, or β2 adrenergic GPCRs. DHM inhibited tethered peptide agonist-stimulated and synthetic peptide agonist-stimulated GPR56 but did not inhibit basal activity, demonstrating that it antagonizes the peptide agonist. DHM is a novel aGPCR antagonist and potentially useful chemical probe that may be developed as a future aGPCR therapeutic.
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Affiliation(s)
- Hannah M Stoveken
- Department of Pharmacology and Physiology (H.M.S., L.L.B., M.W.A., A.P.W., A.V.S.), and Department of Anesthesiology (L.L.B., A.P.W.), University of Rochester Medical Center, Rochester, New York; and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (G.G.T.)
| | - Laura L Bahr
- Department of Pharmacology and Physiology (H.M.S., L.L.B., M.W.A., A.P.W., A.V.S.), and Department of Anesthesiology (L.L.B., A.P.W.), University of Rochester Medical Center, Rochester, New York; and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (G.G.T.)
| | - M W Anders
- Department of Pharmacology and Physiology (H.M.S., L.L.B., M.W.A., A.P.W., A.V.S.), and Department of Anesthesiology (L.L.B., A.P.W.), University of Rochester Medical Center, Rochester, New York; and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (G.G.T.)
| | - Andrew P Wojtovich
- Department of Pharmacology and Physiology (H.M.S., L.L.B., M.W.A., A.P.W., A.V.S.), and Department of Anesthesiology (L.L.B., A.P.W.), University of Rochester Medical Center, Rochester, New York; and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (G.G.T.)
| | - Alan V Smrcka
- Department of Pharmacology and Physiology (H.M.S., L.L.B., M.W.A., A.P.W., A.V.S.), and Department of Anesthesiology (L.L.B., A.P.W.), University of Rochester Medical Center, Rochester, New York; and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (G.G.T.)
| | - Gregory G Tall
- Department of Pharmacology and Physiology (H.M.S., L.L.B., M.W.A., A.P.W., A.V.S.), and Department of Anesthesiology (L.L.B., A.P.W.), University of Rochester Medical Center, Rochester, New York; and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (G.G.T.)
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8
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Lu YC, Nazarko OV, Sando R, Salzman GS, Li NS, Südhof TC, Araç D. Structural Basis of Latrophilin-FLRT-UNC5 Interaction in Cell Adhesion. Structure 2015; 23:1678-1691. [PMID: 26235030 DOI: 10.1016/j.str.2015.06.024] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 06/18/2015] [Accepted: 06/21/2015] [Indexed: 11/24/2022]
Abstract
Fibronectin leucine-rich repeat transmembrane proteins (FLRTs) are cell-adhesion molecules with emerging functions in cortical development and synapse formation. Their extracellular regions interact with latrophilins (LPHNs) to mediate synapse development, and with Uncoordinated-5 (UNC5)/netrin receptors to control the migration of neurons in the developing cortex. Here, we present the crystal structures of FLRT3 in isolation and in complex with LPHN3. The LPHN3/FLRT3 structure reveals that LPHN3 binds to FLRT3 at a site distinct from UNC5. Structure-based mutations specifically disrupt LPHN3/FLRT3 binding, but do not disturb their interactions with other proteins or their cell-membrane localization. Thus, they can be used as molecular tools to dissect the functions of FLRTs and LPHNs in vivo. Our results suggest that UNC5 and LPHN3 can simultaneously bind to FLRT3, forming a trimeric complex, and that FLRT3 may form transsynaptic complexes with both LPHN3 and UNC5. These findings provide molecular insights for understanding the role of cell-adhesion proteins in synapse function.
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Affiliation(s)
- Yue C Lu
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, GCIS W219, Chicago, IL 60637, USA
| | - Olha V Nazarko
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, GCIS W219, Chicago, IL 60637, USA
| | - Richard Sando
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Gabriel S Salzman
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, GCIS W219, Chicago, IL 60637, USA
| | - Nan-Sheng Li
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, GCIS W219, Chicago, IL 60637, USA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Demet Araç
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, GCIS W219, Chicago, IL 60637, USA.
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9
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Shen H, Chen Z, Wang Y, Gao A, Li H, Cui Y, Zhang L, Xu X, Wang Z, Chen G. Role of Neurexin-1β and Neuroligin-1 in Cognitive Dysfunction After Subarachnoid Hemorrhage in Rats. Stroke 2015. [PMID: 26219651 PMCID: PMC4542569 DOI: 10.1161/strokeaha.115.009729] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Supplemental Digital Content is available in the text. Neurexin-1β and neuroligin-1 play an important role in the formation, maintenance, and regulation of synaptic structures. This study is to estimate the potential role of neurexin-1β and neuroligin-1 in subarachnoid hemorrhage (SAH)-induced cognitive dysfunction.
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Affiliation(s)
- Haitao Shen
- From the Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China (H.S., Z.C., Y.W., A.G., H.L., Y.C., L.Z., X.X., Z.W., G.C.); and Department of Neurosurgery, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Province Key Laboratory of Brain Function and Brain Disease, Hefei, Anhui, China (Y.W.)
| | - Zhouqing Chen
- From the Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China (H.S., Z.C., Y.W., A.G., H.L., Y.C., L.Z., X.X., Z.W., G.C.); and Department of Neurosurgery, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Province Key Laboratory of Brain Function and Brain Disease, Hefei, Anhui, China (Y.W.)
| | - Yang Wang
- From the Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China (H.S., Z.C., Y.W., A.G., H.L., Y.C., L.Z., X.X., Z.W., G.C.); and Department of Neurosurgery, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Province Key Laboratory of Brain Function and Brain Disease, Hefei, Anhui, China (Y.W.)
| | - Anju Gao
- From the Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China (H.S., Z.C., Y.W., A.G., H.L., Y.C., L.Z., X.X., Z.W., G.C.); and Department of Neurosurgery, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Province Key Laboratory of Brain Function and Brain Disease, Hefei, Anhui, China (Y.W.)
| | - Haiying Li
- From the Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China (H.S., Z.C., Y.W., A.G., H.L., Y.C., L.Z., X.X., Z.W., G.C.); and Department of Neurosurgery, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Province Key Laboratory of Brain Function and Brain Disease, Hefei, Anhui, China (Y.W.)
| | - Yonghua Cui
- From the Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China (H.S., Z.C., Y.W., A.G., H.L., Y.C., L.Z., X.X., Z.W., G.C.); and Department of Neurosurgery, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Province Key Laboratory of Brain Function and Brain Disease, Hefei, Anhui, China (Y.W.)
| | - Li Zhang
- From the Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China (H.S., Z.C., Y.W., A.G., H.L., Y.C., L.Z., X.X., Z.W., G.C.); and Department of Neurosurgery, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Province Key Laboratory of Brain Function and Brain Disease, Hefei, Anhui, China (Y.W.)
| | - Xiang Xu
- From the Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China (H.S., Z.C., Y.W., A.G., H.L., Y.C., L.Z., X.X., Z.W., G.C.); and Department of Neurosurgery, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Province Key Laboratory of Brain Function and Brain Disease, Hefei, Anhui, China (Y.W.)
| | - Zhong Wang
- From the Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China (H.S., Z.C., Y.W., A.G., H.L., Y.C., L.Z., X.X., Z.W., G.C.); and Department of Neurosurgery, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Province Key Laboratory of Brain Function and Brain Disease, Hefei, Anhui, China (Y.W.)
| | - Gang Chen
- From the Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China (H.S., Z.C., Y.W., A.G., H.L., Y.C., L.Z., X.X., Z.W., G.C.); and Department of Neurosurgery, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Province Key Laboratory of Brain Function and Brain Disease, Hefei, Anhui, China (Y.W.).
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Xiang YY, Dong H, Yang BB, Macdonald JF, Lu WY. Interaction of acetylcholinesterase with neurexin-1β regulates glutamatergic synaptic stability in hippocampal neurons. Mol Brain 2014; 7:15. [PMID: 24594013 PMCID: PMC3973991 DOI: 10.1186/1756-6606-7-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2013] [Accepted: 02/27/2014] [Indexed: 02/11/2023] Open
Abstract
Background Excess expression of acetylcholinesterase (AChE) in the cortex and hippocampus causes a decrease in the number of glutamatergic synapses and alters the expression of neurexin and neuroligin, trans-synaptic proteins that control synaptic stability. The molecular sequence and three-dimensional structure of AChE are homologous to the corresponding aspects of the ectodomain of neuroligin. This study investigated whether excess AChE interacts physically with neurexin to destabilize glutamatergic synapses. Results The results showed that AChE clusters colocalized with neurexin assemblies in the neurites of hippocampal neurons and that AChE co-immunoprecipitated with neurexin from the lysate of these neurons. Moreover, when expressed in human embryonic kidney 293 cells, N-glycosylated AChE co-immunoprecipitated with non-O–glycosylated neurexin-1β, with N-glycosylation of the AChE being required for this co-precipitation to occur. Increasing extracellular AChE decreased the association of neurexin with neuroligin and inhibited neuroligin-induced synaptogenesis. The number and activity of excitatory synapses in cultured hippocampal neurons were reduced by extracellular catalytically inactive AChE. Conclusions Excessive glycosylated AChE could competitively disrupt a subset of the neurexin–neuroligin junctions consequently impairing the integrity of glutamatergic synapses. This might serve a molecular mechanism of excessive AChE induced neurodegeneration.
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Affiliation(s)
| | | | | | | | - Wei-Yang Lu
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada.
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11
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Sindi IA, Tannenberg RK, Dodd PR. Role for the neurexin-neuroligin complex in Alzheimer's disease. Neurobiol Aging 2013; 35:746-56. [PMID: 24211009 DOI: 10.1016/j.neurobiolaging.2013.09.032] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 09/20/2013] [Accepted: 09/22/2013] [Indexed: 11/29/2022]
Abstract
Synaptic damage is a critical hallmark of Alzheimer's disease, and the best correlate with cognitive impairment ante mortem. Synapses, the loci of communication between neurons, are characterized by signature protein combinations arrayed at tightly apposed pre- and post-synaptic sites. The most widely studied trans-synaptic junctional complexes, which direct synaptogenesis and foster the maintenance and stability of the mature terminal, are conjunctions of presynaptic neurexins and postsynaptic neuroligins. Fluctuations in the levels of neuroligins and neurexins can sway the balance between excitatory and inhibitory neurotransmission in the brain, and could lead to damage of synapses and dendrites. This review summarizes current understanding of the roles of neurexins and neuroligins proteolytic processing in synaptic plasticity in the human brain, and outlines their possible roles in β-amyloid metabolism and function, which are central pathogenic events in Alzheimer's disease progression.
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Affiliation(s)
- Ikhlas A Sindi
- Centre for Psychiatry and Clinical Neuroscience, School of Medicine, The University of Queensland, Brisbane, Australia
| | - Rudolph K Tannenberg
- Centre for Psychiatry and Clinical Neuroscience, School of Medicine, The University of Queensland, Brisbane, Australia; School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Peter R Dodd
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia.
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12
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Presynaptic neurexin-3 alternative splicing trans-synaptically controls postsynaptic AMPA receptor trafficking. Cell 2013; 154:75-88. [PMID: 23827676 DOI: 10.1016/j.cell.2013.05.060] [Citation(s) in RCA: 214] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Revised: 04/26/2013] [Accepted: 05/29/2013] [Indexed: 12/28/2022]
Abstract
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.
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13
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Zhang Q, Wang J, Li A, Liu H, Zhang W, Cui X, Wang K. Expression of neurexin and neuroligin in the enteric nervous system and their down-regulated expression levels in Hirschsprung disease. Mol Biol Rep 2012; 40:2969-75. [PMID: 23264101 DOI: 10.1007/s11033-012-2368-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 12/17/2012] [Indexed: 01/15/2023]
Abstract
To investigate the expression levels of neurexins and neuroligins in the enteric nervous system (ENS) in Hirschsprung Disease (HSCR). Longitudinal muscles with adherent mesenteric plexus were obtained by dissection of the fresh gut wall of mice, guinea pigs, and humans. Double labeling of neurexin I and Hu (a neuron marker), neuroligin 1 and Hu, neurexin I and synaptophysin (a presynaptic marker), and neuroligin 1 and PSD95 (a postsynaptic marker) was performed by immunofluorescence staining. Images were merged to determine the relative localizations of the proteins. Expression levels of neurexin and neuroligin in different segments of the ENS in HSCR were investigated by immunohistochemistry. Neurexin and neuroligin were detected in the mesenteric plexus of mice, guinea pigs, and humans with HSCR. Neurexin was located in the presynapse, whereas neuroligin was located in the postsynapse. Expression levels of neurexin and neuroligin were significant in the ganglionic colonic segment of HSCR, moderate in the transitional segment, and negative in the aganglionic colonic segment. The expressions of neurexin and neuroligin in the transitional segments were significantly down-regulated compared with the levels in the normal segments (P < 0.05). Expression levels of neurexin and neuroligin in ENS are significantly down-regulated in HSCR, which may be involved in the pathogenesis of HSCR.
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Affiliation(s)
- Qiangye Zhang
- Department of Pediatric Surgery, Qilu Hospital, Shandong University, 107 Wenhuaxi Road, Jinan 250012, Shandong, China
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14
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Kasai H, Takahashi N, Tokumaru H. Distinct Initial SNARE Configurations Underlying the Diversity of Exocytosis. Physiol Rev 2012; 92:1915-64. [DOI: 10.1152/physrev.00007.2012] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The dynamics of exocytosis are diverse and have been optimized for the functions of synapses and a wide variety of cell types. For example, the kinetics of exocytosis varies by more than five orders of magnitude between ultrafast exocytosis in synaptic vesicles and slow exocytosis in large dense-core vesicles. However, in all cases, exocytosis is mediated by the same fundamental mechanism, i.e., the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. It is often assumed that vesicles need to be docked at the plasma membrane and SNARE proteins must be preassembled before exocytosis is triggered. However, this model cannot account for the dynamics of exocytosis recently reported in synapses and other cells. For example, vesicles undergo exocytosis without prestimulus docking during tonic exocytosis of synaptic vesicles in the active zone. In addition, epithelial and hematopoietic cells utilize cAMP and kinases to trigger slow exocytosis of nondocked vesicles. In this review, we summarize the manner in which the diversity of exocytosis reflects the initial configurations of SNARE assembly, including trans-SNARE, binary-SNARE, unitary-SNARE, and cis-SNARE configurations. The initial SNARE configurations depend on the particular SNARE subtype (syntaxin, SNAP25, or VAMP), priming proteins (Munc18, Munc13, CAPS, complexin, or snapin), triggering proteins (synaptotagmins, Doc2, and various protein kinases), and the submembraneous cytomatrix, and they are the key to determining the kinetics of subsequent exocytosis. These distinct initial configurations will help us clarify the common SNARE assembly processes underlying exocytosis and membrane trafficking in eukaryotic cells.
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Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Hiroshi Tokumaru
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
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15
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Araç D, Boucard AA, Bolliger MF, Nguyen J, Soltis SM, Südhof TC, Brunger AT. A novel evolutionarily conserved domain of cell-adhesion GPCRs mediates autoproteolysis. EMBO J 2012; 31:1364-78. [PMID: 22333914 PMCID: PMC3321182 DOI: 10.1038/emboj.2012.26] [Citation(s) in RCA: 326] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 01/16/2012] [Indexed: 12/02/2022] Open
Abstract
Crystallographic structures encompassing GPCR autoproteolytic sequences (GPS) delineate a novel conserved structural domain called GAIN, which is found in cell-adhesion GPCRs, polycystic kidney disease proteins conserved throughout evolution. The G protein-coupled receptor (GPCR) Proteolysis Site (GPS) of cell-adhesion GPCRs and polycystic kidney disease (PKD) proteins constitutes a highly conserved autoproteolysis sequence, but its catalytic mechanism remains unknown. Here, we show that unexpectedly the ∼40-residue GPS motif represents an integral part of a much larger ∼320-residue domain that we termed GPCR-Autoproteolysis INducing (GAIN) domain. Crystal structures of GAIN domains from two distantly related cell-adhesion GPCRs revealed a conserved novel fold in which the GPS motif forms five β-strands that are tightly integrated into the overall GAIN domain. The GAIN domain is evolutionarily conserved from tetrahymena to mammals, is the only extracellular domain shared by all human cell-adhesion GPCRs and PKD proteins, and is the locus of multiple human disease mutations. Functionally, the GAIN domain is both necessary and sufficient for autoproteolysis, suggesting an autoproteolytic mechanism whereby the overall GAIN domain fine-tunes the chemical environment in the GPS to catalyse peptide bond hydrolysis. Thus, the GAIN domain embodies a unique, evolutionarily ancient and widespread autoproteolytic fold whose function is likely relevant for GPCR signalling and for multiple human diseases.
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Affiliation(s)
- Demet Araç
- Howard Hughes Medical Institute, Stanford, CA, USA.
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16
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Boucard AA, Ko J, Südhof TC. High affinity neurexin binding to cell adhesion G-protein-coupled receptor CIRL1/latrophilin-1 produces an intercellular adhesion complex. J Biol Chem 2012; 287:9399-413. [PMID: 22262843 PMCID: PMC3308797 DOI: 10.1074/jbc.m111.318659] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
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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Affiliation(s)
- Antony A Boucard
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305, USA.
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17
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Chen F, Venugopal V, Murray B, Rudenko G. The structure of neurexin 1α reveals features promoting a role as synaptic organizer. Structure 2011; 19:779-89. [PMID: 21620716 DOI: 10.1016/j.str.2011.03.012] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 03/07/2011] [Accepted: 03/25/2011] [Indexed: 10/18/2022]
Abstract
α-neurexins are essential synaptic adhesion molecules implicated in autism spectrum disorder and schizophrenia. The α-neurexin extracellular domain consists of six LNS domains interspersed by three EGF-like repeats and interacts with many different proteins in the synaptic cleft. To understand how α-neurexins might function as synaptic organizers, we solved the structure of the neurexin 1α extracellular domain (n1α) to 2.65 Å. The L-shaped molecule can be divided into a flexible repeat I (LNS1-EGF-A-LNS2), a rigid horseshoe-shaped repeat II (LNS3-EGF-B-LNS4) with structural similarity to so-called reelin repeats, and an extended repeat III (LNS5-EGF-B-LNS6) with controlled flexibility. A 2.95 Å structure of n1α carrying splice insert SS#3 in LNS4 reveals that SS#3 protrudes as a loop and does not alter the rigid arrangement of repeat II. The global architecture imposed by conserved structural features enables α-neurexins to recruit and organize proteins in distinct and variable ways, influenced by splicing, thereby promoting synaptic function.
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Affiliation(s)
- Fang Chen
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
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18
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Feng JF, Zhang KM, Jiang JY, Gao GY, Fu X, Liang YM. Effect of therapeutic mild hypothermia on the genomics of the hippocampus after moderate traumatic brain injury in rats. Neurosurgery 2011; 67:730-42. [PMID: 20651628 DOI: 10.1227/01.neu.0000378023.81727.6e] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Traumatic brain injury (TBI), a major cause of morbidity and mortality, is a serious public health concern. OBJECTIVE To evaluate the effect of mild hypothermia on gene expression in the hippocampus and to try to elucidate molecular mechanisms of hypothermic neuroprotection after TBI. METHODS Rats were subjected to mild hypothermia (group 1: n = 3, 33 degrees C, 3H) or normothermia (group 2: n = 3; 37 degrees C, 3H) after TBI. Six genome arrays were applied to detect the gene expression profiles of ipsilateral hippocampus. Functional clustering and gene ontology analysis were then carried out. Another 20 rats were randomly assigned to 4 groups (n = 5 per group): group 3, sham-normothermia; group 4, sham-hypothermia; group 5, TBI-normothermia; and group 6, TBI-hypothermia. Real-time fluorescent quantitative reverse-transcription polymerase chain reaction was used to detect specific selected genes. RESULTS We found that 133 transcripts in the hypothermia group were statistically different from those in the normothermia group, including 57 transcripts that were upregulated and 76 that were downregulated after TBI (P < .01). Most of these genes were involved in various pathophysiological processes, and some were critical to cell survival. Analysis showed that 9 gene ontology categories were significantly affected by hypothermia, including the most affected categories: synapse organization and biogenesis (upregulated) and regulation of inflammatory response (downregulated). The mRNA expression of Ank3, Cmbp, Nrxn3, Tgm2, and Fcgr3 was regulated by hypothermia, TBI, or a combination of TBI and hypothermia compared with the sham-normothermia group. Their mRNA expression was significantly regulated by hypothermia in TBI groups. CONCLUSION Posttraumatic mild hypothermia has a significant effect on the gene expression profiles of the hippocampus, especially those genes belonging to the 9 gene ontology categories. Differential expression of those genes may be involved in the most fundamental molecular mechanisms of cerebral protection by mild hypothermia after TBI.
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Affiliation(s)
- Jun-feng Feng
- Department of Neurosurgery, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
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19
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Hiramatsu H, Tadokoro S, Nakanishi M, Hirashima N. Latrotoxin-induced exocytosis in mast cells transfected with latrophilin. Toxicon 2010; 56:1372-80. [DOI: 10.1016/j.toxicon.2010.08.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 08/03/2010] [Accepted: 08/03/2010] [Indexed: 11/27/2022]
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20
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Abstract
Background Neurexin is a synaptic cell adhesion protein critical for synapse formation and function. Mutations in neurexin and neurexin-interacting proteins have been implicated in several neurological diseases. Previous studies have described Drosophila neurexin mutant phenotypes in third instar larvae and adults. However, the expression and function of Drosophila neurexin early in synapse development, when neurexin function is thought to be most important, has not been described. Methodology/Principal Findings We use a variety of techniques, including immunohistochemistry, electron microscopy, in situ hybridization, and electrophysiology, to characterize neurexin expression and phenotypes in embryonic Drosophila neuromuscular junctions (NMJs). Our results surprisingly suggest that neurexin in embryos is present both pre and postsynaptically. Presynaptic neurexin promotes presynaptic active zone formation and neurotransmitter release, but along with postsynaptic neurexin, also suppresses formation of ectopic glutamate receptor clusters. Interestingly, we find that loss of neurexin only affects receptors containing the subunit GluRIIA. Conclusions/Significance Our study extends previous results and provides important detail regarding the role of neurexin in Drosophila glutamate receptor abundance. The possibility that neurexin is present postsynaptically raises new hypotheses regarding neurexin function in synapses, and our results provide new insights into the role of neurexin in synapse development.
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21
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Neurexins physically and functionally interact with GABA(A) receptors. Neuron 2010; 66:403-16. [PMID: 20471353 DOI: 10.1016/j.neuron.2010.04.008] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/23/2010] [Indexed: 11/20/2022]
Abstract
Neurexins are presynaptic cell-adhesion molecules that form trans-synaptic complexes with postsynaptic neuroligins. When overexpressed in nonneuronal cells, neurexins induce formation of postsynaptic specializations in cocultured neurons, suggesting that neurexins are synaptogenic. However, we find that when overexpressed in neurons, neurexins do not increase synapse density, but instead selectively suppressed GABAergic synaptic transmission without decreasing GABAergic synapse numbers. This suppression was mediated by all subtypes of neurexins tested, in a cell-autonomous and neuroligin-independent manner. Strikingly, addition of recombinant neurexin to cultured neurons at submicromolar concentrations induced the same suppression of GABAergic synaptic transmission as neurexin overexpression. Moreover, experiments with native brain proteins and purified recombinant proteins revealed that neurexins directly and stoichiometrically bind to GABA(A) receptors, suggesting that they decrease GABAergic synaptic responses by interacting with GABA(A) receptors. Our findings suggest that besides their other well-documented interactions, presynaptic neurexins directly act on postsynaptic GABA(A) receptors, which may contribute to regulate the excitatory/inhibitory balance in brain.
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22
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Silva JP, Ushkaryov YA. The latrophilins, "split-personality" receptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 706:59-75. [PMID: 21618826 DOI: 10.1007/978-1-4419-7913-1_5] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Latrophilin, a neuronal "adhesion-G protein-coupled receptor", is the major brain receptor for alpha-latrotoxin, a black widow spidertoxin which stimulates strong neuronal exocytosis in vertebrates. Latrophilin has an unusual structure consisting of two fragments that are produced by the proteolytic cleavage of the parental molecule and that behave independently in the plasma membrane. On binding an agonist, the fragments reassociate and send an intracellular signal. This signal, transduced by a heterotrimeric G protein, causes release of calcium from intracellular stores and massive release of neurotransmitters. Latrophilin represents a phylogenetically conserved family of receptors, with orthologues found in all animals and up to three homologues present in most chordate species. From mammalian homologues, latrophilins 1 and 3 are expressed in neurons, while latrophilin 2 is ubiquitous. Latrophilin 1 may control synapse maturation and exocytosis, whereas latrophilin 2 may be involved in breast cancer. Latrophilins may play different roles during development and in adult animals: thus, LAT-1 determines cell fate in early embryogenesis in Caenorhabditis elegans and controls neurotransmitter release in adult nematodes. This diversity suggests that the functions of latrophilins may be determined by their interactions with respective ligands. The finding of the ligand of latrophilin 1, the large postsynaptic protein lasso, is the first step in the quest for the physiological functions of latrophilins.
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Abstract
For more than three decades, the venom of the black widow spider and its principal active components, latrotoxins, have been used to induce release of neurotransmitters and hormones and to study the mechanisms of exocytosis. Given the complex nature of alpha--latrotoxin (alpha-LTX) actions, this research has been continuously overshadowed by many enigmas, misconceptions and perpetual changes of the underlying hypotheses. Some of the toxin's mechanisms of action are still not completely understood. Despite all these difficulties, the extensive work of several generations of neurobiologists has brought about a great deal of fascinating insights into pre-synaptic processes and has led to the discovery of several novel proteins and synaptic systems. For example, alpha-LTX studies have contributed to the widespread acceptance of the vesicular theory of transmitter release. Pre-synaptic receptors for alpha-LTX--neurexins, latrophilins and protein tyrosine phosphatase sigma--and their endogenous ligands have now become centrepieces of their own areas of research, with a potential of uncovering new mechanisms of synapse formation and regulation that may have medical implications. However, any future success of alpha-LTX research will require a better understanding of this unusual natural tool and a more precise dissection of its multiple mechanisms.
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Affiliation(s)
- John-Paul Silva
- Division of Cell and Molecular Biology, Imperial College London, Exhibition Road, London, UK
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Alpha-latrotoxin stimulates a novel pathway of Ca2+-dependent synaptic exocytosis independent of the classical synaptic fusion machinery. J Neurosci 2009; 29:8639-48. [PMID: 19587270 DOI: 10.1523/jneurosci.0898-09.2009] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alpha-latrotoxin induces neurotransmitter release by stimulating synaptic vesicle exocytosis via two mechanisms: (1) A Ca(2+)-dependent mechanism with neurexins as receptors, in which alpha-latrotoxin acts like a Ca(2+) ionophore, and (2) a Ca(2+)-independent mechanism with CIRL/latrophilins as receptors, in which alpha-latrotoxin directly stimulates the transmitter release machinery. Here, we show that the Ca(2+)-independent release mechanism by alpha-latrotoxin requires the synaptic SNARE-proteins synaptobrevin/VAMP and SNAP-25, and, at least partly, the synaptic active-zone protein Munc13-1. In contrast, the Ca(2+)-dependent release mechanism induced by alpha-latrotoxin does not require any of these components of the classical synaptic release machinery. Nevertheless, this type of exocytotic neurotransmitter release appears to fully operate at synapses, and to stimulate exocytosis of the same synaptic vesicles that participate in physiological action potential-triggered release. Thus, synapses contain two parallel and independent pathways of Ca(2+)-triggered exocytosis, a classical, physiological pathway that operates at the active zone, and a novel reserve pathway that is recruited only when Ca(2+) floods the synaptic terminal.
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Abstract
The brain processes information by transmitting signals at synapses, which connect neurons into vast networks of communicating cells. In these networks, synapses not only transmit signals but also transform and refine them. Neurexins and neuroligins are synaptic cell-adhesion molecules that connect presynaptic and postsynaptic neurons at synapses, mediate signalling across the synapse, and shape the properties of neural networks by specifying synaptic functions. In humans, alterations in genes encoding neurexins or neuroligins have recently been implicated in autism and other cognitive diseases, linking synaptic cell adhesion to cognition and its disorders.
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Affiliation(s)
- Thomas C Südhof
- Neuroscience Institute, Department of Molecular and Cellular Physiology, Stanford University, 1050 Arastradero Road B249, Palo Alto, California 94304, USA.
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Shen KC, Kuczynska DA, Wu IJ, Murray BH, Sheckler LR, Rudenko G. Regulation of neurexin 1beta tertiary structure and ligand binding through alternative splicing. Structure 2008; 16:422-31. [PMID: 18334217 DOI: 10.1016/j.str.2008.01.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Revised: 01/13/2008] [Accepted: 01/22/2008] [Indexed: 10/22/2022]
Abstract
Neurexins and neuroligins play an essential role in synapse function, and their alterations are linked to autistic spectrum disorder. Interactions between neurexins and neuroligins regulate inhibitory and excitatory synaptogenesis in vitro through a "splice-insert signaling code." In particular, neurexin 1beta carrying an alternative splice insert at site SS#4 interacts with neuroligin 2 (found predominantly at inhibitory synapses) but much less so with other neuroligins (those carrying an insert at site B and prevalent at excitatory synapses). The structure of neurexin 1beta+SS#4 reveals dramatic rearrangements to the "hypervariable surface," the binding site for neuroligins. The splice insert protrudes as a long helix into space, triggers conversion of loop beta10-beta11 into a helix rearranging the binding site for neuroligins, and rearranges the Ca(2+)-binding site required for ligand binding, increasing its affinity. Our structures reveal the mechanism by which neurexin 1beta isoforms acquire neuroligin splice isoform selectivity.
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Affiliation(s)
- Kaiser C Shen
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
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Graciotti L, Minelli A, Minciacchi D, Procopio A, Fulgenzi G. GABAergic miniature spontaneous activity is increased in the CA1 hippocampal region of dystrophic mdx mice. Neuromuscul Disord 2008; 18:220-6. [DOI: 10.1016/j.nmd.2007.11.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2007] [Revised: 11/22/2007] [Accepted: 11/28/2007] [Indexed: 10/22/2022]
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Abstract
alpha-Latrotoxin (alpha-LTX) from black widow spider venom induces exhaustive release of neurotransmitters from vertebrate nerve terminals and endocrine cells. This 130-kDa protein has been employed for many years as a molecular tool to study exocytosis. However, its action is complex: in neurons, alpha-LTX induces massive secretion both in the presence of extracellular Ca(2+) (Ca(2+) (e)) and in its absence; in endocrine cells, it usually requires Ca(2+) (e). To use this toxin for further dissection of secretory mechanisms, one needs an in-depth understanding of its functions. One such function that explains some alpha-LTX effects is its ability to form cation-permeable channels in artificial lipid bilayers. The mechanism of alpha-LTX pore formation, revealed by cryo-electron microscopy, involves toxin assembly into homotetrameric complexes which harbor a central channel and can insert into lipid membranes. However, in biological membranes, alpha-LTX cannot exert its actions without binding to specific receptors of the plasma membrane. Three proteins with distinct structures have been found to bind alpha-LTX: neurexin Ialpha, latrophilin 1, and receptor-like protein tyrosine phosphatase sigma. Upon binding a receptor, alpha-LTX forms channels permeable to cations and small molecules; the toxin may also activate the receptor. To distinguish between the pore- and receptor-mediated effects, and to study structure-function relationships in the toxin, alpha-LTX mutants have been used.
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Affiliation(s)
- Yuri A Ushkaryov
- Division of Cell and Molecular Biology, Imperial College London, London, SW7 2AY, UK.
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Taniguchi H, Gollan L, Scholl FG, Mahadomrongkul V, Dobler E, Limthong N, Peck M, Aoki C, Scheiffele P. Silencing of neuroligin function by postsynaptic neurexins. J Neurosci 2007; 27:2815-24. [PMID: 17360903 PMCID: PMC2839889 DOI: 10.1523/jneurosci.0032-07.2007] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Revised: 02/02/2007] [Accepted: 02/02/2007] [Indexed: 12/24/2022] Open
Abstract
The formation of neuronal circuits during development involves a combination of synapse stabilization and elimination events. Synaptic adhesion molecules are thought to play an important role in synaptogenesis, and several trans-synaptic adhesion systems that promote the formation and maturation of synapses have been identified. The neuroligin-neurexin complex is a heterophilic adhesion system that promotes assembly and maturation of synapses through bidirectional signaling. In this protein complex, postsynaptic neuroligins are thought to interact trans-synaptically with presynaptic neurexins. However, the subcellular localization of neurexins has not been determined. Using immunoelectron microscopy, we found that endogenous neurexins and epitope-tagged neurexin-1beta are localized to axons and presynaptic terminals in vivo. Unexpectedly, neurexins are also abundant in the postsynaptic density. cis-expression of neurexin-1beta with neuroligin-1 inhibits trans-binding to recombinant neurexins, blocks the synaptogenic activity of neuroligin-1, and reduces the density of presynaptic terminals in cultured hippocampal neurons. Our results demonstrate that the function of neurexin proteins is more diverse than previously anticipated and suggest that postsynaptic cis-interactions might provide a novel mechanism for silencing the activity of a synaptic adhesion complex.
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Affiliation(s)
- Hiroki Taniguchi
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
| | - Leora Gollan
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
| | - Francisco G. Scholl
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
| | | | - Elizabeth Dobler
- Center for Neural Science, New York University, New York, New York 10003
| | - Nicolas Limthong
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
| | - Morgen Peck
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
| | - Chiye Aoki
- Center for Neural Science, New York University, New York, New York 10003
| | - Peter Scheiffele
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
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Rohou A, Nield J, Ushkaryov Y. Insecticidal toxins from black widow spider venom. Toxicon 2006; 49:531-49. [PMID: 17210168 PMCID: PMC2517654 DOI: 10.1016/j.toxicon.2006.11.021] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Accepted: 11/17/2006] [Indexed: 11/27/2022]
Abstract
The biological effects of Latrodectus spider venom are similar in animals from different phyla, but these symptoms are caused by distinct phylum-specific neurotoxins (collectively called latrotoxins) with molecular masses ranging from 110 to 140 kDa. To date, the venom has been found to contain five insecticidal toxins, termed α, β, γ, δ and ε-latroinsectotoxins (LITs). There is also a vertebrate-specific neurotoxin, α-latrotoxin (α-LTX), and one toxin affecting crustaceans, α-latrocrustatoxin (α-LCT). These toxins stimulate massive release of neurotransmitters from nerve terminals and act (1) by binding to specific receptors, some of which mediate an exocytotic signal, and (2) by inserting themselves into the membrane and forming ion-permeable pores. Specific receptors for LITs have yet to be identified, but all three classes of vertebrate receptors known to bind α-LTX are also present in insects. All LTXs whose structures have been elucidated (α-LIT, δ-LIT, α-LTX and α-LCT) are highly homologous and have a similar domain architecture, which consists of a unique N-terminal sequence and a large domain composed of 13–22 ankyrin repeats. Three-dimensional (3D) structure analysis, so far done for α-LTX only, has revealed its dimeric nature and an ability to form symmetrical tetramers, a feature probably common to all LTXs. Only tetramers have been observed to insert into membranes and form pores. A preliminary 3D reconstruction of a δ-LIT monomer demonstrates the spatial similarity of this toxin to the monomer of α-LTX.
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Affiliation(s)
| | | | - Y.A. Ushkaryov
- Corresponding author. Tel.: +44 20 7594 5237; fax: +44 20 7594 5207.
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31
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Dudanova I, Sedej S, Ahmad M, Masius H, Sargsyan V, Zhang W, Riedel D, Angenstein F, Schild D, Rupnik M, Missler M. Important contribution of alpha-neurexins to Ca2+-triggered exocytosis of secretory granules. J Neurosci 2006; 26:10599-613. [PMID: 17035546 PMCID: PMC6674690 DOI: 10.1523/jneurosci.1913-06.2006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alpha-neurexins constitute a family of neuronal cell surface molecules that are essential for efficient neurotransmission, because mice lacking two or all three alpha-neurexin genes show a severe reduction of synaptic release. Although analyses of alpha-neurexin knock-outs and transgenic rescue animals suggested an involvement of voltage-dependent Ca2+ channels, it remained unclear whether alpha-neurexins have a general role in Ca2+-dependent exocytosis and how they may affect Ca2+ channels. Here we show by membrane capacitance measurements from melanotrophs in acute pituitary gland slices that release from endocrine cells is diminished by >50% in adult alpha-neurexin double knock-out and newborn triple knock-out mice. There is a reduction of the cell volume in mutant melanotrophs; however, no ultrastructural changes in size or intracellular distribution of the secretory granules were observed. Recordings of Ca2+ currents from melanotrophs, transfected human embryonic kidney cells, and brainstem neurons reveal that alpha-neurexins do not affect the activation or inactivation properties of Ca2+ channels directly but may be responsible for coupling them to release-ready vesicles and metabotropic receptors. Our data support a general and essential role for alpha-neurexins in Ca2+-triggered exocytosis that is similarly important for secretion from neurons and endocrine cells.
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Affiliation(s)
- Irina Dudanova
- Center for Physiology and Pathophysiology, Georg-August University, Göttingen D-37073, Germany
| | - Simon Sedej
- European Neuroscience Institute Göttingen, Göttingen D-37073, Germany
| | - Mohiuddin Ahmad
- Center for Physiology and Pathophysiology, Georg-August University, Göttingen D-37073, Germany
| | - Henriette Masius
- Center for Physiology and Pathophysiology, Georg-August University, Göttingen D-37073, Germany
| | - Vardanush Sargsyan
- Center for Physiology and Pathophysiology, Georg-August University, Göttingen D-37073, Germany
| | - Weiqi Zhang
- Center for Physiology and Pathophysiology, Georg-August University, Göttingen D-37073, Germany
| | - Dietmar Riedel
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen D-37077, Germany
| | | | - Detlev Schild
- Center for Physiology and Pathophysiology, Georg-August University, Göttingen D-37073, Germany
- German Research Foundation-Research Center of Molecular Physiology of Brain, Göttingen D-37073, Germany, and
| | - Marjan Rupnik
- European Neuroscience Institute Göttingen, Göttingen D-37073, Germany
| | - Markus Missler
- Center for Physiology and Pathophysiology, Georg-August University, Göttingen D-37073, Germany
- Institute of Anatomy, Westfälische Wilhelms-University, Münster D-48149, Germany
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32
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Rissone A, Monopoli M, Beltrame M, Bussolino F, Cotelli F, Arese M. Comparative genome analysis of the neurexin gene family in Danio rerio: insights into their functions and evolution. Mol Biol Evol 2006; 24:236-52. [PMID: 17041151 DOI: 10.1093/molbev/msl147] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Neurexins constitute a family of proteins originally identified as synaptic transmembrane receptors for a spider venom toxin. In mammals, the 3 known Neurexin genes present 2 alternative promoters that drive the synthesis of a long (alpha) and a short (beta) form and contain different sites of alternative splicing (AS) that can give rise to thousands of different transcripts. To date, very little is known about the significance of this variability, except for the modulation of binding to some of the Neurexin ligands. Although orthologs of Neurexins have been isolated in invertebrates, these genes have been studied mostly in mammals. With the aim of investigating their functions in lower vertebrates, we chose Danio rerio as a model because of its increasing importance in comparative biology. We have isolated 6 zebrafish homologous genes, which are highly conserved at the structural level and display a similar regulation of AS, despite about 450 Myr separating the human and zebrafish species. Our data indicate a strong selective pressure at the exonic level and on the intronic borders, in particular on the regulative intronic sequences that flank the exons subject to AS. Such a selective pressure could help conserve the regulation and consequently the function of these genes along the vertebrates evolutive tree. AS analysis during development shows that all genes are expressed and finely regulated since the earliest stages of development, but mark an increase after the 24-h stage that corresponds to the beginning of synaptogenesis. Moreover, we found that specific isoforms of a zebrafish Neurexin gene (nrxn1a) are expressed in the adult testis and in the earliest stages of development, before the beginning of zygotic transcription, indicating a potential delivery of paternal RNA to the embryo. Our analysis suggests the existence of possible new functions for Neurexins, serving as the basis for novel approaches to the functional studies of this complex neuronal protein family and more in general to the understanding of the AS mechanism in low vertebrates.
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Affiliation(s)
- Alberto Rissone
- Department of Oncological Sciences, University of Torino, Strada Provinciale 142, 10060 Candiolo, Torino, Italy
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Sheckler LR, Henry L, Sugita S, Südhof TC, Rudenko G. Crystal structure of the second LNS/LG domain from neurexin 1alpha: Ca2+ binding and the effects of alternative splicing. J Biol Chem 2006; 281:22896-905. [PMID: 16772286 PMCID: PMC2293330 DOI: 10.1074/jbc.m603464200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Neurexins mediate protein interactions at the synapse, playing an essential role in synaptic function. Extracellular domains of neurexins, and their fragments, bind a distinct profile of different proteins regulated by alternative splicing and Ca2+. The crystal structure of n1alpha_LNS#2 (the second LNS/LG domain of bovine neurexin 1alpha) reveals large structural differences compared with n1alpha_LNS#6 (or n1beta_LNS), the only other LNS/LG domain for which a structure has been determined. The differences overlap the so-called hyper-variable surface, the putative protein interaction surface that is reshaped as a result of alternative splicing. A Ca2+-binding site is revealed at the center of the hyper-variable surface next to splice insertion sites. Isothermal titration calorimetry indicates that the Ca2+-binding site in n1alpha_LNS#2 has low affinity (Kd approximately 400 microm). Ca2+ binding ceases to be measurable when an 8- or 15-residue splice insert is present at the splice site SS#2 indicating that alternative splicing can affect Ca2+-binding sites of neurexin LNS/LG domains. Our studies initiate a framework for the putative protein interaction sites of neurexin LNS/LG domains. This framework is essential to understand how incorporation of alternative splice inserts expands the information from a limited set of neurexin genes to produce a large array of synaptic adhesion molecules with potentially very different synaptic function.
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Affiliation(s)
- Lauren R. Sheckler
- Life Sciences Institute and Department of Pharmacology, The University of Michigan, Ann Arbor, Michigan 48109-2216
| | - Lisa Henry
- Department of Biochemistry, University of Texas Southwestern Medical Center, Howard Hughes Medical Institute, Dallas, Texas 75390-9111
| | - Shuzo Sugita
- Center for Basic Neuroscience, University of Texas Southwestern Medical Center, Howard Hughes Medical Institute, Dallas, Texas 75390-9111
| | - Thomas C. Südhof
- Center for Basic Neuroscience, University of Texas Southwestern Medical Center, Howard Hughes Medical Institute, Dallas, Texas 75390-9111
| | - Gabby Rudenko
- Life Sciences Institute and Department of Pharmacology, The University of Michigan, Ann Arbor, Michigan 48109-2216
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Piechotta K, Dudanova I, Missler M. The resilient synapse: insights from genetic interference of synaptic cell adhesion molecules. Cell Tissue Res 2006; 326:617-42. [PMID: 16855838 DOI: 10.1007/s00441-006-0267-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Accepted: 05/31/2006] [Indexed: 01/05/2023]
Abstract
Synaptic cell adhesion molecules (SCAMs) are mostly membrane-anchored molecules with extracellular domains that extend into the synaptic cleft. Prototypical SCAMs interact with homologous or heterologous molecules on the surface of adjacent cells, ensuring the precise apposition of pre- and postsynaptic elements. More recent definitions of SCAMs often include molecules involved in axon pathfinding, cell recognition and synaptic differentiation events, making SCAMs functionally and molecularly a highly diverse group. In this review, we summarize the proposed in vivo functions of a large variety of SCAMs. We mainly focus on results obtained from analyses of genetic model organisms, mostly mouse knockout mutants, lacking expression of the respective candidate genes. In contrast to the substantial effect yielded by some knockouts of molecules involved in synaptic vesicle release, no SCAM mutant has been reported thus far that shows a prominently altered structure of the majority of synapses or even lacks synapses altogether. This surprising resilience of synaptic structure might be explained by a high redundancy between different SCAMs, by the assumption that the crucial molecular players in synapse structure have yet to be discovered or by a grand variability in the mechanisms of synapse formation that underlies the diversity of synapses. Whatever the final answer turns out to be, the genetic dissection of the SCAM superfamilies has led to a much better understanding of the different steps required to form, differentiate and modify a synapse.
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Affiliation(s)
- Kerstin Piechotta
- Center for Physiology and Pathophysiology, Georg-August University, Humboldtallee 23, 37073 Göttingen, Germany
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35
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Li G, Lee D, Wang L, Khvotchev M, Chiew SK, Arunachalam L, Collins T, Feng ZP, Sugita S. N-terminal insertion and C-terminal ankyrin-like repeats of alpha-latrotoxin are critical for Ca2+-dependent exocytosis. J Neurosci 2006; 25:10188-97. [PMID: 16267226 PMCID: PMC6725796 DOI: 10.1523/jneurosci.3560-05.2005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alpha-latrotoxin, a potent stimulator of exocytosis from neurons and neuroendocrine cells, has been studied intensively, but the mechanisms of its actions are poorly understood. Here, we developed a new method to generate active recombinant alpha-latrotoxin and conducted a structure/function analysis of the toxin in stimulating Ca2+-dependent exocytosis. alpha-Latrotoxin consists of a conserved N-terminal domain and C-terminal ankyrin-like repeats. After cleavage of an N-terminally fused purification tag of glutathione S-transferase (GST), the recombinant toxin strongly stimulated exocytosis, whereas the GST-fused toxin was much less potent. The GST-fused toxin bound to the receptors [neurexin 1alpha; CL1 (CIRL/latrophilin 1)] as efficiently as did the GST-cleaved toxin but was much less effective in inserting into the plasma membrane and inducing cation conductance. The toxin with deletion of the last two ankyrin-like repeats still bound the receptors but could neither stimulate exocytosis nor induce cation conductance efficiently. The abilities of the mutated toxins to stimulate exocytosis correlated well with their abilities to induce cation conductance, but not their binding to the receptors. Our results indicate that (1) C-terminal ankyrin-like repeats and a free (unfused) N terminus are both required for the toxin to form pores, which is essential for Ca2+-dependent exocytosis, and (2) receptor binding alone is not sufficient to stimulate Ca2+-dependent exocytosis.
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Affiliation(s)
- Gang Li
- Division of Cellular and Molecular Biology, Toronto Western Research Institute, University Health Network, Toronto, Ontario, M5T 2S8, Canada
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36
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Zhang W, Rohlmann A, Sargsyan V, Aramuni G, Hammer RE, Südhof TC, Missler M. Extracellular domains of alpha-neurexins participate in regulating synaptic transmission by selectively affecting N- and P/Q-type Ca2+ channels. J Neurosci 2006; 25:4330-42. [PMID: 15858059 PMCID: PMC6725120 DOI: 10.1523/jneurosci.0497-05.2005] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Neurexins constitute a large family of highly variable cell-surface molecules that may function in synaptic transmission and/or synapse formation. Each of the three known neurexin genes encodes two major neurexin variants, alpha- and beta-neurexins, that are composed of distinct extracellular domains linked to identical intracellular sequences. Deletions of one, two, or all three alpha-neurexins in mice recently demonstrated their essential role at synapses. In multiple alpha-neurexin knock-outs, neurotransmitter release from excitatory and inhibitory synapses was severely reduced, primarily probably because voltage-dependent Ca2+ channels were impaired. It remained unclear, however, which neurexin variants actually influence exocytosis and Ca2+ channels, which domain of neurexins is required for this function, and which Ca2+-channel subtypes are regulated. Here, we show by electrophysiological recordings that transgenic neurexin 1alpha rescues the release and Ca2+-current phenotypes, whereas transgenic neurexin 1beta has no effect, indicating the importance of the extracellular sequences for the function of neurexins. Because neurexin 1alpha rescued the knock-out phenotype independent of the alpha-neurexin gene deleted, these data are consistent with a redundant function among different alpha-neurexins. In both knock-out and transgenically rescued mice, alpha-neurexins selectively affected the component of neurotransmitter release that depended on activation of N- and P/Q-type Ca2+ channels, but left L-type Ca2+ channels unscathed. Our findings indicate that alpha-neurexins represent organizer molecules in neurotransmission that regulate N- and P/Q-type Ca2+ channels, constituting an essential role at synapses that critically involves the extracellular domains of neurexins.
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Affiliation(s)
- Weiqi Zhang
- Center for Physiology and Pathophysiology, Georg-August University, D-37073 Göttingen, Germany
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37
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Sons MS, Busche N, Strenzke N, Moser T, Ernsberger U, Mooren FC, Zhang W, Ahmad M, Steffens H, Schomburg ED, Plomp JJ, Missler M. alpha-Neurexins are required for efficient transmitter release and synaptic homeostasis at the mouse neuromuscular junction. Neuroscience 2006; 138:433-46. [PMID: 16406382 DOI: 10.1016/j.neuroscience.2005.11.040] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Revised: 11/16/2005] [Accepted: 11/16/2005] [Indexed: 11/26/2022]
Abstract
Neurotransmission at chemical synapses of the brain involves alpha-neurexins, neuron-specific cell-surface molecules that are encoded by three genes in mammals. Deletion of alpha-neurexins in mice previously demonstrated an essential function, leading to early postnatal death of many double-knockout mice and all triple mutants. Neurotransmitter release at central synapses of newborn knockouts was severely reduced, a function of alpha-neurexins that requires their extracellular sequences. Here, we investigated the role of alpha-neurexins at neuromuscular junctions, presynaptic terminals that lack a neuronal postsynaptic partner, addressing an important question because the function of neurexins was hypothesized to involve cell-adhesion complexes between neurons. Using systems physiology, morphological analyses and electrophysiological recordings, we show that quantal content, i.e. the number of acetylcholine quanta released per nerve impulse from motor nerve terminals, and frequency of spontaneous miniature endplate potentials at the slow-twitch soleus muscle are reduced in adult alpha-neurexin double-knockouts, consistent with earlier data on central synapses. However, the same parameters at diaphragm muscle neuromuscular junctions showed no difference in basal neurotransmission. To reconcile these observations, we tested the capability of control and alpha-neurexin-deficient diaphragm neuromuscular junctions to compensate for an experimental reduction of postsynaptic acetylcholine receptors by a compensatory increase of presynaptic release: Knockout neuromuscular junctions produced significantly less upregulation of quantal content than synapses from control mice. Our data suggest that alpha-neurexins are required for efficient neurotransmitter release at neuromuscular junctions, and that they may perform a role in the molecular mechanism of synaptic homeostasis at these peripheral synapses.
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Affiliation(s)
- M S Sons
- Center for Physiology and Pathophysiology, Georg-August University, Humboldtallee 23, 37073 Göttingen, Germany
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38
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α-LTX and α-LTXN4C induce [Ca2+]i elevation through different mechanisms in pancreatic β cells. ACTA ACUST UNITED AC 2006. [DOI: 10.1007/s11434-005-1029-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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39
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Paraoanu LE, Becker-Roeck M, Christ E, Layer PG. Expression patterns of neurexin-1 and neuroligins in brain and retina of the chick embryo: Neuroligin-3 is absent in retina. Neurosci Lett 2005; 395:114-7. [PMID: 16300891 DOI: 10.1016/j.neulet.2005.10.076] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Revised: 10/17/2005] [Accepted: 10/26/2005] [Indexed: 11/26/2022]
Abstract
Neuroligins (NLs) constitute a family of cell-surface proteins that interact with neurexins (beta-Nxs), another class of neuronal cell-surface proteins, one of each class functioning together in synapse formation. The localization of the various neurexins and neuroligins, however, has not yet been clarified in chicken. Therefore, we studied the expression patterns of neurexin-1 (Nx-1) and neuroligin-1 and -3 during embryonic development of the chick retina and brain by reverse-transcriptase polymerase chain reaction (RT-PCR) and in situ hybridization (ISH). While neurexin-1 increased continuously in both brain and retina, the expression of both neuroligins was more variable. As shown by ISH, Nx-1 is expressed in the inner half retina along with differentiation of ganglion and amacrine cells. Transcripts of NL-1 were detected as early as day 4 and increased with the maturation of the different brain regions. In different brain regions, NL-1 showed a different time regulation. Remarkably, neuroligin-3 was entirely absent in retina. This study indicates that synaptogenetic processes in brain and retina use different molecular machineries, whereby the neuroligins might represent the more distinctly regulated part of the neurexin-neuroligin complexes. Noticeably, NL-3 does not seem to be involved in the making of retinal synapses.
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Affiliation(s)
- Laura Elena Paraoanu
- Developmental Biology and Neurogenetics, Darmstadt University of Technology, Schnittspahnstrasse 3, D-64287, Darmstadt, Germany.
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40
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Beglopoulos V, Montag-Sallaz M, Rohlmann A, Piechotta K, Ahmad M, Montag D, Missler M. Neurexophilin 3 is highly localized in cortical and cerebellar regions and is functionally important for sensorimotor gating and motor coordination. Mol Cell Biol 2005; 25:7278-88. [PMID: 16055736 PMCID: PMC1190246 DOI: 10.1128/mcb.25.16.7278-7288.2005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neurexophilin 3 (Nxph3) is a specific ligand of synaptic alpha-neurexins that are essential for efficient neurotransmitter release. Previous biochemical work demonstrated that Nxph3 interacts with an extracellular domain of alpha-neurexins in a tight complex; however, no information is available on the localization or functional role of Nxph3 in the brain. Here, we generated lacZ reporter gene knock-in mice to investigate the distribution of Nxph3 at the single-cell level and Nxph3 knockout mice to examine its functional importance. Nxph3 expression was restricted mostly to subplate-derived neurons in cortical layer 6b, granule cells in the vestibulocerebellum, and Cajal-Retzius cells during development. Colabeling experiments demonstrated that neurons expressing Nxph3 do not belong to a uniform cell type. Morphological analyses and systematic behavioral testing of knockout mice revealed no anatomical defects but uncovered remarkable functional abnormalities in sensory information processing and motor coordination, evident by increased startle response, reduced prepulse inhibition, and poor rotarod performance. Since Nxph3-deficient mice behaved normally while performing a number of other tasks, our data suggest an important role for Nxph3 as a locally and temporally regulated neuropeptide-like molecule, presumably acting in a complex with alpha-neurexins in select neuronal circuits.
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Affiliation(s)
- Vassilios Beglopoulos
- Center for Physiology and Pathophysiology, Georg-August University, Göttingen, Germany
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41
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Liu J, Wan Q, Lin X, Zhu H, Volynski K, Ushkaryov Y, Xu T. α-Latrotoxin Modulates the Secretory Machinery via Receptor-Mediated Activation of Protein Kinase C. Traffic 2005; 6:756-65. [PMID: 16101679 DOI: 10.1111/j.1600-0854.2005.00313.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The hypothesis whether alpha-latrotoxin (LTX) could directly regulate the secretory machinery was tested in pancreatic beta cells using combined techniques of membrane capacitance (Cm) measurement and Ca2+ uncaging. Employing ramp increase in [Ca2+]i to stimulate exocytosis, we found that LTX lowers the Ca2+ threshold required for exocytosis without affecting the size of the readily releasable pool (RRP). The burst component of exocytosis in response to step-like [Ca2+]i increase generated by flash photolysis of caged Ca2+ was also speeded up by LTX treatment. LTX increased the maximum rate of exocytosis compared with control responses with similar postflash [Ca2+]i and shifted the Ca2+ dependence of the exocytotic machinery toward lower Ca2+ concentrations. LTXN4C, a LTX mutant which cannot form membrane pores or penetrate through the plasma membrane but has similar affinity for the receptors as the wild-type LTX, mimicked the effect of LTX. Moreover, the effects of both LTX and LTXN4C) were independent of intracellular or extracellular Ca2+ but required extracellular Mg2+. Our data propose that LTX, by binding to the membrane receptors, sensitizes the fusion machinery to Ca2+ and, hence, may permit release at low [Ca2+]i level. This sensitization is mediated by activation of protein kinase C.
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Affiliation(s)
- Jie Liu
- Institute of Biophysics and Biochemistry, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074. P. R. China
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42
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Chubykin AA, Liu X, Comoletti D, Tsigelny I, Taylor P, Südhof TC. Dissection of Synapse Induction by Neuroligins. J Biol Chem 2005; 280:22365-74. [PMID: 15797875 DOI: 10.1074/jbc.m410723200] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To study synapse formation by neuroligins, we co-cultured hippocampal neurons with COS cells expressing wild type and mutant neuroligins. The large size of COS cells makes it possible to test the effect of neuroligins presented over an extended surface area. We found that a uniform lawn of wild type neuroligins displayed on the cell surface triggers the formation of hundreds of uniformly sized, individual synaptic contacts that are labeled with neurexin antibodies. Electron microscopy revealed that these artificial synapses contain a presynaptic active zone with docked vesicles and often feature a postsynaptic density. Neuroligins 1, 2, and 3 were active in this assay. Mutations in two surface loops of neuroligin 1 abolished neuroligin binding to neurexin 1beta, a presumptive presynaptic binding partner for postsynaptic neuroligins, and blocked synapse formation. An analysis of mutant neuroligins with an amino acid substitution that corresponds to a mutation described in patients with an autistic syndrome confirmed previous reports that these mutant neuroligins have a compromised capacity to be transported to the cell surface. Nevertheless, the small percentage of mutant neuroligins that reached the cell surface still induced synapse formation. Viewed together, our data suggest that neuroligins generally promote artificial synapse formation in a manner that is associated with beta-neurexin binding and results in morphologically well differentiated synapses and that a neuroligin mutation found in autism spectrum disorders impairs cell-surface transport but does not completely abolish synapse formation activity.
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Affiliation(s)
- Alexander A Chubykin
- Center for Basic Neuroscience, Department of Molecular Genetics, and Howard Hughes Medical Institute, The University of Texas Southwestern Medical Center at Dallas, 6000 Harry Hines Boulevard, Dallas, TX 75390-9111, USA
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43
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Homma K, Kikuno RF, Nagase T, Ohara O, Nishikawa K. Alternative Splice Variants Encoding Unstable Protein Domains Exist in the Human Brain. J Mol Biol 2004; 343:1207-20. [PMID: 15491607 DOI: 10.1016/j.jmb.2004.09.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2004] [Revised: 07/30/2004] [Accepted: 09/07/2004] [Indexed: 10/26/2022]
Abstract
Alternative splicing has been recognized as a major mechanism by which protein diversity is increased without significantly increasing genome size in animals and has crucial medical implications, as many alternative splice variants are known to cause diseases. Despite the importance of knowing what structural changes alternative splicing introduces to the encoded proteins for the consideration of its significance, the problem has not been adequately explored. Therefore, we systematically examined the structures of the proteins encoded by the alternative splice variants in the HUGE protein database derived from long (>4 kb) human brain cDNAs. Limiting our analyses to reliable alternative splice junctions, we found alternative splice junctions to have a slight tendency to avoid the interior of SCOP domains and a strong statistically significant tendency to coincide with SCOP domain boundaries. These findings reflect the occurrence of some alternative splicing events that utilize protein structural units as a cassette. However, 50 cases were identified in which SCOP domains are disrupted in the middle by alternative splicing. In six of the cases, insertions are introduced at the molecular surface, presumably affecting protein functions, while in 11 of the cases alternatively spliced variants were found to encode pairs of stable and unstable proteins. The mRNAs encoding such unstable proteins are much less abundant than those encoding stable proteins and tend not to have corresponding mRNAs in non-primate species. We propose that most unstable proteins encoded by alternative splice variants lack normal functions and are an evolutionary dead-end.
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Affiliation(s)
- Keiichi Homma
- Laboratory of Gene-Product Informatics, Center for Information Biology-DNA Data Bank of Japan, National Institute of Genetics, Research Organization of Information and Systems, Shizuoka 411-8540, Japan
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44
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Ushkaryov YA, Volynski KE, Ashton AC. The multiple actions of black widow spider toxins and their selective use in neurosecretion studies. Toxicon 2004; 43:527-42. [PMID: 15066411 DOI: 10.1016/j.toxicon.2004.02.008] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The black widow spider venom contains several large protein toxins--latrotoxins--that are selectively targeted against different classes of animals: vertebrates, insects, and crustaceans. These toxins are synthesised as large precursors that undergo proteolytic processing and activation in the lumen of the venom gland. The mature latrotoxins demonstrate strong functional structure conservation and contain multiple ankyrin repeats, which mediate toxin oligomerisation. The three-dimensional structure has been determined for alpha-latrotoxin (alphaLTX), a representative venom component toxic to vertebrates. This reconstruction explains the mechanism of alphaLTX pore formation by showing that it forms tetrameric complexes, harbouring a central channel, and that it is able to insert into lipid membranes. All latrotoxins cause massive release of neurotransmitters from nerve terminals of respective animals after binding to specific neuronal receptors. A G protein-coupled receptor latrophilin and a single-transmembrane receptor neurexin have been identified as major high-affinity receptors for alphaLTX. Latrotoxins act by several Ca(2+)-dependent and -independent mechanisms based on pore formation and activation of receptors. Mutant recombinant alphaLTX that does not form pores has been used to dissect the multiple actions of this toxin. As a result, important insights have been gained into the receptor signalling and the role of intracellular Ca(2+) stores in the effect of alphaLTX.
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Affiliation(s)
- Y A Ushkaryov
- Department of Biological Sciences, Imperial College, London, SW7 2AY, UK.
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45
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Kattenstroth G, Tantalaki E, Südhof TC, Gottmann K, Missler M. Postsynaptic N-methyl-D-aspartate receptor function requires alpha-neurexins. Proc Natl Acad Sci U S A 2004; 101:2607-12. [PMID: 14983056 PMCID: PMC356997 DOI: 10.1073/pnas.0308626100] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Alpha-neurexins are neuron-specific cell-surface molecules that are essential for the functional organization of presynaptic Ca2+ channels and release sites. We have now examined postsynaptic glutamate receptor function in alpha-neurexin knockout (KO) mice by using whole-cell recordings in cultured neocortical slices. Unexpectedly, we find that alpha-neurexins are required for normal activity of N-methyl-D-aspartate (NMDA)- but not alpha-amino-3-hydroxy-5-methyl-4-isoxyzolepropionic acid (AMPA)-type glutamate receptors. In alpha-neurexin-deficient mice, the ratio of NMDA- to AMPA-receptor currents, recorded as evoked synaptic responses, was diminished approximately 50%. Furthermore, the NMDA-receptor-dependent component of spontaneous synaptic miniature responses was reduced approximately 50%, whereas the AMPA-receptor-dependent component was unaffected. No alterations in the levels of NMDA- or AMPA-receptor proteins were detected. These results suggest that alpha-neurexins are required to maintain normal postsynaptic NMDA-receptor function. The decrease in NMDA-receptor activity in alpha-neurexin-deficient synapses could be due to a transsynaptic effect on the postsynaptic neuron (i.e., alpha-neurexins on the presynaptic inputs guide postsynaptic NMDA-receptor function) or to a cell-autonomous postsynaptic effect of alpha-neurexins on NMDA-receptor activity. To distinguish between these two possibilities, we cocultured WT GFP-labeled neurons with neocortical slices from alpha-neurexin-deficient or control mice. No difference was found between WT neurons innervated by inputs that contained or lacked alpha-neurexins, indicating that the absence of presynaptic alpha-neurexins alone does not depress postsynaptic NMDA-receptor function. Our data suggest that, in addition to the previously described presynaptic impairments, loss of alpha-neurexins induces postsynaptic changes by a cell-autonomous mechanism.
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46
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Volynski KE, Capogna M, Ashton AC, Thomson D, Orlova EV, Manser CF, Ribchester RR, Ushkaryov YA. Mutant alpha-latrotoxin (LTXN4C) does not form pores and causes secretion by receptor stimulation: this action does not require neurexins. J Biol Chem 2003; 278:31058-66. [PMID: 12782639 DOI: 10.1074/jbc.m210395200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alpha-latrotoxin (LTX) causes massive release of neurotransmitters via a complex mechanism involving (i) activation of receptor(s) and (ii) toxin insertion into the plasma membrane with (iii) subsequent pore formation. Using cryo-electron microscopy, electrophysiological and biochemical methods, we demonstrate here that the recently described toxin mutant (LTXN4C) is unable to insert into membranes and form pores due to its inability to assemble into tetramers. However, this mutant still binds to major LTX receptors (latrophilin and neurexin) and causes strong transmitter exocytosis in synaptosomes, hippocampal slice cultures, neuromuscular junctions, and chromaffin cells. In the absence of mutant incorporation into the membrane, receptor activation must be the only mechanism by which LTXN4C triggers exocytosis. An interesting feature of this receptor-mediated transmitter release is its dependence on extracellular Ca2+. Because Ca2+ is also strictly required for LTX interaction with neurexin, the latter might be the only receptor mediating the LTXN4C action. To test this hypothesis, we used conditions (substitution of Ca2+ in the medium with Sr2+) under which LTXN4C does not bind to any member of the neurexin family but still interacts with latrophilin. We show that, in all the systems tested, Sr2+ fully replaces Ca2+ in supporting the stimulatory effect of LTXN4C. These results indicate that LTXN4C can cause neurotransmitter release just by stimulating a receptor and that neurexins are not critical for this receptor-mediated action.
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Affiliation(s)
- Kirill E Volynski
- Department of Biological Sciences, Imperial College London, London SW7 2AY, United Kingdom
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47
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Dean C, Scholl FG, Choih J, DeMaria S, Berger J, Isacoff E, Scheiffele P. Neurexin mediates the assembly of presynaptic terminals. Nat Neurosci 2003; 6:708-16. [PMID: 12796785 PMCID: PMC1646425 DOI: 10.1038/nn1074] [Citation(s) in RCA: 463] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2003] [Accepted: 05/21/2003] [Indexed: 11/09/2022]
Abstract
Neurexins are a large family of proteins that act as neuronal cell-surface receptors. The function and localization of the various neurexins, however, have not yet been clarified. Beta-neurexins are candidate receptors for neuroligin-1, a postsynaptic membrane protein that can trigger synapse formation at axon contacts. Here we report that neurexins are concentrated at synapses and that purified neuroligin is sufficient to cluster neurexin and to induce presynaptic differentiation. Oligomerization of neuroligin is required for its function, and we find that beta-neurexin clustering is sufficient to trigger the recruitment of synaptic vesicles through interactions that require the cytoplasmic domain of neurexin. We propose a two-step model in which postsynaptic neuroligin multimers initially cluster axonal neurexins. In response to this clustering, neurexins nucleate the assembly of a cytoplasmic scaffold to which the exocytotic apparatus is recruited.
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Affiliation(s)
- Camin Dean
- Department of Molecular and Cell Biology, University of California, Berkeley, 271 LSA, California 94720, USA
| | - Francisco G Scholl
- Columbia University, Department of Physiology & Cellular Biophysics, College of Physicians & Surgeons, Center for Neurobiology and Behavior, New York, New York 10032, USA
| | - Jenny Choih
- Department of Molecular and Cell Biology, University of California, Berkeley, 271 LSA, California 94720, USA
| | - Shannon DeMaria
- Department of Molecular and Cell Biology, University of California, Berkeley, 271 LSA, California 94720, USA
| | - James Berger
- Department of Molecular and Cell Biology, University of California, Berkeley, 271 LSA, California 94720, USA
| | - Ehud Isacoff
- Department of Molecular and Cell Biology, University of California, Berkeley, 271 LSA, California 94720, USA
| | - Peter Scheiffele
- Columbia University, Department of Physiology & Cellular Biophysics, College of Physicians & Surgeons, Center for Neurobiology and Behavior, New York, New York 10032, USA
- * Correspondence should be addressed to P.S. ()
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48
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Yap CC, Liang F, Yamazaki Y, Muto Y, Kishida H, Hayashida T, Hashikawa T, Yano R. CIP98, a novel PDZ domain protein, is expressed in the central nervous system and interacts with calmodulin-dependent serine kinase. J Neurochem 2003; 85:123-34. [PMID: 12641734 DOI: 10.1046/j.1471-4159.2003.01647.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Receptors and various molecules in neurons are localized at precise locations to perform their respective functions, especially in synaptic sites. Among synaptic molecules, PDZ domain proteins play major roles in scaffolding and anchoring membrane proteins for efficient synaptic transmission. In the present study, we isolated CIP98, a novel protein (98 kDa) consisting of three PDZ domains and a proline-rich region, which is widely expressed in the central nervous system. In situ hybridization and immunohistochemical staining patterns demonstrate that CIP98 is expressed strongly in certain types of neurons, i.e. pyramidal cells in layers III-V of the cerebral cortex, projecting neurons in the thalamus and interneurons in the cerebellum. The results of immunocytochemical staining and electron microscopy revealed that CIP98 is localized both in dendrites and axons. Interestingly, CIP98 interacts with CASK (calmodulin-dependent serine kinase), a member of the membrane-associated guanylate kinase (MAGUK) family that plays important roles in the molecular organization of proteins at synapses. CIP98 was shown to co-localize with CASK along the dendritic processes of neurons. In view of its direct association with CASK, CIP98 may be involved in the formation of CASK scaffolding proteins complex to facilitate synaptic transmission in the CNS.
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Affiliation(s)
- Chan Choo Yap
- Laboratories for Cellular Information Processing, Brain Science Institute (BSI), RIKEN, Wako, Saitama, Japan
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49
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Occhi G, Rampazzo A, Beffagna G, Antonio Danieli G. Identification and characterization of heart-specific splicing of human neurexin 3 mRNA (NRXN3). Biochem Biophys Res Commun 2002; 298:151-5. [PMID: 12379233 DOI: 10.1016/s0006-291x(02)02403-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Three neurexin (NRXN) genes are known in humans, each transcribed from two promoters and extensively spliced at five canonical positions, thus generating thousands of isoforms. For NRXN3, only neuronal expression was reported so far. We reported here on the expression of NRXN3 in additional tissues (lung, pancreas, heart, placenta, liver, and kidney) and on the identification and characterization of heart-specific splicing variants of NRXN3. Cardiac isoforms of NRXN3 probably participate in a complex involving dystroglycan and proteins of extracellular matrix, involved in intercellular connections.
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Affiliation(s)
- Gianluca Occhi
- Department of Biology, University of Padua, Via U. Bassi 58/B, Padua I-35131, Italy.
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50
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Krasnoperov V, Bittner MA, Mo W, Buryanovsky L, Neubert TA, Holz RW, Ichtchenko K, Petrenko AG. Protein-tyrosine phosphatase-sigma is a novel member of the functional family of alpha-latrotoxin receptors. J Biol Chem 2002; 277:35887-95. [PMID: 12110683 DOI: 10.1074/jbc.m205478200] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Receptor-like protein-tyrosine phosphatase sigma (PTPvarsigma) is essential for neuronal development and function. Here we report that PTPvarsigma is a target of alpha-latrotoxin, a strong stimulator of neuronal exocytosis. alpha-Latrotoxin binds to the cell adhesion-like extracellular region of PTPvarsigma. This binding results in the stimulation of exocytosis. The toxin-binding site is located in the C-terminal part of the PTPvarsigma ectodomain and includes two fibronectin type III repeats. The intracellular catalytic domains of PTPvarsigma are not required for the alpha-latrotoxin binding and secretory response triggered by the toxin in chromaffin cells. These features of PTPvarsigma resemble two other previously described alpha-latrotoxin receptors, neurexin and CIRL. Thus, alpha-latrotoxin represents an unusual example of the neurotoxin that has three independent, equally potent, and yet structurally distinct targets. The known structural and functional characteristics of PTPvarsigma, neurexin, and CIRL suggest that they define a functional family of neuronal membrane receptors with complementary or converging roles in presynaptic function via a mechanism that involves cell-to-cell and cell-to-matrix interaction.
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MESH Headings
- Animals
- Binding Sites
- Blotting, Western
- Brain/metabolism
- COS Cells
- Calcium/metabolism
- Catalysis
- Cell Membrane/metabolism
- Chromaffin Cells/metabolism
- Cross-Linking Reagents/pharmacology
- Detergents/pharmacology
- Dose-Response Relationship, Drug
- Electrophoresis, Polyacrylamide Gel
- Exocytosis
- Gene Deletion
- Glycoproteins
- Human Growth Hormone/pharmacology
- Humans
- Ligands
- Mass Spectrometry
- Membrane Proteins
- Models, Genetic
- Mutagenesis
- Mutation
- Nerve Tissue Proteins/metabolism
- Neurons/metabolism
- Neuropeptides
- Plasmids/metabolism
- Precipitin Tests
- Protein Binding
- Protein Structure, Tertiary
- Protein Tyrosine Phosphatases/chemistry
- Protein Tyrosine Phosphatases/physiology
- Rats
- Receptor-Like Protein Tyrosine Phosphatases, Class 2
- Receptors, G-Protein-Coupled
- Receptors, Peptide/chemistry
- Receptors, Peptide/isolation & purification
- Receptors, Peptide/metabolism
- Recombinant Proteins/metabolism
- Sepharose/pharmacology
- Silver Staining
- Transfection
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Affiliation(s)
- Valery Krasnoperov
- Department of Pharmacology, New York University School of Medicine, New York, New York 10016, USA
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