title: Synaptotagmin interaction with the syntaxin/SNAP-25 dimer is mediated by an evolutionarily conserved motif and is sensitive to inositol hexakisphosphate.
abstract: Synaptotagmins are membrane proteins that possess tandem C2 domains and play an important role in regulated membrane fusion in metazoan organisms. Here we show that both synaptotagmins I and II, the two major neuronal isoforms, can interact with the syntaxin/synaptosomal-associated protein of 25 kDa (SNAP-25) dimer, the immediate precursor of the soluble NSF attachment protein receptor (SNARE) fusion complex. A stretch of basic amino acids highly conserved throughout the animal kingdom is responsible for this calcium-independent interaction. Inositol hexakisphosphate modulates synaptotagmin coupling to the syntaxin/SNAP-25 dimer, which is mirrored by changes in chromaffin cell exocytosis. Our results shed new light on the functional importance of the conserved polybasic synaptotagmin motif, suggesting that synaptotagmin interacts with the t-SNARE dimer to up-regulate the probability of SNARE-mediated membrane fusion.
authors.affiliation: Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom.
authors.forename: Colin
authors.initials: C
authors.lastname: Rickman
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Archer
authors.forename: Frederic A
authors.initials: FA
authors.lastname: Meunier
authors.forename: Molly
authors.initials: M
authors.lastname: Craxton
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Fukuda
authors.forename: Robert D
authors.initials: RD
authors.lastname: Burgoyne
authors.forename: Bazbek
authors.initials: B
authors.lastname: Davletov
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins; D002395:Catecholamines / Q000378:metabolism / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D019439:Chromaffin Cells / Q000378:metabolism; D003001:Cloning, Molecular; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D019143:Evolution, Molecular; D005089:Exocytosis; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry*; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010833:Phytic Acid / Q000494:pharmacology*; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D050765:Qa-SNARE Proteins; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050825:Synaptosomal-Associated Protein 25; D050857:Synaptotagmins; D013997:Time Factors
chemical_list: D002135:Calcium-Binding Proteins; D002395:Catecholamines; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D050765:Qa-SNARE Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C494208:SNAP25 protein, human; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25; D050857:Synaptotagmins; D010833:Phytic Acid; D005982:Glutathione Transferase; D002118:Calcium