Synaptotagmin interaction with the syntaxin/SNAP-25 dimer is mediated by an evolutionarily conserved motif and is sensitive to inositol hexakisphosphate.
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.
Rickman
Colin
C
Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom.
Archer
Deborah A
DA
Meunier
Frederic A
FA
Craxton
Molly
M
Fukuda
Mitsunori
M
Burgoyne
Robert D
RD
Davletov
Bazbek
B
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
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