title: The SNARE Vti1a-beta is localized to small synaptic vesicles and participates in a novel SNARE complex.
abstract: Specific soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor (SNARE) proteins are required for different membrane transport steps. The SNARE Vti1a has been colocalized with Golgi markers and Vti1b with Golgi and the trans-Golgi network or endosomal markers in fibroblast cell lines. Here we study the distribution of Vti1a and Vti1b in brain. Vti1b was found in synaptic vesicles but was not enriched in this organelle. A brain-specific splice variant of Vti1a was identified that had an insertion of seven amino acid residues next to the putative SNARE-interacting helix. This Vti1a-beta was enriched in small synaptic vesicles and clathrin-coated vesicles isolated from nerve terminals. Vti1a-beta also copurified with the synaptic vesicle R-SNARE synaptobrevin during immunoisolation of synaptic vesicles and endosomes. Therefore, both synaptobrevin and Vti1a-beta are integral parts of synaptic vesicles throughout their life cycle. Vti1a-beta was part of a SNARE complex in nerve terminals, which bound N-ethylmaleimide-sensitive factor and alpha-SNAP. This SNARE complex was different from the exocytic SNARE complex because Vti1a-beta was not coimmunoprecipitated with syntaxin 1 or SNAP-25. These data suggest that Vti1a-beta does not function in exocytosis but in a separate SNARE complex in a membrane fusion step during recycling or biogenesis of synaptic vesicles.
authors.affiliation: Zentrum Biochemie und Molekulare Zellbiologie, Abteilung Biochemie II, Universität Göttingen, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Antonin
authors.forename: D
authors.initials: D
authors.lastname: Riedel
authors.forename: G F
authors.initials: GF
authors.lastname: von Mollard
mesh_terms: D017398:Alternative Splicing / Q000502:physiology; D000818:Animals; D000906:Antibodies; D001692:Biological Transport / Q000502:physiology; D001921:Brain / Q000166:cytology; D002352:Carrier Proteins / Q000032:analysis / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D002966:Clathrin / Q000378:metabolism; D003001:Cloning, Molecular; D018699:Coated Vesicles / Q000737:chemistry / Q000378:metabolism; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional / Q000502:physiology; D052066:N-Ethylmaleimide-Sensitive Proteins; D009474:Neurons / Q000737:chemistry / Q000378:metabolism; D011233:Precipitin Tests; D017729:Presynaptic Terminals / Q000737:chemistry / Q000378:metabolism; D050766:Qb-SNARE Proteins; D050683:R-SNARE Proteins; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits; D051381:Rats; D050600:SNARE Proteins; D017386:Sequence Homology, Amino Acid; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D013572:Synaptic Vesicles / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D016708:Synaptophysin / Q000032:analysis / Q000378:metabolism; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins
chemical_list: D000906:Antibodies; D002352:Carrier Proteins; D002966:Clathrin; D008565:Membrane Proteins; D050766:Qb-SNARE Proteins; D050683:R-SNARE Proteins; D012333:RNA, Messenger; D050600:SNARE Proteins; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; C494214:Stx1a protein, mouse; C494213:Stx1a protein, rat; D016708:Synaptophysin; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins; C491417:Vti1a protein, rat; C491415:Vti1b protein, mouse; D052066:N-Ethylmaleimide-Sensitive Proteins; C498733:Nsf protein, mouse; C498737:Nsf protein, rat