Abstract
The importance of soluble N-ethyl maleimide (NEM)-sensitive fusion protein (NSF) attachment protein (SNAP) receptors (SNAREs) in synaptic vesicle exocytosis is well established because it has been demonstrated that clostridial neurotoxins (NTs) proteolyze the vesicle SNAREs (v-SNAREs) vesicle-associated membrane protein (VAMP)/brevins and their partners, the target SNAREs (t-SNAREs) syntaxin 1 and SNAP25. Yet, several exocytotic events, including apical exocytosis in epithelial cells, are insensitive to numerous clostridial NTs, suggesting the presence of SNARE-independent mechanisms of exocytosis. In this study we found that syntaxin 3, SNAP23, and a newly identified VAMP/brevin, tetanus neurotoxin (TeNT)-insensitive VAMP (TI-VAMP), are insensitive to clostridial NTs. In epithelial cells, TI-VAMP-containing vesicles were concentrated in the apical domain, and the protein was detected at the apical plasma membrane by immunogold labeling on ultrathin cryosections. Syntaxin 3 and SNAP23 were codistributed at the apical plasma membrane where they formed NEM-dependent SNARE complexes with TI-VAMP and cellubrevin. We suggest that TI-VAMP, SNAP23, and syntaxin 3 can participate in exocytotic processes at the apical plasma membrane of epithelial cells and, more generally, domain-specific exocytosis in clostridial NT-resistant pathways.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Antigens, Surface / metabolism
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Base Sequence
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Botulinum Toxins / pharmacology
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Caco-2 Cells
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Carrier Proteins / genetics
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Carrier Proteins / metabolism
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Cell Membrane / metabolism
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DNA, Complementary
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Dithiothreitol / pharmacology
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Enzyme Inhibitors / pharmacology
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Epithelial Cells / drug effects
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Epithelial Cells / metabolism*
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Epithelial Cells / ultrastructure
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Ethylmaleimide / pharmacology
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Humans
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Metalloendopeptidases / pharmacology*
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Molecular Sequence Data
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Nerve Tissue Proteins / metabolism
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Qa-SNARE Proteins
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Qb-SNARE Proteins
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Qc-SNARE Proteins
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R-SNARE Proteins
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Rabbits
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Rats
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SNARE Proteins
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Sequence Homology, Amino Acid
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Synaptosomal-Associated Protein 25
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Syntaxin 1
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Tetanus Toxin / pharmacology*
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Vesicle-Associated Membrane Protein 3
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Vesicular Transport Proteins*
Substances
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Antigens, Surface
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Carrier Proteins
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DNA, Complementary
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Enzyme Inhibitors
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Membrane Proteins
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Nerve Tissue Proteins
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Qa-SNARE Proteins
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Qb-SNARE Proteins
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Qc-SNARE Proteins
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R-SNARE Proteins
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SNAP23 protein, human
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SNAP25 protein, human
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SNARE Proteins
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STX1A protein, human
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Snap25 protein, rat
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Stx1a protein, rat
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Synaptosomal-Associated Protein 25
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Syntaxin 1
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Tetanus Toxin
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VAMP7 protein, human
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Vamp7 protein, rat
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Vesicle-Associated Membrane Protein 3
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Vesicular Transport Proteins
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tetanospasmin
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Metalloendopeptidases
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Botulinum Toxins
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Ethylmaleimide
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Dithiothreitol
Associated data
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GENBANK/U32315
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GENBANK/U55936