A novel tetanus neurotoxin-insensitive vesicle-associated membrane protein in SNARE complexes of the apical plasma membrane of epithelial cells.
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.
Pubmed ID: 9614185 RIS Download
Amino Acid Sequence | Animals | Antigens, Surface | Base Sequence | Botulinum Toxins | Caco-2 Cells | Carrier Proteins | Cell Membrane | DNA, Complementary | Dithiothreitol | Enzyme Inhibitors | Epithelial Cells | Ethylmaleimide | Humans | Membrane Proteins | Metalloendopeptidases | Molecular Sequence Data | Nerve Tissue Proteins | Qa-SNARE Proteins | Qb-SNARE Proteins | Qc-SNARE Proteins | R-SNARE Proteins | Rabbits | Rats | SNARE Proteins | Sequence Homology, Amino Acid | Synaptosomal-Associated Protein 25 | Syntaxin 1 | Tetanus Toxin | Vesicle-Associated Membrane Protein 3 | Vesicular Transport Proteins