This entry includes vesicle-associated membrane proteins VAMP1/synaptobrevin-1, VAMP2/synaptobrevin-2, VAMP3/synaptobrevin-3 and VAMP8/endobrevin.VAMPs are a group of small, integral membrane proteins of synaptic vesicles that is mostly involved in vesicle fusion. The heterotrimeric SNARE complex isformed by syntaxin 1, synaptosomal-associated protein 25kDa (SNAP25), and vesicle-associated membrane protein (VAMP)/synaptobrevin []. VAMP1 plays an essential, non-redundant role in Ca2+-triggered vesicle exocytosis at the mouse neuromuscular junction []. VAMP2 is extensively expressed in the central nervous system []. Neurotransmitter release involves the assembly of a heterotrimeric SNARE complex composed of SNAP25, VAMP2 and syntaxin 1 []. VAMP8 may be involved in regulated exocytosis of the exocrine system [, ].
Syntaxin 8 forms a complex with syntaxin 7 (Qa), Vti1b (Qb) and either VAMP7 or VAMP8 (R-SNARE) and is involved in the transport from early endosomes to the lysosome [, ]. Syntaxin 8 is a member of the Qc subgroup of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, which consist of coiled-coil helices (called SNARE motifs) that mediate the interactions between SNARE proteins, and a transmembrane domain []. The SNARE complexes mediate membrane fusion, important for trafficking of newly synthesized proteins, recycling of pre-existing proteins and organelle formation []. SNARE proteins are classified into four groups, Qa-, Qb-, Qc- and R-SNAREs, depending on whether the residue in the hydrophilic centre layer of the four-helical bundle is a glutamine (Q) or arginine (R). Qa-, as well as Qb- and Qc-SNAREs, are localized to target organelle membranes, while R-SNARE is localized to vesicle membranes. They form unique complexes consisting of one member of each subgroup, that mediate fusion between a specific type of vesicles and their target organelle [].
