The SNAREs vti1a and vti1b have distinct localization and SNARE complex partners

Two mammalian proteins, vtila and vtilb, are homologous to the yeast Q-SNARE Vtilp which is part of several SNARE complexes in different transport steps. In vitro experiments suggest distinct functions for vtila and vtilb. Here we compared the subcellular localization of endogenous vtila and vtilb by immunofluorescence and immuno-electron microscopy. Both proteins had a distinct but overlapping localization. vtila was found predominantly on the Golgi and the TGN, vtilb mostly on tubules and vesicles in the TGN area and on endosomes. vti1a coimmunoprecipitated with VAMP-4, syntaxin 6, and syntaxin 16. These four SNAREs could assemble into a SNARE complex of conserved structure because one SNARE motif of each subgroup is present. vtila-beta, VAMP-4, syntaxin 6, and syntaxin 16 are coenriched with small synaptic vesicles and with clathrin-coated vesicles isolated from rat brain synaptosomes. Therefore, this SNARE complex may have a role in synaptic vesicle biogenesis or recycling.