Identification and characterization of Snapin as a ubiquitously expressed SNARE-binding protein that interacts with SNAP23 in non-neuronal cells.
Members of the SNARE (soluble N -ethylmaleimide-sensitive fusion protein attachment protein receptor) superfamily [syntaxins, VAMPs (vesicle-associated membrane proteins) and SNAP25 (synaptosome-associated protein-25)-related proteins] are required for intracellular membrane-fusion events in eukaryotes. In neurons, assembly of SNARE core complexes comprising the presynaptic membrane-associated SNAREs syntaxin 1 and SNAP25, and the vesicle-associated SNARE VAMP2, is necessary for synaptic vesicle exocytosis. Several accessory factors have been described that associate with the synaptic SNAREs and modulate core complex assembly or mediate Ca2+ regulation. One such factor, Snapin, has been reported to be a brain-specific protein that interacts with SNAP25, and regulates association of the putative Ca2+-sensor synaptotagmin with the synaptic SNARE complex [Ilardi, Mochida and Sheng (1999) Nat. Neurosci. 2, 119-124]. Here we demonstrate that Snapin is expressed ubiquitously in neuronal and non-neuronal cells. Furthermore, using protein-protein-interaction assays we show that Snapin interacts with SNAP23, the widely expressed homologue of SNAP25, and that the predicted C-terminal helical domain of Snapin contains the SNAP23-binding site. Subcellular localization experiments revealed that Snapin is a soluble protein that exists in both cytosolic and peripheral membrane-bound pools in adipocytes. Moreover, association of Snapin with the plasma membrane was detected in cells overexpressing a Snapin-green fluorescent protein fusion protein. Finally, we show that Snapin is able to form a ternary complex with SNAP23 and syntaxin 4, suggesting that it is a component of non-neuronal SNARE complexes. An important implication of our results is that Snapin is likely to perform a general role in SNARE-mediated vesicle fusion events in non-neuronal cells in addition to its participation in Ca2+-regulated neurosecretion.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to scicrunch, however this is not currently a free service.