Plays a role in the control of regulated secretion in neural and endocrine cells, enhancing selectively low-frequency neurotransmission. Positively regulates vesicle fusion by maintaining the readily releasable pool of secretory vesicles (By similarity). ; (Microbial infection) Receptor for the C.botulinum neurotoxin type A2 (BoNT/A, botA); glycosylation is not essential but enhances the interaction (PubMed:29649119). Probably also serves as a receptor for the closely related C.botulinum neurotoxin type A1.