Probably plays a role in the control of regulated secretion in neural and endocrine cells. (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. Interacts with SYT1 in a calcium-independent manner. Forms a complex with SYT1, syntaxin-1 and SNAP25 (By similarity). (Microbial infection) Interacts with C.botulinum neurotoxin type A2 (BoNT/A, botA) (PubMed:29649119). Interaction is improved by glycosylation of SV2 (PubMed:29649119). Associated with synaptic-like microvesicles but not with insulin-containing vesicles in insulin-secreting cells of the pancreas (By similarity). Localizes to microvesicles in the pinealocytes. Localizes to the acrosome in spermatids (By similarity). N-glycosylated. The N-terminal cytoplasmic domain is phosphorylated by CK1. Belongs to the major facilitator superfamily. Extended N-terminus.