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Description

Vesicle-associated membrane protein-associated protein B (UniProt O95292, also known as VAMP-associated protein B, VAMP-B, VAP-B) is encoded by the VAPB (also known as ALS8, UNQ484/PRO983) gene (Gene ID 9217) in human. VAMP-associated proteins (VAPs) are type IV membrane proteins that are well conserved among species. There exist three human VAPs encoded by two genes, with VAPA encoding VAP-A and VAPB encoding VAP-B and VAP-C. VAPs generally localize at the endoplasmic reticulum (ER), although they are also reported to localize at other subcellular organelles in some species and cell types. VAPs were shown to have important roles in non-vesicular lipid transport, lipid metabolism, the regulation of ER structure, and the unfolded protein response through MSP domain-mediated interaction with FFAT motifs. VAP-B functions as an adaptor protein to recruit target proteins to the ER and execute various cellular functions, including lipid transport, membrane traffic, and ER stress response. VAP-B binds the catalytic subunit Rab3 GTPase activating protein 1 (Rab3GAP1), but not the non-catalytic subunit Rab3GAP2 of the heterodimeric Rab3GAP complex. VAP-B and Rab3GAP interaction is mediated through the Rab3GAP1 acidic tract (FFAT)-like motif and is essential for VAP-B-dependent regulation of the nuclear envelope protein transport through the ER-Golgi intermediate compartment (ERGIC). VAP-B contains a major sperm protein (MSP, a.a. 7-124) domain at the N-terminal cytoplasmic region, followed by a coiled-coil region (a.a. 2-222), and a transmembrane (TM) domain (a.a. 223-243).