Vesicle-associated membrane protein-associated protein B/C (VAPB) is also known as VAMP-associated protein B/C (VAMP-B/VAMP-C or VAP-B/VAP-C), which is a single-pass type IV membrane protein and belongs to the VAMP-associated protein ( VAP ) family. Involved in cellular calcium homeostasis regulation, VAPB participates in the endoplasmic reticulum unfolded protein response (UPR) by inducing ERN1/IRE1 activity as well. VAPB can interact with VAMP1 ,VAMP2, HCV NS5A, NS5B ,ZFYVE27 (via MSP domain) and RMDN3. Human VAPB is involved in hepatitis C virus replication through interaction with NS5A and NS5B.