Endoplasmic reticulum (ER)-anchored protein that mediates the formation of contact sites between the ER and endosomes via interaction with FFAT motif-containing proteins such as STARD3 or WDR44 (PubMed:32344433, PubMed:33124732). STARD3-VAPA interaction enables cholesterol transfer from the ER to endosomes (PubMed:33124732). Via interaction with WDR44 participates in neosynthesized protein export (PubMed:32344433). In addition, recruited to the plasma membrane through OSBPL3 binding (PubMed:25447204). The OSBPL3-VAPA complex stimulates RRAS signaling which in turn attenuates integrin beta-1 (ITGB1) activation at the cell surface (PubMed:25447204). With OSBPL3, may regulate ER morphology (PubMed:16143324). May play a role in vesicle trafficking (PubMed:11511104, PubMed:19289470). {ECO:0000269|PubMed:11511104, ECO:0000269|PubMed:16143324, ECO:0000269|PubMed:19289470, ECO:0000269|PubMed:25447204, ECO:0000269|PubMed:32344433, ECO:0000269|PubMed:33124732}. This is the function of VAPA (VAMP associated protein A, ENSG00000101558).