Phosphoinositide-3-kinase adapter protein 1 (PIK3AP1)

Phosphoinositide-3-kinase adapter protein 1 (PIK3AP1, also known as BCAP) is a large adaptor protein primarily expressed in B cells, macrophages, and certain other hematopoietic cells[1][2][3][4]. It lacks intrinsic enzymatic activity and acts by linking receptors—including the B-cell receptor (BCR) and Toll-like receptors (TLRs)—to activation of the phosphoinositide 3-kinase (PI3K)-Akt signaling pathway[1][2][3][4]. BCAP contains multiple protein–protein interaction domains (including YxxM motifs and a TIR domain), allowing it to modulate cell signaling cascades fundamental to immune cell activation and differentiation[1][3][4]. BCAP serves a dual function: in B cells, it amplifies activation signals following antigen engagement, while in macrophages, it links TLR signaling to PI3K activation and can limit excessive inflammatory cytokine production, representing a regulatory node in immune homeostasis and inflammation[2][3][4]. Its pathway specificity and cell-type dependent roles make BCAP a potential therapeutic target in inflammatory, infectious, or autoimmune settings[2][3].

Other names

B cell adaptor for phosphoinositide 3-kinaseBCAPFLJ35564B-cell phosphoinositide 3-kinase adapter protein 1B cell adaptor protein

Modulation of PI3K/Akt signaling pathway; Regulation of TLR-mediated downstream signaling