Positive effector of BCR-stimulated responses. Couples the B-cell antigen receptor (BCR) to the mobilization of calcium ion either through a phosphoinositide 3-kinase-dependent pathway, when not phosphorylated on tyrosines of the linker region, or through a phospholipase C-gamma-dependent pathway, when phosphorylated on Tyr-342 and Tyr-346. Thus the differential phosphorylation of Syk can determine the pathway by which BCR is coupled to the regulation of intracellular calcium ion. Likewise, mediates responses to ITGB2 signaling and plays an important role in the regulation of down-stream signaling cascades. Phosphorylates USP25 and regulates its intracellular levels.
Specificity
Natural and recombinant Mouse Tyrosine-protein kinase SYK
Interacts with YWHAG/1433-gamma, which attenuates BCR-induced membrane translocation and activation (By similarity). Interacts (phosphorylated form) with SLA; the interaction may link it to CBL, leading to its destruction. Interacts with FCRL3. Interacts (via the second SH2 domain) with USP25 (via C-terminus) (By similarity). Interacts with RHOH, GAB2 and with NFAM1 (phosphorylated form). Interacts (via its SH2 domains) with CD79A (via its phosphorylated ITAM domain); the interaction stimulates SYK autophosphorylation and activation. Interacts with ITGB2 and FGR.