Phosphoinositide-specific phospholipase C (PLC) plays a critical role in the initiation of receptor mediated signal transduction through the generation of the two second messengers, inositol 1,4,5-triphosphate and diacylglycerol from phosphatidylinositol 4,5-bisphosphate.There are many mammalian PLC isozymes, including PLC β1, PLC β2, PLC β3, PLC β4, PLC γ1, PLC γ2, PLC δ1, PLC δ2 and PLC e. After stimulation of the collagen receptor glycoprotein VI in human platelets, PLC γ2 associates with several tyrosine-phosphorylated proteins (Syk, SLP-76, Lyn, linker for activation of T cells (LAT) and the FcR γ chain), which bind to its C-terminal SH2 domain. PLC γ1 associates with Syk in B cells, but PLC γ2 does not associate with Syk in platelets. The C-terminal SH2 domain is involved in the regulation of PLC γ2. In addition, Btk can induce PLC γ2 tyrosine phosphorylation and initiate calcium moblization in CD72-stimulated B lymphocytes.