PLC (Phosphoinositide-specific phospholipase C) plays a significant role in transmembrane signaling. Four members of PLCs have been identified: PLCβ, PLCg, PLCd, and PLCe. In response to extracellular stimuli (e.g., hormone, growth factors, neurotransmitters), PLC hydrolizes phosphatidylinositol 4,5-biphosphate (PIP2) into two secondary messengers: inositol 1,4,5-triphosphate (IP3) and diacylglycerol (DAG). PLCg2 is engaged in antigen-dependent signaling in B-cells and collagen-dependent signaling in platelets.