INTRACELLULAR SIGNALING BY PHOSPHOLIPID HYDROLYSIS AND PROTEIN-KINASE-C ACTIVATION

Inositol phospholipid hydrolysis was once thought to be the sole mechanism to produce diacylglycerol that relays information of extracellular signals into intracellular events through activation of protein kinase C. It is now clear that agonist-induced hydrolysis of various membrane phospholipids, particularly choline phospholipid, by phospholipase D and phospholipase A, also takes part in subsequent cellular responses such as cell proliferation and differentiation. Possibly, the members of the protein kinase C family may be activated differently by various combinations of phospholipid degradation products, and play roles in the transmembrane control of cellular functions.