Phosphoinositide turnover and calcium ion mobilization in receptor activation.

Ca2+ is now recognized to play a central role in the cellular signal transduction system. The hydrolysis of inositol phospholipids is an initial and essential event in Ca2+-mobilizing receptor activation. Phospholipase C cleaves phosphatidylinositol 4,5-bisphosphate to yield two intracellular messengers: inositol 1,4,5-trisphosphate that mobilizes Ca2+ from intracellular storage sites, and 1,2-diacylglycerol that activates protein kinase C. In this chapter, I will describe the functional role of phosphoinositide breakdown during receptor activation and the regulatory mechanism of phospholipase C.