Hormone and growth factor receptor-mediated regulation of phospholipase C activity

The broad importance of receptor-activated phosphoinositide hydrolysis in the physiological action of hormones, neurotransmitters and growth factors has sparked interest in the study of transmembrane signalling events responsible for activation of phospholipase C. As with receptors involved in regulation of adenylyl cyclase, ion channels and phototransmission, it is clear that a guanine nucleotide regulatory protein (G protein) is a necessary component of the hormone- and neurotransmitter-regulated phosphoinositide signalling mechanism. Recent evidence to support a possible second mode of regulation of phospholipase C by growth factor receptors is emerging in the form of realization that at least one isozyme of phospholipase C serves as a substrate for the tyrosine kinase activity of growth factor receptors known to stimulate phosphoinositide hydrolysis. In this review, José Boyer and colleagues summarize progress towards delineating the properties and identity of the G protein(s) involved in this pathway, recent advances in purification and molecular cloning of phospholipase C isozymes, and the current understanding of growth factor receptor-mediated regulation of phosphoinositide hydrolysis.