Protein kinase C: properties and possible role in cellular division and differentiation.

Protein kinase C was first described some eight years ago. Recent results indicate that this kinase may have a crucial role in signal transduction for substances involved in cellular differentiation and division. Protein kinase C is activated by attachment to plasma membranes, in the presence of calcium and diacylglycerol. The activator is produced in the membrane following the signal-induced breakdown of phosphoinositides. Tumor promoters, such as phorbol ester, can substitute for diacylglycerol. The recent findings that: tyrosine kinases might be involved in the phosphoinositide turnover and, phosphorylation of growth factor receptors by protein kinase C regulates some of their functions, indicate more and more clearly that this kinase is involved in the control of cell growth division and differentiation. Purification procedures, properties and mechanisms of regulation will be summarized and discussed.