Effect of polyamines on protein kinase C activation process.

Abstract

Protein phosphorylation and dephosphorylation are major mechanisms for signal transduction in biological systems (Krebs, 1985) and are fundamental in the regulation of many cellular activities (Rubin and Rosen, 1975). The Ca2+ and phospholipid-dependent protein kinase C (PKC) is a key regulatory enzyme believed to be involved in basic cell functions such as proliferation and differentiation (Schwantke et al., 1985). Activation of PKC by diacylglycerol (DAG) has linked the activity of this enzyme to the function of many stimuli acting via phosphatidylinositol turnover (Berridge, 1987). Indeed DAG has been postulated to be the second messenger able to activate PKC without a change in cytosolic Ca2+ concentration. Biologically active phorbol esters which usually act as tumor promoters also activate PKC and are presumed to exert their functions in this way; indeed this enzyme appears to be a cellular phorbol ester receptor (Ashendel, 1985).