Purification of Protein Kinase C and Identification of Isozymes in Vascular Smooth Muscle

Abstract

Although protein kinase C (PKC) is known to be present in vascular smooth muscle (VSM), its physiologic significance is not understood. Among its actions, PKC has been proposed to regulate tonic contractile responses (Rasmussen et al., 1987) and mediate, at least in part, intracellular responses to growth stimuli (Woodgett et al., 1987). Functional roles for PKC have been inferred largely from studies using pharmacological activators of the kinase (phorbol esters) and putative selective inhibitors (e.g. H-7, staurosporine). These studies are indirect and interpretation of them must be tempered by the possibility that phorbol ester-induced activation of PKC is not equivalent to physiological agonist-induced activation and that currently available kinase inhibitors are not completely selective (for review, see Woodgett et al., 1987). Another approach used has been to predict and observe the effects of phorbol ester-stimulated down regulation of PKC activity (Rozengurt et al., 1983; Coughlin et al., 1985).