The role of protein kinase C isoforms in insulin action.

Insulin action on target tissues is mediated by specific tyrosine kinase receptors. Upon ligand binding insulin receptors autophosphorylate and phosphorylate intracellular substrates on tyrosine residues. These early events of insulin action are followed by the activation of a number of enzymes, including protein kinase C (PKC). At least 14 PKC isoforms have been identified and cloned to date. PKCs appear to play dual roles in insulin signaling. For instance, they are involved in transduction of specific insulin signals but also contribute to the generation of insulin resistance. In this article, we will analyze the experimental evidence addressing the mechanism by which insulin might activate individual PKC isoforms as well as the role of single PKCs in insulin-induced bioeffects.