Insulin-stimulated tyrosine phosphorylation of protein kinase C alpha: evidence for direct interaction of the insulin receptor and protein kinase C in cells.
Insulin, in the presence of phorbol esters, was observed to stimulate the tyrosine phosphorylation of a major 80 kDa protein by immunoblotting with anti-phosphotyrosine antibodies in Chinese hamster ovary cells overexpressing the insulin receptor and protein kinase C alpha. The protein was specifically immunoprecipitated by antibodies to protein kinase C and anti-phosphotyrosine antibodies were capable of immunoprecipitating protein kinase C enzymatic activity from these cells. When this tyrosine phosphorylated protein kinase C was treated with a tyrosine-specific phosphatase, a 35% decrease in its enzymatic activity was observed and this inhibition was blocked by inclusion of a tyrosine phosphatase inhibitor, vanadate, in the reaction mixture. These results indicate that under certain conditions insulin can stimulate the tyrosine phosphorylation of protein kinase C and this phosphorylation can affect its enzymatic activity.
Liu
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F
Department of Molecular Pharmacology, Stanford University School of Medicine, CA 94305.
Roth
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RA
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D007328:Insulin / Q000494:pharmacology; D046911:Macromolecular Substances; D019000:Phosphotyrosine; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*; D011994:Recombinant Proteins; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D007328:Insulin; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D011972:Receptor, Insulin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate