Modulation of insulin receptor substrate-1 tyrosine phosphorylation and function by mitogen-activated protein kinase.
Increased serine phosphorylation of insulin receptor substrate-1 (IRS-1) has been observed in several systems to correlate with a decreased ability of the insulin receptor to tyrosine-phosphorylate this endogenous substrate and to inhibit its subsequent association with phosphatidylinositol 3-kinase. In the present studies we have examined the potential role of the mitogen-activated protein (MAP) kinase in the increased serine phosphorylation of IRS-1 observed in human embryonic kidney cells treated with an activator of protein kinase C, phorbol 12-myristate 13-acetate. First, recombinantly produced kinase was shown to phosphorylate intact IRS-1 in a way that decreased the ability of isolated insulin receptor to phosphorylate the tyrosines recognized by the SH2 domains of the phosphatidylinositol 3-kinase. Second, an inhibitor of MAP kinase activation, PD98059, blocked the phorbol 12-myristate 13-acetate-induced inhibition of the insulin-stimulated increase in IRS-1 associated phosphatidylinositol 3-kinase. Third, activation of MAP kinase in intact cells via a regulatable upstream kinase, a RAF:estrogen receptor construct, could also inhibit the insulin-stimulated increase in IRS-1-associated phosphatidylinositol 3-kinase. Fourth, an in gel kinase assay showed that MAP kinase was the primary renaturable kinase in cell extracts capable of phosphorylating an IRS-1 fusion protein. Finally, IRS-1 was found to associate in coprecipitation studies with endogenous MAP kinase. These studies implicate MAP kinase as one of the kinases capable of phosphorylating and regulating IRS-1 tyrosine phosphorylation.
De Fea
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Department of Molecular Pharmacology, Stanford University School of Medicine, Stanford, California 94305, USA.
Roth
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D000818:Animals; D016466:CHO Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D006224:Cricetinae; D004789:Enzyme Activation; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D007668:Kidney / Q000196:embryology; D048369:MAP Kinase Kinase 1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism*
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D055504:Insulin Receptor Substrate Proteins; D048369:MAP Kinase Kinase 1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011994:Recombinant Proteins; D012694:Serine; D013755:Tetradecanoylphorbol Acetate; D014443:Tyrosine; C526292:IRS1 protein, human; C482125:MAP2K1 protein, human