Effect of phosphotyrosyl-IRS-1 level and insulin receptor tyrosine kinase activity on insulin-stimulated phosphatidylinositol 3, MAP, and S6 kinase activities.
The role of tyrosine phosphorylation of the insulin receptor substrate 1 (IRS-1) was studied utilizing parental CHO cells or CHO cells that overexpress IRS-1, the insulin receptor, or both IRS-1 and the insulin receptor. Insulin stimulation of these four cell lines led to progressive levels of IRS-1 tyrosine phosphorylation of one, two, four, and tenfold. Maximal insulin-stimulated IRS-1 associated PtdIns 3'-kinase activit in these cells was 1-, 1.5-, 3-, and 3-fold, while insulin sensitivity, as determined by ED50, was 1-, 2.5-, 10-, and 10-fold. Both sensitivity and maximal response paralleled the increased level of phosphotyrosyl-IRS-1; however, the increased level of phosphotyrosyl-IRS-1 seen in CHO/IR/IRS-1 cells did not further increase these responses. Likewise, maximal insulin-stimulated MAP kinase activity in these cell lines increased in parallel with IRS-1 tyrosine phosphorylation except in the CHO/IR/IRS-1 cell lines with activity levels of one-, five-, nine-, and ninefold. However, insulin sensitivity of the MAP and S6 kinases and maximal insulin-stimulated S6 kinase activity was not changed by a twofold increase in phosphotyrosyl-IRS-1, but an increase was observed with insulin-stimulated receptor autophosphorylation and kinase activity in CHO/IR cells which led to a tenfold increase in insulin receptor autophosphorylation and a fourfold increase in IRS-1 tyrosine phosphorylation. Thus, these three kinase activities may be differentially coupled to the activation of the insulin receptor kinase activity via IRS-1 and other possible cellular substrates.
Wilden
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PA
Department of Pharmacology, University of Missouri-Columbia, School of Medicine 65212.
Broadway
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DE
D019870:1-Phosphatidylinositol 4-Kinase; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D006224:Cricetinae; D038362:Glycogen Synthase Kinase 3; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*; D019893:Ribosomal Protein S6 Kinases; D014443:Tyrosine / Q000378:metabolism*
D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D010750:Phosphoproteins; D014443:Tyrosine; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); D019870:1-Phosphatidylinositol 4-Kinase; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3