A common amino acid polymorphism in insulin receptor substrate-1 causes impaired insulin signaling. Evidence from transfection studies.
Insulin receptor substrates-1 (IRS-1) is the major cytoplasmic substrate of the insulin and IGF-1 receptors. Recent studies have identified multiple sequence variants of IRS-1, especially in patients with non-insulin-dependent diabetes mellitus. In the present study, we have examined insulin-stimulated processes in 32D(IR) cells, a myeloid progenitor cell stably overexpressing the insulin receptor, transfected with wild-type human-IRS-1 or the most common human variant of IRS-1 in which glycine 972 is replaced by arginine. As compared to wild-type IRS-1, insulin stimulation of cells transfected with mutant IRS-1 exhibited a 32% decrease in incorporation of [3H]thymidine into DNA (P = 0.002), a 36% decrease in IRS-1 associated phosphatidylinositol (PI) 3-kinase activity (P = 0.004) and a 25% decrease in binding of the p85 regulatory subunit of PI 3-kinase to IRS-1 (P = 0.002). There was also a tendency for a decrease in Grb2 binding to IRS-1 and insulin-stimulated mitogen-activated protein kinase activity, however, these were not statistically significant. The changes occurred with no change in insulin receptor or IRS-1 tyrosine phosphorylation. These data indicate that the mutation in codon 972 in IRS-1 impairs insulin-stimulated signaling, especially along the PI 3-kinase pathway, and may contribute to insulin resistance in normal and diabetic populations.
Almind
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Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215, USA.
Inoue
G
G
Pedersen
O
O
Kahn
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CR
D001120:Arginine; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics; D004789:Enzyme Activation; D015870:Gene Expression; D005998:Glycine; D006412:Hematopoietic Stem Cells; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D016297:Mutagenesis, Site-Directed; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism*; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011972:Receptor, Insulin / Q000096:biosynthesis / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013936:Thymidine / Q000378:metabolism; D014162:Transfection
C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; D004247:DNA; D001120:Arginine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011972:Receptor, Insulin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D005998:Glycine; D013936:Thymidine