IRS-1 activates phosphatidylinositol 3'-kinase by associating with src homology 2 domains of p85.
IRS-1 is an insulin receptor substrate that undergoes tyrosine phosphorylation and associates with the phosphatidylinositol (PtdIns) 3'-kinase immediately after insulin stimulation. Recombinant IRS-1 protein was tyrosine phosphorylated by the insulin receptor in vitro and associated with the PtdIns 3'-kinase from lysates of quiescent 3T3 fibroblasts. Bacterial fusion proteins containing the src homology 2 domains (SH2 domains) of the 85-kDa subunit (p85) of the PtdIns 3'-kinase bound quantitatively to tyrosine phosphorylated, but not unphosphorylated, IRS-1, and this association was blocked by phosphotyrosine-containing synthetic peptides. Moreover, the phosphorylated peptides and the SH2 domains each inhibited binding of PtdIns 3'-kinase to IRS-1. Phosphorylated IRS-1 activated PtdIns 3'-kinase in anti-p85 immunoprecipitates in vitro, and this activation was blocked by SH2 domain fusion proteins. These data suggest that the interaction between PtdIns 3'-kinase and IRS-1 is mediated by tyrosine phosphorylated motifs on IRS-1 and the SH2 domains of p85, and IRS-1 activates PtdIns 3'-kinase by binding to the SH2 domains of p85. Thus, IRS-1 likely serves to transmit the insulin signal by binding and regulating intracellular enzymes containing SH2 domains.
Myers
M G
MG
Joslin Diabetes Center, Department of Medicine, Harvard Medical School, Boston, MA 02215.
Backer
J M
JM
Sun
X J
XJ
Shoelson
S
S
Hu
P
P
Schlessinger
J
J
Yoakim
M
M
Schaffhausen
B
B
White
M F
MF
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D004247:DNA / Q000235:genetics; D004789:Enzyme Activation; D016391:Genes, src; D005982:Glutathione Transferase / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D007700:Kinetics; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D019869:Phosphatidylinositol 3-Kinases; D010748:Phosphopeptides / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D046911:Macromolecular Substances; D010748:Phosphopeptides; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D004247:DNA; D005982:Glutathione Transferase; D010770:Phosphotransferases; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin