Insulin stimulates association of insulin receptor substrate-1 with the protein abundant Src homology/growth factor receptor-bound protein 2.
Insulin activates the ras proto-oncogene product p21ras (Ras) by stimulating conversion of the inactive GDP-bound form of Ras to the active GTP-bound form. The protein ASH (for abundant Src homology) (Matuoka, K., Shibata, M., Yamakawa, A., and Takenawa, T. (1992) Proc. Natl. Acad. Sci. U. S. A. 89, 9015-9019) is composed of one Src homology (SH)2 and two SH3 domains and highly homologous to the Caenorhabditis elegans protein sem-5 that couples a tyrosine kinase to a Ras protein. We have studied an interaction of ASH with insulin-stimulated tyrosine-phosphorylated proteins in Chinese hamster ovary cells overexpressing human insulin receptors (CHO-HIR cells). In an anti-ASH (alpha ASH) immunoprecipitates, we detected a 170-kDa phosphoprotein that was recognized by an anti-phosphotyrosine antibody and an anti-insulin receptor substrate 1 antibody (alpha IRS-1) from the insulin-stimulated [32P]orthophosphate-labeled CHO-HIR cells. We failed to detect the tyrosine phosphorylation of the protein ASH. These data suggested that insulin stimulates IRS-1.ASH complex formation in intact cells. Incubation of an ASH fusion protein with the lysates of insulin-stimulated CHO-HIR cells revealed that the fusion protein of ASH was able to bind the tyrosine-phosphorylated 170-kDa protein that was recognized by alpha IRS-1. We also demonstrated that fusion protein of ASH was able to bind the fusion protein of tyrosine-phosphorylated IRS-1 fragments, suggesting that ASH is able to bind tyrosine-phosphorylated IRS-1 directly. These data suggest that IRS-1.ASH complex formation may play a role in coupling the insulin receptor kinase to a Ras signaling pathway. Furthermore, we observed an insulin-stimulated phosphatidylinositol (PI) 3-kinase activity in alpha ASH immunoprecipitates, suggesting the formation of an ASH.IRS-1.PI 3-kinase complex. This complex formation was detected as early as 10 s after insulin stimulation in intact CHO-HIR cells. This is the first report that supports the notion that IRS-1 binds several signal transducing molecules containing SH2 domains, thus serves as an SH2 docking protein that transduces insulin's signal multidirectionally.
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
K
K
Tobe
K
K
Matuoka
H
H
Tamemoto
K
K
Ueki
Y
Y
Kaburagi
S
S
Asai
T
T
Noguchi
M
M
Matsuda
S
S
Tanaka
S
S
Hattori
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D016466:CHO Cells; D006224:Cricetinae; D066246:ErbB Receptors / Q000378:metabolism*; D051380:GRB2 Adaptor Protein; D011905:Genes, ras; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D007700:Kinetics; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000276:immunology; D010710:Phosphates / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000032:analysis / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
D048868:Adaptor Proteins, Signal Transducing; D000906:Antibodies; D066246:ErbB Receptors; D051380:GRB2 Adaptor Protein; D005982:Glutathione Transferase; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D009842:Oligopeptides; D010710:Phosphates; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D010770:Phosphotransferases; D011506:Proteins; D000090063:Proto-Oncogene Mas; D011972:Receptor, Insulin; D011993:Recombinant Fusion Proteins; C495948:GRB2 protein, human; C526292:IRS1 protein, human; C000715470:MAS1 protein, human