Insulin receptor substrate-1 as a signaling molecule for focal adhesion kinase pp125(FAK) and pp60(src).
Insulin receptor substrate-1 (IRS-1) is a major substrate of insulin and insulin-like growth factor-I receptors, which upon phosphorylation on tyrosine docks several signaling molecules. Recently, IRS-1 was found to interact with alphav beta3 integrins upon insulin stimulation. Integrins are transmembrane proteins that play an important role in adhesion between cells and between cells and extracellular matrix. One of the major proteins implicated in integrin signaling is pp125(FAK), a cytosolic tyrosine kinase, which upon integrin engagement becomes tyrosine-phosphorylated and subsequently binds to c-Src. Here, we established a mammalian two-hybrid system to show that pp125(FAK) binds to IRS-1. This association depends largely on the C terminus of pp125(FAK) but not on pp125(FAK) tyrosine kinase activity. Furthermore, we observed co-immunoprecipitation of pp125(FAK) with IRS-1 in 293 cells, suggesting a possible biological function of this association. When IRS-1 was expressed in 293 cells together with pp125(FAK) or Src, we found extensive IRS-1 tyrosine phosphorylation. In pp125(FAK)-expressing cells, this was concomitant with increased association of IRS-1 with Src homology 2-containing proteins such as growth factor receptor-bound protein 2, phosphatidylinositol (PI) 3-kinase p85alpha subunit, and Src homology 2-containing protein-tyrosine phosphatase-2. In addition, pp125(FAK)-induced association of IRS-1 with PI 3-kinase resulted in increased PI 3-kinase activity. In contrast, no change in mitogen-activated protein kinase activity was observed, indicating that pp125(FAK)-induced association between IRS-1 and growth factor receptor-bound protein 2 does not affect the mitogen-activated protein kinase pathway. Moreover, we found that engagement of integrins induced IRS-1 tyrosine phosphorylation. Considering our results together, we suggest that integrins and insulin/insulin-like growth factor-I receptor signaling pathways converge at an early point in the signaling cascade, which is the IRS-1 protein.
Lebrun
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INSERM U145, Avenue de Valombrose, 06107 Nice Cédex 2, France.
Mothe-Satney
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I
Delahaye
L
L
Van Obberghen
E
E
Baron
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V
D019943:Amino Acid Substitution; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002460:Cell Line; D003001:Cloning, Molecular; D016326:Extracellular Matrix Proteins / Q000502:physiology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D017930:Genes, Reporter; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D007668:Kidney; D008156:Luciferases / Q000096:biosynthesis; D016297:Mutagenesis, Site-Directed; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D018909:src Homology Domains
D015815:Cell Adhesion Molecules; D016326:Extracellular Matrix Proteins; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D008156:Luciferases; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D016392:Proto-Oncogene Proteins pp60(c-src)