title: Recruitment of the tyrosine phosphatase Src homology 2 domain tyrosine phosphatase-2 to the p85 subunit of phosphatidylinositol-3 (PI-3) kinase is required for insulin-like growth factor-I-dependent PI-3 kinase activation in smooth muscle cells.
abstract: IGF-I stimulates smooth muscle cell (SMC) migration and the phosphatidylinositol-3 (PI-3) kinase pathway plays an important role in mediating the IGF-I-induced migratory response. Prior studies have shown that the tyrosine phosphatase Src homology 2 domain tyrosine phosphatase (SHP)-2 is necessary to activate PI-3 kinase in response to growth factors and expression of a phosphatase inactive form of SHP-2 (SHP-2/C459S) impairs IGF-I-stimulated cell migration. However, the mechanism by which SHP-2 phosphatase activity or the recruitment of SHP-2 to other signaling molecules contributes to IGF-I stimulated PI-3 kinase activation has not been determined. SMCs that had stable expression of SHP-2/C459S had reduced cell migration and Akt activation in response to IGF-I, compared with SMC-expressing native SHP-2. Similarly in cells expressing native SHP-2, IGF-I induced SHP-2 binding to p85, whereas in cells expressing SHP-2/C459S, there was no increase. Because the C459S substitution results in loss of the ability of SHP-2 to disassociate from its substrates, making it inaccessible not only to p85 but also the other proteins, a p85 mutant in which tyrosines 528 and 556 were changed to phenylalanines was prepared to determine whether this would disrupt the p85/SHP-2 interaction and whether the loss of this specific interaction would alter IGF-I stimulated the cell migration. Substitution for these tyrosines in p85 resulted in loss of SHP-2 recruitment and was associated with a reduction in association of the p85/p110 complex with insulin receptor substrate-1. Cells stably expressing this p85 mutant also showed a decrease in IGF-I-stimulated PI-3 kinase activity and cell migration. Preincubation of cells with a cell-permeable peptide that contains the tyrosine556 motif of p85 also disrupted SHP-2 binding to p85 and inhibited the IGF-I-induced increase in cell migration. The findings indicate that tyrosines 528 and 556 in p85 are required for SHP-2 association. SHP-2 recruitment to p85 is required for IGF-I-stimulated association of the p85/p110 complex with insulin receptor substrate-1 and for the subsequent activation of the PI-3 kinase pathway leading to increased cell migration.
authors.affiliation: Division of Endocrinology, 6111 Thurston-Bowles, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7170, USA.
authors.forename: Mijin
authors.initials: M
authors.lastname: Kwon
authors.forename: Yan
authors.initials: Y
authors.lastname: Ling
authors.forename: Laura A
authors.initials: LA
authors.lastname: Maile
authors.forename: Jane
authors.initials: J
authors.lastname: Badley-Clark
authors.forename: David R
authors.initials: DR
authors.lastname: Clemmons
mesh_terms: D000818:Animals; D001011:Aorta / Q000378:metabolism; D002465:Cell Movement; D002478:Cells, Cultured; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D015233:Models, Statistical; D009130:Muscle, Smooth / Q000166:cytology*; D009154:Mutation; D010649:Phenylalanine / Q000737:chemistry; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry* / Q000378:metabolism; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013552:Swine; D014443:Tyrosine / Q000737:chemistry
chemical_list: D014443:Tyrosine; D010649:Phenylalanine; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases; C098706:INPPL1 protein, human; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases