title: p66shc inhibits insulin-like growth factor-I signaling via direct binding to Src through its polyproline and Src homology 2 domains, resulting in impairment of Src kinase activation.
abstract: p66(shc) is increased in response to cell stress, and these increases regulate growth factor actions. These studies were conducted to determine how p66(shc) alters IGF-I-stimulated Src activation, leading to decreased IGF-I actions. Our results show that p66(shc) binds to Src through a polyproline sequence motif contained in the CH2 domain, a unique domain in p66(shc), and IGF-I stimulates this interaction. Disruption of this interaction using a synthetic peptide containing the p66(shc) polyproline domain or expression of a p66(shc) mutant containing substitutions for the proline residues (P47A/P48A/P50A) resulted in enhanced Src kinase activity, p52(shc) phosphorylation, MAPK activation, and cell proliferation in response to IGF-I. To determine the mechanism of inhibition, the full-length CH2 domain and intact p66(shc) were tested for their ability to directly inhibit Src kinase activation in vitro. The CH2 domain peptide was clearly inhibitory, but full-length p66(shc) had a greater effect. Deletion of the C-terminal Src homology 2 domain in p66(shc) reduced its ability to inhibit Src kinase activation. These findings demonstrate that p66(shc) utilizes a novel mechanism for modulating Src kinase activation and that this interaction is mediated through both its collagen homologous region 2 and Src homology 2 domains.
authors.affiliation: Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Xi
authors.forename: Xinchun
authors.initials: X
authors.lastname: Shen
authors.forename: David R
authors.initials: DR
authors.lastname: Clemmons
mesh_terms: D000818:Animals; D000943:Antigens, Differentiation / Q000235:genetics / Q000378:metabolism; D001011:Aorta / Q000166:cytology; D002478:Cells, Cultured; D004789:Enzyme Activation; D051380:GRB2 Adaptor Protein / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000502:physiology; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013552:Swine; D018909:src Homology Domains; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000943:Antigens, Differentiation; D051380:GRB2 Adaptor Protein; D046912:Multiprotein Complexes; D010455:Peptides; D011971:Receptors, Immunologic; D055765:Shc Signaling Adaptor Proteins; D019000:Phosphotyrosine; C011083:polyproline; D007334:Insulin-Like Growth Factor I; D019061:src-Family Kinases; D020928:Mitogen-Activated Protein Kinases