Abstract
The major substrates for the type I insulin-like growth factor (IGF-I) receptor are Shc and insulin receptor substrate (IRS) proteins. In the current study, we report that IGF-I induces a sustained tyrosine phosphorylation of Shc and its association with Grb2 in SH-SY5Y human neuroblastoma cells. The time course of Shc tyrosine phosphorylation parallels the time course of IGF-I-stimulated activation of extracellular signal-regulated kinase (ERK). Transfection of SH-SY5Y cells with a p52 Shc mutant decreases Shc tyrosine phosphorylation and Shc-Grb2 association. This results in the inhibition of IGF-I-mediated ERK tyrosine phosphorylation and neurite outgrowth. In contrast, IGF-I induces a transient tyrosine phosphorylation of IRS-2 and an association of IRS-2 with Grb2. The time course of IRS-2 tyrosine phosphorylation and IRS-2-Grb2 and IRS-2-p85 association closely resembles the time course of IGF-I-mediated membrane ruffling. Treating cells with the phosphatidylinositol 3'-kinase inhibitors wortmannin and LY294002 blocks IGF-I-induced membrane ruffling. The ERK kinase inhibitor PD98059, as well as transfection with the p52 Shc mutant, has no effect on IGF-I-mediated membrane ruffling. Immunolocalization studies show IRS-2 and Grb2, but not Shc, concentrated at the tip of the extending growth cone where membrane ruffling is most active. Collectively, these results suggest that the association of Shc with Grb2 is essential for IGF-I-mediated neurite outgrowth, whereas the IRS-2-Grb2-phosphatidylinositol 3'-kinase complex may regulate growth cone extension and membrane ruffling.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing*
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Adaptor Proteins, Vesicular Transport*
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Androstadienes / pharmacology
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Cell Membrane / physiology
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Cell Membrane / ultrastructure
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Chromones / pharmacology
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Enzyme Inhibitors / pharmacology
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Epidermal Growth Factor / pharmacology
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Epidermal Growth Factor / physiology
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Flavonoids / pharmacology
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GRB2 Adaptor Protein
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Humans
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Insulin Receptor Substrate Proteins
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Insulin-Like Growth Factor I / pharmacology*
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Insulin-Like Growth Factor I / physiology
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Intracellular Signaling Peptides and Proteins
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Models, Biological
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Morpholines / pharmacology
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Neurites / physiology
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Neuroblastoma
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Phosphoinositide-3 Kinase Inhibitors
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Phosphoproteins / genetics
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Phosphoproteins / metabolism*
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Phosphorylation
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Phosphotyrosine / metabolism
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Proteins / genetics
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Proteins / metabolism*
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Receptor, Insulin / physiology*
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Recombinant Proteins / metabolism
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Shc Signaling Adaptor Proteins
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Signal Transduction / physiology*
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Src Homology 2 Domain-Containing, Transforming Protein 1
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Transfection
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Tumor Cells, Cultured
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Wortmannin
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src Homology Domains
Substances
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Adaptor Proteins, Signal Transducing
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Adaptor Proteins, Vesicular Transport
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Androstadienes
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Chromones
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Enzyme Inhibitors
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Flavonoids
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GRB2 Adaptor Protein
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GRB2 protein, human
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IRS2 protein, human
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Insulin Receptor Substrate Proteins
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Intracellular Signaling Peptides and Proteins
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Morpholines
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Phosphoinositide-3 Kinase Inhibitors
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Phosphoproteins
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Proteins
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Recombinant Proteins
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SHC1 protein, human
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Shc Signaling Adaptor Proteins
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Src Homology 2 Domain-Containing, Transforming Protein 1
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Phosphotyrosine
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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Epidermal Growth Factor
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Insulin-Like Growth Factor I
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Receptor, Insulin
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2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
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Wortmannin