Abstract
Insulin stimulates glucose transport largely by mediating translocation of the insulin-sensitive glucose transporter (GLUT4) from an intracellular compartment to the plasma membrane. Using single cell microinjection of 3T3-L1 adipocytes, coupled with immunofluorescence detection of GLUT4 proteins, we have determined that inhibition of endogenous p21ras or injection of oncogenic p21ras has no effect on insulin-stimulated GLUT4 translocation. On the other hand, microinjection of anti-phosphotyrosine antibodies or inhibition of endogenous phosphatidylinositol 3-kinase by microinjection of a GST-p85 SH2 fusion protein markedly inhibits this biologic effect of insulin. These data suggest that the p21ras/mitogen-activated protein kinase pathway is not involved in this metabolic effect of insulin, whereas tyrosine phosphorylation and stimulation of phosphatidylinositol 3-kinase activity are critical components of this signaling pathway.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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1-Methyl-3-isobutylxanthine / pharmacology
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3T3 Cells
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Adipocytes / cytology
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Adipocytes / drug effects
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Adipocytes / metabolism*
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Animals
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Cell Differentiation
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Cell Line
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Cell Membrane / metabolism
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Dexamethasone / pharmacology
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Fibroblasts
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Genes, ras
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Glucose Transporter Type 4
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Humans
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Insulin / pharmacology*
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Kinetics
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Mice
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Monosaccharide Transport Proteins / metabolism*
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Muscle Proteins*
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Proto-Oncogene Proteins p21(ras) / biosynthesis
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Proto-Oncogene Proteins p21(ras) / metabolism
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Rats
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Receptor, Insulin / biosynthesis
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Receptor, Insulin / drug effects
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Receptor, Insulin / physiology*
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Signal Transduction* / drug effects
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Swine
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Transfection
Substances
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Glucose Transporter Type 4
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Insulin
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Monosaccharide Transport Proteins
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Muscle Proteins
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SLC2A4 protein, human
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Slc2a4 protein, mouse
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Slc2a4 protein, rat
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Dexamethasone
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Receptor, Insulin
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HRAS protein, human
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Proto-Oncogene Proteins p21(ras)
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1-Methyl-3-isobutylxanthine