Ligand-independent GLUT4 translocation induced by guanosine 5'-O-(3-thiotriphosphate) involves tyrosine phosphorylation

Endocrinology
T HarutaJ M Olefsky

Abstract

To delineate the signaling pathway leading to glucose transport protein (GLUT4) translocation, we examined the effect of microinjection of the nonhydrolyzable GTP analog, guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS), into 3T3-L1 adipocytes. Thirty minutes after the injection of 5 mM GTPgammaS, 40% of injected cells displayed surface GLUT4 staining indicative of GLUT4 translocation compared with 55% for insulin-treated cells and 10% in control IgG-injected cells. Treatment of the cells with the phosphatidylinositol 3-kinase inhibitor wortmannin or coinjection of GST-p85 SH2 fusion protein had no effect on GTPgammaS-mediated GLUT4 translocation. On the other hand, coinjection of antiphosphotyrosine antibodies (PY20) blocked GTPgammaS-induced GLUT4 translocation by 65%. Furthermore, microinjection of GTPgammaS led to the appearance of tyrosine-phosphorylated proteins around the periphery of the plasma membrane, as observed by immunostaining with PY20. Treatment of the cells with insulin caused a similar phosphotyrosine-staining pattern. Electroporation of GTPgammaS stimulated 2-deoxy-D-glucose transport to 70% of the extent of insulin stimulation. In addition, immunoblotting with phosphotyrosine antibodies after electroporation...Continue Reading

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Citations

Jan 31, 2003·Molecular and Cellular Biology·Takeshi Ijuin, Tadaomi Takenawa
Oct 29, 2011·Gastroenterología y hepatología·Pedro J Rosón RodríguezMari Carmen Lopez Vega
Jan 18, 2012·São Paulo Medical Journal = Revista Paulista De Medicina·Gustavo Dias FerreiraEdison Capp
Sep 22, 1999·Molecular and Cellular Biology·T ImamuraJ M Olefsky
Apr 25, 2000·The Journal of Biological Chemistry·N NakashimaJ M Olefsky

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