Expression of a dominant interfering dynamin mutant in 3T3L1 adipocytes inhibits GLUT4 endocytosis without affecting insulin signaling - PubMed (original) (raw)

. 1998 Sep 25;273(39):25450-7.

doi: 10.1074/jbc.273.39.25450.

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Expression of a dominant interfering dynamin mutant in 3T3L1 adipocytes inhibits GLUT4 endocytosis without affecting insulin signaling

A W Kao et al. J Biol Chem. 1998.

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Abstract

To examine the role of clathrin-coated vesicle endocytosis in insulin receptor signaling and GLUT4 trafficking, we used recombinant adenovirus to express a dominant interfering mutant of dynamin (K44A/dynamin) in 3T3L1 adipocytes. Functional expression of K44A/dynamin, as measured by inhibition of transferrin receptor internalization, did not affect insulin-stimulated insulin receptor autophosphorylation, Shc tyrosine phosphorylation, or mitogen-activated protein kinase activation. Although the tyrosine phosphorylation of insulin receptor substrate-1 was slightly reduced, correlating with a 25% decrease in insulin receptor substrate-1-associated phosphatidylinositol 3-kinase activity, insulin-stimulated Akt kinase activation was unaffected. In contrast, expression of K44A/dynamin resulted in the cell-surface accumulation of GLUT4 under basal conditions and an inhibition of GLUT4 endocytosis without affecting insulin-stimulated GLUT4 exocytosis. These data demonstrate that disruption of clathrin-mediated endocytosis does not significantly perturb insulin receptor signal transduction pathways. Furthermore, K44A/dynamin expression causes an accumulation of GLUT4 at the cell surface, suggesting that GLUT4 vesicles exist in at least two distinct intracellular compartments, one that undergoes continuous recycling and a second that is responsive to insulin.

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