G_α11 Signaling through ARF6 Regulates F-Actin Mobilization and GLUT4 Glucose Transporter Translocation to the Plasma Membrane

Abstract

The action of insulin to recruit the intracellular GLUT4 glucose transporter to the plasma membrane of 3T3-L1 adipocytes is mimicked by endothelin 1, which signals through trimeric G_αq or G_α11 proteins. Here we report that murine G_α11 is most abundant in fat and that expression of the constitutively active form of G_α11 [G_α11(Q209L)] in 3T3-L1 adipocytes causes recruitment of GLUT4 to the plasma membrane and stimulation of 2-deoxyglucose uptake. In contrast to the action of insulin on GLUT4, the effects of endothelin 1 and G_α11 were not inhibited by the phosphatidylinositol 3-kinase inhibitor wortmannin at 100 nM. Signaling by insulin, endothelin 1, or G_α11(Q209L) also mobilized cortical F-actin in cultured adipocytes. Importantly, GLUT4 translocation caused by all three agents was blocked upon disassembly of F-actin by latrunculin B, suggesting that the F-actin polymerization caused by these agents may be required for their effects on GLUT4. Remarkably, expression of a dominant inhibitory form of the actin-regulatory GTPase ARF6 [ARF6(T27N)] in cultured adipocytes selectively inhibited both F-actin formation and GLUT4 translocation in response to endothelin 1 but not insulin. These data indicate that ARF6 is a required downstream element in endothelin 1 signaling through G_α11 to regulate cortical actin and GLUT4 translocation in cultured adipocytes, while insulin action involves different signaling pathways.

ACKNOWLEDGMENTS

We sincerely thank Hiroshi Itoh for providing the pCMV5-G_α11 (wild type) and pCMV5-G_α11(Q209L) constructs and Bert Vogelstein for the pAdTrack-CMV and pAdEasy-1 plasmids. We also thank Morris J. Birnbaum and John T. R. Lawrence for discussions and critical reading of the manuscript.

This work was supported in part by National Institutes of Health grant DK30648 (M.P.C.) and by a mentor-based fellowship to A.B. from the American Diabetes Association