Bose A, Cherniack A D, Langille S E, Nicoloro S M, Buxton J M, Park J G, Chawla A, Czech M P
Program in Molecular Medicine and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical Center, Worcester, Massachusetts 01605, USA.
Mol Cell Biol. 2001 Aug;21(15):5262-75. doi: 10.1128/MCB.21.15.5262-5275.2001.
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(alpha)q or G(alpha)11 proteins. Here we report that murine G(alpha)11 is most abundant in fat and that expression of the constitutively active form of G(alpha)11 [G(alpha)11(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(alpha)11 were not inhibited by the phosphatidylinositol 3-kinase inhibitor wortmannin at 100 nM. Signaling by insulin, endothelin 1, or G(alpha)11(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(alpha)11 to regulate cortical actin and GLUT4 translocation in cultured adipocytes, while insulin action involves different signaling pathways.
内皮素1可模拟胰岛素的作用，促使细胞内的GLUT4葡萄糖转运体转运至3T3-L1脂肪细胞的质膜，内皮素1通过三聚体G(α)q或G(α)11蛋白进行信号传导。我们在此报告，小鼠G(α)11在脂肪中含量最为丰富，在3T3-L1脂肪细胞中表达组成型活性形式的G(α)11 [G(α)11(Q209L)]会导致GLUT4转运至质膜，并刺激2-脱氧葡萄糖摄取。与胰岛素对GLUT4的作用不同，100 nM的磷脂酰肌醇3-激酶抑制剂渥曼青霉素不会抑制内皮素1和G(α)11的作用。胰岛素、内皮素1或G(α)11(Q209L)的信号传导也会使培养的脂肪细胞中的皮质F-肌动蛋白发生动员。重要的是，用拉特罗毒素B破坏F-肌动蛋白后，这三种物质引起的GLUT4易位均被阻断，这表明这些物质引起的F-肌动蛋白聚合可能是它们对GLUT4产生作用所必需的。值得注意的是，在培养的脂肪细胞中表达肌动蛋白调节GTP酶ARF6的显性抑制形式[ARF6(T27N)]，可选择性抑制内皮素1诱导的F-肌动蛋白形成和GLUT4易位，但对胰岛素无此作用。这些数据表明，ARF6是内皮素1通过G(α)11进行信号传导以调节培养的脂肪细胞中皮质肌动蛋白和GLUT4易位所必需的下游元件，而胰岛素的作用涉及不同的信号通路。
