Lipid raft microdomain compartmentalization of TC10 is required for insulin signaling and GLUT4 translocation

Recent studies indicate that insulin stimulation of glucose transporter (GL UT)4 translocation requires at least two distinct insulin receptor-mediated signals: one leading to the activation of phosphatidylinositol 3 (PI-3) ki nase and the other to the activation of the small GTP binding protein TC10. We now demonstrate that TC10 is processed through the secretory membrane t rafficking system and localizes to caveolin-enriched lipid raft microdomain s. Although insulin activated the wildtype TC10 protein and a TC10/H-Ras ch imera that were targeted to lipid raft microdomains, it was unable to activ ate a TC10/K-Ras chimera that was directed to the non-lipid raft domains. S imilarly, only the lipid raft-localized TC10/H-Ras chimera inhibited GLUT4 translocation, whereas the TC10/K-Ras chimera showed no significant inhibit ory activity. Furthermore, disruption of lipid raft microdomains by express ion of a dominant-interfering caveolin 3 mutant (Cav3/DGV) inhibited the in sulin stimulation of GLUT4 translocation and TC10 lipid raft localization a nd activation without affecting PI-3 kinase signaling. These data demonstra te that the insulin stimulation of GLUT4 translocation in adipocytes requir es the spatial separation and distinct compartmentalization of the PI-3 kin ase and TC10 signaling pathways.