Rab‐GAP AS160 is differentially regulated by multiple effectors of glucose transport in mouse skeletal muscle

Insulin and contraction increase glucose transport via GLUT4 translocation in skeletal muscle, although distinct signaling mechanisms are thought to lead to translocation. Akt substrate of 160 kDa (AS160) mediates insulin‐stimulated GLUT4 translocation in L6 myotubes, presumably through activation of Akt. Using in vivo , in vitro and in situ methods, we found that insulin and contraction increased AS160 phosphorylation by 2‐ to 3‐fold in mouse skeletal muscle, and that combined insulin and contraction treatment was partially additive. Insulin‐stimulated AS160 phosphorylation was fully blunted by wortmannin in vitro , and in Akt2 knockout (KO) mice in vivo . In contrast, contraction‐stimulated AS160 phosphorylation was only partially decreased by wortmannin and unaffected in Akt2 KO mice, suggesting an Akt‐independent regulatory mechanism. To determine if AMPK mediates contraction‐stimulated AS160 phosphorylation we used AICAR (AMPK activator) and AMPK α2‐inactive transgenic (TG) mice. AICAR increased AS160 phosphorylation in wild type, but not TG mice. However, contraction‐stimulated AS160 phosphorylation was preserved in TG mice suggesting compensation by Akt and/or regulation by another contraction‐sensitive kinase. In conclusion, AS160 may function as a point of convergence linking insulin, contraction, and AICAR effects on GLUT4 translocation. While Akt and AMPK activities are essential for AS160 phosphorylation by insulin and AICAR, respectively, neither kinase is indispensable for contraction‐stimulated AS160 phosphorylation. NIH AR42338