Calmodulin-Binding Domain of AS160 Regulates Contraction- but Not Insulin-Stimulated Glucose Uptake in Skeletal Muscle

• DOI: 10.2337/db07-0681
• Publication Date: 2007-08-24T01:40:05Z
• Authors: Henning F. Kramer; Eric B. Taylor; Carol A. Witczak; Nobuharu Fujii; Michael F. Hirshman; Laurie J. Goodyear
• Keywords: GLUT4; Snf3

Insulin and contraction increase skeletal muscle glucose uptake through distinct additive mechanisms. However, recent reports have demonstrated that both signals converge on the Akt substrate of 160 kDa (AS160), a protein regulates GLUT4 translocation. Although AS160 phosphorylation is believed to be primary factor affecting its activity, also possesses calmodulin-binding domain (CBD). This raises possibility contraction-stimulated increases in Ca(2+)/calmodulin could modulate function.To evaluate CBD muscle, empty-vector, wild-type, or CBD-mutant cDNAs were injected into mouse muscles followed by vivo electroporation. One week later, was overexpressed approximately 14-fold over endogenous protein.Immunoprecipitates wild-type incubated with biotinylated calmodulin presence Ca(2+). Wild-type AS160, but not associated calmodulin. Next, we measured insulin- vivo. Compared empty-vector insulin-stimulated altered expressing AS160. In contrast, significantly decreased CBD-mutant-expressing muscles. inhibitory effect aberrant phosphorylation. Interestingly, Rab-GAP (GTPase-activating protein) point mutations (CBD + R/K) fully restored uptake.Our results suggest directly contraction-induced provides an additional means modulating function independent These findings define novel signaling component, unique insulin, leading muscle.