Globular adiponectin induces LKB1/AMPK-dependent glucose uptake via actin cytoskeleton remodeling

Previous studies have shown that many metabolic actions of adiponectin are mediated via the activation of AMP kinase and that adiponectin stimulates GLUT4 translocation and glucose uptake in the muscle. In this study, we demonstrate that adiponectin stimulates actin cytoskeleton remodeling, with increased phosphorylation of cofilin, and that blocking of cytoskeletal remodeling with cytochalasin D prevents adiponectin-stimulated AMPK phosphorylation in L6 myoblasts. LKB1 is an upstream kinase of AMPK, and we observed the colocalization of LKB1 with filamentous actin in response to adiponectin. Adiponectin-stimulated translocation of LKB1 from a nuclear to a cytoplasmic location to activate AMPK was also dependent on actin cytoskeleton remodeling. Cytoskeletal remodeling visualized by rhodamine-phalloidin immunofluorescence indicated that adiponectin-stimulated reorganization resulted in the formation membrane ruffles, which were also clearly visible by scanning electron microscopy in L6-GLUT4(myc) myoblasts. The stimulation of glucose uptake, but not of GLUT4-myc translocation to the cell surface, by adiponectin was also dependent on actin cytoskeleton remodeling. These results suggest that actin remodeling induced by adiponectin is essential for mediating LKB1/AMPK signaling and glucose uptake in skeletal muscle cells.