Morphological characterization of perinuclear GLUT4 distribution in L6 myoblasts.

摘要

Glucose transporter-4 (GLUT4) cycles to and from the plasma membrane and shows predominant perinuclear localization in unstimulated muscle and adipose tissues. This area is also occupied by recycling endosomes (RE), the Golgi complex, and the trans-Golgi network. Thorough characterization of insulin-responsive perinuclear compartments is lacking. Therefore, we evaluated insulin's effect on (i) the presence of GLUT4 in these compartments and (ii) the dynamics of perinuclear GLUT4 redistribution. We observed that insulin stimulation reduces the association of GLUT4 only with the RE and induces perinuclear GLUT4 remodelling that parallels the exocytic and internalization profiles of the transporter. Insulin-mediated GLUT4 translocation requires input from phosphatidylinositol-3-kinase (PI3-K), but the steps regulated are unknown. We show that mutants of (PI3-K), and its downstream molecule Akt Substrate 160 kDa (AS160) inhibit insulin-induced perinuclear GLUT4 remodelling. In summary, we characterize a novel insulin effect of perinuclear GLUT4 remodelling and demonstrate that it is regulated by the (PI3-K), → AS160 pathway.