Insulin elicits a ROS-activated and an IP[sub 3]-dependent Ca2+ release, which both impinge on GLUT4 translocation.

Insulin signaling includes generation of low levels of H[sub 2]O[sub 2]; however, its origin and contribution to insulin-stimulated glucose transport are unknown. We tested the impact of H[sub 2]O[sub 2] on insulin-dependent glucose transport and GLUT4 translocation in skeletal muscle cells. H[sub 2]O[sub 2] increased the translocation of GLUT4 with an exofacial Myc-epitope tag between the first and second transmembrane domains (GLUT4myc), an effect additive to that of insulin. The anti-oxidants /V-acetyl L-cysteine and Trolox, the p47[sup phox]-NOX2 NADPH oxidase inhibitory peptide gp91-ds-tat or p47[sup phox] knockdown each reduced insulin-dependent GLUT4myc translocation. Importantly, gp91-ds-tat suppressed insulin-dependent H[sub 2]O[sub 2] production. A ryanodine receptor (RyR) channel agonist stimulated GLUT4myc translocation and insulin stimulated RyR1-mediated Ca2+ release by promoting RyR1 S-glutathionylation. This pathway acts in parallel to insulin-mediated stimulation of inositol-1,4,5-trisphosphate (IP[sub 3])-activated Ca2+ channels, in response to activation of phosphatidylinositol 3-kinase and its downstream target phospholipase C, resulting in Ca2+ transfer to the mitochondria. An inhibitor of IP[sub 3] receptors, Xestospongin B, reduced both insulin-dependent IP[sub 3] production and GLUT4myc translocation. We propose that, in addition to the canonical α,β phosphatidylinositol 3-kinase to Akt pathway, insulin engages both RyR-mediated Ca2+ release and IP[sub 3]-receptor-mediated mitochondrial Ca2+ uptake, and that these signals jointly stimulate glucose uptake. [ABSTRACT FROM AUTHOR]