Myosin Motor Myo1C and Its Receptor$NEMO/IKK-\gamma$Promote$TNF-\alpha-Induced$ $Serine^{307}$Phosphorylation of IRS-1

Tumor necrosis$factor-\alpha$($TNF-\alpha$) signaling through the Iκ B kinase (IKK) complex attenuates insulin action via the phosphorylation of insulin receptor substrate 1 (IRS-1) at$Ser^{307}$. However, the precise molecular mechanism by which the IKK complex phosphorylates IRS-1 is unknown. In this study, we report nuclear factor κ B essential modulator$(NEMO)/IKK-\gamma$subunit accumulation in membrane ruffles followed by an interaction with IRS-1. This intracellular trafficking of NEMO requires insulin, an intact actin cytoskeletal network, and the motor protein Myo1c. Increased Myo1c expression enhanced the NEMO-IRS-1 interaction, which is essential for$TNF-\alpha-induced$phosphorylation of$Ser^{307}-IRS-1$. In contrast, dominant inhibitory Myolc cargo domain expression diminished this interaction and inhibited IRS-1 phosphorylation. NEMO expression also enhanced$TNF-\alpha-induced$ $Ser^{307}-IRS-1$phosphorylation and inhibited glucose uptake. In contrast, a deletion mutant of NEMO lacking the$IKK-\beta-binding$domain or silencing NEMO blocked the$TNF-\alpha$signal. Thus, motor protein Myolc and its receptor protein NEMO act cooperatively to form the IKK-IRS-1 complex and function in$TNF-\alpha-induced$insulin resistance.