Sequestosome 1/p62 and TRAF6 are necessary for Akt ubiquitination, translocation and activation

Abstract

Defects in protein-protein interactions of the insulin signaling pathway result in insulin resistance that precedes type 2 diabetes. The protein Akt is the primary modulator of cellular glucose uptake through the GLUT4 transporter. On insulin stimulation, Akt is reported to undergo ubiquitination by the TRAF6 ligase before recruitment to the membrane. We have previously shown in our lab that p62 and TRAF6 serve as a bridge to connect IRS-1 with Akt. TRAF6 is known to form a complex with p62, modulating activation and increasing E3 ubiquitin ligase activity. Investigations in L6 myotubes and TRAF6-/- and p62-/- Mouse Embryonic Fibroblasts (MEF) indicate p62 and TRAF6 serve in Akt ubiquitination on insulin stimulation. Further study in TRAF6-/- and p62-/- MEF cells confirmed interactions with p62 and TRAF6 are necessary for Akt translocation and activation on insulin stimulation. Wild-type MEF cells stimulated with insulin exhibited Akt membrane recruitment and activation, whereas insulin stimulated TRAF6-/- and p62-/- MEF cells exhibited impaired membrane recruitment and activation of Akt. Therefore, the TRAF6/p62 complex is necessary for Akt ubiquitination, translocation to the plasma membrane, and activation.