Transfected cells were harvested 48 hours after transfection. Total cell lysate preparation and western blot analysis were performed according to previously described procedures [26] . In brief, cell lysates were prepared, electrophoresed on SDS-PAGE gels, and transferred to polyvinylidene difluoride (PVDF) membranes. Membranes were blocked with 5% nonfat milk in TBST (20 mM Tris-HCl [pH 7.5], 150 mM NaCl, and 0.05% [v/v] Tween 20) and incubated with IRAS or GFP mAbs (Cell Signaling Technology Inc). Blots were incubated with horseradish peroxidase (HRP) conjugated goat antimouse antibodies (Santa Cruz) after primary antibody incubation, and blots were developed with enhanced electrochemiluminescence (ECL, Cell Signaling Technology Inc).