Fig. 3.

Nox4 is required for IGF-I-induced Akt phosphorylation. A: PTCs were infected with either an adenovirus expressing dominant negative Nox4 (Ad-Nox4 ΔFAD/ΔNAD) or Ad-GFP as a control. After 48 h, cells were then treated with IGF-I (250 ng/ml) for 10 min. Dominant negative Nox4 adenovirus abolished IGF-I-induced Akt phosphorylation at serine 473 as assessed by Western blot analysis. B: small interfering RNA (siRNA) against Nox4 results in a significant reduction of Nox4 protein levels (middle) and a concomitant reduction in IGF-I-induced Akt phosphorylation (top). Scr, scrambled siRNA. Histograms (bottom) represent the intensity of the p-Akt bands to the total Akt or GAPDH, respectively, and values are expressed as a percentage of control.