Figure 2

Gαs activated PP2A in a PKA dependent manner, which decreased the radiation-induced phosphorylation of ATM in H1299 lung cancer cells. (A) Effect of okadaic acid (OA) on the radiation-induced ATM phosphorylation. (B) Effect of Gαs on PP2A B56δ phosphorylation. (C) Effect of PKA inhibition on the phosphorylation of PP2A B56δ and ATM. (D) Effect of Gαs on PP2A activity. H1299 cells were transfected with GαsQL, vector (V), or dominant negative PKA (dnPKA) and incubated for 24 h. siRNA against B56δ (siB56δ) or control siRNA was transfected and the cells were incubated for 48 h before the treatment. The cells were pretreated with 500 nM okadaic acid, 10 μM H89, or DMSO as a vehicle for 30 min, and then the cells were irradiated with γ-rays (5 Gy). After incubation for 30 min, the cells were harvested and analyzed by western blotting and for PP2A activity. Phosphorylated AKT (p-AKT) was analyzed as a positive control for PP2A activity. Asterisks (*) on the histograms indicate a statistically significant difference from the vector-transfected control cells; the double asterisks (**) represent a statistically significant difference from the GαsQL-transfected control cells (p < 0.05, Mann–Whitney U test, D).