Purine receptor P2Y6 mediates cellular response to γ-ray-induced DNA damage

We previously showed that nucleotide P2 receptor agonists such as ATP and UTP amplify gamma-ray-induced focus formation of phosphorylated histone H2A variant H2AX (gamma H2AX), which is considered to be an indicator of DNA damage so far, by activating purine P2Y(6) and P2Y(12) receptors. Therefore, we hypothesized that these P2 receptors play a role in inducing the repair response to gamma-ray-induced DNA damage. In the present study, we tested this idea by using human lung cancer A549 cells. First, reverse-transcription polymerase chain reaction (RT-PCR) showed that P2Y(6) receptor is highly expressed in A549 cells, but P2Y(12) receptor is only weakly expressed. Next, colony formation assay revealed that P2Y(6) receptor antagonist MRS2578 markedly reduced the survival rate of gamma-ray-exposed A549 cells. The survival rate was also significantly reduced in P2Y(6)-knock-down cells, compared with scramble siRNA-transfected cells. Since it has reported that phosphorylation of ERK1/2 after activation of EGFR via P2Y(6) and P2Y(12) receptors is involved in the repair response to gamma-ray-induced DNA damage, we next examined whether gamma-ray-induced phosphorylation of ERK1/2 was also inhibited by MRS2578 in A549 cells. We found that it was. Taken together, these findings indicate that purinergic signaling through P2Y(6) receptor, followed by ERK1/2 activation, promotes the cellular repair response to gamma-ray-induced DNA damage.