H(2)O(2)-dependent Hyperoxidation of Peroxiredoxin 6 (Prdx6) Plays a Role in Cellular Toxicity via Up-regulation of iPLA2 Activity

Abstract

Peroxiredoxin 6 (Prdx6) is a bifunctional enzyme with peroxidase activity and Ca(2+)-independent phospholipase A2 (iPLA2) activity. Here, we report that H(2)O(2)-induced cellular toxicity acts through Prdx6 hyperoxidation. Under high concentrations of H(2)O(2) (> 100 mu M), Prdx6, and 2-Cys Prdxs were hyperoxidized. Contrary to hyperoxidation of 2-Cys Prdxs, hyperoxidation of Prdx6 was irreversible in vivo. Surprisingly, H(2)O(2)-induced cell cycle arrest at the G2/M transition correlated with hyperoxidation and increased iPLA2 activity of Prdx6. This arrest was also associated with up-regulation of p53 and p21 and with down-regulation of cyclin B1. Furthermore, the H(2)O(2)-mediated increase in iPLA2 activity was dramatically abolished in a hyperoxidation mutant (C47A), an iPLA2 mutant (S32A), and a double mutant (C47A/S32A) of Prdx6, demonstrating the essential requirement of Prdx6 C47 hyperoxidation for its iPLA2 activity. Together, our results demonstrate that H(2)O(2)-mediated hyperoxidation of Prdx6 induces cell cycle arrest at the G2/M transition through up-regulation of iPLA2 activity.