Nrf2 Is a Direct PERK Substrate and Effector of PERK-Dependent Cell Survival

Abstract

Activation of PERK following the accumulation of unfolded proteins in the endoplasmic reticulum (ER) promotes translation inhibition and cell cycle arrest. PERK function is essential for cell survival following exposure of cells to ER stress, but the mechanisms whereby PERK signaling promotes cell survival are not thoroughly understood. We have identified the Nrf2 transcription factor as a novel PERK substrate. In unstressed cells, Nrf2 is maintained in the cytoplasm via association with Keap1. PERK-dependent phosphorylation triggers dissociation of Nrf2/Keap1 complexes and inhibits reassociation of Nrf2/Keap1 complexes in vitro. Activation of PERK via agents that trigger the unfolded protein response is both necessary and sufficient for dissociation of cytoplasmic Nrf2/Keap1 and subsequent Nrf2 nuclear import. Finally, we demonstrate that cells harboring a targeted deletion of Nrf2 exhibit increased cell death relative to wild-type counterparts following exposure to ER stress. Our data demonstrate that Nrf2 is a critical effector of PERK-mediated cell survival.

ACKNOWLEDGMENTS

We thank Y.W. Kan and J. Chan for providing the Nrf2^−/− MEFs and the Nrf2 cDNA; D. Scheuner for the eIF2α(S51A) MEFs; M. Olson for providing the Jac6 and 3F10 monoclonal antibodies; R. Wek for providing anti-PERK antiserum; D. Ron and H. Harding for providing the PERK cDNA and the PERK^−/− fibroblasts; C. B. Thompson for providing TNF-α; and M. C. Simon for providing luciferase cDNA.

This work was supported by AHA grant 0060360Z and the Abramson Family Cancer Research Institute (J.A.D.) and grants GM59213 and ES11721 (M.H.).