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Targeted redox inhibition of protein phosphatase 1 by Nox4 regulates eIF2α-mediated stress signaling

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Celio Xc Santos, Anne D. Hafstad, Matteo Beretta, Min Zhang, Chris Molenaar, Jola Kopec, Dina Fotinou, Thomas V. Murray, Andrew M. Cobb, Daniel Martin, Maira Zeh Silva, Narayana Anilkumar, Katrin Schröder, Catherine M. Shanahan, Alison Brewer, Ralf P. Brandes, Eric Blanc, Maddy Parsons, Vsevelod Belousov, Richard Cammack & 3 more Robert C. Hider, Roberto A. Steiner, Ajay M. Shah

Original languageEnglish
Pages (from-to)319-334
Number of pages16
JournalThe EMBO journal
Volume35
Issue number2
Early online date18 Jan 2016
DOIs
Accepted/In press2 Dec 2015
E-pub ahead of print18 Jan 2016
Published1 Feb 2016

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Abstract

Phosphorylation of translation initiation factor 2α (eIF2α) attenuates global protein synthesis but enhances translation of activating transcription factor 4 (ATF4) and is a crucial evolutionarily conserved adaptive pathway during cellular stresses. The serine-threonine protein phosphatase 1 (PP1) deactivates this pathway whereas prolonging eIF2α phosphorylation enhances cell survival. Here, we show that the reactive oxygen species-generating NADPH oxidase-4 (Nox4) is induced downstream of ATF4, binds to a PP1-targeting subunit GADD34 at the endoplasmic reticulum, and inhibits PP1 activity to increase eIF2α phosphorylation and ATF4 levels. Other PP1 targets distant from the endoplasmic reticulum are unaffected, indicating a spatially confined inhibition of the phosphatase. PP1 inhibition involves metal center oxidation rather than the thiol oxidation that underlies redox inhibition of protein tyrosine phosphatases. We show that this Nox4-regulated pathway robustly enhances cell survival and has a physiologic role in heart ischemia-reperfusion and acute kidney injury. This work uncovers a novel redox signaling pathway, involving Nox4-GADD34 interaction and a targeted oxidative inactivation of the PP1 metal center, that sustains eIF2α phosphorylation to protect tissues under stress.

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