Hyperactivity of the Ero1? oxidase elicits endoplasmic reticulum stress but no broad antioxidant response.

ABSTRACT: Oxidizing equivalents for the process of oxidative protein folding in the endoplasmic reticulum (ER) of mammalian cells are mainly provided by the Ero1? oxidase. The molecular mechanisms that regulate Ero1? activity in order to harness its oxidative power are quite well understood. However, the overall cellular response to oxidative stress generated by Ero1? in the lumen of the mammalian ER is poorly characterized. Here we investigate the effects of overexpressing a hyperactive mutant (C104A/C131A) of Ero1?. We show that Ero1? hyperactivity leads to hyperoxidation of the ER oxidoreductase ERp57 and induces expression of two established unfolded protein response (UPR) targets, BiP (immunoglobulin-binding protein) and HERP (homocysteine-induced ER protein). These effects could be reverted or aggravated by N-acetylcysteine and buthionine sulfoximine, respectively. Because both agents manipulate the cellular glutathione redox buffer, we conclude that the observed effects of Ero1?-C104A/C131A overexpression are likely caused by an oxidative perturbation of the ER glutathione redox buffer. In accordance, we show that Ero1? hyperactivity affects cell viability when cellular glutathione levels are compromised. Using microarray analysis, we demonstrate that the cell reacts to the oxidative challenge caused by Ero1? hyperactivity by turning on the UPR. Moreover, this analysis allowed the identification of two new targets of the mammalian UPR, CRELD1 and c18orf45. Interestingly, a broad antioxidant response was not induced. Our findings suggest that the hyperoxidation generated by Ero1?-C104A/C131A is addressed in the ER lumen and is unlikely to exert oxidative injury throughout the cell.

SUBMITTER: Hansen HG 

PROVIDER: S-EPMC3501080 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature