title: GPx8 peroxidase prevents leakage of H2O2 from the endoplasmic reticulum.
abstract: Unbalanced endoplasmic reticulum (ER) homeostasis (ER stress) leads to increased generation of reactive oxygen species (ROS). Disulfide-bond formation in the ER by Ero1 family oxidases produces hydrogen peroxide (H2O2) and thereby constitutes one potential source of ER-stress-induced ROS. However, we demonstrate that Ero1α-derived H2O2 is rapidly cleared by glutathione peroxidase (GPx) 8. In 293 cells, GPx8 and reduced/activated forms of Ero1α co-reside in the rough ER subdomain. Loss of GPx8 causes ER stress, leakage of Ero1α-derived H2O2 to the cytosol, and cell death. In contrast, peroxiredoxin (Prx) IV, another H2O2-detoxifying rough ER enzyme, does not protect from Ero1α-mediated toxicity, as is currently proposed. Only when Ero1α-catalyzed H2O2 production is artificially maximized can PrxIV participate in its reduction. We conclude that the peroxidase activity of the described Ero1α-GPx8 complex prevents diffusion of Ero1α-derived H2O2 within and out of the rough ER. Along with the induction of GPX8 in ER-stressed cells, these findings question a ubiquitous role of Ero1α as a producer of cytoplasmic ROS under ER stress.
authors.affiliation: Division of Molecular and Systems Toxicology, Department of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ramming
authors.affiliation: Department of Biology, University of Copenhagen, 2200 Copenhagen N, Denmark.
authors.forename: Henning G
authors.initials: HG
authors.lastname: Hansen
authors.affiliation: Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 803-8555, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Nagata
authors.affiliation: Department of Biology, University of Copenhagen, 2200 Copenhagen N, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Ellgaard
authors.affiliation: Division of Molecular and Systems Toxicology, Department of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland. Electronic address: Christian.Appenzeller@unibas.ch.
authors.forename: Christian
authors.initials: C
authors.lastname: Appenzeller-Herzog
mesh_terms: D000818:Animals; D004220:Disulfides / Q000494:pharmacology; D059865:Endoplasmic Reticulum Stress / Q000235:genetics*; D005979:Glutathione Peroxidase / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D004220:Disulfides; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; C558642:GPX8 protein, human; D010544:Peroxidases; D005979:Glutathione Peroxidase
keywords: Apoptosis; Endoplasmic reticulum stress; Free radicals; Hydrogen peroxide; Peroxidases; Redox homeostasis