title: Endoplasmic reticulum: reduced and oxidized glutathione revisited.
abstract: The reducing power of glutathione, expressed by its reduction potential EGSH, is an accepted measure for redox conditions in a given cell compartment. In the endoplasmic reticulum (ER), EGSH is less reducing than elsewhere in the cell. However, attempts to determine EGSH(ER) have been inconsistent and based on ineligible assumptions. Using a codon-optimized and evidently glutathione-specific glutaredoxin-coupled redox-sensitive green fluorescent protein (roGFP) variant, we determined EGSH(ER) in HeLa cells as -208±4 mV (at pH 7.0). At variance with existing models, this is not oxidizing enough to maintain the known redox state of protein disulfide isomerase family enzymes. Live-cell microscopy confirmed ER hypo-oxidation upon inhibition of ER Ca(2+) import. Conversely, stressing the ER with a glycosylation inhibitor did not lead to more reducing conditions, as reported for yeast. These results, which for the first time establish the oxidative capacity of glutathione in the ER, illustrate a context-dependent interplay between ER stress and EGSH(ER). The reported development of ER-localized EGSH sensors will enable more targeted in vivo redox analyses in ER-related disorders.
authors: Division of Molecular and Systems Toxicology, Department of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland.
authors: Julia
authors: J
authors: Birk
authors: Mariangela
authors: M
authors: Meyer
authors: Isabel
authors: I
authors: Aller
authors: Henning G
authors: HG
authors: Hansen
authors: Alex
authors: A
authors: Odermatt
authors: Tobias P
authors: TP
authors: Dick
authors: Andreas J
authors: AJ
authors: Meyer
authors: Christian
authors: C
authors: Appenzeller-Herzog
mesh_terms: D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D019803:Glutathione Disulfide / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D010084:Oxidation-Reduction; D056811:Unfolded Protein Response / Q000235:genetics / Q000502:physiology
chemical_list: D049452:Green Fluorescent Proteins; D005978:Glutathione; D019803:Glutathione Disulfide
keywords: Endoplasmic reticulum; Glutathione; Green fluorescent protein; Reduction potential; Unfolded protein response