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J Cell Sci. 2013 Apr 1;126(Pt 7):1604-17. doi: 10.1242/jcs.117218. Epub 2013 Feb 19.

Endoplasmic reticulum: reduced and oxidized glutathione revisited.

Author information

1
Division of Molecular and Systems Toxicology, Department of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland.

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.

KEYWORDS:

Endoplasmic reticulum; Glutathione; Green fluorescent protein; Reduction potential; Unfolded protein response

PMID:
23424194
DOI:
10.1242/jcs.117218
[Indexed for MEDLINE]
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