Hyperactivity of the Ero1α Oxidase Elicits Endoplasmic Reticulum Stress but No Broad Antioxidant Response

Abstract

Background:The oxidase activity of human Ero1␣ generates hydrogen peroxide in the ER. Results: Overexpression of a hyperactive Ero1␣ mutant induces the unfolded protein response but does not cause a broad antioxidant response. Conclusion: Ero1␣ hyperactivity elicits ER stress through local ER lumenal hyperoxidation. Significance: These findings show how the cell negotiates oxidative stress generated specifically in the lumen of the ER.

Composition of the redox environment of the endoplasmic reticulum and sources of hydrogen peroxide

“…However, the actual direction of hydrogen peroxide flux has not been elucidated. Overexpression of a hyperactive Ero1α mutant resulted in ER stress, but not in a general antioxidant response of the cell [131]. This observation suggests that local hydrogen peroxide overproduction can be taken care of within the ER.…”

Endoplasmic reticulum: Reduced and oxidized glutathione revisited

“…Since Grx is normally absent from the ER, the finding that fusion of Grx1 to roGFP1-iE ER increases its steady-state oxidation could potentially be explained by Grx1-mediated changes in overall ER redox conditions, which would be expected to elicit the UPR (Hansen et al, 2012). We therefore set out to test these possibilities.…”

“…The formal possibility that Grx1 catalyzes deglutathionylation of ER proteins, which would increase GSSG levels in the ER, can at present not be excluded. However, we consider this possibility unlikely, because (i) the abundance of glutathionylated ER proteins is low ) and (ii) unnaturally increased GSSG levels would elicit the UPR (Hansen et al, 2012). We next examined whether the increased oxidation of Grx1-roGFP1-iE in the ER could be the result of altered redox properties of this sensor compared to roGFP1-iE.…”

Different Interaction Modes for Protein-disulfide Isomerase (PDI) as an Efficient Regulator and a Specific Substrate of Endoplasmic Reticulum Oxidoreductin-1α (Ero1α)

“…1A (7,14,23). First, we checked the controversial regulatory function of Cys85-Cys391 by taking advantage of retarded protein mobility on nonreducing SDS-PAGE caused by long-range disulfide breakage.…”

“…First, we checked the controversial regulatory function of Cys85-Cys391 by taking advantage of retarded protein mobility on nonreducing SDS-PAGE caused by long-range disulfide breakage. Three Ero1␣ Cys-to-Ala mutants C85/391A, C104/131A, and C85/104/131/ 391A were prepared to serve as a disulfide ruler, mimicking the reduction of long-range disulfide of Cys85-Cys391, Cys94-Cys131, and the both, respectively (23). As shown in Fig.…”