ERO1 Activity: A Potential Source of ER-Derived Oxidative Stress.

Tue, 05/15/2012 - 09:41

Disulfide bond formation is a pivotal step in the maturation and release of secretory proteins that are controlled by specific endoplasmic reticulum (ER) resident enzymes. An important element in this process is ERO (ER oxidoreduction), a glycosylated flavoenzyme tightly associated with oxidative protein folding that lacks the known ER retention motifs. ER resident protein 44kDa (ERp44) is an ER resident protein that mediates ERO1 localization in ER and thus prevents the secretion of unassembled cargo proteins with unpaired cysteine (1).

Immunocytochemistry/Immunofluorescence: ERO1L Antibody Immunocytochemistry/Immunofluorescence: ERO1L Antibody

The production of secretory proteins at the ER depends on a ready supply of energy and metabolites as well as close monitoring of the biochemical conditions that favor oxidative protein folding. ER oxidoreductases and chaperones fold nascent proteins into their export-competent three-dimensional structure. Interference with these protein folding enzymes leads to the accumulation of unfolded proteins within the ER lumen, causing an acute organellar stress that triggers the unfolded protein response (2). Ero1 alpha antibody studies have revealed expression is almost exclusively found on the mitochondria-associated membrane (MAM). The localization of ERO1-alpha on the MAM is dependent on oxidizing conditions within the ER. Chemical reduction of the ER environment, but not ER stress in general leads to release of ERO1 alpha from the MAM. In addition, the correct localization of ERO1alpha to the MAM also requires normoxic but not hypoxic conditions (3). ERO1 oxidizes protein disulfide isomerase (PDI), which, in turn, introduces disulfides into ER client proteins. To maintain an oxidized state, ERO1 couples disulfide transfer to PDI with reduction of molecular oxygen, forming hydrogen peroxide thus, ERO1 activity constitutes a potential source of ER-derived oxidative stress (4).

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