ERO1-L, a Human Protein That Favors Disulfide Bond Formation in the Endoplasmic Reticulum

Abstract

Oxidizing conditions must be maintained in the endoplasmic reticulum (ER) to allow the formation of disulfide bonds in secretory proteins. Here we report the cloning and characterization of a mammalian gene (ERO1-L) that shares extensive homology with the Saccharomyces cerevisiae ERO1 gene, required in yeast for oxidative protein folding. When expressed in mammalian cells, the product of the human ERO1-L gene colocalizes with ER markers and displays Endo-H-sensitive glycans. In isolated microsomes, ERO1-L behaves as a type II integral membrane protein. ERO1-L is able to complement several phenotypic traits of the yeast thermosensitive mutant ero1-1, including temperature and dithiothreitol sensitivity, and intrachain disulfide bond formation in carboxypeptidase Y. ERO1-L is no longer functional when either one of the highly conserved Cys-394 or Cys-397 is mutated. These results strongly suggest that ERO1-L is involved in oxidative ER protein folding in mammalian cells.

Endoplasmic Reticulum Oxidoreductin 1-Lβ (ERO1-Lβ), a Human Gene Induced in the Course of the Unfolded Protein Response

“…Also, in this assay, the mobility shift induced by deglycosylation is greater for ERO1-L␤ than for ERO1-L␣. As previously observed for ERO1-L␣ translated in the presence of canine microsomal membranes (26), the electrophoretic mobility of the translocated and deglycosylated ERO1-L␣ is undistinguishable from that of the protein synthesized in the absence of membranes. This seems to be the case also for ERO1-L␤, suggesting that the leader peptides of the two human ERO1-L genes might not undergo cleavage.…”

“…We showed that the products of the ERO1-L gene are able to complement several functions of the endogenous ERO1 in yeast, suggesting the existence of similar oxidative protein folding pathways in human and Saccharomyces cerevisiae (26).…”

“…and Mouse-We have recently described the isolation of ERO1-L, a human gene that is likely to be involved in disulfide bond formation in the ER (26). The ERO1-L sequence was used to perform a survey of the Expressed Sequence Tag division of GenBank TM ; this led to the identification of a human sequence very similar to, but distinct from, ERO1-L, which was used as a probe to screen a human cDNA library.…”

ERp57 Is a Multifunctional Thiol-Disulfide Oxidoreductase

“…In S. cerevisiae, an additional protein, Erv2p, performs a similar function to that of Ero1 (4,5). Although orthologues of Erv2p do not seem to exist in higher eukaryotes, two human isoforms of Ero1 have been identified, Ero1␣ and Ero1␤ (6,7).…”

Interplay between redox and protein homeostasis

“…39 Ero1-a is widely expressed, yet both isoforms have enzymatic activities that are controlled by regulatory disulfides formed among catalytic and non-catalytic cysteines to avoid futile oxidation cycles, which prevents excess hydrogen peroxide production. [40][41][42] PDI and Ero1 represent for the ER a feedback regulatory system that is able to sense and respond to different redox conditions. 43,44 The interplay between Ero1-a and PDI has been studied and some mechanical aspects are well characterized.…”