Biochemical evidence that regulation of Ero1? activity in human cells does not involve the isoform-specific cysteine 262.

ABSTRACT: In the ER (endoplasmic reticulum) of human cells, disulfide bonds are predominantly generated by the two isoforms of Ero1 (ER oxidoreductin-1): Ero1? and Ero1?. The activity of Ero1? is tightly regulated through the formation of intramolecular disulfide bonds to help ensure balanced ER redox conditions. Ero1? is less tightly regulated, but the molecular details underlying control of activity are not as well characterized as for Ero1?. Ero1? contains an additional cysteine residue (Cys262), which has been suggested to engage in an isoform-specific regulatory disulfide bond with Cys100 However, we show that the two regulatory disulfide bonds in Ero1? are likely conserved in Ero1? (Cys90-Cys130 and Cys95-Cys100). Molecular modelling of the Ero1? structure predicted that the side chain of Cys262 is completely buried. Indeed, we found this cysteine to be reduced and partially protected from alkylation in the ER of living cells. Furthermore, mutation of Cys100-but not of Cys262-rendered Ero1? hyperactive in cells, as did mutation of Cys130 Ero1? hyperactivity induced the UPR (unfolded protein response) and resulted in oxidative perturbation of the ER redox state. We propose that features other than a distinct pattern of regulatory disulfide bonds determine the loose redox regulation of Ero1? relative to Ero1?.

SUBMITTER: Hansen HG 

PROVIDER: S-EPMC3971451 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature