biostudies-literatureKonno TWellcome Trust253-9https://www.ebi.ac.uk/biostudies/studies/S-EPMC4621842biostudies-literatureUnknown211(2)The endoplasmic reticulum (ER)-localized peroxiredoxin 4 (PRDX4) supports disulfide bond formation in eukaryotic cells lacking endoplasmic reticulum oxidase 1 (ERO1). The source of peroxide that fuels PRDX4-mediated disulfide bond formation has remained a mystery, because ERO1 is believed to be a major producer of hydrogen peroxide (H2O2) in the ER lumen. We report on a simple kinetic technique to track H2O2 equilibration between cellular compartments, suggesting that the ER is relatively isolated from cytosolic or mitochondrial H2O2 pools. Furthermore, expression of an ER-adapted catalase to degrade lumenal H2O2 attenuated PRDX4-mediated disulfide bond formation in cells lacking ERO1, whereas depletion of H2O2 in the cytosol or mitochondria had no similar effect. ER catalase did not effecThe Journal of cell biologyERO1-independent production of H2O2 within the endoplasmic reticulum fuels Prdx4-mediated oxidative protein folding.PMC4621842100140084812Konno TRon DLopes CAvezov EPinho Melo ELenzen SMehmeti IfalseERO1-independent production of H2O2 within the endoplasmic reticulum fuels Prdx4-mediated oxidative protein folding.The endoplasmic reticulum (ER)-localized peroxiredoxin 4 (PRDX4) supports disulfide bond formation in eukaryotic cells lacking endoplasmic reticulum oxidase 1 (ERO1). The source of peroxide that fuels PRDX4-mediated disulfide bond formation has remained a mystery, because ERO1 is believed to be a major producer of hydrogen peroxide (H2O2) in the ER lumen. We report on a simple kinetic technique to track H2O2 equilibration between cellular compartments, suggesting that the ER is relatively isolated from cytosolic or mitochondrial H2O2 pools. Furthermore, expression of an ER-adapted catalase to degrade lumenal H2O2 attenuated PRDX4-mediated disulfide bond formation in cells lacking ERO1, whereas depletion of H2O2 in the cytosol or mitochondria had no similar effect. ER catalase did not effec2015-01-01T00:00:00Z2015 Oct2025-04-06T19:45:21.961Z2019-03-27T02:00:50ZS-EPMC46218422650416610.1083/jcb.201506123