title: Production of H₂O₂ in the endoplasmic reticulum promotes in vivo disulfide bond formation.
abstract: OBJECTIVE
  Oxidative protein folding in the luminal compartment of endoplasmic reticulum (ER) is thought to be accompanied by the generation of H₂O₂, as side-product of disulfide bond formation. We aimed to examine the role of H₂O₂ produced in the lumen, which on one hand can lead to redox imbalance and hence can contribute to ER stress caused by overproduction of secretory proteins; on the other hand, as an excellent electron acceptor, H₂O₂ might serve as an additional pro-oxidant in physiological oxidative folding.
  
  
  RESULTS
  Stimulation of H₂O₂ production in the hepatic ER resulted in a decrease in microsomal GSH and protein-thiol contents and in a redox shift of certain luminal oxidoreductases in mice. The oxidative effect, accompanied by moderate signs of ER stress and reversible dilation of ER cisternae, was prevented by concomitant reducing treatment. The imbalance also affected the redox state of pyridine nucleotides in the ER. Antibody producing cells artificially engineered with powerful luminal H₂O₂ eliminating system showed diminished secretion of mature antibody polymers, while incomplete antibody monomers/dimers were accumulated and/or secreted.
  
  
  METHODS
  Evidence are provided by using in vivo models that hydrogen peroxide can promote disulfide bond formation in the ER.
  
  
  CONCLUSIONS
  The results indicate that local H₂O₂ production promotes, while quenching of H₂O₂ impairs disulfide formation. The contribution of H₂O₂ to disulfide bond formation previously observed in vitro can be also shown in cellular and in vivo systems.
authors.affiliation: Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
authors.forename: Éva
authors.initials: É
authors.lastname: Margittai
authors.forename: Péter
authors.initials: P
authors.lastname: Löw
authors.forename: Ibolya
authors.initials: I
authors.lastname: Stiller
authors.forename: Alessandra
authors.initials: A
authors.lastname: Greco
authors.forename: Jose Manuel
authors.initials: JM
authors.lastname: Garcia-Manteiga
authors.forename: Niccolo
authors.initials: N
authors.lastname: Pengo
authors.forename: Angelo
authors.initials: A
authors.lastname: Benedetti
authors.forename: Roberto
authors.initials: R
authors.lastname: Sitia
authors.forename: Gábor
authors.initials: G
authors.lastname: Bánhegyi
mesh_terms: D000818:Animals; D002460:Cell Line; D004220:Disulfides / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006168:Guinea Pigs; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007136:Immunoglobulins / Q000737:chemistry / Q000378:metabolism; D008297:Male; D051379:Mice; D010084:Oxidation-Reduction; D017510:Protein Folding
chemical_list: D004220:Disulfides; D007136:Immunoglobulins; D006861:Hydrogen Peroxide