title: Intact protein folding in the glutathione-depleted endoplasmic reticulum implicates alternative protein thiol reductants.
abstract: Protein folding homeostasis in the endoplasmic reticulum (ER) requires efficient protein thiol oxidation, but also relies on a parallel reductive process to edit disulfides during the maturation or degradation of secreted proteins. To critically examine the widely held assumption that reduced ER glutathione fuels disulfide reduction, we expressed a modified form of a cytosolic glutathione-degrading enzyme, ChaC1, in the ER lumen. ChaC1(CtoS) purged the ER of glutathione eliciting the expected kinetic defect in oxidation of an ER-localized glutathione-coupled Grx1-roGFP2 optical probe, but had no effect on the disulfide editing-dependent maturation of the LDL receptor or the reduction-dependent degradation of misfolded alpha-1 antitrypsin. Furthermore, glutathione depletion had no measurable effect on induction of the unfolded protein response (UPR); a sensitive measure of ER protein folding homeostasis. These findings challenge the importance of reduced ER glutathione and suggest the existence of alternative electron donor(s) that maintain the reductive capacity of the ER.DOI: http://dx.doi.org/10.7554/eLife.03421.001.
authors: Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom Wellcome Trust MRC Institute of Metabolic Science, Cambridge, United Kingdom NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom.
authors: Satoshi
authors: S
authors: Tsunoda
authors: Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom Wellcome Trust MRC Institute of Metabolic Science, Cambridge, United Kingdom NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom.
authors: Edward
authors: E
authors: Avezov
authors: Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom Wellcome Trust MRC Institute of Metabolic Science, Cambridge, United Kingdom NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom.
authors: Alisa
authors: A
authors: Zyryanova
authors: Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom Wellcome Trust MRC Institute of Metabolic Science, Cambridge, United Kingdom NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom.
authors: Tasuku
authors: T
authors: Konno
authors: Centre for Molecular and Structural Biomedicine, Universidade do Algarve, Faro, Portugal.
authors: Leonardo
authors: L
authors: Mendes-Silva
authors: Centre for Molecular and Structural Biomedicine, Universidade do Algarve, Faro, Portugal.
authors: Eduardo
authors: E
authors: Pinho Melo
authors: Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom Wellcome Trust MRC Institute of Metabolic Science, Cambridge, United Kingdom NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom hph23@cam.ac.uk.
authors: Heather P
authors: HP
authors: Harding
authors: Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom Wellcome Trust MRC Institute of Metabolic Science, Cambridge, United Kingdom NIHR Cambridge Biomedical Research Centre, Cambridge, United Kingdom dr360@medschl.cam.ac.uk.
authors: David
authors: D
authors: Ron
mesh_terms: D000818:Animals; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006706:Homeostasis; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D010084:Oxidation-Reduction; D017510:Protein Folding; D011973:Receptors, LDL / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism; D056811:Unfolded Protein Response; D005722:gamma-Glutamylcyclotransferase
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D011973:Receptors, LDL; D011994:Recombinant Proteins; D013438:Sulfhydryl Compounds; C586183:Chac1 protein, mouse; D005722:gamma-Glutamylcyclotransferase; D005978:Glutathione
keywords: UPR; glutathione; protein folding; redox