title: Cytosolic thioredoxin reductase 1 is required for correct disulfide formation in the ER.
abstract: Folding of proteins entering the secretory pathway in mammalian cells frequently requires the insertion of disulfide bonds. Disulfide insertion can result in covalent linkages found in the native structure as well as those that are not, so-called non-native disulfides. The pathways for disulfide formation are well characterized, but our understanding of how non-native disulfides are reduced so that the correct or native disulfides can form is poor. Here, we use a novel assay to demonstrate that the reduction in non-native disulfides requires NADPH as the ultimate electron donor, and a robust cytosolic thioredoxin system, driven by thioredoxin reductase 1 (TrxR1 or TXNRD1). Inhibition of this reductive pathway prevents the correct folding and secretion of proteins that are known to form non-native disulfides during their folding. Hence, we have shown for the first time that mammalian cells have a pathway for transferring reducing equivalents from the cytosol to the ER, which is required to ensure correct disulfide formation in proteins entering the secretory pathway.
authors.affiliation: The Institute of Molecular, Cell and Systems Biology, CMVLS, University of Glasgow, Glasgow, UK.
authors.forename: Greg J
authors.identifier: 0000-0002-9923-5218
authors.initials: GJ
authors.lastname: Poet
authors.affiliation: The Institute of Molecular, Cell and Systems Biology, CMVLS, University of Glasgow, Glasgow, UK.
authors.forename: Ojore Bv
authors.initials: OB
authors.lastname: Oka
authors.affiliation: The Institute of Molecular, Cell and Systems Biology, CMVLS, University of Glasgow, Glasgow, UK.
authors.forename: Marcel
authors.initials: M
authors.lastname: van Lith
authors.affiliation: The Institute of Molecular, Cell and Systems Biology, CMVLS, University of Glasgow, Glasgow, UK.
authors.forename: Zhenbo
authors.initials: Z
authors.lastname: Cao
authors.affiliation: The Institute of Molecular, Cell and Systems Biology, CMVLS, University of Glasgow, Glasgow, UK.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Robinson
authors.affiliation: The Institute of Molecular, Cell and Systems Biology, CMVLS, University of Glasgow, Glasgow, UK.
authors.forename: Marie Anne
authors.initials: MA
authors.lastname: Pringle
authors.affiliation: Division of Biochemistry, Department of Medical Biochemistry and Biophysics (MBB), Karolinska Institutet, Stockholm, Sweden.
authors.forename: Elias Sj
authors.identifier: 0000-0002-4807-6114
authors.initials: ES
authors.lastname: Arnér
authors.affiliation: The Institute of Molecular, Cell and Systems Biology, CMVLS, University of Glasgow, Glasgow, UK neil.bulleid@glasgow.ac.uk.
authors.forename: Neil J
authors.identifier: 0000-0002-9839-5279
authors.initials: NJ
authors.lastname: Bulleid
mesh_terms: D002460:Cell Line; D004220:Disulfides / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D006801:Humans; D009249:NADP / Q000378:metabolism; D054481:Thioredoxin Reductase 1 / Q000378:metabolism*
chemical_list: D004220:Disulfides; D009249:NADP; D054481:Thioredoxin Reductase 1
keywords: disulfide formation; endoplasmic reticulum; protein disulfide isomerase; redox homeostasis; thioredoxin reductase