Open AccessThe mammalian cytosolic thioredoxin reductase pathway acts via a membrane protein to reduce ER-localised proteins
Author(s) -
Xiaofei Cao,
Sérgio Lilla,
Zhenbo Cao,
Marie Anne Pringle,
Ojore Oka,
Philip J. Robinson,
Tomasz Szmaja,
Marcel van Lith,
Sara Zanivan,
Neil J. Bulleid
Publication year - 2020
Publication title -
journal of cell science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.384
H-Index - 278
eISSN - 1477-9137
pISSN - 0021-9533
DOI - 10.1242/jcs.241976
Subject(s) - cytosol , thioredoxin , biology , microbiology and biotechnology , thioredoxin reductase , biochemistry , protein folding , membrane protein , secretory pathway , endoplasmic reticulum , membrane , enzyme , golgi apparatus
Folding of proteins entering the mammalian secretory pathway requires the insertion of the correct disulfides. Disulfide formation involves both an oxidative pathway for their insertion and a reductive pathway to remove incorrectly formed disulfides. Reduction of these disulfides is crucial for correct folding and degradation of misfolded proteins. Previously, we showed that the reductive pathway is driven by NADPH generated in the cytosol. Here, by reconstituting the pathway using purified proteins and ER microsomal membranes, we demonstrate that the thioredoxin reductase system provides the minimal cytosolic components required for reducing proteins within the ER lumen. In particular, saturation of the pathway and its protease sensitivity demonstrates the requirement for a membrane protein to shuttle electrons from the cytosol to the ER. These results provide compelling evidence for the crucial role of the cytosol in regulating ER redox homeostasis, ensuring correct protein folding and facilitating the degradation of misfolded ER proteins.