Poet Greg J, Oka Ojore Bv, van Lith Marcel, Cao Zhenbo, Robinson Philip J, Pringle Marie Anne, Arnér Elias Sj, Bulleid Neil J
The Institute of Molecular, Cell and Systems Biology, CMVLS, University of Glasgow, Glasgow, UK.
Division of Biochemistry, Department of Medical Biochemistry and Biophysics (MBB), Karolinska Institutet, Stockholm, Sweden.
EMBO J. 2017 Mar 1;36(5):693-702. doi: 10.15252/embj.201695336. Epub 2017 Jan 16.
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.
进入哺乳动物细胞分泌途径的蛋白质折叠通常需要插入二硫键。二硫键的插入可导致在天然结构中发现的共价连接以及那些非天然结构中的共价连接，即所谓的非天然二硫键。二硫键形成的途径已得到充分表征，但我们对非天然二硫键如何被还原从而形成正确或天然二硫键的了解却很少。在这里，我们使用一种新的检测方法来证明非天然二硫键的还原需要NADPH作为最终电子供体，以及由硫氧还蛋白还原酶1（TrxR1或TXNRD1）驱动的强大的胞质硫氧还蛋白系统。抑制这种还原途径会阻止已知在折叠过程中形成非天然二硫键的蛋白质的正确折叠和分泌。因此，我们首次表明哺乳动物细胞具有将还原当量从细胞质转移到内质网的途径，这是确保进入分泌途径的蛋白质形成正确二硫键所必需的。
