Appenzeller-Herzog Christian, Riemer Jan, Christensen Brian, Sørensen Esben S, Ellgaard Lars
Department of Biology, University of Copenhagen, Copenhagen Ø, Denmark.
EMBO J. 2008 Nov 19;27(22):2977-87. doi: 10.1038/emboj.2008.202. Epub 2008 Oct 2.
Oxidative maturation of secretory and membrane proteins in the endoplasmic reticulum (ER) is powered by Ero1 oxidases. To prevent cellular hyperoxidation, Ero1 activity can be regulated by intramolecular disulphide switches. Here, we determine the redox-driven shutdown mechanism of Ero1alpha, the housekeeping Ero1 enzyme in human cells. We show that functional silencing of Ero1alpha in cells arises from the formation of a disulphide bond-identified by mass spectrometry--between the active-site Cys(94) (connected to Cys(99) in the active enzyme) and Cys(131). Competition between substrate thiols and Cys(131) creates a feedback loop where activation of Ero1alpha is linked to the availability of its substrate, reduced protein disulphide isomerase (PDI). Overexpression of Ero1alpha-Cys131Ala or the isoform Ero1beta, which does not have an equivalent disulphide switch, leads to augmented ER oxidation. These data reveal a novel regulatory feedback system where PDI emerges as a central regulator of ER redox homoeostasis.
内质网（ER）中分泌蛋白和膜蛋白的氧化成熟由Ero1氧化酶驱动。为防止细胞过度氧化，Ero1活性可通过分子内二硫键开关进行调节。在此，我们确定了人类细胞中看家Ero1酶Ero1α的氧化还原驱动的关闭机制。我们表明，细胞中Ero1α的功能沉默源于质谱鉴定的活性位点半胱氨酸（Cys）94（与活性酶中的Cys99相连）和Cys131之间形成的二硫键。底物硫醇与Cys131之间的竞争形成了一个反馈回路，其中Ero1α的激活与其底物——还原型蛋白质二硫键异构酶（PDI）的可用性相关联。Ero1α-Cys131Ala或没有等效二硫键开关的异构体Ero1β的过表达导致内质网氧化增强。这些数据揭示了一种新型调节反馈系统，其中PDI成为内质网氧化还原稳态的核心调节因子。
