The Endoplasmic Reticulum (ER) is responsible for the folding and post-translational modification of secretory proteins, as well as for triaging misfolded proteins. During folding, there is a complex yet only partially understood interplay between disulfide bond formation, which is an enzyme catalyzed event in the oxidizing environment of the ER, along with other post-translational modifications (PTMs) and chaperone-supported protein folding. Here, we used the glycoprotein torsinA as a model substrate to explore the impact of ER redox homeostasis on PTMs and protein biogenesis. TorsinA is a AAA+ ATPase with unusual oligomeric properties and controversial functions. The deletion of a C-terminal glutamic acid residue (∆E) is associated with the development of Early-Onset Torsion Dystonia, a severe movement disorder. TorsinA differs from other AAA+ ATPases since it is an ER resident, and as a result of its entry into the ER torsinA contains two N-linked glycans and at least one disulfide bond. The role of these PTMs on torsinA biogenesis and function and the identity of the enzymes that catalyze them are poorly defined. Using a yeast torsinA expression system, we demonstrate that a specific protein disulfide isomerase, Pdi1, affects the folding and N-linked glycosylation of torsinA and torsinA∆E in a redox-dependent manner, suggesting that the acquisition of early torsinA folding intermediates is sensitive to perturbed interactions between Cys residues and the quality control machinery. We also highlight the role of specific Cys residues during torsinA biogenesis and demonstrate that torsinA∆E is more sensitive than torsinA when these Cys residues are mutated.

内质网 (ER) 负责分泌蛋白的折叠和翻译后修饰，以及对错误折叠的蛋白进行分类。在折叠过程中，二硫键形成（这是 ER 氧化环境中的酶催化事件）与其他翻译后修饰 (PTM) 和伴侣支持的蛋白质折叠之间存在复杂但仅部分了解的相互作用。在这里，我们使用糖蛋白 torsinA 作为模型底物来探索 ER 氧化还原稳态对 PTM 和蛋白质生物合成的影响。TorsinA 是一种 AAA+ ATPase，具有不寻常的寡聚特性和有争议的功能。C 末端谷氨酸残基 (ΔE) 的缺失与早发性扭转性肌张力障碍（一种严重的运动障碍）的发展有关。N-连接聚糖和至少一个二硫键。这些翻译后修饰对 torsinA 生物发生和功能的作用以及催化它们的酶的身份尚不清楚。使用酵母 torsinA 表达系统，我们证明了一种特定的蛋白质二硫键异构酶 Pdi1，以氧化还原依赖性方式影响 torsinA 和 torsinAΔE的折叠和N-连接糖基化，这表明早期 torsinA 折叠中间体的获得是敏感的扰乱半胱氨酸残基和质量控制机制之间的相互作用。我们还强调了特定 Cys 残基在 torsinA 生物发生过程中的作用，并证明当这些 Cys 残基发生突变时，torsinAΔE 比 torsinA 更敏感。