The voltage-gated potassium ion channel K11.1 plays a critical role in cardiac repolarization. Genetic variants that render Kv11.1 dysfunctional cause long QT syndrome (LQTS), which is associated with fatal arrhythmias. Approximately 90% of LQTS-associated variants cause intracellular protein transport (trafficking) dysfunction, which pharmacological chaperones like E-4031 can rescue. Protein folding and trafficking decisions are regulated by chaperones, protein quality control factors, and trafficking machinery comprising the cellular proteostasis network. Here, we test whether trafficking dysfunction is associated with alterations in the proteostasis network of pathogenic Kv11.1 variants and whether pharmacological chaperones can normalize the proteostasis network of responsive variants. We used affinity-purification coupled with tandem mass tag–based quantitative mass spectrometry to assess protein interaction changes of WT K11.1 or trafficking-deficient channel variants in the presence or absence of E-4031. We identified 572 core K11.1 protein interactors. Trafficking-deficient variants K11.1-G601S and K11.1-G601S-G965 had significantly increased interactions with proteins responsible for folding, trafficking, and degradation compared to WT. We confirmed previous findings that the proteasome is critical for K11.1 degradation. Our report provides the first comprehensive characterization of protein quality control mechanisms of K11.1. We find extensive interactome remodeling associated with trafficking-deficient K11.1 variants and with pharmacological chaperone rescue of K11.1 cell surface expression. The identified protein interactions could be targeted therapeutically to improve K11.1 trafficking and treat LQTS.

中文翻译：

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与长 QT 综合征相关的电压门控钾通道 KV11.1 运输缺陷变体的蛋白质稳态相互作用组


电压门控钾离子通道 K11.1 在心脏复极中发挥着关键作用。导致 Kv11.1 功能障碍的基因变异会导致长 QT 综合征 (LQTS)，这与致命性心律失常有关。大约 90% 的 LQTS 相关变异会导致细胞内蛋白质转运（运输）功能障碍，而 E-4031 等药理学伴侣可以挽救这种功能障碍。蛋白质折叠和运输决策受到分子伴侣、蛋白质质量控​​制因素和构成细胞蛋白质稳态网络的运输机制的调节。在这里，我们测试运输功能障碍是否与致病性 Kv11.1 变异的蛋白质稳态网络的改变有关，以及药理学伴侣是否可以使响应性变异的蛋白质稳态网络正常化。我们使用亲和纯化结合基于串联质量标签的定量质谱法来评估 WT K11.1 或运输缺陷通道变体在存在或不存在 E-4031 的情况下的蛋白质相互作用变化。我们鉴定了 572 个核心 K11.1 蛋白相互作用因子。与 WT 相比，运输缺陷型变体 K11.1-G601S 和 K11.1-G601S-G965 与负责折叠、运输和降解的蛋白质的相互作用显着增加。我们证实了之前的研究结果，即蛋白酶体对于 K11.1 降解至关重要。我们的报告首次全面描述了 K11.1 的蛋白质质量控​​制机制。我们发现广泛的相互作用组重塑与运输缺陷的 K11.1 变体以及 K11.1 细胞表面表达的药理学伴侣拯救相关。已确定的蛋白质相互作用可以作为治疗目标，以改善 K11.1 运输并治疗 LQTS。