Ubiquitin ligases (E3s) embedded in the endoplasmic reticulum (ER) membrane regulate essential cellular activities including protein quality control, calcium flux, and sterol homeostasis. At least 25 different, transmembrane domain (TMD)-containing E3s are predicted to be ER-localised, but for most their organisation and cellular roles remain poorly defined. Using a comparative proteomic workflow, we mapped over 450 protein-protein interactions for 21 stably expressed, full-length E3s. Bioinformatic analysis linked ER-E3s and their interactors to multiple homeostatic, regulatory, and metabolic pathways. Among these were four membrane-embedded interactors of RNF26, a polytopic E3 whose abundance is auto-regulated by ubiquitin-proteasome dependent degradation. RNF26 co-assembles with TMEM43, ENDOD1, TMEM33 and TMED1 to form a complex capable of modulating innate immune signalling through the cGAS-STING pathway. This RNF26 complex represents a new modulatory axis of STING and innate immune signalling at the ER membrane. Collectively, these data reveal the broad scope of regulation and differential functionalities mediated by ER-E3s for both membrane-tethered and cytoplasmic processes.

中文翻译：

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内质网泛素连接酶的相互作用图谱鉴定了先天免疫信号的调节剂


嵌入内质网 (ER) 膜中的泛素连接酶 (E3) 调节重要的细胞活动，包括蛋白质质量控​​制、钙流动和甾醇稳态。预计至少有 25 个不同的、含有跨膜结构域 (TMD) 的 E3 位于内质网，但对于大多数来说，它们的组织和细胞作用仍然不明确。使用比较蛋白质组学工作流程，我们绘制了 21 个稳定表达的全长 E3 的 450 多个蛋白质-蛋白质相互作用。生物信息学分析将 ER-E3 及其相互作用因子与多种稳态、调节和代谢途径联系起来。其中有四个膜嵌入的 RNF26 相互作用子，RNF26 是一种多胞体 E3，其丰度通过泛素蛋白酶体依赖性降解自动调节。 RNF26 与 TMEM43、ENDOD1、TMEM33 和 TMED1 共同组装，形成能够通过 cGAS-STING 途径调节先天免疫信号传导的复合物。这种 RNF26 复合物代表了 STING 和 ER 膜先天免疫信号传导的新调节轴。总的来说，这些数据揭示了 ER-E3 介导的膜束缚过程和细胞质过程的广泛调节和差异功能。