Ludwig Institute for Cancer Research, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7DQ, UK.
Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne 50931, Germany.
J Cell Sci. 2017 Oct 1;130(19):3322-3335. doi: 10.1242/jcs.206847. Epub 2017 Aug 21.
The mammalian ubiquitin ligase Hrd1 is the central component of a complex facilitating degradation of misfolded proteins during the ubiquitin-proteasome-dependent process of ER-associated degradation (ERAD). Hrd1 associates with cofactors to execute ERAD, but their roles and how they assemble with Hrd1 are not well understood. Here, we identify crucial cofactor interaction domains within Hrd1 and report a previously unrecognised evolutionarily conserved segment within the intrinsically disordered cytoplasmic domain of Hrd1 (termed the HAF-H domain), which engages complementary segments in the cofactors FAM8A1 and Herp (also known as HERPUD1). This domain is required by Hrd1 to interact with both FAM8A1 and Herp, as well as to assemble higher-order Hrd1 complexes. FAM8A1 enhances binding of Herp to Hrd1, an interaction that is required for ERAD. Our findings support a model of Hrd1 complex formation, where the Hrd1 cytoplasmic domain and FAM8A1 have a central role in the assembly and activity of this ERAD machinery.
哺乳动物泛素连接酶 Hrd1 是一个复合物的核心组成部分，该复合物有助于在泛素-蛋白酶体依赖的内质网相关降解（ERAD）过程中降解错误折叠的蛋白质。Hrd1 与辅助因子结合以执行 ERAD，但它们的作用以及它们与 Hrd1 如何组装尚不清楚。在这里，我们确定了 Hrd1 中的关键辅助因子相互作用结构域，并报告了 Hrd1 内在无序的细胞质结构域（称为 HAF-H 结构域）内以前未被识别的进化保守片段，该片段与辅助因子 FAM8A1 和 Herp（也称为 HERPUD1）中的互补片段结合。该结构域是 Hrd1 与 FAM8A1 和 Herp 相互作用以及组装更高阶 Hrd1 复合物所必需的。FAM8A1 增强了 Herp 与 Hrd1 的结合，这种相互作用是 ERAD 所必需的。我们的发现支持 Hrd1 复合物形成的模型，其中 Hrd1 细胞质结构域和 FAM8A1 在该 ERAD 机制的组装和活性中起核心作用。
