The E3 Ubiquitin Ligase Ring Finger Protein 5 Ameliorates NASH Through Ubiquitin-Mediated Degradation of 3-Hydroxy-3-Methylglutaryl CoA Reductase Degradation Protein 1
The E3 Ubiquitin Ligase Ring Finger Protein 5 Ameliorates NASH Through Ubiquitin-Mediated Degradation of 3-Hydroxy-3-Methylglutaryl CoA Reductase Degradation Protein 1
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DOI：
10.1002/hep.32061
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发表时间：
2021-08-31
期刊：
影响因子：
13.5
通讯作者：
Li, Hongliang
中科院分区：
文献类型：
--
作者：
Yang, Qin;Chen, Xi;Li, Hongliang
背景和目标 NAFLD 是世界范围内最常见的慢性肝病，但尚无有效的药物治疗方法可供临床使用。 NASH 是 NAFLD 的更严重阶段。在此过程中，内质网 (ER) 相关通路和蛋白质的失调是主要标志之一。我们的目的是揭示环指蛋白 5 (RNF5)（一种内质网定位的 E3 泛素蛋白连接酶）在 NASH 中的作用，并探索其潜在机制。方法和结果我们首先检查了 RNF5 的表达水平，发现在包括人类在内的多个物种的 NASH 肝脏中，RNF5 的表达水平显着降低。然后，我们将用于 Rnf5 过表达或敲低的腺病毒引入原代小鼠肝细胞，发现棕榈酸/油酸 (PAOA) 诱导的肝细胞脂质积累和炎症因 Rnf5 过表达而显着减弱，但因 Rnf5 基因沉默而加剧。肝细胞特异性 Rnf5 敲除显着加剧了饮食诱导的 NASH 小鼠的肝脏脂肪变性、炎症反应和纤维化。从机制上讲，我们通过系统的相互作用组学分析确定了 3-羟基-3-甲基戊二酰辅酶 A 还原酶降解蛋白 1 (HRD1) 作为 RNF5 的结合伴侣。 RNF5 直接与 HRD1 结合，促进其赖氨酸 48 (K48) 连接和 K33 连接泛素化以及随后的蛋白酶体降解。此外，Hrd1过表达显着加剧PAOA诱导的脂质积累和炎症，而短发夹RNA介导的Hrd1敲低则产生相反的效果。值得注意的是，Hrd1 敲低显着减少了 PAOA 诱导的脂质沉积，并且肝细胞中 Rnf5 消除导致相关基因上调。结论 这些数据表明 RNF5 通过靶向泛素介导的蛋白酶体途径中的 HRD1 来抑制 NASH 进展。靶向 RNF5-HRD1 轴可能有助于深入了解 NASH 的发病机制，并为制定 NASH 预防和治疗策略铺平道路。
Background and Aims NAFLD is the most prevalent chronic liver disease worldwide, but no effective pharmacological therapeutics are available for clinical use. NASH is the more severe stage of NAFLD. During this progress, dysregulation of endoplasmic reticulum (ER)-related pathways and proteins is one of the predominant hallmarks. We aimed to reveal the role of ring finger protein 5 (RNF5), an ER-localized E3 ubiquitin-protein ligase, in NASH and to explore its underlying mechanism. Approach and Results We first inspected the expression level of RNF5 and found that it was markedly decreased in livers with NASH in multiple species including humans. We then introduced adenoviruses for Rnf5 overexpression or knockdown into primary mouse hepatocytes and found that palmitic acid/oleic acid (PAOA)-induced lipid accumulation and inflammation in hepatocytes were markedly attenuated by Rnf5 overexpression but exacerbated by Rnf5 gene silencing. Hepatocyte-specific Rnf5 knockout significantly exacerbated hepatic steatosis, inflammatory response, and fibrosis in mice challenged with diet-induced NASH. Mechanistically, we identified 3-hydroxy-3-methylglutaryl CoA reductase degradation protein 1 (HRD1) as a binding partner of RNF5 by systematic interactomics analysis. RNF5 directly bound to HRD1 and promoted its lysine 48 (K48)-linked and K33-linked ubiquitination and subsequent proteasomal degradation. Furthermore, Hrd1 overexpression significantly exacerbated PAOA-induced lipid accumulation and inflammation, and short hairpin RNA-mediated Hrd1 knockdown exerted the opposite effects. Notably, Hrd1 knockdown significantly diminished PAOA-induced lipid deposition, and up-regulation of related genes resulted from Rnf5 ablation in hepatocytes. Conclusions These data indicate that RNF5 inhibits NASH progression by targeting HRD1 in the ubiquitin-mediated proteasomal pathway. Targeting the RNF5-HRD1 axis may provide insights into the pathogenesis of NASH and pave the way for developing strategies for NASH prevention and treatment.