Hrd1-mediated ACLY Ubiquitination alleviate NAFLD in db/db mice.,Metabolism

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Hrd1-mediated ACLY Ubiquitination alleviate NAFLD in db/db mice.
Metabolism ( IF 10.8 ) Pub Date : 2020-09-02 , DOI: 10.1016/j.metabol.2020.154349
Kai Li ₁ , Kaini Zhang ₂ , Hai Wang ₂ , Yangyang Wu ₁ , Nuoqi Chen ₃ , Jinfeng Chen ₃ , Chen Qiu ₄ , Pengpeng Cai ₅ , Min Li ₂ , Xiubin Liang ₆ , Dongming Su ₇

Affiliation

Background

The functions of Acly in regulating nonalcoholic fatty liver disease (NAFLD) have been identified; however, the dynamic control of Acly expression under the pathological state of metabolic disorders has not been fully elucidated. Previous studies reported an ubiquitin-proteasome–mediated degradation of Acly, but the mechanism is still largely unknown.

Methods

Co-IP–based mass spectrum (MS/MS) assays were performed in HepG2 and Hepa1–6 hepatocytes and mouse liver tissue. The protein-protein interaction and ubiquitin modification of Hrd1 on Acly were confirmed by co-IP based immuno-blotting. Acetyl-CoA levels and lipogenesis rates were determined. The roles of Hrd1 on NAFLD and insulin resistance were tested by adenovirus-mediated overexpression in db/db mice or in separated primary hepatocytes.

Results

Hrd1, a subunit of the endoplasmic reticulum-associated degradation (ERAD) complex, interacted with and ubiquitinated Acly, thereby reducing its protein level. Hrd1 suppressed the acetyl-CoA level and inhibited lipogenesis through an Acly-dependent pathway. The expression of hepatic Hrd1 was negatively associated with NAFLD, whereas overexpression of Hrd1 ameliorated hepatic steatosis and enhanced insulin sensitivity, both in db/db mice and in separated mouse primary hepatocytes.

Conclusions

Our results suggest that Acly, a master enzyme that regulates lipogenesis, is degraded by Hrd1 through ubiquitin modification. The activation of Hrd1 in hepatocytes might therefore represent a strategic approach for NAFLD therapy.

中文翻译：

Hrd1介导的ACLY泛素化可减轻db / db小鼠的NAFLD。

背景

已经确定了Acly在调节非酒精性脂肪肝疾病（NAFLD）中的功能；然而，尚未完全阐明在代谢紊乱的病理状态下对Acly表达的动态控制。先前的研究报道了泛素-蛋白酶体介导的Acly降解，但机理尚不清楚。

方法

在HepG2和Hepa1-6肝细胞和小鼠肝组织中进行了基于Co-IP的质谱（MS / MS）分析。通过基于co-IP的免疫印迹证实了Acly上Hrd1的蛋白相互作用和泛素修饰。确定了乙酰辅酶A水平和脂肪生成速率。通过在db / db小鼠或分离的原代肝细胞中腺病毒介导的过表达测试了Hrd1对NAFLD和胰岛素抵抗的作用。

结果

内质网相关降解（ERAD）复合体的亚基Hrd1与Acly相互作用并被泛素化，从而降低了其蛋白水平。Hrd1抑制乙酰辅酶A水平，并通过Acly依赖性途径抑制脂肪生成。肝Hrd1的表达与NAFLD呈负相关，而Hrd1的过表达改善了db / db小鼠和分离的小鼠原代肝细胞的肝脂肪变性并增强了胰岛素敏感性。