Ni Dongsheng, Qi Zhaolai, Ma Shuang, Wang Yuefeng, Liang Dehuan, Zhang Xiyue, Man Yong, Chen Jingzhou, Dou Kefei, Li Guoping
The Key Laboratory of Geriatrics, Beijing Institute of Geriatrics, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing Hospital/National Center of Gerontology of National Health Commission, Beijing, 100730, PR China; Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100730, PR China.
The Key Laboratory of Geriatrics, Beijing Institute of Geriatrics, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing Hospital/National Center of Gerontology of National Health Commission, Beijing, 100730, PR China.
Mol Metab. 2025 Jun;96:102137. doi: 10.1016/j.molmet.2025.102137. Epub 2025 Apr 4.
Metabolic dysfunction-associated fatty liver disease (MAFLD) has emerged as an important public health concern that poses a significant threat to human health and imposes a substantial economic burden. Research has demonstrated that ubiquitin ligase-mediated substrate protein ubiquitination is a pivotal factor influencing liver lipid homeostasis and metabolic abnormalities in MAFLD. Nevertheless, the specific enzyme molecules implicated in this regulatory process remain to be elucidated. We have published a transcriptome-overexpressing ubiquitin ligase, membrane-associated ring-CH-type finger 2 (MARCH2), in HepG2 cells, and subsequent reanalysis of these transcriptome data revealed a close association between MARCH2 and lipid metabolism.
By employing a range of methodologies, including recombinant adeno-associated virus (rAAV) transduction, lentiviral transduction, immunoblotting, quantitative PCR, tissue section staining, ubiquitination assays, serum biochemical analysis, immunoprecipitation, and mass spectrometry, this study investigated the functions and mechanisms of MARCH2 in the progression of MAFLD at the molecular, cellular, and organismal levels.
Overexpression of MARCH2, but not its catalytically inactive ligase variant, inhibited lipid accumulation in HepG2 cells. Additionally, MARCH2 undergoes K48-linked self-polyubiquitination and subsequent proteasomal degradation in response to oleic acid/palmitic acid stimulation. Furthermore, knockout of MARCH2 exacerbates the progression of MAFLD-related phenotypes, including increased body weight, impaired glucose tolerance, reduced insulin sensitivity, hypercholesterolemia, hepatic lipid accumulation, and steatosis, in high-fat diet-fed mice, irrespective of sex. Mechanistically, MARCH2 facilitates the polyubiquitination and degradation of fatty acid synthase (FASN) in the de novo lipogenesis pathway. And liver-specific overexpression of MARCH2 by rAAV effectively reduces FASN levels and further ameliorates MAFLD in ob/ob mice.
MARCH2 undergoes self-ubiquitination and plays an important role in maintaining the liver lipid homeostasis of MAFLD, and drug intervention in the MARCH2-FASN axis is a promising approach for treating systemic metabolic abnormalities in MAFLD.
代谢功能障碍相关脂肪性肝病（MAFLD）已成为一个重要的公共卫生问题，对人类健康构成重大威胁并带来巨大经济负担。研究表明，泛素连接酶介导的底物蛋白泛素化是影响MAFLD中肝脏脂质稳态和代谢异常的关键因素。然而，参与这一调节过程的具体酶分子仍有待阐明。我们曾发表过在HepG2细胞中过表达泛素连接酶膜相关环-CH型指蛋白2（MARCH2）的转录组数据，随后对这些转录组数据的重新分析揭示了MARCH2与脂质代谢之间的密切关联。
本研究采用了一系列方法，包括重组腺相关病毒（rAAV）转导、慢病毒转导、免疫印迹、定量PCR、组织切片染色、泛素化测定、血清生化分析、免疫沉淀和质谱分析，在分子、细胞和机体水平上研究MARCH2在MAFLD进展中的功能和机制。
MARCH2的过表达而非其催化无活性的连接酶变体抑制了HepG2细胞中的脂质积累。此外，MARCH2在油酸/棕榈酸刺激下会发生K48连接的自身多聚泛素化并随后被蛋白酶体降解。此外，敲除MARCH2会加剧高脂饮食喂养小鼠（无论性别）中MAFLD相关表型的进展，包括体重增加、糖耐量受损、胰岛素敏感性降低、高胆固醇血症、肝脏脂质积累和脂肪变性。机制上，MARCH2促进了从头脂肪生成途径中脂肪酸合酶（FASN）的多聚泛素化和降解。通过rAAV在肝脏特异性过表达MARCH2可有效降低FASN水平，并进一步改善ob/ob小鼠的MAFLD。
MARCH2发生自身泛素化，并在维持MAFLD的肝脏脂质稳态中发挥重要作用，对MARCH2-FASN轴进行药物干预是治疗MAFLD系统性代谢异常的一种有前景的方法。
