Department of Biochemistry & Molecular Biology, Seoul, Republic of Korea.
Graduate School of Medical Science, Brain Korea 21 Project, Seoul, Republic of Korea.
Cell Death Dis. 2023 Nov 27;14(11):776. doi: 10.1038/s41419-023-06317-7.
Dysregulation of the ubiquitin-proteasome system has been implicated in the pathogenesis of several metabolic disorders, including obesity, diabetes, and non-alcoholic fatty liver disease; however, the mechanisms controlling pathogenic metabolic disorders remain unclear. Transcription factor CCAAT/enhancer binding protein beta (C/EBPβ) regulates adipogenic genes. The study showed that the expression level of C/EBPβ is post-translationally regulated by the deubiquitinase ubiquitin-specific protease 1 (USP1) and that USP1 expression is remarkably upregulated during adipocyte differentiation and in the adipose tissue of mice fed a high-fat diet (HFD). We found that USP1 directly interacts with C/EBPβ. Knock-down of USP1 decreased C/EBPβ protein stability and increased its ubiquitination. Overexpression of USP1 regulates its protein stability and ubiquitination, whereas catalytic mutant of USP1 had no effect on them. It suggests that USP1 directly deubiquitinases C/EBPβ and increases the protein expression, leading to adipogenesis and lipid accumulation. Notably, the USP1-specific inhibitor ML323-originally developed to sensitize cancer cells to DNA-damaging agents-decreased adipocyte differentiation and lipid accumulation in 3T3-L1 cells without cytotoxicity. Oral gavage of ML323 was administered to HFD-fed mice, which showed weight loss and improvement in insulin and glucose sensitivity. Both fat mass and adipocyte size in white adipose tissues were significantly reduced by ML323 treatment, which also reduced the expression of genes involved in adipogenesis and inflammatory responses. ML323 also reduced lipid accumulation, hepatic triglycerides, free fatty acids, and macrophage infiltration in the livers of HFD-fed mice. Taken together, we suggest that USP1 plays an important role in adipogenesis by regulating C/EBPβ ubiquitination, and USP1-specific inhibitor ML323 is a potential treatment option and further study by ML323 is needed for clinical application for metabolic disorders.
泛素-蛋白酶体系统的失调与几种代谢紊乱有关，包括肥胖、糖尿病和非酒精性脂肪肝；然而，控制致病代谢紊乱的机制仍不清楚。转录因子 CCAAT/增强子结合蛋白β（C/EBPβ）调节脂肪生成基因。研究表明，C/EBPβ的表达水平受去泛素化酶泛素特异性蛋白酶 1（USP1）的翻译后调控，USP1 在脂肪细胞分化过程中和高脂饮食喂养的小鼠脂肪组织中表达显著上调。我们发现 USP1 与 C/EBPβ直接相互作用。USP1 的敲低降低了 C/EBPβ蛋白的稳定性并增加了其泛素化。USP1 的过表达调节其蛋白稳定性和泛素化，而 USP1 的催化突变体对它们没有影响。这表明 USP1 直接去泛素化 C/EBPβ并增加其蛋白表达，导致脂肪生成和脂质积累。值得注意的是，USP1 特异性抑制剂 ML323-最初开发用于使癌细胞对 DNA 损伤剂敏感-在没有细胞毒性的情况下减少 3T3-L1 细胞中的脂肪细胞分化和脂质积累。向高脂饮食喂养的小鼠口服给予 ML323，其表现出体重减轻和胰岛素和葡萄糖敏感性改善。ML323 处理显著降低白色脂肪组织中的脂肪量和脂肪细胞大小，还降低了参与脂肪生成和炎症反应的基因的表达。ML323 还减少了高脂饮食喂养小鼠肝脏中的脂质积累、肝甘油三酯、游离脂肪酸和巨噬细胞浸润。综上所述，我们认为 USP1 通过调节 C/EBPβ泛素化在脂肪生成中起重要作用，USP1 特异性抑制剂 ML323 是一种潜在的治疗选择，需要进一步研究 ML323 用于代谢紊乱的临床应用。
