Engineering Research Center of Cell and Therapeutic Antibody, Ministry of Education, and School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China.
Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303, United States.
Biochemistry. 2023 Apr 4;62(7):1274-1286. doi: 10.1021/acs.biochem.2c00624. Epub 2023 Mar 15.
Nonalcoholic fatty liver disease (NAFLD) is substantiated by the reprogramming of liver metabolic pathways that disrupts the homeostasis of lipid and glucose metabolism and thus promotes the progression of the disease. The metabolic pathways associated with NAFLD are regulated at different levels from gene transcription to various post-translational modifications including ubiquitination. Here, we used a novel orthogonal ubiquitin transfer platform to identify pyruvate dehydrogenase A1 (PDHA1) and acetyl-CoA acetyltransferase 1 (ACAT1), two important enzymes that regulate glycolysis and ketogenesis, as substrates of E3 ubiquitin ligase UBE3A/E6AP. We found that overexpression of UBE3A accelerated the degradation of PDHA1 and promoted glycolytic activities in HEK293 cells. Furthermore, a high-fat diet suppressed the expression of UBE3A in the mouse liver, which was associated with increased ACAT1 protein levels, while forced expression of UBE3A in the mouse liver resulted in decreased ACAT1 protein contents. As a result, the mice with forced expression of UBE3A in the liver exhibited enhanced accumulation of triglycerides, cholesterol, and ketone bodies. These results reveal the role of UBE3A in NAFLD development by inducing the degradation of ACAT1 in the liver and promoting lipid storage. Overall, our work uncovers an important mechanism underlying the regulation of glycolysis and lipid metabolism through UBE3A-mediated ubiquitination of PDHA1 and ACAT1 to regulate their stabilities and enzymatic activities in the cell.
非酒精性脂肪性肝病（NAFLD）是由肝脏代谢途径的重编程所证实的，这种重编程破坏了脂质和葡萄糖代谢的内稳态，从而促进了疾病的进展。与 NAFLD 相关的代谢途径在不同水平上受到调节，从基因转录到各种翻译后修饰，包括泛素化。在这里，我们使用一种新的正交泛素转移平台来鉴定丙酮酸脱氢酶 A1（PDHA1）和乙酰辅酶 A 乙酰转移酶 1（ACAT1），这两种重要的酶分别调节糖酵解和酮体生成，作为 E3 泛素连接酶 UBE3A/E6AP 的底物。我们发现，UBE3A 的过表达加速了 PDHA1 的降解，并促进了 HEK293 细胞中的糖酵解活性。此外，高脂肪饮食抑制了小鼠肝脏中 UBE3A 的表达，这与 ACAT1 蛋白水平的增加有关，而在小鼠肝脏中强制表达 UBE3A 则导致 ACAT1 蛋白含量降低。结果，肝脏中强制表达 UBE3A 的小鼠表现出甘油三酯、胆固醇和酮体的积累增加。这些结果揭示了 UBE3A 通过诱导肝脏中 ACAT1 的降解并促进脂质储存，从而在 NAFLD 发展中的作用。总的来说，我们的工作揭示了通过 UBE3A 介导的 PDHA1 和 ACAT1 的泛素化来调节它们在细胞中的稳定性和酶活性，从而调节糖酵解和脂质代谢的重要机制。
