Department of Molecular & Integrative Physiology, University of Michigan Medical School, 1137 Catherine Street, Med Sci II 7712, Ann Arbor, MI 48109, USA.
Department of Molecular & Integrative Physiology, University of Michigan Medical School, 1137 Catherine Street, Med Sci II 7712, Ann Arbor, MI 48109, USA; Department of Infectious Diseases, The Second Xianya Hospital, Central South University, Changsha City 410083, Hunan Province, PR China.
Metabolism. 2020 Jun;107:154222. doi: 10.1016/j.metabol.2020.154222. Epub 2020 Apr 1.
Fructose over-consumption contributes to the development of liver steatosis in part by stimulating ChREBPα-driven de novo lipogenesis. However, the mechanisms by which fructose activates ChREBP pathway remain largely undefined. Here we performed affinity purification of ChREBPα followed by mass spectrometry and identified DDB1 as a novel interaction protein of ChREBPα in the presence of fructose. Depletion and overexpression of Ddb1 showed opposite effects on the ChREBPα stability in hepatocytes. We next tested the impact of hepatic Ddb1 deficiency on the fructose-induced ChREBP pathway. After 3-week high-fructose diet feeding, both Ddb1 liver-specific knockout and AAV-TBG-Cre-injected Ddb1 mice showed significantly reduced ChREBPα, lipogenic enzymes, as well as triglycerides in the liver. Mechanistically, DDB1 stabilizes ChREBPα through CRY1, a known ubiquitination target of DDB1 E3 ligase. Finally, overexpression of a degradation-resistant CRY1 mutant (CRY1-585KA) reduces ChREBPα and its target genes in the mouse liver following high-fructose diet feeding. Our data revealed DDB1 as an intracellular sensor of fructose intake to promote hepatic de novo lipogenesis and liver steatosis by stabilizing ChREBPα in a CRY1-dependent manner.
果糖摄入过多会刺激 ChREBPα 驱动的从头合成脂肪生成，从而导致肝脏脂肪变性。然而，果糖激活 ChREBP 通路的机制在很大程度上仍未确定。在这里，我们进行了 ChREBPα 的亲和纯化，然后进行了质谱分析，在果糖存在的情况下鉴定出 DDB1 是 ChREBPα 的一种新的相互作用蛋白。Ddb1 的耗竭和过表达对肝细胞中 ChREBPα 的稳定性表现出相反的影响。接下来，我们测试了肝 Ddb1 缺陷对果糖诱导的 ChREBP 通路的影响。在 3 周的高果糖饮食喂养后，Ddb1 肝特异性敲除和 AAV-TBG-Cre 注射的 Ddb1 小鼠的 ChREBPα、脂肪生成酶以及肝脏中的甘油三酯均显著降低。在机制上，DDB1 通过 CRY1 稳定 ChREBPα，CRY1 是 DDB1 E3 连接酶的已知泛素化靶标。最后，过表达一种不易降解的 CRY1 突变体 (CRY1-585KA) 可减少高果糖饮食喂养后小鼠肝脏中的 ChREBPα 和其靶基因。我们的数据揭示了 DDB1 作为果糖摄入的细胞内传感器，通过 CRY1 依赖性方式稳定 ChREBPα，从而促进肝脏从头合成脂肪生成和肝脂肪变性。
