School of Basic Medical Sciences, Peking University, Beijing, China.
Department of Surgery, University of Michigan Medical Center, Ann Arbor, MI, USA.
FASEB J. 2020 Nov;34(11):14946-14959. doi: 10.1096/fj.202001234R. Epub 2020 Sep 14.
R-spondins (Rspos) are endogenous ligands of leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4). Rspos-LGR4 signaling plays important roles in embryogenesis, gastrointestinal homeostasis, and food intake. Here, we investigated the impacts of Rspos-LGR4 on hepatic cholesterol synthesis. Rspo1/3 and Lgr4 knockdown mice were used to investigate the impacts of Rspo1/3-LGR4 on hepatic cholesterol synthesis. AMPKα agonist, antagonist, and shRNA were used to explore the downstream targets of Rspos-LGR4 signaling. In our study, we reported that LGR4, Rspo1, and Rspo3 were highly expressed in hepatocytes and their expressions were sensitive to energy states. Rspo1 and Rspo3 reversed OA-induced cholesterol synthesis, accompanying with increased the phosphorylation of AMPKα Thr172, reduced SREBP2 nuclear translocation, and Srebf2 mRNA expression. Conversely, hepatic LGR4 knockdown increased hepatic cholesterol synthesis and decreased the phosphorylation of AMPKα both in vitro and in vivo. Activation or inhibition of AMPKα significantly abolished the effects of LGR4 deficiency or Rspos, respectively, on cholesterol synthesis. Knockdown of AMPKα1 or/and AMPKα2 repressed Rspos-induced inhibition on cholesterol synthesis. Our study indicates that Rspo1/Rspo3-LGR4 signaling in hepatocytes suppresses cholesterol synthesis via the AMPKα-SREBP2 pathway.
R 螺旋结构域蛋白（Rspos）是富含亮氨酸重复的 G 蛋白偶联受体 4（LGR4）的内源性配体。Rspos-LGR4 信号在胚胎发生、胃肠道稳态和食物摄入中发挥重要作用。在这里，我们研究了 Rspos-LGR4 对肝脏胆固醇合成的影响。使用 Rspo1/3 和 Lgr4 敲低小鼠来研究 Rspo1/3-LGR4 对肝脏胆固醇合成的影响。使用 AMPKα 激动剂、拮抗剂和 shRNA 来探索 Rspos-LGR4 信号的下游靶点。在我们的研究中，我们报告 LGR4、Rspo1 和 Rspo3 在肝细胞中高表达，其表达对能量状态敏感。Rspo1 和 Rspo3 逆转 OA 诱导的胆固醇合成，伴随着 AMPKα Thr172 的磷酸化增加、SREBP2 核易位减少和 Srebf2 mRNA 表达降低。相反，肝 LGR4 敲低在体外和体内均增加了肝胆固醇合成并降低了 AMPKα 的磷酸化。AMPKα 的激活或抑制分别显著消除了 LGR4 缺失或 Rspos 对胆固醇合成的影响。AMPKα1 和/或 AMPKα2 的敲低抑制了 Rspos 诱导的胆固醇合成抑制。我们的研究表明，肝细胞中的 Rspo1/Rspo3-LGR4 信号通过 AMPKα-SREBP2 途径抑制胆固醇合成。
