背景:作为终末期肝病的主要原因,非酒精性脂肪性肝病(NAFLD)主要由血脂异常引起。内源性环状RNA(circularRNAs,circRNAs)的翻译与多种疾病的发生发展密切相关。但尚未确定circRNAs在NAFLD中的参与。
方法:组合高通量circRNA谱用于鉴定具有翻译潜力的circRNA。通过RNA测序研究了潜在的分子机制,下拉/MS和位点特异性诱变。
结果:在这项研究中,我们重点研究了circ-SLC9A6,这是一种在NAFLD发展过程中在人和小鼠肝脏组织中异常高表达的circRNA,它通过编码一种名为SLC9A6-126aa的新型肽在体内和体外加剧了肝细胞的代谢紊乱.发现YTHDF2介导的m6A修饰的circ-SLC9A6的降解对于调节SLC9A6-126aa表达至关重要。我们进一步发现,AKT对SLC9A6-126aa的磷酸化对其细胞质定位和维持生理稳态至关重要,而高脂肪应激诱导未磷酸化的SLC9A6-126aa大量易位到细胞核,导致脂质代谢功能障碍的恶性循环。核SLC9A6-126aa通过调节MOF介导的组蛋白H4K16乙酰化来促进靶基因CD36的转录激活并增强其对CD36启动子基因座的占用。肝CD36耗竭显着改善SLC9A6-126aa转基因小鼠中过度活化的MAPK信号传导和脂质紊乱。临床上,在NAFLD进展期间观察到SLC9A6-126aa水平升高,并发现与CD36和MAPK级联呈正相关.
结论:本研究揭示了circ-SLC9A6来源的SLC9A6-126aa在表观遗传修饰介导的脂质代谢调节中的作用。我们的发现可能为NAFLD提供有希望的治疗靶点,并为代谢性疾病的病理机制提供新的见解。
结论:在正常情况下,由M6A改装驱动,YTHDF2直接识别并降解circ-SLC9A6,从而抑制SLC9A6-126aa的翻译。此外,AKT1磷酸化并抑制SLC9A6-126aa的核易位。在NAFLD,脂质超负荷导致YTHDF2和AKT1缺乏,最终增加SLC9A6-126aa的表达和核输入。核SLC9A6-126aa直接与CD36启动子结合并启动CD36转录,诱导脂质代谢异常。
BACKGROUND: As the leading cause of end-stage liver disease, nonalcoholic fatty liver disease (NAFLD) is mainly induced by lipid dyshomeostasis. The translation of endogenous circular RNAs (circRNAs) is closely related to the progression of various diseases, but the involvement of circRNAs in NAFLD has not been determined.
METHODS: Combined high-throughput circRNA profiles were used to identify circRNAs with translational potential. The underlying molecular mechanisms were investigated by RNA sequencing, pull-down/MS and site-specific mutagenesis.
RESULTS: In this study, we focused on circ-SLC9A6, an abnormally highly expressed circRNA in human and mouse liver tissue during NAFLD development that exacerbates metabolic dyshomeostasis in hepatocytes by encoding a novel peptide called SLC9A6-126aa in vivo and in vitro. YTHDF2-mediated degradation of m6A-modified circ-SLC9A6 was found to be essential for the regulation of SLC9A6-126aa expression. We further found that the phosphorylation of SLC9A6-126aa by AKT was crucial for its cytoplasmic localization and the maintenance of physiological homeostasis, whereas high-fat stress induced substantial translocation of unphosphorylated SLC9A6-126aa to the nucleus, resulting in a vicious cycle of lipid metabolic dysfunction. Nuclear SLC9A6-126aa promotes transcriptional activation of the target gene CD36 and enhances its occupancy of the CD36 promoter locus by regulating MOF-mediated histone H4K16 acetylation. Hepatic CD36 depletion significantly ameliorated hyperactivated MAPK signalling and lipid disturbance in SLC9A6-126aa transgenic mice. Clinically, increasing levels of SLC9A6-126aa were observed during NAFLD progression and were found to be positively correlated with the CD36 and MAPK cascades.
CONCLUSIONS: This study revealed the role of circ-SLC9A6-derived SLC9A6-126aa in the epigenetic modification-mediated regulation of lipid metabolism. Our findings may provide promising therapeutic targets for NAFLD and new insights into the pathological mechanisms of metabolic diseases.
CONCLUSIONS: Under normal circumstances, driven by m6A modification, YTHDF2 directly recognizes and degrades circ-SLC9A6, thereby inhibiting the translation of SLC9A6-126aa. Additionally, AKT1 phosphorylates and inhibits the nuclear translocation of SLC9A6-126aa. In NAFLD, lipid overload leads to YTHDF2 and AKT1 deficiency, ultimately increasing the expression and nuclear import of SLC9A6-126aa. Nuclear SLC9A6-126aa binds directly to the CD36 promoter and initiates CD36 transcription, which induces lipid dyshomeostasis.