Role of hepatic Mettl14 pathways in liver metabolism and body metabolic homeostasis

肝脏Mettl14通路在肝脏代谢和机体代谢稳态中的作用

• 批准号: 10621821
• 负责人: LIANGYOU RUI
• 金额: $ 39万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10621821
• 关键词: Ablation; Adult; Amino Acids; Attenuated; Binding; Binding Proteins; Catalytic Domain; Cell physiology; Complex; Development; Diabetes Mellitus; Disease; Embryo; Embryo Deaths; Fatty Acids; Fatty Liver; Genetic; Genetic Transcription; Genomics; Glucagon; Gluconeogenesis; Glucose; Glucose Intolerance; Health; Hepatic; Hepatocyte; High Fat Diet; Homeostasis; Hyperglycemia; Injury; Insulin; Insulin Resistance; Knockout Mice; Lipids; Liver; Liver diseases; Mediating; Mediator; Messenger RNA; Metabolic; Metabolic Diseases; Metabolic Pathway; Metabolic dysfunction; Metabolic hormone; Methylation; Methyltransferase; Modeling; Modification; Morbidity - disease rate; Mus; Non-Insulin-Dependent Diabetes Mellitus; Nuclear Export; Obesity; Obesity associated liver disease; Organ; Outcome; Pathway interactions; Post-Transcriptional RNA Processing; Production; Protein Biosynthesis; Proteins; RNA; RNA Splicing; RNA metabolism; RNA methylation; RNA-Binding Proteins; RNA-Protein Interaction; Role; Signal Pathway; Signal Transduction; Slice; Transcript; Transcriptional Regulation; epigenetic regulation; epitranscriptomics; fatty liver disease; genetic information; glucose metabolism; glucose production; hepatic gluconeogenesis; improved; lipid biosynthesis; lipid metabolism; liver ablation; liver function; liver metabolism; mRNA Decay; mRNA Precursor; molecular targeted therapies; mortality; non-alcoholic fatty liver disease; novel; oxidation; programs; repaired; response; trafficking; transcriptome sequencing; translational genetics

Messenger RNA mediates translation of genetic information into protein synthesis and cell functions. Levels of translationally-competent mRNA are determined by RNA transcription, post-transcriptional modifications, and RNA interactions with proteins. Genetic and epigenetic regulations of transcription have been extensively investigated; by contrast, there is a gap in our understanding of mRNA modifications, RNA-protein interactions, and their impacts on cellular responses. N6-methyladenosine (m6A) is the predominant mRNA modification, and is catalyzed by a Mettl3 (catalytic subunit)/Mettl14 (structural subunit) methyltransferase complex. M6A motif is recognized by and bound to Ythdc1 or related RNA-binding proteins, which in turn control pre-mRNA splicing, nuclear export, intracellular localization, decay, and/or translational efficiency of target mRNAs. Global deletion of Mettl3, Mettl14, or Ythdc1 results in embryonic death, revealing the essential role of these epitranscriptomic mediators in development and survival. Liver is an essential metabolic organ. Liver disease, including nonalcoholic fatty liver disease (NAFLD) and metabolic dysfunctions, is a main cause for mortality and morbidity. However, Mettl14/Ythdc1-based epitranscriptomic programs have not been explored in the liver. In the preliminary study, we generated adult-onset, hepatocyte-specific Mettl14 and Ythdc1 knockout mice. Ablation of hepatic Mettl14 attenuated high fat diet (HFD)-induced hyperglycemia, glucose intolerance, and liver steatosis. Likewise, hepatocyte-specific deletion of Ythdc1 also improved glucose metabolism in HFD-fed mice. In liver slice cultures, Mettl14 deficiency blunted glucagon-stimulated liver glucose production. RNA-seq analysis showed that deletion of hepatic Mettl14 changed levels of many liver mRNA transcripts encoding proteins involved in glucose/lipid metabolism and signaling pathways. Based on these results, we hypothesize that Mettl14 mediates m6A methylation in mRNAs encoding mediators/modulates for hepatic gluconeogenesis, lipogenesis, and related signaling pathways. Ythdc1 binds to m6A motif, and controls pre-mRNA splicing, nuclear export, and/or degradation of a subset of Mettl14 substrates. Moreover, obesity-related factors increase expression and stability of hepatic Mettl14 and Ythdc1, thereby eliciting Mettl14/Ythdc1-based epitranscriptomic reprogramming of liver metabolism. Mettl14/m6A/Ythdc1-elicited epitranscriptomic reprogramming provides a new mechanism underlying obesity-associated NAFLD and type 2 diabetes. Aim 1 determines whether hepatic Mettl14 directly promotes liver glucose production and liver steatosis by an epitranscriptomic mechanism. Aim 2 determines whether Ythdc1 mediates the metabolic action of Mettl14 in the liver. Aim 3 determines whether Mettl14/Ythdc1-elicited epitranscriptomic reprogramming mediates obesity- associated liver disease. The outcomes of this project are expected to establish a new Mett14/Ythdc1-based epitranscriptomic reprogramming paradigm governing liver metabolism in health and disease.

信使RNA介导遗传信息转化为蛋白质合成和细胞功能。有翻译能力的 mRNA 水平由 RNA 转录、转录后修饰以及 RNA 与蛋白质的相互作用决定。转录的遗传和表观遗传调控已被广泛研究；相比之下，我们对 mRNA 修饰、RNA-蛋白质相互作用及其对细胞反应的影响的理解存在差距。 N6-甲基腺苷 (m6A) 是主要的 mRNA 修饰，由 Mettl3（催化亚基）/Mettl14（结构亚基）甲基转移酶复合物催化。 M6A 基序被 Ythdc1 或相关 RNA 结合蛋白识别并结合，进而控制靶 mRNA 的前 mRNA 剪接、核输出、细胞内定位、衰变和/或翻译效率。 Mettl3、Mettl14 或 Ythdc1 的整体缺失会导致胚胎死亡，揭示了这些表观转录介质在发育和生存中的重要作用。肝脏是重要的代谢器官。肝病，包括非酒精性脂肪肝病（NAFLD）和代谢功能障碍，是死亡和发病的主要原因。然而，基于 Mettl14/Ythdc1 的表观转录组程序尚未在肝脏中进行探索。在初步研究中，我们生成了成年发病的肝细胞特异性 Mettl14 和 Ythdc1 基因敲除小鼠。消除肝脏 Mettl14 可减轻高脂饮食 (HFD) 引起的高血糖、葡萄糖耐受不良和肝脏脂肪变性。同样，肝细胞特异性删除 Ythdc1 也改善了 HFD 喂养小鼠的葡萄糖代谢。在肝切片培养物中，Mettl14 缺乏会减弱胰高血糖素刺激的肝脏葡萄糖产生。 RNA-seq 分析表明，肝脏 Mettl14 的缺失改变了许多编码参与葡萄糖/脂质代谢和信号通路的蛋白质的肝脏 mRNA 转录物的水平。基于这些结果，我们假设 Mettl14 介导编码肝糖异生、脂肪生成和相关信号通路介导/调节因子的 mRNA 中的 m6A 甲基化。 Ythdc1 与 m6A 基序结合，并控制前 mRNA 剪接、核输出和/或 Mettl14 底物子集的降解。此外，肥胖相关因素增加肝脏Mettl14和Ythdc1的表达和稳定性，从而引发基于Mettl14/Ythdc1的肝脏代谢表观转录组重编程。 Mettl14/m6A/Ythdc1 引发的表观转录组重编程提供了肥胖相关 NAFLD 和 2 型糖尿病的新机制。目标 1 确定肝脏 Mettl14 是否通过表观转录组机制直接促进肝脏葡萄糖产生和肝脏脂肪变性。目标 2 确定 Ythdc1 是否介导 Mettl14 在肝脏中的代谢作用。目标 3 确定 Mettl14/Ythdc1 引发的表观转录组重编程是否介导肥胖相关的肝病。该项目的成果预计将建立一个新的基于 Mett14/Ythdc1 的表观转录组重编程范式，控制健康和疾病中的肝脏代谢。