Role of Retinoid X Receptor Alpha in regulating PCSK9 transcription in the liver

视黄醇 X 受体 Alpha 在调节肝脏 PCSK9 转录中的作用

• 批准号: 10634069
• 负责人: QING MIAO
• 金额: $ 62.99万
• 依托单位: NYU LONG ISLAND SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-04-01 至 2027-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10634069
• 关键词: Acetylation; Acetyltransferase; Affect; Atherosclerosis; CRISPR/Cas technology; Cardiovascular Diseases; Cause of Death; Cholesterol; Cholesterol Homeostasis; Data; Deacetylase; Development; Down-Regulation; Fatty Liver; Gene set enrichment analysis; Genes; Genetic Transcription; Health; Hepatic; Hepatocyte; Heterodimerization; High Fat Diet; Histone Deacetylase; Human; Impairment; Inflammatory; Knockout Mice; Knowledge; LDL Cholesterol Lipoproteins; LXRalpha protein; Lead; Lipids; Liver; Liver diseases; Low Density Lipoprotein Receptor; Mediating; Metabolic Diseases; Mission; Molecular; Monoclonal Antibodies; Mus; Nuclear Receptors; Nuclear Translocation; PPAR alpha; Pathogenesis; Pathway interactions; Patients; Plasma; Population; Post-Translational Protein Processing; Prevention therapy; Production; Proprotein Convertases; RXRA gene; Repression; Research; Risk Factors; Role; Signal Pathway; Signal Transduction; Subtilisins; TNF gene; Testing; United States; United States National Institutes of Health; Up-Regulation; cardiovascular disorder risk; cytokine; disability; hypercholesterolemia; improved; in vivo; lipid biosynthesis; mouse model; mutant; non-alcoholic fatty liver; non-alcoholic fatty liver disease; novel; novel strategies; obesity prevention; overexpression; preservation; prevent; resilience factor; success; therapy development; transcriptome sequencing

PROJECT SUMMARY Cardiovascular disease (CVD) still is the leading cause of death in the United States. The demand for novel treatments lead to the recent discovery of proprotein convertase subtilisin kexin 9 (PCSK9), which promotes the degradation of low-density lipoprotein receptor (LDLR) to increase atherogenic lipoprotein LDL cholesterol (LDL- C) levels. Many treatments targeting PCSK9 have been developed but have limited efficacy in lowing LDL- C. This proposal fills the critical knowledge gap by challenging the underlying presumption that RXRα is essential to regulate the transcription of PCSK9 in the liver of nonalcoholic fatty liver diseases (NAFLD) patients. RXRα is the core nuclear receptor, which always is considered to constitutively forms heterodimerization with other nuclear receptors. Our preliminary data showed that hepatic depletion of RXRα leads to hepatic lipid accumulation and PCSK9 induction, which can be abolished by AAV8-mediated hepatic overexpression of RXRα. Consistently, we observed the increased cholesterol and LDL-C in the plasma of RXRα hepatocyte-specific knockout (hepKO) mice, and hepatic overexpression of RXRα can significantly reduce the plasma cholesterol and LDL-C levels. These preliminary data bring two scientific questions needed to be determined in this proposal: 1) why RXRα deficiency has primary effects on the PPARα signaling pathway; 2) how RXRα regulates PCSK9 expression in the liver. To find answers, we focus on elucidating the effects of RXRα protein post-translational modification (PTM) on managing the partnership with PPARα and regulating PCSK9. Recently, we identified a previously unrecognized acetylation residue of RXRα, which controls the heterodimerization between RXRα and PPARα. The inhibitory effects of RXRα constitutively acetylated mutant further indicate that acetylation of RXRα is essential for preventing the induction of PCSK9 in the liver of RXRα hepKO mice. Our data are the first to show that RXRα is acetylated by CBP, and TNFα, the inflammatory cytokine presented in the NALFD liver, impairs the CBP-mediated acetylation of RXRα. Interestingly, we also observed the decreased acetylation of RXRα in the liver of high-fat diet (HFD)-fed mice and human NAFLD patients. These results suggest a central hypothesis that RXRα acetylation is required for regulating the PPARα-mediated transcription of PCSK9 in the liver, and impaired RXRα acetylation in the NAFLD liver results in the increased cholesterol and LDL-C. We will test this hypothesis with the following two aims: Aim 1: Determine the molecular mechanism by which RXRα regulates the transcription of PCSK9 in the liver; Aim 2: Determine if and the extent to which RXRα acetylation is a resilience factor to prevent the induction of PCSK9 and cholesterol in the fatty liver. Successful completion of studies proposed in this proposal will identify the mechanisms by which acetylated RXRα coordinates with PPARα to regulate PCSK9 transcription and prevent obesity-promoted hypercholesterolemia. This identification will allow for the development of new alternative strategies for attenuating PCSK9 induction in the NAFLD liver, which will help mitigate CVD risk, an NIH's mission directive.

项目摘要 心血管疾病（CVD）仍然是美国死亡的主要原因。对小说的需求 治疗导致最近发现的前蛋白转化酶枯草杆菌蛋白酶kexin 9（PCSK 9），它促进了 低密度脂蛋白受体（LDLR）的降解增加致动脉粥样硬化脂蛋白LDL胆固醇（LDL- C）水平。已经开发了许多靶向PCSK 9的治疗方法，但在降低LDL-1方面的疗效有限。 C.该提案通过挑战RXRα是必不可少的基本假设，填补了关键的知识空白 调节非酒精性脂肪性肝病（NAFLD）患者肝脏中PCSK 9的转录。RXRα是 核心核受体，它总是被认为是组成性形成异源二聚体与其他 核受体我们的初步数据表明，肝脏RXRα的消耗会导致肝脏脂质增加 AAV 8介导的RXRα肝脏过表达可消除PCSK 9的诱导和蓄积。 同时，我们观察到RXRα肝细胞特异性的血浆胆固醇和LDL-C升高， RXRα基因敲除（hepKO）小鼠，肝脏过表达可显著降低血浆胆固醇 和LDL-C水平。这些初步数据带来了本提案中需要确定的两个科学问题： 1)为什么RXRα缺乏对PPARα信号通路有主要影响; 2）RXRα如何调节PCSK 9 在肝脏中的表达。为了找到答案，我们致力于阐明RXRα蛋白的翻译后作用， 修饰（PTM）管理与PPARα的伙伴关系和调节PCSK 9。最近，我们发现了一个 以前未被识别的RXRα的乙酰化残基，其控制RXRα和 过氧化物酶体增殖物激活受体α。RXRα组成型乙酰化突变体的抑制作用进一步表明，RXRα的乙酰化 对于防止RXRα hepKO小鼠肝脏中PCSK 9的诱导至关重要。我们的数据是第一个 显示RXRα被CBP乙酰化，TNFα，NALFD肝脏中存在的炎性细胞因子， 削弱CBP介导的RXRα乙酰化。有趣的是，我们还观察到， 高脂饮食（HFD）喂养小鼠和人类NAFLD患者肝脏中的RXRα。这些结果表明， 假设RXRα乙酰化是调节PPARα介导的PCSK 9转录所必需的， NAFLD肝脏中RXRα乙酰化受损导致胆固醇和LDL-C升高。我们将 我们将从以下两个方面来验证这一假设：目的1：确定RXRα 调节肝脏中PCSK 9的转录;目的2：确定RXRα乙酰化是否和程度 是一种弹性因子，可防止脂肪肝中PCSK 9和胆固醇的诱导。成功完成 该提案中提出的研究将确定乙酰化RXRα与 PPARα调节PCSK 9转录并预防肥胖促进的高胆固醇血症该识别 将允许开发用于减弱NAFLD肝脏中PCSK 9诱导的新的替代策略， 这将有助于减轻心血管疾病的风险，这是NIH的使命指令。