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.

项目概要 心血管疾病（CVD）仍然是美国的主要死亡原因。 治疗导致最近发现了前蛋白转化酶枯草杆菌蛋白酶 9 (PCSK9)，它促进 低密度脂蛋白受体 (LDLR) 降解，增加致动脉粥样硬化脂蛋白 LDL 胆固醇 (LDL- 许多针对 PCSK9 的治疗方法已被开发出来，但在降低 LDL- 方面效果有限。 C. 该提案通过挑战 RXRα 至关重要的基本假设来填补关键知识空白 调节非酒精性脂肪肝 (NAFLD) 患者肝脏中 PCSK9 的转录。 核心核受体，始终被认为与其他受体构成异二聚化 我们的初步数据表明，RXRα 的肝脏耗竭会导致肝脂质增加。 积累和 PCSK9 诱导，可以通过 AAV8 介导的 RXRα 肝脏过度表达来消除。 一致地，我们观察到 RXRα 肝细胞特异性血浆中胆固醇和 LDL-C 增加 敲除（hepKO）小鼠，肝脏过表达RXRα可显着降低血浆胆固醇 这些初步数据带来了本提案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 PCSK9； 为了找到答案，我们重点阐明 RXRα 蛋白翻译后的影响。 最近，我们确定了一个关于管理与 PPARα 的伙伴关系和调节 PCSK9 的修改（PTM）。 RXRα 先前未被识别的乙酰化残基，它控制 RXRα 和 RXRα 之间的异二聚化 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 PCSK9 的诱导至关重要，我们的数据是第一个。 显示 RXRα 被 CBP 和 TNFα（NALFD 肝脏中存在的炎症细胞因子）乙酰化， 损害 CBP 介导的 RXRα 乙酰化有意义，我们还观察到 RXRα 的乙酰化减少。 高脂饮食 (HFD) 喂养的小鼠和人类 NAFLD 患者肝脏中的 RXRα 存在中枢性。 假设 RXRα 乙酰化是调节 PPARα 介导的 PCSK9 转录所必需的 NAFLD 肝脏中 RXRα 乙酰化受损会导致胆固醇和 LDL-C 升高。 通过以下两个目标检验该假设： 目标 1：确定 RXRα 的分子机制 调节肝脏中 PCSK9 的转录；目标 2：确定 RXRα 是否乙酰化以及乙酰化程度 是防止脂肪肝中 PCSK9 和胆固醇诱导的弹性因子。 本提案中提出的研究将确定乙酰化 RXRα 与 PPARα 调节 PCSK9 转录并预防肥胖引起的高胆固醇血症。 将允许开发新的替代策略来减弱 NAFLD 肝脏中 PCSK9 的诱导， 这将有助于降低 CVD 风险，这是 NIH 的任务指令。