Hepatic Rap1a in cholesterol homeostasis

项目总结 标题：肝脏RAP1a在胆固醇稳态中的作用 动脉粥样硬化性心血管疾病是全球主要的死亡原因，并降低了致动脉粥样硬化的风险。 低密度脂蛋白(LDL)胆固醇(LDL-C)水平是治疗的主要目标。最近的工作有 枯草杆菌前蛋白转换酶9(PCSK9)被认为是一种有希望的调节 血清低密度脂蛋白-C尽管它是低密度脂蛋白受体(LDLR)的重要调节者，而且作为一种 药理靶点，调控PCSK9的机制(S)在很大程度上仍不清楚。有趣的是， 最广泛用于降低血浆胆固醇的处方药他汀类药物呈剂量依赖性地增加PCSK9 这在很大程度上抵消了他汀类药物引起的肝脏低密度脂蛋白受体的进一步增加，并减弱了其疗效。 然而，我们对这种调节的潜在细胞和分子机制的理解仍然存在。 不完整。这一建议是基于我们实验室的一项新发现，该发现表明，激活小的 RAS超家族的G蛋白Rap1a可降低PCSK9和血浆低密度脂蛋白-C水平。此外，Rap1a 在他汀类药物处理的肝细胞和人肝脏中，香叶基香叶素预烯基化和活性受到抑制，并恢复 细胞内香叶基香叶基异戊二烯水平可阻止他汀类药物诱导的PCSK9，并进一步降低低密度脂蛋白-C。我们 提示肝脏Rap1a是PCSK9蛋白的一种新的调节因子，其抑制作用可能是通过降低细胞内水平来实现的。 类异戊二烯水平可能为解释他汀类药物如何增加PCSK9提供了另一种机制。在此基础上， 我们将定义Rap1a调节PCSK9和LDL-C代谢的机制(目标1)，阐明它的 在他汀类药物介导的PCSK9诱导(AIM 2)中的作用，并探讨他汀类药物和Rap1a联合激活的作用 在预防动脉粥样硬化病变的发展方面。(目标3)。我们将在体内和体外测试这些新想法， 使用小鼠遗传、生理和生化方法的组合。

PROJECT SUMMARY Title: Hepatic Rap1a in cholesterol homeostasis Atherosclerotic cardiovascular disease is the leading cause of death worldwide and lowering of proatherogenic low-density lipoprotein (LDL) cholesterol (LDL-C) levels is the primary target of therapy. Recent work has identified proprotein convertase subtilisin/ kexin type 9 (PCSK9) as a promising therapeutic target that regulates serum LDL-C. Despite its critical role as a regulator of the LDL receptor (LDLR) and attractiveness as a pharmacological target, the mechanism(s) by which PCSK9 is regulated remain largely unknown. Interestingly, the most widely prescribed drugs for lowering plasma cholesterol, statins, dose-dependently increase PCSK9 levels, which largely negate further statin-induced increases in hepatic LDLR and attenuate their efficacy. However, our understanding of the underlying cellular and molecular mechanisms of this regulation remains incomplete. This proposal is based on a new finding from our laboratory suggesting that activation of the small G protein of the Ras superfamily, Rap1a, lowers PCSK9 and plasma LDL-C levels. Further, Rap1a geranylgeranyl prenylation and activity is inhibited in statin-treated hepatocytes and human liver, and restoring intracellular geranylgeranyl isoprenoid levels prevents statin-induced PCSK9 and further lowers LDL-C. We propose that hepatic Rap1a is a novel regulator of PCSK9 protein, and its inhibition via lower intracellular isoprenoid levels may provide an additional mechanism to explain how statins increase PCSK9. Based on these, we will define the mechanisms by which Rap1a regulates PCSK9 and LDL-C metabolism (Aim 1), elucidate it’s in role statin-mediated PCSK9 induction (Aim 2), and explore the effect of combined statin and Rap1a activation in the prevention of atherosclerotic lesion development. (Aim 3). We will test these new ideas in vivo and ex vivo, using a combination of mouse genetic, physiological, and biochemical approaches.