Apolipoprotein A-l and HDL: Structure, Formation and Function

简介(申请人提供)：心血管疾病和其他脂类代谢疾病仍然是导致健康问题和死亡的头号原因。虽然从生物化学和细胞生物学的角度对细胞内脂蛋白和脂类的代谢和运输有了很多了解，但这些生理过程发生的分子细节和机制仍然知之甚少。对血浆脂蛋白、其组成的载脂蛋白及其受体的详细结构描述对于理解脂蛋白代谢生理学以及动脉粥样硬化和其他脂代谢疾病的病理生理学中所涉及的分子机制至关重要。这项研究的长期目标是确定这一分子细节，并了解这些过程背后的结构-功能关系。载脂蛋白A-I是高密度脂蛋白的主要蛋白质，在胆固醇逆向转运中起着重要作用。与ABCA1转运蛋白的相互作用可以去除形成新生高密度脂蛋白颗粒的细胞膜上的胆固醇。ApoA-I激活LCAT导致胆固醇酯化，并转化为成熟的高密度脂蛋白颗粒。最后，apoA-I是肝脏SR-B1受体的配体，通过它将胆固醇输送到肝脏。在具体目标1中，我们将在了解D(185-243)apoA-I的分子结构或最新进展的基础上，从机制上了解apoA-1的分子特征，这对于在分子水平上理解脂质相互作用、LCAT结合和激活以及高密度脂蛋白的形成和功能至关重要。这些研究将使用通过我们对载脂蛋白A-I的新结构理解而设计的突变。在特定的目标2中，我们将把目标1中的分子细节与功能研究联系起来，以了解高密度脂蛋白形成、LCAT相互作用以及ABCA1和Abcg1介导的胆固醇外流的分子机制。因此，在特定目标1中从结构观点制定和研究的分子假说将在特定目标2中在功能水平上进行探索。我们的结构研究将提供关于这些过程的关键知识。完成这些目标后的结果将是我们对反向胆固醇运输和代谢中的关键角色的分子细节和相互作用的理解的显著增强，这将推动我们开发基于分子的策略来预防或控制血脂异常和脂代谢疾病的能力。

DESCRIPTION (provided by applicant): Cardiovascular disease, together with other diseases of lipid metabolism, remains the number one cause of health problems and mortality. Although much is known about the metabolism and transport of lipoproteins and lipids by cells from the biochemical and cell biology standpoint, the molecular details and mechanisms by which these physiological processes take place remain poorly understood. A detailed structural description of the plasma lipoproteins, their constituent apolipoproteins, and their receptors is crucial to understanding the molecular mechanisms involved in the physiology of lipoprotein metabolism and the pathophysiology of atherosclerosis and other diseases of lipid metabolism. The long-term objectives of this research are to determine this molecular detail and to understand the structure-function relationships underlying these processes. ApoA-I, the major protein of High Density Lipoprotein (HDL), plays important roles in reverse cholesterol transport. Interaction with the ABCA1 transporter removes cholesterol the cell membrane forming the nascent HDL particle. Activation of LCAT by ApoA-I results in cholesterol esterification, and the transformation to the mature HDL particle. Finally, apoA-I is a ligand for the hepatic SR-B1 receptor through which cholesterol is delivered to the liver. In Specific Aim 1, we will build on or recent advance in understanding of the molecular structure of D(185-243)apoA-I to provide a mechanistic understanding of the molecular features of apoA-1 crucial to understanding the mechanisms of lipid interaction, LCAT binding and activation and HDL formation and function at a molecular level. These studies will use mutations designed through our new structural understanding of apoA-I. In Specific Aim 2, we will correlate the molecular details derived in Aim 1 with functional studies to understand the molecular mechanisms of HDL formation, LCAT interaction, and cholesterol efflux mediated by ABCA1 and ABCG1. Thus, the molecular hypotheses formulated and studied from the structural standpoint in Specific Aim 1, will be probed at the functional level in Specific Aim 2. Our structural studies will provide critical knowledge on these processes. The outcome on completion of these aims will be a significant enhancement in our understanding of the molecular details and interactions of the crucial players in reverse cholesterol transport and metabolism that will drive our ability to develop molecularly based strategies to prevent or control dyslipoproteinemias and diseases of lipid metabolism.