New Pathway Limits Cellular Cholesterol Content

新途径限制细胞胆固醇含量

• 批准号: 6638470
• 负责人: PHOEBE E FIELDING
• 金额: $ 21.87万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-04-01 至 2005-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6638470
• 关键词: SDS polyacrylamide gel electrophoresis; apolipoproteins; binding proteins; biological signal transduction; caveolins; cell line; cholesterol; gel mobility shift assay; homeostasis; human tissue; macrophage; membrane lipids; membrane proteins; membrane transport proteins; phosphatase inhibitor; phospholipids; phosphorylation; protein structure function; protein tyrosine phosphatase; tissue support frame; transfection; vascular smooth muscle; western blottings

DESCRIPTION (Applicant's abstract): Rates of efflux of free cholesterol (FC) and phospholipid (PL) play major regulatory roles in lipid homestasis in vascular cells. Foam cell formation may represent, at least in part, a failure of lipid efflux. The ABC1 transporter protein and caveolin, the structural protein of FC-rich cell surface caveolae are two important determinants of cell lipid levels. Caveolin forms a scaffold whose association with signal transduction proteins is regulated by FC. ABC 1 catalyses the transport of cellular PL to apolipoprotein A-1 (apo A-1) the major high density lipoprotein (HDL) protein. In Specific Aim 1 the hypothesis is tested that caveolae can also serve as sensors reporting changes in membrane FC content via internally generated signals that among other effects, transcriptionally regulate caveolin expression, the organization of caveolae at the cell surface, and FC transport between the cell surface and internal FC pools. Transfer of cell surface FC to ABC1-generated apo A-1/PL complexes will be used to perturb FC levels in caveolae. Effects on signal transduction and nuclear response to FC efflux will be determined. In Specific Aim 2, paradoxical findings on the effect of oxysterols on cell FC homeostasis, FC efflux and caveolin expression will be investigated. The hypothesis will be tested that 7-ketocholesterol, a major oxysterol of human atherosclerotic lesions, downgrades normal FC-dependent signaling from caveolae thereby promoting inappropriate FC accumulation. ABC1 deficiency is associated with human Tangier disease, where normal HDL is absent from the circulation. ABC1 levels are usually up regulated by FC; but regulation in response to oxysterols and cAMP differs markedly among different vascular cells. The molecular basis of the transcriptional regulation of ABC1 expression in response to FC, oxysterols and cAMP will be determined in Specific Aim 3. PL efflux by ABC1 is dependent upon extracellular apo A-1 and, it has been proposed, on cell surface phosphatidylserine distribution. In Specific Aim 4, systematic mutagenesis of apo A-1 domains and individual charged amino acids will be carried out to identify sequences essential for ABC1 activity. Each of these studies has significant relevance to the basis of FC accumulation in atherosclerosis.

描述（申请人的摘要）：自由胆固醇外排（FC） 和磷脂（PL）在脂质寄宿中起主要的调节作用 血管细胞。泡沫细胞的形成至少部分代表失败 脂质外排。 ABC1转运蛋白和小窝蛋白，结构 富含Fc的细胞表面小窝的蛋白质是细胞的两个重要决定因素 脂质水平。小窝蛋白形成一个脚手架，其与信号的关联 转导蛋白由FC调节。 ABC 1催化运输 细胞PL至载脂蛋白A-1（APO A-1）主要高密度脂蛋白 （HDL）蛋白质。在特定的目标1中，检验了假设可以说Caveolae可以 还用作传感器，报告通过内部报告膜FC含量的变化 产生的信号表明，在其他效果中，转录调节小窝蛋白 表达，小窝在细胞表面的组织和FC运输 在细胞表面和内部FC池之间。细胞表面FC转移到 ABC1生成的Apo A-1/PL复合物将用于扰动FC水平 小屋。对信号转导和对FC外排的核反应的影响将 可以确定。在特定目标2中，关于影响的矛盾的发现 细胞FC稳态，FC外排和小窝蛋白表达的氧蛋白酶将是 调查。该假设将被检验为7-酮胆脂酯，这是一个主要的 人动脉粥样硬化病变的氧蛋白酶，降低了正常的FC依赖性 从小窝发出信号，从而促进了不适当的FC积累。 ABC1 缺乏与不存在正常HDL的人类探针疾病有关 从循环中。 ABC1水平通常受FC的调节；但 响应氧化酚和cAMP的调节在不同的不同 血管细胞。 ABC1转录调控的分子基础 响应FC的表达，将在 特定的目标3。ABC1的PL外排取决于细胞外apo A-1和， 已经在细胞表面磷脂酰丝氨酸分布上提出了它。在 特定目标4，Apo A-1域和个体的系统诱变 将执行带电的氨基酸以识别序列 ABC1活动。这些研究中的每一个都与 FC在动脉粥样硬化中的积累。