REGULATION OF CETP BY LIPID TRANSFER INHIBITOR PROTEIN

脂质转移抑制剂蛋白对 CETP 的调节

• 批准号: 6040833
• 负责人: RICHARD E MORTON
• 金额: $ 24.32万
• 依托单位: CLEVELAND CLINIC FOUNDATION
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-02-25 至 2004-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6040833
• 关键词: apoptosis; blood lipoprotein biosynthesis; blood lipoprotein metabolism; cholesterol esters; gene deletion mutation; high density lipoproteins; homeostasis; human tissue; immunoregulation; inhibitor /antagonist; laboratory rabbit; lipid biosynthesis; lipid metabolism; lipid transport; low density lipoprotein; protein binding; protein degradation; protein structure function; recombinant proteins; tissue /cell culture; transport proteins; very low density lipoprotein

In human plasma, the composition and concentration of circulating lipoproteins is strongly influenced by cholesteryl ester transfer protein (CETP). Given its importance in lipoprotein metabolism and potential influence on atherosclerosis, the regulation of CETP activity has been the subject of extensive study. We have identified a plasma protein, lipid transfer inhibitor protein (LTIP), that regulates CETP activity. Recently, we purified, cloned and expressed LTIP and demonstrated its identity with apolipoprotein F, a protein with no known function. We propose that LTIP is a lipid flux switch that regulates CETP, not by suppressing CETP activity generally, but by selectively interfering with lipid transfer events to and from LDL. This selectivity toward LDL appears to be mediated by the preferential association of LTIP with LDL in plasma. Several lines of evidence from in vitro and in vivo studies strongly suggest that LTIP is a physiological modulator of lipoprotein concentration and composition. Our long-term objective is to define the role of LTIP in regulating lipoprotein metabolism and to define its impact on atherogenesis. In this proposal we further define the role of LTIP in vivo, identify its mechanism of action, and characterize mechanisms regulating its synthesis and secretion. In vitro and in vivo studies test the hypothesis that remnants of VLDL catabolism acquire LTIP as they near LDL in size, which alters their CETP-substrate status and determines the nature of the end- products of VLDL catabolism (Aim 1). Kinetic and lipid monolayer studies with recombinant LTIP, and lipoprotein modification and LTIP mutagenesis studies will determine the mechanism of LTIP's action and define the properties of lipoproteins and the structural features of LTIP that are required for activity (Aim 2). Finally, biochemical and molecular studies with cultured cells and tissue-specific expression analyses will be used to test the hypothesis that LTIP and CETP are co-expressed and co- regulated in response to cellular cholesterol homeostasis (Aim 3). Overall, these studies will provide novel insights into a poorly characterized modulator of cholesterol flux in human plasma.

在人血浆中，循环脂蛋白的组成和浓度受胆固醇酯转移蛋白（CETP）的强烈影响。 鉴于其在脂蛋白代谢中的重要性和对动脉粥样硬化的潜在影响，CETP活性的调节一直是广泛研究的主题。 我们已经确定了调节CETP活性的血浆蛋白，脂质转移抑制剂蛋白（LTIP）。 最近，我们纯化，克隆并表达了LTIP，并证明了其与无知功能的蛋白质F的载脂蛋白F的身份。 我们建议LTIP是一种调节CETP的脂质通量开关，而不是通过通常抑制CETP活动，而是通过选择性地干扰与LDL的脂质转移事件。 对LDL的这种选择性似乎是由LTIP与血浆中LDL的优先关联介导的。 来自体外和体内研究的几种证据很强地表明，LTIP是脂蛋白浓度和组成的生理调节剂。我们的长期目标是定义LTIP在调节脂蛋白代谢中的作用，并定义其对动脉粥样硬化的影响。 在此提案中，我们进一步定义了LTIP在体内的作用，确定其作用机理，并表征调节其合成和分泌的机制。 体外和体内研究检验了以下假设：VLDL分解代谢的残留物在大小的LDL附近获得LTIP，从而改变了其CETP-substrate状态并确定VLDL分解代谢的最终产物的性质（AIM 1）。 通过重组LTIP以及脂蛋白修饰和LTIP诱变研究的动力学和脂质单层研究将确定LTIP作用的机制，并定义脂蛋白的特性以及活性所需的LTIP的结构特征（AIM 2）。最后，将使用培养细胞和组织特异性表达分析的生化和分子研究来检验以下假设：LTIP和CETP共表达并响应细胞胆固醇稳态而进行调节（AIM 3）。总体而言，这些研究将为人类血浆中胆固醇通量的调节剂提供新的见解。