Regulation of CETP by lipid transfer inhibitor protein

脂质转移抑制蛋白对 CETP 的调节

• 批准号: 7056766
• 负责人: RICHARD E MORTON
• 金额: $ 33.62万
• 依托单位: CLEVELAND CLINIC LERNER COM-CWRU
• 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 2009-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7056766
• 关键词: apoptosis; blood lipoprotein biosynthesis; blood lipoprotein metabolism; cholesterol esters; clinical research; 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

'DESCRIPTION (provided by applicant): Plasma cholesterol and low density lipoprotein (LDL) concentrations are major risk factors for atherosclerosis, whereas elevated high density lipoprotein (HDL) levels decreased risk. Cholesteryl ester transfer protein (CETP) transports lipids between lipoproteins and, consequently, directly affects lipoprotein metabolism and alters LDL and HDL concentrations. CETP levels are highly responsive to dietary lipids and genetic factors. Additionally, CETP activity is regulated by lipid transfer inhibitor protein (LTIP). We have demonstrated that LTIP does not lower CETP activity generically but selectively suppresses CETP activity on LDL, and to a lesser extent on HDL2, but stimulates CETP activity on HDL3. Consequently, cholesterol flux through HDL is enhanced and plasma cholesteryl ester synthesis rates are increased. Thus LTIP tailors CETP-mediated lipid transfer events resulting in a lipoprotein profile that is different from that achieved by raising or lowering CETP levels alone. In this continuation application we will more fully define the functions of LTIP, and characterize its regulation and mechanism of action. We hypothesize that LTIP alters CETP activities to generate a more beneficial or atheroprotective lipoprotein profile. Three specific aims will be addressed: AIM 1) Define the mechanism by which LTIP inhibits CETP and identify the structural features of LTIP important for this activity. We will quantify binding kinetics of LTIP to LDL, HDL2 and HDL3 and determine how LTIP binding relates to CETP inhibition and the displacement of CETP from the lipoprotein surface, and define how LTIP binding influences the composition and structure of the lipoprotein surface. Mutagenesis studies will define regions and specific amino acids required for LTIP function. AIM 2) Determine the role of LTIP in regulating lipoprotein metabolism. The effects of adenoviral-mediated LTIP overexpression or LTIP suppression on lipoprotein composition and on VLDL and HDL metabolism will be defined in vivo in a hamster model. The effects of altered LTIP expression on prebeta-HDL formation and the capacity of plasma to promote cholesterol efflux from cells will also be quantified. Biochemical studies with reconstituted components will define the capacity of LTIP to influence specific aspects of VLDL and HDL metabolism, and provide a mechanistic basis for interpreting in vivo observations. AIM 3) Characterize the inactive LTIP complex and define its role in regulating LTIP activity. We have observed that LTIP is controlled by sequestration into an inactive complex. We will isolate this complex and define its protein and lipid components. Further, as association with this complex is dynamic, we will determine how metabolic processes and changes in plasma lipid levels alter the distribution of LTIP between active and inactive pools. Overall, these studies will provide novel insight into the control of CETP by LTIP and add to our understanding of how intravascular lipoprotein remodeling events contribute to steady-state lipoprotein concentration and composition.

描述（由申请人提供）：血浆胆固醇和低密度脂蛋白（LDL）浓度是动脉粥样硬化的主要危险因素，而高密度脂蛋白（HDL）水平升高可降低风险。胆固醇酯转移蛋白（CETP）在脂蛋白之间转运脂质，从而直接影响脂蛋白代谢并改变LDL和HDL浓度。CETP水平对膳食脂质和遗传因素有高度反应。此外，CETP活性受脂质转移抑制蛋白（LTIP）的调控。我们已经证明，LTIP不会普遍降低CETP活性，但会选择性地抑制LDL上的CETP活性，并在较小程度上抑制HDL2上的CETP活性，但会刺激HDL3上的CETP活性。因此，通过HDL的胆固醇通量增强，血浆胆固醇酯合成速率增加。因此，LTIP调整了CETP介导的脂质转移事件，导致脂蛋白谱不同于单独提高或降低CETP水平。