HUMAN PLASMA PHOSPHOLIPID TRANSFER PROTEINS

高密度脂蛋白（HDL）已收到相当大的 注意由于HDL-胆固醇的负相关性 水平和心血管疾病。 在人血浆中， 胆固醇通过高密度脂蛋白系统取决于 卵磷脂：胆固醇酰基转移酶（LCAT）， 将游离胆固醇和磷脂酰胆碱转化为 胆固醇酯和脂质转移蛋白， 底物磷脂转移蛋白（PTP），并除去 胆固醇酯转移蛋白（CETP） 反应 这些脂质的动力学、机制和特异性 转移蛋白仍不明确，它们对 正常和患病状态下的胆固醇流量不确定。 本提案的目的是分离和表征 人血浆CETP和PTP，以确定 脂蛋白底物的组成和结构特征 调节它们的活性，以确定 PTP和CETP机制，以表征天然和模型 PTP修饰的HDL作为LCAT的底物及其受体 细胞胆固醇，并表征受体的作用， 脂蛋白对CETP清除产物LCAT的抑制作用。 这些研究将使用具有已知表面的模型脂蛋白 组成和性能，以允许对 脂质转移的速率控制因素。 充分表征 载脂蛋白-磷脂-胆固醇重组体和 载脂蛋白-磷脂-甘油三酯微乳剂将 采用 动力学分析将利用的荧光特性， 芘基脂质，其允许在没有 脂蛋白颗粒的物理分离。 这次调查 将涉及蛋白质分离，脂质合成，荧光和 脂质转移，脂蛋白组装， 平衡结合技术和脂质物理化学。 这项研究的长期目标是描绘结构 调节脂质作用的血浆脂蛋白的特征 转移蛋白和脂解酶。 了解 这些蛋白质的单独贡献在以下方面是重要的： 解释高密度脂蛋白在人血浆胆固醇通量中的作用。

The high density lipoproteins (HDL) have received considerable attention due to the inverse correlation of HDL-cholesterol levels and cardiovascular disease. In human plasma, the flux of cholesterol through the HDL system depends on the interrelationships of lecithin:cholesterol acyltransferase (LCAT), which converts free cholesterol and phosphatidylcholine to cholesteryl ester, and the lipid transfer proteins which provide the substrate, phospholipid transfer protein (PTP), and remove the product, cholesteryl ester transfer protein (CETP), of the reaction. The kinetics, mechanism, and specificities of these lipid transfer proteins remain undefined and their regulation of cholesterol flux in normal and diseased states uncertain. The objectives of this proposal are to isolate and characterize CETP and PTP from human plasma, to determine the compositional and structural features of the lipoprotein substrate which regulate their activity, to determine the molecular mechanisms of PTP and CETP, to characterize native and model HDL modified by PTP as substrates for LCAT and acceptors of cellular cholesterol, and to characterize the role of acceptor lipoproteins on the CETP removal of product inhibition of LCAT. These studies will use model lipoproteins with known surface composition and properties to allow critical examination of the rate-controlling factors in lipid transfer. Well-characterized apolipoprotein-phospholipid-cholesterol recombinants and apolipoprotein-phospholipid-triglyceride microemulsions will be used. Kinetic analysis will utilize the fluorescent properties of pyrenyl lipids which allows measurements to be made without the physical separation of the lipoprotein particles. This investigation will involve protein isolation, lipid synthesis, fluorescent and radioactive assays of lipid transfer, lipoprotein assembly, equilibrium binding techniques and lipid physical chemistry. The long-term goal of this research is to delineate the structural features of plasma lipoproteins which regulate the action of lipid transfer proteins and lipolytic enzymes. Understanding the individual contributions of these proteins is important in interpreting the role of HDL in cholesterol flux in human plasma.