Cells Processing High Density Lipoproteins

从高密度脂蛋白等脂蛋白颗粒中选择性摄取胆固醇酯(CE)的过程是这样一个过程： 高密度脂蛋白核心-CE被带入细胞，而不会平行摄取和降解高密度脂蛋白颗粒本身。它 代表了将CES输送到啮齿动物和人类产生类固醇的组织的主要途径。 清道夫受体，B类，I型(SR-BI)，是CD36超家族蛋白质中的一员，已经被认为是 被鉴定为一种真实的高密度脂蛋白受体，通过这一过程调节高密度脂蛋白-CEs的摄取，以及 免疫化学分析表明，它在类固醇生成细胞和肝脏中表达最丰富。 我们发表的和初步的数据提供了证据，证明SR-BI蛋白的物理状态和 SR-BI表达引起的组织结构改变对组织修复的效率有重要影响 选择性途径。这些数据使我们认为SR-BI的二聚体和更高阶齐聚形式 密切参与调节SR-BI介导的选择性高密度脂蛋白-CE运输，而且，这些 SR-BI的物理状态有助于细胞表面(微绒毛)通道的形成，进一步增强 选择性途径的效率。这项建议的具体目的是：1)确定 SR-BI C末端胞质结构域在调节SR-BI二聚体形成中的作用；2)确定 SR-BI胞外区(ECD)的贡献可以是独立的，也可以是与C-BI协同的。 末端结构域，调节SR-BI的二聚化和功能；以及3)确定SR-BI是否 相互作用的辅助蛋白(即，含有PDZ结构域的蛋白和/或ERM家族蛋白 与肌动蛋白细胞骨架的连接)有助于SR-BI二聚体的形成和/或在 SR-BI功能。推动这一提议的假设是二聚体的形成和伴随的表面 结构的改变对于脂蛋白胆固醇酯通过“选择性”高效输送是必要的。 摄取过程。提出的实验将确定这在多大程度上是正确的，同时， 尝试鉴定SR-BI分子和SR-BI相互作用的辅助蛋白(PDZ， ERM和肌动蛋白)，它们参与二聚化过程和微绒毛通道的形成。

The selective uptake of cholesteryl ester (CE) from lipoprotein particles such as HDL is a process by which HDL core-CE is taken into cells without a parallel uptake and degradation of the HDL particle itself. It represents a major route for the delivery of CEs to steroid producing tissues of rodents and humans. Scavenger receptor, class B, type I (SR-BI), a member of the CD36 super-family of proteins, has been identified as an authentic HDL receptor that mediates-the uptake of HDL-CEs via this process, and immunochemical analyses indicate that it is expressed most abundantly in the steroidogenic cells and liver. Our published and preliminary data provide evidence that the physical state of the SR-BI protein and architectural changes in tissue induced by the expression of SR-BI .have major effects on the efficiency of the selective pathway. These data led us to suggest that the dimeric and higher order oligomeric forms of SR-BI are intimately involved in regulating SR-BI-mediated selective HDL-CE transport, and moreover, that these physical states of SR-BI contribute to the formation of cell surface (microvillar) channels to further enhance the efficiency of the selective pathway. The specific aims of this proposal are: 1) to determine the contribution of SR-BI's C-terminal cytoplasmic domain in regulating SR-BI dimer formation; 2) to determine the contribution of the extracellular domain (ECD) of SR-BI either independently, or in cooperation with C- terminal domain, in regulating SR-BI dimerization and function; and 3) to determine whether SR-BI interacting accessory proteins (i.e., PDZ domain containing proteins and/or ERM family proteins in connection with the actin cytoskeleton) contribute to SR-BI dimer formation and/or play an essential role in SR-BI function. The hypothesis which drives this proposal is that dimer formation and concomitant surface architectural changes are necessary for efficient delivery of lipoprotein cholesteryl esters via the "selective" uptake process. The experiments proposed will determine to what extent this is true, and at the same time, attempt to identify specific sites on both the SR-BI molecule and SR-BI interacting accessory proteins (PDZ, ERM, and actin proteins) which are involved in the dimerization process and in microvillar channel formation.