THE DYNAMICS OF CHOLESTEROL IN MEMBRANES

所提出的研究的长期目标是解释 胆固醇在哺乳动物细胞中的分布、动态和功能 膜。 虽然胆固醇是血浆的主要成分， 膜，它的精确配置和功能在很大程度上是 未知 胆固醇在组织和血浆间转移的机制 以及生物膜之间的未知。 文献中包含 非中介转移机制的建议分为两个方面 类别：通过水相的扩散和转移过程中， 碰撞复合体的形成。 这些机制可以区分为 从转移速率对供体浓度的依赖性和 接受者 我们将研究[3 H]-胆固醇与红细胞之间的交换， 细胞本身以及红细胞、超声处理的脂质体和血浆之间 脂蛋白，以确定胆固醇转移的机制。 我们将 使用胆固醇氧化酶，一种催化胆固醇氧化的酶， 作为研究胆固醇分布和转移的探针， 培养细胞的质膜和内部细胞器。 我们以前的 研究表明，胆固醇富集的红细胞， 生理水平导致膜重组。 的研究 提出了这种变化的分子基础。 我们之前展示过， 胆固醇在红细胞中的跨膜运动非常迅速。 我们现在 我建议在零度以下的温度下研究这种运动有多快 并确定红细胞中胆固醇的跨双层分布， 细胞膜 胆固醇的快速跨膜运动可能在于 其功能的核心。 我们将检验这样一种假设， 胆固醇跨膜的再分布是由于 应力，例如由形状变形或在 外源分子如溶血素的外膜小叶。 在这些研究中，抗生素菲律宾，形成复合物与 固醇，将被用作胆固醇分布的探针。

The long term objective of the research proposed is the explication of the distribution, dynamics and function of cholesterol in mammalian cell membranes. Although cholesterol is a major constituent of plasma membrances, its precise disposition and function are to a large degree unknown. The mechanisms of cholesterol transfer between tissues and plasma and between biological membrances ae unknown. The literature contains proposals for mechanisms of unmediated transfer which fall into two categories: diffusion through the aqueous phase and transfer during the formation of a collision complex. These mechanisms can be distinguished from the dependence of transfer rate on concentration of donor and acceptor. We shall examine the exchange of [3H]-cholesterol between red cells themselves and between red cells, sonicated liposomes and plasma lipoproteins to determine the mechanism of cholesterol transfer. We shall use cholesterol oxidase, an enzyme which catalyzes cholesterol oxidation, as a probe to study cholesterol distribution and transfer between the plasma membrane and internal organelles of cultured cells. Our previous studies showed that cholesterol enrichment of red cells to just above the physiological levels leads to membrane reorganization. A study of the molecular basis of this change is proposed. We showed previously that cholesterol transmembrane movement in red cells is extremely rapid. We now propose studies at subzero temperature to examine how rapid this motion is and to determine the transbilayer distribution of cholesterol in the red cell membrane. The rapid transmembrane movement of cholesterol may lie at the heart of its function. We shall examine the hypothesis that redistribution of cholesterol across the membrane occurs in response to stress such as that imposed by shape deformation or the incorporation at the outer membrane leaflet of an exogenous molecule such as lysolecithin. In these studies the antibiotic filipin, which forms complexes with sterols, will be used as a probe for cholesterol distribution.