Cellular cholesterol movement and homeostasis

描述（由申请人提供）：质膜磷脂与胆固醇形成化学计量复合物。超过磷脂结合能力的过量胆固醇会产生一种具有高化学活性的新型胆固醇池。然后，这种高活性胆固醇充当体内平衡信号；例如，通过调节内质网影响细胞胆固醇平衡和线粒体氧化甾醇的生物合成。本提案将考虑活性质膜胆固醇的两个额外的和未开发的调节作用；即，在线粒体甾体生成和质膜胆固醇通过清净受体SR-BI和ABCA1转运体向循环高密度脂蛋白的转移中。对全身麻醉的神秘分子机制提出了一个新的假设。我们认为，广泛的麻醉药通过插入神经元的质膜双层起作用，从而取代并激活其胆固醇的一小部分。这些活跃的胆固醇会扰乱神经元离子通道，导致麻醉。这一假设将通过检测激活胆固醇的两通路库对离子通道活性的影响来验证。还将测试胆固醇本身和胆固醇络合磷脂对离子通道活性的影响。我们注意到许多质膜蛋白的功能依赖于或受到胆固醇的影响。这些现象与胆固醇驱动的横向相分离（即筏形形成）有关的前提是强有力的，但有争议的。因此，我们将表征不同的水溶性插层两路作为探针，可以增加，减少或以其他方式扰乱假定的质膜筏的形成，允许对其进行分析和操作。这些探针通过与双层磷脂络合，取代和取代它们的胆固醇，从而改变侧向相分配的驱动力。调节筏/微结构域形成和行为的插层两通路可能具有基本的科学和治疗用途。这些研究将检验有关活性胆固醇生理学的新假设。它们将极大地增加我们对这一基本膜成分的基本理解，它与各种重要的医学问题有关，如心血管疾病、筏载蛋白介导的（病理）生理过程和临床麻醉。公共卫生相关性：由于动脉粥样硬化性心血管疾病对健康造成的巨大负担，细胞胆固醇引起了普遍的兴趣和关注。人们普遍认为，动脉粥样硬化是正常的生理过程出错，需要深入了解真核细胞固有的基本固醇管理系统。阐明膜胆固醇复合物和胆固醇活性的生理和实际意义，有望在胆固醇相关疾病的治疗和预防方法的发展中发挥作用。

DESCRIPTION (provided by applicant): Plasma membrane phospholipids form stoichiometric complexes with cholesterol. Excess cholesterol beyond the binding capacity of the phospholipids creates a novel pool of cholesterol with a high chemical activity. This high-activity cholesterol then serves as a homeostatic signal; for example, by regulating endoplasmic reticulum effectors of cell cholesterol balance and mitochondrial oxysterol biosynthesis. The present proposal will consider two additional and unexplored regulatory roles for active plasma membrane cholesterol; namely, in mitochondrial steroidogenesis and in the transfer of plasma membrane cholesterol to circulating high density lipoproteins by the scavenger receptor SR-BI and the ABCA1 transporter. A novel hypothesis for the mysterious molecular mechanism of general anesthesia is also proposed. We suggest that a wide range of anesthetics act by intercalating into the plasma membrane bilayer of neurons, displacing and thereby activating a small fraction of their cholesterol. This pool of active cholesterol would then perturb neuronal ion channels, leading to anesthesia. This hypothesis will be tested by examining the influence on ion channel activity of a library of amphipaths that activate cholesterol. The effects of cholesterol itself and of cholesterol-complexing phospholipids on ion channel activity will also be tested. We note that the function of numerous plasma membrane proteins is dependent on or otherwise influenced by cholesterol. The premise that these phenomena are related to cholesterol-driven lateral phase separation (i.e., raft formation) is powerful but controversial. We shall therefore characterize diverse water-soluble intercalating amphipaths as probes that can increase, decrease or otherwise perturb the formation of putative plasma membrane rafts, allowing for both their analysis and manipulation. These probes act by complexing with bilayer phospholipids, displacing and substituting for their cholesterol so as to alter the driving force for lateral phase partition. Intercalated amphipaths that modulate raft/microdomain formation and behavior could have basic scientific and perhaps therapeutic utility. These studies will test new hypotheses about the physiology of active cholesterol. They will greatly increase our fundamental understanding of this essential membrane component, bearing on varied and important medical issues, such as cardiovascular disease, (patho)physiological processes mediated by raft-embedded proteins and clinical anesthesia. PUBLIC HEALTH RELEVANCE: Cell cholesterol is of universal interest and concern because of the enormous burden on health imposed by atherosclerotic cardiovascular disease. It is widely appreciated that atherogenesis is to be understood as normal physiological processes gone awry and that insights are needed into the basic sterol management systems inherent in eukaryotic cells. Elucidating the physiology and practical implications of membrane cholesterol complexes and cholesterol activity will hopefully play a role in the development of therapeutic and preventive approaches to cholesterol-related diseases. .