Cells Processing High Density Lipoproteins

描述（由申请人提供）：清除率受体B类，I型（SR-BI）促进从脂蛋白颗粒（如高密度脂蛋白（HDL））中选择性摄取胆固醇酯（CE），在此过程中HDL核心-CE被带入细胞，而HDL颗粒本身没有平行摄取和降解。这种sr - bi介导的“选择性”途径代表了将CEs递送到啮齿动物和人类的肝脏和类固醇组织的主要途径，分别用于胆汁酸和类固醇激素的生物合成。除了促进选择性CE转运外，SR-BI还促进胆固醇逆向转运（RCT）并发挥动脉粥样硬化保护作用。虽然我们对SR-BI的各种功能了解很多，但调控SR-BI功能表达的细胞机制尚未完全确定。这项竞争性更新应用的总体目标是阐明某些正、负调节剂调节SR-BI在肝脏、肾上腺和性腺中的表达和功能的机制。具体而言，我们拟确定SF-1/LRH-1、NHERF1/2和SIK-1对SR-BI表达、SR-BI介导的选择性CE转运以及肝脏和类固醇生成组织中胆汁酸和类固醇合成的刺激和抑制作用。该提案的具体目的是：1)表征和确定LRH-1和SF-1在激素诱导的SR-BI在完整肝脏和甾体源性组织和分离细胞中的表达和功能中的作用；2)利用肝细胞、类固醇细胞和遗传小鼠模型，确定NHERF1和NHERF2对SR-BI表达、细胞定位和SR-BI介导的选择性HDL-CE摄取的潜在影响；3)确定SIK-1在体内和体外肝脏和类固醇细胞模型系统中抑制sr - bi依赖的选择性HDL-CE摄取的潜在机制。本研究利用最先进的分子、细胞、生物化学和生物物理方法以及独特的细胞和动物模型来剖析介导核受体SF-1和LRH-1、含pdz结构域蛋白NHERF1/2和激素调节的SIK-1蛋白的调节作用的分子事件。拟议研究的成功完成可能会确定新的靶点，可用于开发治疗胆汁酸和类固醇激素相关疾病的新疗法。在更广泛的范围内，由于SR-BI具有动脉粥样硬化保护作用，目前的研究也可能有助于在心血管疾病的临床管理中开发新的治疗和预防策略。

DESCRIPTION (provided by applicant): Scavenger receptor class B, type I (SR-BI) facilitates selective uptake of cholesteryl ester (CE) from lipoprotein particles such as high-density lipoprotein (HDL) by a process in which HDL core-CE is taken into cells without a parallel uptake and degradation of the HDL particle itself. This SR-BI-mediated 'selective' pathway represents a major route for the delivery of CEs to the liver and steroidogenic tissues of rodents and humans for the biosynthesis of bile acids and steroid hormones, respectively. Besides facilitating selective CE transport, SR-BI also promotes reverse cholesterol transport (RCT) and exerts atheroprotective actions. Although much is known about these various functions of SR-BI, the cellular mechanisms controlling functional expression of SR-BI are not fully established. The overall goal of this competitive renewal application is to elucidate mechanisms by which certain positive and negative modulators regulate the expression and function of SR-BI in the liver, adrenal and gonads. Specifically, we propose to determine the stimulatory and inhibitory actions of SF-1/LRH-1 and NHERF1/2 and SIK-1 on SR-BI expression, SR-BI mediated selective CE transport and bile acid and steroid synthesis in liver and steroidogenic tissues. The specific aims of the proposal are to: 1) characterize and establish the roles of LRH-1 and SF-1 in hormone-induced SR-BI expression and function in intact hepatic and steroidogenic tissues and isolated cells; 2) determine how NHERF1 and NHERF2 potentially impact SR-BI expression, its cellular localization and SR-BI-mediated selective HDL-CE uptake in vitro and in vivo using hepatic and steroidogenic cells and genetic mouse models; and 3) identify underlying mechanisms by which SIK-1 inhibits SR-BI-dependent selective HDL-CE uptake in vivo and in hepatic and steroidogenic cell model systems in vitro. This proposal utilizes state-of-the-art molecular, cellular and biochemical and biophysical approaches and unique cell and animal models to dissect the molecular events mediating the modulatory actions of nuclear receptors SF-1 and LRH-1, PDZ-domain containing proteins NHERF1/2 and hormone-regulated SIK-1 protein. Successful completion of the proposed studies is likely to identify novel targets that can be exploited for the development of new therapies to treat bile acids and steroid hormone related diseases. On a broader scope, since SR-BI is atheroprotective, the current studies may also aid in the development of new therapeutic and preventive strategies in the clinical management of cardiovascular disease.