SR-B1 Sorting Signals in HDL Metabolism

SR-B1 HDL 代谢中的信号排序

• 批准号: 7013069
• 负责人: David Silver
• 金额: $ 29.01万
• 依托单位: ALBERT EINSTEIN COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-05 至 2011-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7013069
• 关键词: Adenoviridae; basolateral membrane; bile circulation; biological signal transduction; blood lipoprotein metabolism; blood lipoprotein transport; cholesterol; cholesterol esters; confocal scanning microscopy; genetically modified animals; high density lipoproteins; laboratory mouse; liver cells; liver metabolism; membrane proteins; protein protein interaction; protein sequence; protein structure function; scavenger receptor; secretion; subcellular fractionation; transcription factor; transcytosis; transfection /expression vector

DESCRIPTION (provided by applicant): Plasma high density lipoprotein (HDL) is the principal carrier of plasma cholesterol for biliary cholesterol secretion. The HDL receptor Scavenger Receptor B-l (SR-BI) mediates the uptake of HDL cholesterol and cholesteryl ester for excretion into bile and its expression correlates with biliary cholesterol secretion. SR-BI knockout mice have a significant decrease in biliary cholesterol secretion, indicating an important role of SR-BI in that process. However, little is known regarding the molecular mechanisms by which SR-BI mediates hepatobiliary secretion of cholesterol. SR-BI is expressed on both sinusoidal and canalicular membranes in liver, and undergoes transcytosis to the canalicular membrane. The sorting signals necessary for SR-BI basolateral targeting and transcytosis to the canalicular membrane are unknown. We have defined three important factors that may regulate SR-BI subcellular sorting in liver and thus SR-BI- dependent biliary cholesterol secretion. One factor is PDZK1, a PDZ domain protein that has been shown to interact with SR-BI and to be essential to maintain hepatic SR-BI levels. A second factor is a basolateral targeting signal in the C-terminus of SR-BI, and a third factor is a cholesterol binding domain in the C- terminal transmembrane domain of SR-BI. The C-terminal transmembrane domain of SR-BI can directly bind cholesterol but is not important for SR-BI-mediated selective uptake or cholesterol efflux. Cholesterol binding by SR-BI in liver may play a role in SR-BI transcytosis. Specific Aim 1 will determine the role of PDZK1 in SR-BI sorting. We have generated a PDZK1 knockout mouse model and will use both PDZK1 deficient mice and in vitro polarized cells models to examine the role of PDZK1 in SR-BI sorting. Specific Aim 2 will delimit the basolateral targeting signal of SR-BI and test the role of this sequence in SR-BI sorting in vivo and in vitro as well as in biliary cholesterol secretion in vivo. Specific Aim 3 will test the hypothesis that the SR-BI cholesterol binding domain plays a role in SR-BI transcytosis. We will test the role of this domain in biliary cholesterol secretion in vivo and SR-BI transcytosis in vitro. These studies will provide fundamental insights into the mechanisms regulating SR-BI sorting and biliary cholesterol secretion.

描述（申请人提供）：血浆高密度脂蛋白（HDL）是胆汁胆固醇分泌的血浆胆固醇的主要载体。 HDL 受体清道夫受体 B-1 (SR-BI) 介导 HDL 胆固醇和胆固醇酯的摄取以排泄到胆汁中，其表达与胆汁胆固醇分泌相关。 SR-BI 敲除小鼠胆汁胆固醇分泌显着减少，表明 SR-BI 在此过程中发挥重要作用。然而，关于 SR-BI 介导肝胆胆固醇分泌的分子机制知之甚少。 SR-BI在肝的肝窦膜和小管膜上表达，并经历转胞吞作用至小管膜。 SR-BI 基底外侧靶向和转胞吞至小管膜所需的分选信号尚不清楚。我们已经确定了三个可能调节肝脏中 SR-BI 亚细胞分选以及 SR-BI 依赖性胆汁胆固醇分泌的重要因素。其中一个因素是 PDZK1，这是一种 PDZ 结构域蛋白，已被证明与 SR-BI 相互作用，并且对于维持肝脏 SR-BI 水平至关重要。第二个因素是SR-BI C端的基底外侧靶向信号，第三个因素是SR-BI C端跨膜结构域中的胆固醇结合结构域。 SR-BI的C端跨膜结构域可以直接结合胆固醇，但对于SR-BI介导的选择性摄取或胆固醇流出并不重要。肝脏中 SR-BI 与胆固醇的结合可能在 SR-BI 转胞吞作用中发挥作用。具体目标 1 将确定 PDZK1 在 SR-BI 分选中的作用。我们已经建立了 PDZK1 敲除小鼠模型，并将使用 PDZK1 缺陷小鼠和体外极化细胞模型来检查 PDZK1 在 SR-BI 分选中的作用。具体目标2将界定SR-BI的基底外侧靶向信号，并测试该序列在体内和体外SR-BI分选以及体内胆汁胆固醇分泌中的作用。具体目标 3 将检验 SR-BI 胆固醇结合域在 SR-BI 转胞吞作用中发挥作用的假设。我们将测试该结构域在体内胆汁胆固醇分泌和体外 SR-BI 转胞吞作用中的作用。这些研究将为调节 SR-BI 分选和胆汁胆固醇分泌的机制提供基本见解。