Role of Star Proteins in Bile Acid and Cholesterol Metabolism

星蛋白在胆汁酸和胆固醇代谢中的作用

• 批准号: 7866643
• 负责人: GREGORIO GIL
• 金额: $ 35.52万
• 依托单位: VIRGINIA COMMONWEALTH UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2013-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7866643
• 关键词: 25-hydroxycholesterol; 27-hydroxycholesterol; Anabolism; Animal Model; Apoptotic; Arteriosclerosis; Bile Acid Biosynthesis Pathway; Bile Acids; Bile fluid; Binding; Binding Proteins; CYP7A1 gene; Carrier Proteins; Cell Nucleus; Cell membrane; Cell secretion; Cells; Cholesterol; Cholesterol Esters; Cholesterol Homeostasis; Development; Esterification; Family; Fatty acid glycerol esters; Golgi Apparatus; Heart Diseases; Hepatocyte; Homeostasis; Homologous Gene; Human; In Vitro; Inner mitochondrial membrane; Inorganic Sulfates; Intestinal Absorption; Laboratories; Ligands; Lipid Binding; Lipids; Liver; Maintenance; Mammalian Cell; Messenger RNA; Microarray Analysis; Mitochondria; Molecular; Movement; Mus; Nuclear; Pathway interactions; Physiological; Play; Protein Binding; Protein Family; Proteins; Regulation; Role; Signal Transduction; Sorting - Cell Movement; Sterols; Stress; System; Tertiary Protein Structure; Time; Tissues; Unspecified or Sulfate Ion Sulfates; Vitamin D; Water; cell growth regulation; cholesterol-binding protein; feeding; in vivo; in vivo Model; insight; macrophage; novel; overexpression; phosphatidylcholine transfer protein; public health relevance; response; steroid hormone; sterol carrier proteins; tissue culture; uptake

DESCRIPTION (provided by applicant): Cholesterol homeostasis is maintained through the coordinated regulation of cholesterol uptake, synthesis, transport, esterification, secretion, and degradation. Recent advances have led to a more complete understanding of the way cholesterol's sorting and transport contribute to the maintenance of cholesterol homeostasis. However, the role of many intracellular cholesterol- binding proteins within various cells in the body, and their effect on cholesterol metabolism/degradation, remains unknown. The overall aim of this application is to elucidate the role of two START domain proteins (StarD4, StarD5) play in cholesterol and bile acid homeostasis in hepatocytes and macrophages using both in vitro and in vivo models. The P.I.s' labs have recently shown that cholesterol transport to the inner mitochondrial membrane represents the rate-determining step controlling bile acid synthesis via the 'acidic' pathway, and that the 'acidic' pathway is able to control nuclear levels of the known regulatory oxysterols, 27-hydroxycholesterol, 25-hydroxycholesterol, and at least one novel sulfated oxysterol. In addition to StarD1, there exists a family of proteins containing a StarD1 homologue domain that potentially is capable of binding and transporting sterols within cells. All proteins in this family have a similar structural lipid-binding domain referred to as the StarD1- related lipid transfer (START) domain. Most recently, they have also shown the following: 1) a coordinated response in the levels of StarD1, 27-hydroxycholesterol, and StarD5; 2) an intracellular redistribution of StarD5 protein from the Golgi to the plasma membrane in response to cholesterol; 3) that cholesterol is a ligand for both StarD4 and StarD5; the later also binds 25- hydroxycholesterol; and, 4) an increase in bile acid synthesis and cholesterol ester formation following StarD4 overexpression. In the studies proposed in this application, in vitro and in vivo models will be used to study the regulation, and physiological function of StarD4, and StarD5 in hepatocytes and in macrophages. Specifically, studies are proposed to: 1) characterize the regulation and subcellular movement of StarD4 and StarD5 in macrophages and hepatocytes (StarD4) in response to cholesterol; 2) characterize the function of StarD4, and StarD5 in macrophages and hepatocytes (StarD4); 3) characterize the physiological role(s) of StarD4 in cholesterol homeostasis in vivo. An understanding of the mechanisms of regulation of cholesterol homeostasis in hepatocytes and macrophages is very relevant to the understanding of the development of arteriosclerosis and heart disease in humans. PUBLIC HEALTH RELEVANCE: Bile acids are required for intestinal absorption and solubilization of cholesterol and fats. In addition, bile acids play an additional crucial role in cholesterol homeostasis. Bile acids are made from cholesterol. Because cholestrol is not soluble in water, it binds to proteins to move within the cell. We propose to study novel proteins that bind and transport cholesterol within the cell and, among other things, regulate the bile acid biosynthetic pathway. The successful completion of this study will provide us with new insights into the molecular mechanisms involved in the regulation of bile acid biosynthesis and cholesterol homeostasis.

描述（由申请方提供）：通过协调调节胆固醇摄取、合成、转运、酯化、分泌和降解来维持胆固醇稳态。最近的进展使人们对胆固醇的分选和运输有助于维持胆固醇稳态的方式有了更全面的了解。然而，许多细胞内胆固醇结合蛋白在体内各种细胞内的作用及其对胆固醇代谢/降解的影响仍然未知。本申请的总体目的是使用体外和体内模型阐明两种START结构域蛋白（StarD 4、StarD 5）在肝细胞和巨噬细胞中胆固醇和胆汁酸稳态中的作用。P.I.s的实验室最近表明，胆固醇转运到线粒体内膜代表了通过“酸性”途径控制胆汁酸合成的速率决定步骤，并且“酸性”途径能够控制已知的调节性氧固醇、27-羟基胆固醇、25-羟基胆固醇和至少一种新型硫酸化氧固醇的核水平。除了StarD 1之外，还存在一个含有StarD 1同源结构域的蛋白质家族，该结构域可能能够在细胞内结合和转运固醇。该家族中的所有蛋白质都具有类似的结构脂质结合结构域，称为StarD 1相关脂质转移（START）结构域。最近，他们还显示了以下内容：1）StarD 1、27-羟基胆固醇和StarD 5水平的协调反应; 2）StarD 5蛋白质响应于胆固醇从高尔基体到质膜的细胞内再分布; 3）胆固醇是StarD 4和StarD 5两者的配体;后者也结合25-羟基胆固醇;和4）在StarD 4过表达后胆汁酸合成和胆固醇酯形成增加。在本申请中提出的研究中，将使用体外和体内模型来研究肝细胞和巨噬细胞中StarD 4和StarD 5的调节和生理功能。具体而言，提出了以下研究：1）表征StarD 4和StarD 5在巨噬细胞和肝细胞（StarD 4）中响应胆固醇的调节和亚细胞运动; 2）表征StarD 4和StarD 5在巨噬细胞和肝细胞（StarD 4）中的功能; 3）表征StarD 4在体内胆固醇稳态中的生理作用。对肝细胞和巨噬细胞中胆固醇稳态调节机制的理解与对人类动脉硬化和心脏病发展的理解非常相关。公共卫生相关性：胆汁酸是肠道吸收和溶解胆固醇和脂肪所必需的。此外，胆汁酸在胆固醇稳态中起着额外的关键作用。胆汁酸是由胆固醇制成的。因为胆固醇不溶于水，它与蛋白质结合在细胞内移动。我们建议研究新的蛋白质，结合和运输胆固醇的细胞内，除其他外，调节胆汁酸生物合成途径。这项研究的成功完成将为我们提供新的见解参与调节胆汁酸生物合成和胆固醇稳态的分子机制。