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: 7738647
• 负责人: GREGORIO GIL
• 金额: $ 35.88万
• 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/7738647
• 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（由申请人提供）：胆固醇稳态是通过胆固醇摄取、合成、运输、酯化、分泌和降解的协调调节来维持的。最近的进展使人们对胆固醇的分类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以及它们对胆固醇代谢/降解的影响仍然未知。本申请的总体目标是利用体外和体内模型阐明两种 START 结构域蛋白（StarD4、StarD5）在肝细胞和巨噬细胞胆固醇和胆汁酸稳态中的作用。 P.I.s 实验室最近表明，胆固醇转运至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”途径能够控制已知调节性氧甾醇、27-羟基胆固醇、25-羟基胆固醇和至少一种新型硫酸酯的核水平。 氧甾醇。除了 StarD1 之外，还存在一个含有 StarD1 同源结构域的蛋白质家族，该蛋白质家族可能能够在细胞内结合和运输甾醇。该家族中的所有蛋白质都具有相似的结构脂质结合域，称为 StarD1 相关脂质转移 (START) 域。最近，他们还显示了以下内容：1）StarD1、27-羟基胆固醇和 StarD5 水平的协调反应； 2) StarD5 蛋白响应胆固醇而在细胞内从高尔基体重新分布到质膜； 3) 胆固醇是 StarD4 和 StarD5 的配体；后者还结合25-羟基胆固醇； 4) StarD4 过表达后胆汁酸合成和胆固醇酯形成增加。在本申请提出的研究中，将使用体外和体内模型来研究StarD4和StarD5在肝细胞和巨噬细胞中的调节和生理功能。具体来说，建议研究：1）表征巨噬细胞和肝细胞（StarD4）中StarD4和StarD5响应胆固醇的调节和亚细胞运动； 2)表征巨噬细胞和肝细胞中StarD4和StarD5的功能(StarD4)； 3) 表征 StarD4 在体内胆固醇稳态中的生理作用。了解肝细胞和巨噬细胞中胆固醇稳态的调节机制与了解人类动脉硬化和心脏病的发展非常相关。公众健康相关性：肠道吸收和溶解胆固醇和脂肪需要胆汁酸。此外，胆汁酸在胆固醇稳态中发挥着额外的重要作用。胆汁酸由胆固醇制成。由于胆固醇不溶于水，因此它与蛋白质结合在细胞内移动。我们建议研究在细胞内结合和运输胆固醇的新型蛋白质，尤其是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有关胆汁酸生物合成和胆固醇稳态调节的分子机制的新见解。