ILEAL BILE ACID TRANSPORTER METABOLISM AND REGULATION

回肠胆汁酸转运蛋白的代谢和调节

• 批准号: 2147973
• 负责人: PAUL A DAWSON
• 金额: $ 9.8万
• 依托单位: WAKE FOREST UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-05-10 至 1999-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2147973
• 关键词: bile circulation; brush border membrane; cholanate compound; gastrointestinal absorption /transport; gastrointestinal epithelium; hamsters; ileum; laboratory rabbit; liver metabolism; membrane transport proteins; molecular cloning; nutrition related tag; protein structure function; tissue /cell culture

In lipid metabolism, bile acids play a critical role in the digestion of dietary fat and the absorption of dietary metabolites and cholesterol. To maintain their enterohepatic circulation, bile acids are conserved by active ileal uptake. Using isolated intestinal sections and enterocytes, the kinetic properties and chemical specificity of ileal bile acid transport has been examined. However, the proteins responsible for transport have not been isolated, and the process has not been studied at the molecular level. This has hindered understanding the mechanism of ileal bile acid transport, its regulation, and its role in bile acid and cholesterol metabolism. The proposed research will employ a recently identified bile acid transporter cDNA clone to examine the regulation and mechanism of the ileal bile acid transport. The following questions will be addressed: 1. What are the general properties of the ileal bile acid transporter? Bile acid transport across the ileum is believed to be mediated by a Na+- dependent transporter on the brush border membrane. To identify and characterize the transporter, my laboratory used an expression cloning strategy to isolate a candidate cDNA clone (IBAT) for the ileal bile acid transporter. To verify the identity of the candidate cDNA and extend previous studies of the transporter, IBAT's transport and expression properties will be determined. 2. Is the ileal bile acid transporter regulated by bile acid availability? Very recent in vivo studies have suggested that ileal bile acid transport activity is regulated by bile acid availability and may be a crucial determinant of bile acid and cholesterol homeostasis. To determine a) whether the transporter is regulated by changes in hamster intestinal bile acid availability (as previously hypothesized) and b) what level this reulation occurs, ileal Na+-dependent bile acid transporter activity, protein, mRNA, and gene transcription levels will be examined. 3. How does the ileal bile acid transporter function to carry bile acids across the enterocyte? To begin studying the cellular mechanism of bile acid transport, CaCo-2 cells will be used as a model system to express the ileal bile acid transporter cDNA. IBAT's transport properties will studied to test the hypothesis that the brush border membrane transporter is the rate limiting step in transcellular trafficking of bile acids across the ileal epithelium.

在脂质代谢中，胆汁酸在消化 膳食脂肪和膳食代谢物和胆固醇的吸收。 到 维持其肝肠循环，胆汁酸通过 回肠主动摄取。 使用分离的肠切片和肠细胞， 回肠胆汁酸的动力学性质和化学特异性 运输已经检查。 然而，负责 运输尚未被隔离，该过程尚未被研究。 分子水平。 这就阻碍了我们理解 回肠胆汁酸转运、其调节及其在胆汁酸和 胆固醇代谢 这项研究将采用最近 鉴定了胆汁酸转运蛋白cDNA克隆以检查调节， 回肠胆汁酸转运的机制。 以下问题将 应处理： 1. 回肠胆汁酸转运蛋白的一般特性是什么？ 胆汁酸通过回肠的转运被认为是由Na+-ATP酶介导的。 刷状缘膜上的依赖性转运蛋白。 识别和 我的实验室用表达克隆技术 分离回肠胆汁酸候选cDNA克隆（IBAT）的策略 传送器。 为了验证候选cDNA的身份， IBAT转运蛋白的转运和表达 属性将被确定。 2. 回肠胆汁酸转运体是否受胆汁酸利用率的调节？ 最近的体内研究表明，回肠胆汁酸转运 活性受胆汁酸可用性调节，可能是关键的 胆汁酸和胆固醇稳态的决定因素。 确定a） 转运蛋白是否受仓鼠肠胆汁变化的调节 酸的可用性（如先前假设的）和B）这是什么水平 调节发生，回肠Na+依赖性胆汁酸转运蛋白活性， 将检查蛋白质、mRNA和基因转录水平。 3. 回肠胆汁酸转运蛋白是如何转运胆汁酸的 穿过肠上皮细胞 开始研究胆汁的细胞机制 酸转运，CaCo-2细胞将被用作模型系统来表达 回肠胆汁酸转运蛋白cDNA。 研究了IBAT的输运性质 为了验证刷状缘膜转运蛋白是 胆汁酸跨细胞转运的限速步骤 回肠上皮