Phase II UDP-glucuronosyltransferases by PXR

II 期 UDP-葡萄糖醛酸基转移酶（PXR）

• 批准号: 7062074
• 负责人: Wen Xie
• 金额: $ 28.68万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2008-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7062074
• 关键词: bilirubin; genetic promoter element; genetic regulation; genetic transcription; genetically modified animals; glucuronosyltransferase; laboratory mouse; molecular cloning; nuclear receptors; polymerase chain reaction; reporter genes; tissue /cell culture; uridine diphosphate

DESCRIPTION (provided by applicant): The long-term goal of the proposed research is to study the transcriptional regulation of the phase II drug-metabolizing and clearing enzymes by the xenobiotic nuclear receptor PXR. The phase II conjugating enzymes such as the UDP-glucuronosyltransferases (UGTs) function in concert with the oxidative phase I cytochrome P450 enzymes (CYPs) to eliminate xenobiotics such as prescription drugs and over-the-counter medications, and endobiotics such as bilirubin, steroid hormones and bile acids. The nuclear receptor PXR was initially identified as a xenosensor to regulate the expression of CYP genes via its binding to the PXR-response elements found within the mammalian CYP gene promoters. The identity of PXR as a species-specific xenosensor has been established by previous transgenic and gene knockout studies. Having established CYP genes as PXR targets, the presence of candidate PXR response elements in genes encoding the phase II UGT gene products raises the potential for a broader physiological function of PXR in xenobiotic response and clearance. However, whether UGTs are induced by PXR is unclear. To investigate UGTs as potential transcriptional targets of PXR, we propose to: (1) clone the UGT1A1 promoter and characterize its regulation by PXR; (2) examine the regulation of hepatic UGTs in mouse models bearing heightened (VP-hPXR transgenic), compromised (PXR knockout), or "humanized" (PXR knockout/hPXR transgenic) receptor activity; (3) examine the effect of altered PXR activity on bilirubin homeostasis; (4) examine the regulation of intestinal UGTs by PXR. If the regulation of phase II enzymes such as the UGTs by PXR proven to be true, we are toward establishing PXR as a master transcriptional regulator of the mammalian xenobiotic response. The results of these studies will provide novel elements in understanding the transcriptional regulation of UGT. It is anticipated that elucidation of the molecular basis of UGT regulation using the "humanized" mice will have great implication in human physiology and diseases. These include bilirubin and hormonal homeostasis, drug metabolism, and chemical carcinogenesis.

描述（由申请人提供）：拟议研究的长期目标是研究异生物质核受体PXR对II期药物代谢和清除酶的转录调控。II相缀合酶如UDP-葡糖醛酸基转移酶（UGT）与氧化性I相细胞色素P450酶（CYP）协同作用以消除异生物质如处方药和非处方药，以及内源性如胆红素、类固醇激素和胆汁酸。核受体PXR最初被鉴定为异种传感器，其通过与哺乳动物β-内酰胺酶基因启动子内发现的PXR反应元件结合来调节β-内酰胺酶基因的表达。PXR作为物种特异性异种传感器的身份已经通过先前的转基因和基因敲除研究建立。已经建立了PXR靶基因，在编码II期UGT基因产物的基因中候选PXR应答元件的存在提高了PXR在异生物质应答和清除中更广泛的生理功能的潜力。然而，UGT是否由PXR诱导尚不清楚。为了研究UGT作为PXR潜在的转录靶点，我们提出：（1）克隆UGT 1A 1启动子并表征其受PXR的调控;（2）在高脂血症小鼠模型中检测肝UGT的调控。（VP-hPXR转基因），受损（PXR敲除）或“人源化”（PXR敲除/hPXR转基因）受体活性;（3）检查改变的PXR活性对胆红素稳态的影响;（4）检查PXR对肠UGT的调节。如果PXR对II相酶如UGT的调节被证明是正确的，我们将把PXR作为哺乳动物异生物质反应的主要转录调节因子。这些研究结果将为理解UGT的转录调控提供新的基础。预期使用“人源化”小鼠阐明UGT调节的分子基础将对人类生理学和疾病具有重大意义。这些包括胆红素和激素稳态，药物代谢和化学致癌作用。