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）：拟议的研究的长期目标是研究II期药物代谢和清除酶的转录调控，这是异生物核受体PXR的转录调节。与氧化I期细胞色素P450酶（CYPS）一致的II期结合酶，例如UDP-葡萄糖基转移酶（UGTS），以消除异种生物学，例如处方药和外部药物，以及诸如胆红素，乙酰氨基纤维素，固醇，固醇，类药物，以消除异种生物。激素和胆汁酸。核受体PXR最初被鉴定为异种传感器，通过与哺乳动物CYP基因启动子中发现的PXR反应元件结合来调节CYP基因的表达。先前的转基因和基因敲除研究已经建立了PXR作为特异性异种传感器的身份。建立CYP基因作为PXR靶标后，编码II期UGT基因产物的基因中的候选PXR反应元件的存在提高了PXR在异种生物响应和清除率中的更广泛生理功能的潜力。但是，是否尚不清楚UGT是否是由PXR诱导的。为了研究UGT作为PXR的潜在转录靶标，我们提出：（1）克隆UGT1A1启动子，并通过PXR进行调控； （2）检查带有增强（VP-HPXR转基因）的小鼠模型中肝UGT的调节，受损（PXR敲除）或“人性化”（PXR敲除/HPXR转基因）受体活性； （3）检查PXR活性改变对胆红素稳态的影响； （4）检查PXR对肠道UGT的调节。如果证明对PXR的II期酶（例如UGT）的调节是正确的，那么我们将建立PXR作为哺乳动物异生元反应的主要转录调节剂。这些研究的结果将为理解UGT的转录调控提供新的要素。预计使用“人性化”小鼠对UGT调节的分子基础阐明将对人类的生理和疾病具有很大的影响。这些包括胆红素和激素稳态，药物代谢和化学癌变。