Signaling of the Pregnane X Receptor

孕烷X受体(PXR)被认为是化学清除蛋白表达的主要调节因子。 TION基因，如细胞色素P450 3A4(CYP3A4)，是最丰富的CYP酶，负责 超过50%的治疗药物的代谢。PXR信号调制器的研究 将DEC转录因子与细胞因子抑制的PXR和CyP3A的表达联系起来。促炎性 ：细胞因子(如IL-6)显著增加DEC1和DEC2水平，同时抑制 PXR和CyP3A的表达。DECS共转染可有效抑制PXR和CYP3A启动子。 对CYP3A4转录的基因组基础的研究证实，PXR反式激活 CYP3A4启动子通过两个区域：近端和远端。PXR在这两个组织中都存在 区域通过PXR元件，然而，远端区域的删除不再响应PXR。这个 拟议的研究旨在检验远端和近端区域协调的假设 支持辅阻遏子和辅活化子PXR定向置换/募集，以及PXR和CyP3A 基因是DEC转录因子的序列特异性靶标。拟议研究的具体目标 是：(1)确定远端和近端区域在PXR指导的转录中的不同作用，以及(2) 目的：阐明DECS抑制PXR和CyP3A表达的机制。要确定该地区- 将对PXR、辅抑制子SMRT和辅活化子执行具体的协调制子、芯片招聘 SRC-1(被发现调节PXR导向的转录)。PXR中介导相互作用的重要残基-- 我们将会建立一系列的规则。阐明DECs抑制PXR和PXR表达的分子基础 将进行慢病毒转导以上调或下调DECs，以及对PXR的影响 并测定细胞色素P3A的表达。将进行一系列实验，以在PXR和 CYP3A启动子支持去抑制的DMA序列。PXR诱导和细胞因子- 介导的药物代谢酶抑制是消除药物代谢酶的两个主要决定因素 化学制品。因此，这些研究将有助于我们基本理解PXR是如何， CYP3A和DECS作为一组结构不同但功能相关的蛋白质，参与了多种药物的研究。 COLOGIC测定与外源生物解毒/生物活性。 行业相关性：两种或两种以上同时使用的药物可能会相互干扰。细菌/病毒 感染会降低药物的清除能力。拟议研究的结果将提供重要的 关于如何防止药物不相容和在感染期间调整剂量的信息。

The pregnane X receptor (PXR) is recognized as a master regulator on the expression of chemical elimina- tion genes such as cytochrome P450 3A4 (CYP3A4), the most abundant CYP enzyme that is responsible for the metabolism of more than 50% of therapeutic agents. Studies on the modulators for PXR signaling have linked DEC transcription factors to cytokine-suppressed expression of PXR and CYP3A. Proinflammatory :ytokines (e.g., IL-6) markedly increase the levels of DEC1 and DEC2, and simultaneously suppress the expression of PXR and CYP3A. Co-transfection of DECs effectively represses PXR and CYP3A promoters. Studies on the genomic basis for CYP3A4 transcription have established that PXR transactivates the CYP3A4 promoter through two regions: the proximal and distal regions. PXR is physically present in both regions through a PXR element, however, deletion of the distal region no longer responds to PXR. The proposed studies are designed to test the hypotheses that the distal and proximal regions coordinately support PXR-directed displacement/recruitment of corepressor and coactivator, and that PXR and CYP3A genes are sequence-specific targets of DEC transcription factors. The specific aims of the proposed studies are: (1) to define the differential roles of the distal and proximal regions in PXR-directedtranscription, and (2) to elucidate the mechanisms on DECs-repressed expression of PXR and CYP3A. To determine the region- specific recruitment of co-regulators, ChIP will be performed for PXR, corepressor SMRT and coactivator SRC-1 (found to regulate PXR-directed transcription). The important residues in PXR to mediate the interac- tions will be established. To elucidate the molecular basis for .DECs-repressed expression of PXR and CYP3A, lentiviral transduction will be performed to up-regulate or knockdown DECs, and the effect on PXR and CYP3A expression will be determined. A set of experiments will be conducted to locate in the PXR and CYP3A promoters DMA sequences that support DECs-repression. PXR-directed induction and cytokines- mediated suppression of drug-metabolizing enzymes are two major determinants on the elimination of chemicals. Therefore, these studies will contribute significantly to our basic understanding of how PXR, CYP3A and DECs, as a group of structurally distinct but functionally related proteins, are involved in pharma- cologic determination and xenobiotic detoxication/bioactivation. Lay Relevance: Two or more drugs concurrently administered may interfere with each other. Bacterial/viral infection lowers the capacity of drug-elimination. Results from the proposed studies will provide important information on how to prevent drug incompatibility and adjust dosage during infection.