Signaling of the Pregnane X Receptor

PXR受体被认为是化学消除蛋白表达的主要调节因子。 细胞色素P450 3A 4（CYP 3A 4）是一种最丰富的代谢酶， 超过50%的治疗药物的代谢。对PXR信号转导调节剂的研究已经 将DEC转录因子与奎宁抑制的PXR和CYP 3A表达联系起来。促炎 ：细胞因子（例如，IL-6）显著增加DEC 1和DEC 2的水平，同时抑制DEC 1和DEC 2的表达。 PXR和CYP 3A的表达。德克斯的共转染有效地抑制PXR和CYP 3A启动子。 对CYP 3A 4转录的基因组基础的研究已经确定，PXR反式激活CYP 3A 4转录。 CYP 3A 4启动子通过两个区域：近端和远端区域。PXR实际上存在于 然而，远端区域的缺失不再响应PXR。的 提出的研究旨在检验远端和近端区域协调的假设， 支持辅阻遏物和辅激活物PXR定向置换/募集，以及PXR和CYP 3A 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 目的是：（1）确定PXR指导转录的远端和近端区域的不同作用，（2） 阐明DECs抑制PXR和CYP 3A表达的机制。为了确定区域- 将对PXR、辅阻遏物SMRT和辅激活物进行辅调节剂的特异性募集、ChIP SRC-1（发现调节PXR定向转录）。PXR中介导相互作用的重要残基， 将建立。为了阐明DECs抑制PXR表达的分子基础， 将进行CYP 3A、慢病毒转导以上调或敲低德克斯，并观察对PXR的影响 并测定CYP 3A表达。将进行一组实验，以在PXR中定位， CYP 3A启动子支持DEC抑制的DMA序列。PXR导向的诱导和细胞因子- 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。 化学品因此，这些研究将大大有助于我们对PXR， CYP 3A和德克斯是一组结构不同但功能相关的蛋白质，参与药物代谢。 生物学测定和异生物质解毒/生物活化。 非专业相关性：两种或多种药物同时给药可能会相互干扰。细菌/病毒 感染降低了药物清除能力。研究结果将提供重要的 如何预防药物不相容性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.