DNA SEQUENCE DIVERSITY IN THE HUMAN PREGNANE X RECEPTOR

孕烷X受体（PXR）的发现使人们对细胞色素P4503 A和潜在的其他药物解毒酶上调的基本机制有了更深入的了解。 我们假设CYP 3A 4基因中PXR或其同源结合元件（PXRE）的序列变异（包括单核苷酸多态性，SNP）是基础和诱导型CYP 3A表达的人类变异的核心。 为了深入研究PXR单核苷酸多态性对CYP 3A调控的重要性，需要一种安全、可靠、方便的检测方法来确定个体的PXR基因型。 为了实现这一目标，我们已经克隆，绘制和测序PXR。 我们的总体目标是：（1）鉴定PXR（或CYP 3A 4 PXRE）中的序列变异并确定其功能重要性;（2）将PXR SNP与CYP 3A中的表型变异相关联;（3）确定PXR中序列变异的总体频率和模式;和（4）确定PXR SNP的功能重要性和导致细胞和生物化学测定中的非功能性PXR的分子机制。 我们的药物基因组学方法利用了我们独特的资源-来自CYP 3A表型人类组织和人类研究人群的基因组DNA，这些基因组DNA来自使用CYP 3A底物和诱导剂的众多临床试验。 此外，我们将使用CYP 3A诱导表型分析的人肝细胞培养物前瞻性识别诱导药物应答中的离群值。 我们研究的目标是同时使用这些确定的患者群体作为基因型-表型关系的来源和SNP发现资源。 我们的假设驱动的方法将立即阐明PXR或PXRE SNP不仅对PXR功能而且对CYP 3A药物反应的功能后果，并将作为重要的基因型-表型/SNP药物基因组学模型，并提供对CYP 3A代谢药物的高度可变的药代动力学机制的进一步见解。

The discovery of the Pregnane X receptor (PXR) has led to a greater understanding of the fundamental mechanisms underlying upregulation of cytochrome P4503A and potentially other drug detoxification enzymes. We hypothesize that sequence variations (including single nucleotide polymorphisms, SNPs) in PXR or its cognate binding element (PXRE) in the CYP3A4 gene are central to human variation in both basal and inducible CYP3A expression. To critically study the importance of PXR SNPs to regulation of CYP3A a safe, reliable, and convenient assay will be needed to determine an individual s PXR genotype. Towards this goal we have cloned, mapped and are sequencing PXR. Our overall objectives are: (1) to identify sequence variations in PXR (or in the CYP3A4 PXRE) and determine their functional importance; (2) to correlate PXR SNPs to phenotypic variations in CYP3A; (3) to determine the overall frequency and pattern of sequence variations in PXR; and (4) to determine the functional importance of PXR SNPs and the molecular mechanisms leading to non- functional PXR in cellular and biochemical assays. Our pharmacogenomic approach takes advantage of our unique resources - genomic DNAs from CYP3A phenotyped human tissues and human study populations from numerous clinical trials with CYP3A substrates and inducers. Additionally, using cultures of human hepatocytes phenotyped for CYP3A induction we will prospectively identify the outliers in inductive drug response. The goal of our study is to use these defined patient populations simultaneously as a source of genotype-phenotype relationships and as a SNP discovery resource. Our hypothesis driven approach will immediately elucidate the functional consequences of PXR or PXRE SNPs to not only PXR function but CYP3A drug response as well and will serve as an important gentotype-phenotype/SNP pharmacogenomics model and provide further insights into mechanisms responsible for the highly variable pharmacokinetics of CYP3A metabolized drugs.