Pharmacogenomics of Human P450 Oxidoreductase

描述(申请人提供)：药物基因组学领域致力于描述导致药物反应不同的遗传因素，包括一个种族群体中的个人和不同群体之间的差异。到目前为止，药物基因组学的大部分工作都集中在药物代谢肝脏细胞色素P450(CYP)酶的多态变异上。这项建议将解决以前未被探索的药物代谢变异的潜在基础，NADPH依赖的P450氧化还原酶(POR)。对于微粒体细胞色素P450‘S来说，POR是实现催化所需电子的唯一来源。POR接受来自NADPH的电子，并将它们转移到P450。虽然POR基因敲除小鼠的表型是胚胎致死的，但令人惊讶的是，我们最近发现人类POR错义突变导致了广泛的人类疾病，从正常的闭经女性表型到患有Antley-Bixler综合征(ABS)的严重畸形婴儿。其他数据表明，POR突变扰乱了胎儿的药物代谢，显然使一种原本良性的药物(氟康唑)具有致畸性。POR错义突变的频率、严重程度和种族分布尚不清楚，无论是那些严重到足以致病的突变，还是那些可能表现为沉默的突变。为了评估POR序列变体在药物反应变化中的潜在作用，我们提出了以下四个特定目标：目的1.鉴定和表征导致可识别的人类疾病的POR突变谱。目的2.描述正常人群中POR序列变异和多态的谱带。目的3.研究POR错义突变或变异对肝脏8种最重要的P450酶(CYP1A2、2A6、2C8、2C9、2C19、2D6、2E1和3A4)的影响。目的4.确定单独具有最小活性损失的POR和CYP酶的序列变体是否可以组合在一起导致这些酶的活性显著降低。这些目标的成功实现将大大增加对导致药物反应变化的遗传因素的了解。

DESCRIPTION (provided by applicant): The field of Pharmacogenomics seeks to delineate the genetic factors responsible for variations in drug response, both among individuals in one ethnic group and between population groups. To date, most effort in pharmacogenomics has focused on polymorphic variants in drug-metabolizing hepatic cytochrome P450 (CYP) enzymes. This proposal will address a previously unexplored potential basis for variation in drug metabolism, NADPH-dependent P450 oxidoreductase (POR). For microsomal cytochrome P450's POR is the only source of the electrons necessary to achieve catalysis. POR accepts electrons from NADPH and transfers them to the P450. Although the phenotype of POR knockout mice is an embryonic lethal, surprisingly we recently found that human POR missense mutations are responsible for a broad spectrum of human disease, ranging from a normal female phenotype with amenorrhea, to severely malformed infants with the Antley-Bixler syndrome (ABS). Other data suggest that POR mutations disrupt fetal drug metabolism, apparently rendering an otherwise benign drug (fluconazole) teratogenic. The frequency, severity and ethnic distribution of POR missense mutations, either those severe enough to cause disease or those that may be phenotypically silent, is unknown. To assess the potential role of POR sequence variants in variations in drug response, we propose the following four Specific Aims: Aim 1. Identify and characterize the spectrum of POR mutations causing identifiable human disease. Aim 2. Delineate the spectrum of POR sequence variants and polymorphisms in the normal human population. Aim 3. Assess the impact of POR missense mutants or variants on the eight most important hepatic P450 enzymes (CYP1A2, 2A6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4). Aim 4. Determine whether sequence variants of POR and CYP enzymes that have minimal loss of activity individually can, in combination, lead to significant diminution in the activity of these enzymes. Successful completion of these aims will substantially increase knowledge about the genetic factors leading to variations in drug response.