Molecular and Cellular Effects of Human Mutations in Cytochrome P450 Reductase

总结/摘要 NADPH-细胞色素P450氧化还原酶（CYPOR，由POR基因编码）缺陷与Antley-Bixler综合征（ABS）的骨骼和类固醇生成异常相关，尽管其对细胞色素P450（CYP）介导的外源性和内源性代谢的具体影响尚未解决。最近发现的40种天然存在的人CYPOR变体，代表了广泛的残留活性，已根据表型相关性和初步酶学进行了分类。本研究计划旨在分子和细胞水平上解决天然存在的POR突变和多态性变异如何影响CYPOR的结构排列和催化功能，以支持细胞过程。具体目标1？POR变体的分子分析将检查特定残基突变时产生具有改变的电子传递和/或氧化/还原伴侣相互作用性质的蛋白质的假设。为了实现这一目标，将利用溶液（光谱、动力学和热力学）和晶体学（X射线衍射）技术。初步证据表明，从治疗的角度来看，特定的缺陷可能是可以解决的。此外，预计CYPOR缺乏以及随后的代谢产物的不平衡会导致基因表达谱的改变，从而导致发育缺陷。因此，CYPOR缺陷下游事件的特定目标2？细胞分析将利用受不同程度CYPOR缺陷影响的组织的细胞模型。为了实现这一目标，将缺陷POR基因引入原代（从POR[lox/lox]小鼠组织中分离）和转化的人（肝、肠和骨）细胞模型中，以测量对外源性/内源性挑战的直接代谢（CYP介导的活性测定）和下游反应（功能测定和基因表达谱分析）。

SUMMARY/ABSTRACT NADPH-cytochrome P450 oxidoreductase (CYPOR, encoded by the POR gene) deficiency has been correlated with the skeletal and steroidogenic anomalies of Antley-Bixler syndrome (ABS), although its specific effects on cytochrome P450 (CYP)-mediated xenobiotic and endobiotic metabolism remain unresolved. Forty naturally occurring human CYPOR variants, recently discovered and representing a broad range of residual activities, have been categorized based on phenotypic correlation and preliminary enzymology. This research plan is designed to address, on a molecular and cellular level, how naturally occurring POR mutations and polymorphic variations affect the structural arrangement and catalytic function of CYPOR in supporting cellular processes. Specific Aim 1 ¿ Molecular Analysis of POR Variants will examine the hypothesis that specific residues, when mutated, produce proteins with altered electron transport and/or oxidation/reduction partner interaction properties. To address this aim, both solution (spectroscopic, kinetic, and thermodynamic) and crystallographic (X-ray diffractions) techniques will be utilized. Preliminary evidence suggests that specific deficiencies may be addressable from a therapeutic perspective. Furthermore, CYPOR deficiency, as well as the subsequent imbalance of CYP metabolites, is predicted to result in altered gene expression profiles that lead to developmental defects. Therefore, Specific Aim 2 ¿ Cellular Analysis of Downstream Events in CYPOR Deficiency will utilize cellular models of tissues affected by varying degrees of CYPOR deficiency. To address this aim, defective POR genes will be introduced into both primary (isolated from POR[lox/lox] mouse tissues) and transformed human (liver, intestinal, and bone) cell models in order to measure the direct metabolic (CYP-mediated activity assays) and downstream response (functional assays and gene expression profiling) to xenobiotic/endobiotic challenge.