Structure & Function of the Human PON1 Polymorphism

描述（由申请方提供）：拟定研究的主要目的是了解在人对氧磷酶（PON 1）遗传变异体中观察到的功能差异的结构基础。我们已经部分表征了五个编码区多态性和五个上游调控多态性的影响。Q192 R多态性影响PON 1对多种底物水解的催化效率，而-108C/T多态性影响PON 1表达。三个新发现的多态性导致PON 1等位基因失活。我们的目标是了解这些多态性的功能基因组学。我们将使用PON 1小鼠模型来检查急性暴露于有机磷（OP）化合物的影响。小鼠模型包括PON 1敲除小鼠以及表达一个或多个拷贝的每个人PON 1-Q192 R等位基因的敲除小鼠。该模型系统将使我们能够测试的假设，即一个多态性PON 1-Q192 R等位基因在给定的水平上表达将提供一个特定程度的抗性直接水解PON 1或代谢通过细胞色素P450 /PON 1途径的环境因子的毒性。该模型还将使我们能够研究PON 1多态性在调节低水平OP暴露对大脑基因表达的影响中的作用，这是一个以前无法接近的研究领域。我们建议调查五个方面的PON 1遗传变异，将提供信息的功能基因组学的多态性的人类PON 1基因。具体目标1研究了急性接触二氮嗪（DZO）的毒理学效应，具体目的2检测PON 192变体对PON 1基因被一个或两个拷贝的人PON 1 Q192或R192取代的小鼠的毒性基因组学表达谱的调节作用。192只转基因小鼠暴露于CPO和DZO。具体目标3旨在鉴定通过暴露于CPO而修饰的新蛋白质靶标。具体目标4涉及测定人PON 1的晶体结构和表征具有增加的OP水解效率的重组PON 1变体。具体目标5涉及使用表达不同水平的每种人PON 1 -192同种型的人源化转基因PON 1敲除小鼠开发有机磷暴露的人药代动力学/药效学（PDPK/PD）模型。

DESCRIPTION (provided by applicant): The major objective of the proposed research is to understand the structural basis for the functional differences observed in human paraoxonase (PON1) genetic variants. We have partially characterized the effects of five coding region polymorphisms and five upstream regulatory polymorphisms. The Q192R polymorphism affects the catalytic efficiency of PON1 for hydrolysis of a number of substrates, while the position -108C/T polymorphism affects PON1 expression. Three newly discovered polymorphisms result in inactive PON1 alleles. Our goal is to understand the functional genomics of these polymorphisms. We will use a PON1 mouse model to examine the effects of acute exposure to organophosphorus (OP) compounds. The mouse model includes PON1 knockout mice as well as knockout mice expressing one or more copies of each human PON1-Q192R allele. This model system will allow us to test the hypothesis that a polymorphic PON1-Q192R allele expressed at a given level will provide a specific degree of resistance to the toxicity of environmental agents hydrolyzed directly by PON1 or metabolized through the cytochrome P450 /PON1 pathway. The model will also allow us to investigate the effects of PON1 polymorphisms in modulating the effects of low level OP exposure on gene expression in the brain, an area of research that has not been previously approachable. We propose to investigate five facets of PON1 genetic variability that will provide information on the functional genomics of the polymorphisms of the human PON1 gene. Specific aim 1 examines the toxicological effects of acute exposures of diazoxon (DZO), chlorpyrifos oxon (CPO) and chlorpyrifos (CPS) on mice whose PON1 genes have been replaced with one or two copies of human PON1 Q192 or R192.Specific aim 2 examines the modulating effects of the PON192 variants on the toxicogenomic expression profile of genes in the affected subregions/cells of brains of PON1-192 transgenic mice exposed to CPO and DZO. Specific aim 3 is aimed at identifying new protein targets modified by exposure to CPO. Specific aim 4 involves determination of the crystal structure of human PON1 and characterization of recombinant PON1 variants with increased efficiency of OP hydrolysis. Specific aim 5 involves development of a human pharmacokinetic/pharmacodynamic (PDPK/PD) model of organophosphate exposure using humanized transgenic PON1 knockout mice expressing varying levels of each human PON1-192 isoform.