Biochemical analysis of the human vs. mouse Ah receptor

描述（由申请人提供）：在啮齿动物模型中，Ah受体（AhR）已被证明与2,3,7,8-四氯对二恶英（TCDD）的致癌和毒性有关。虽然人类暴露于低剂量的TCDD和其他一些AhR配体，但暴露对健康的实际影响仍有待确定。无论在小鼠模型中产生的数据能否有效地外推到人类身上，都需要更好地了解物种之间潜在的遗传差异。待验证的中心假设是，人类AhR与小鼠AhR在生物化学上存在差异，这些差异导致AhR介导的活性发生改变。拟议研究的另一个目标是更好地理解AhR调节的多种机制。我们实验室的初步发现支持了中心假设。在这个应用中，人类AhR的生化和转录活性将被表征，并与小鼠AhR进行比较。提出了三个具体目标；1)确定核心无配体受体复合体中人和小鼠Ah受体的生化行为，并检测XAP2改变人和小鼠AhR活性的能力；2)通过使用嵌合受体比较人AhR与小鼠AhR的转激活电位、共激活剂募集特异性和核胞质穿梭特性。3)比较配体人AhR与小鼠AhR改变AhR缺失tsSV-40转化小鼠肝细胞系基因表达的能力。在这些目标中，小鼠AhR和人类AhR将在同一细胞系中进行研究，以允许直接确定独立于先前研究中存在的细胞环境变化的物种差异。总的来说，这些研究将确定人类与小鼠AhR功能的差异水平，并应允许更好地评估人类暴露于TCDD的重要性。

DESCRIPTION (provided by applicant): The Ah receptor (AhR) has been shown to be responsible for the carcinogenic and toxic properties of 2,3,7,8- tetrachloro-p-dioxin (TCDD) in rodent models. The human population is exposed to low doses of TCDD, and a number of other AhR ligands, the actual health effects of exposure remain to be established. Whether or not data generated in the mouse model can be effectively extrapolated to humans will require a better understanding of potential genetic differences between species. The central hypothesis to be tested is that the human AhR is biochemically different from the mouse AhR and these differences result in altered AhR-mediated activity. An additional goal of the proposed studies is to better understand the multiple mechanisms of regulation of the AhR. The central hypothesis is supported by preliminary findings from our laboratory. In this application the biochemical and transcriptional activity of the human AhR will be characterized and compared with the mouse AhR(s). Three specific aims are proposed; l) Determine the biochemical behavior of the human vs. mouse Ah receptor in the core unliganded receptor complex, and examine the ability of XAP2 to alter the activity of the human vs. mouse AhR, 2) Examine the transactivation potential, co-activator recruitment specificity and nucleocytoplasmic shuttling properties of the human AhR compared with the mouse AhR through the use of chimeric receptors, and 3) Compare the ability of the liganded human AhR vs. the mouse AhR to alter gene expression in AhR-null tsSV-40 transformed mouse hepatocyte cell lines. In these aims the mouse AhR and human AhR will be studied in the same cell line to allow a direct determination of species differences independent of cell context variation present in previous studies. Collectively, these studies will establish the level of divergence in human vs. mouse AhR function and should allow a better assessment of the significance of human exposure to TCDD.