Biochemical analysis of the human vs. mouse Ah receptor

描述（由申请方提供）：在啮齿动物模型中，Ah受体（AhR）已被证明是2，3，7，8-四氯-对-二恶英（TCDD）致癌和毒性的原因。人类暴露于低剂量的TCDD和其他一些AhR配体，暴露的实际健康影响仍有待确定。无论小鼠模型中产生的数据是否可以有效地外推到人类，都需要更好地了解物种之间的潜在遗传差异。要测试的中心假设是，人类AhR是从小鼠AhR的生化不同，这些差异导致改变AhR介导的活动。拟议研究的另一个目标是更好地了解AhR的多种调节机制。我们实验室的初步发现支持了中心假设。在本申请中，将表征人AhR的生物化学和转录活性并与小鼠AhR进行比较。提出了三个具体目标; 1）确定核心未配体受体复合物中人与小鼠Ah受体的生物化学行为，并检查XAP 2改变人与小鼠AhR活性的能力，2）通过使用嵌合受体检查人AhR与小鼠AhR相比的反式激活潜力、共激活因子募集特异性和核质穿梭性质，和3）比较配体化的人AhR与小鼠AhR改变AhR-无效tsSV-40转化的小鼠肝细胞系中基因表达的能力。在这些目标中，将在相同的细胞系中研究小鼠AhR和人AhR，以允许直接确定与先前研究中存在的细胞环境变化无关的种属差异。总的来说，这些研究将建立人类与小鼠AhR功能的差异水平，并应允许更好地评估人类暴露于TCDD的意义。

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.