Investigating the molecular mechanisms in controlling the aryl hydrocarbon recept

描述(申请人提供)：芳烃受体(AhR)是一种配体激活的碱性-螺旋-环-螺旋-PAS转录因子。这种受体负责我们身体对环境污染物如多环芳烃、多氯联苯和二恶英的反应。2，3，7，8-四氯二苯并对二恶英(TCDD)是研究最多、最著名的AhR配体之一。AhR在人类肿瘤和T细胞分化过程中表达上调。影响AhR基因表达的事件的故障无疑会在癌症、异常免疫反应、干细胞发育以及我们对有毒环境化学物质的反应方面造成问题。然而，我们对AhR蛋白水平在缺乏配体的情况下是如何维持的了解非常有限。最近，我们建立了p23敲除稳定细胞，并发现在缺乏配体的情况下，人肝癌(Hep3B)和宫颈(HeLa)细胞中p23水平的下调通过减少AhR蛋白的降解来抑制AhR蛋白的水平。在这项拨款计划中，我们将利用这些稳定的细胞来研究在缺乏配体的情况下调节人类AhR蛋白水平的分子机制。具体地说，我们将进行以下实验：(1)研究未连接的AhR复合体的构象是否控制AhR蛋白的稳定性(目标1)和(2)研究p23是否以及如何在AhR复合体水平局部作用来控制AhR蛋白的稳定性(目标2)和(3)研究非蛋白酶体降解机制的参与，并确定和表征负责控制人类AhR蛋白降解的新的蛋白质靶点(S)(目标3)。

DESCRIPTION (provided by applicant): The aryl hydrocarbon receptor (AhR) is a ligand-activated basic-helix-loop-helix-PAS transcription factor. This receptor is responsible for our bodily response to exposure of environmental pollutants such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and dioxins. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is one of the most studied and best known ligand of AhR. Expression of AhR is up-regulated in human cancers and during T cell differentiation. Malfunction of the events affecting the AhR gene expression would undoubtedly cause problems in cancer, aberrant immune response, stem cell development, and our response to toxic environmental chemicals. However, our knowledge of how the AhR protein levels are maintained in the absence of ligand is very limited. Recently, we generated p23-knockdown stable cells and discovered that compromised p23 levels in human hepatoma (Hep3B) and cervical (HeLa) cells suppress the AhR protein levels by reducing its protein degradation in the absence of ligand. In this grant proposal, we wil ultilize these stable cells to investigate the molecular mechanisms that regulate the human AhR protein levels in the absence of ligand. Specifically, we will perform the following experiments: (1) investigate whether conformation of the unliganded AhR complex governs the AhR protein stability (Aim 1) and (2) investigate whether and how p23 acts locally at the AhR complex level to control AhR protein stability (Aim 2) and (3) investigate the involvement of non-proteasomal degradation mechanisms and identify and characterize new protein target(s) which are responsible for controlling the human AhR protein degradation (Aim 3).