Regulation and Function of Drosophila Nuclear Receptors

描述（由申请人提供）：果蝇拥有18个核受体（NR）基因，明显少于人类的48个基因，跨越所有脊椎动物NR亚类，编码人类关键受体的同源物，包括RXR（果蝇中的USP）， NGFI-B/NURR (DHR38), ERR (dERR), SXR （DHR96）和HNF4 （dHNF4）。果蝇NR的这些特征，结合广泛收集的遗传和基因组工具，使果蝇成为研究NR调控和功能分子机制的理想模型系统。在本研究中，我们重点研究了两种主要的nr调控的生物学途径：类固醇触发的成熟和脂质代谢。像脊椎动物一样，果蝇的成熟是由类固醇激素及其受体触发的，通过复杂的转录级联反应，在果蝇中被识别和表征。相比之下，迄今为止还没有研究涉及果蝇NRs在脂质代谢中的作用。我们将研究发生在最后幼虫阶段的一个鲜为人知的转变的类固醇调节，当动物承诺结束其幼年生长阶段并通过变态开始成熟时。我们将确定由α -蜕皮激素（E，果蝇的主要分泌类固醇，活性激素20-羟基蜕皮激素或20E的前体）调节的基因，并询问这些作用是否通过DHR38 E受体及其RXR伙伴USP。我们将确定DHR38和EcR是否作为部分冗余类固醇受体启动成熟。我们将确定dERR是否受20E的转录控制，研究其在启动变态中的可能作用，并确定其是否控制脂质或固醇代谢。我们将继续观察DHR96与胆固醇共纯化，DHR96零突变体需要胆固醇才能在最小培养基上存活。最后，我们将描述dHNF4的表达和功能，以确定其在脂质代谢和发育中的作用。代谢谱分析和微阵列将用于更全面地了解dERR、DHR96和dHNF4功能的分子机制。选定的基因将被定义为直接调控目标。这些研究将扩大我们对NR信号通路的理解，对人类同源NR功能的直接影响，以及它们对与NR功能障碍相关的关键人类疾病的贡献，包括心血管疾病、糖尿病和肥胖。

DESCRIPTION (provided by applicant): The fruit fly Drosophila melanogaster has 18 nuclear receptor (NR) genes, significantly fewer than the 48 genes found in humans, spanning all vertebrate NR subclasses and encoding orthologs of key human receptors, including RXR (USP in flies), NGFI-B/NURR (DHR38), ERR (dERR), SXR (DHR96), and HNF4 (dHNF4). These characteristics of Drosophila NRs, combined with an extensive collection of genetic and genomic tools, establish the fly as an ideal model system for studying the molecular mechanisms of NR regulation and function. In this proposal, we focus on 2 major NR-regulated biological pathways: steroid-triggered maturation and lipid metabolism. Like vertebrates, Drosophila maturation is triggered by steroid hormones and their receptors, via complex transcriptional cascades that were identified and characterized in the fly. In contrast, no studies to date have addressed roles for Drosophila NRs in lipid metabolism. We will study the steroid regulation of a poorly understood transition that occurs during the last larval stage, when the animal commits to terminating its juvenile growth phase and initiating maturation via metamorphosis. We will identify genes regulated by alpha-ecdysone (E, the primary secreted steroid in Drosophila and the precursor to the active hormone 20-hydroxyecdysone, or 20E) and ask if these effects go through the DHR38 E receptor and its RXR partner, USP. We will determine if DHR38 and EcR function as partially redundant steroid receptors to initiate maturation. We will determine if dERR is transcriptionally controlled by 20E, examine its possible roles in initiating metamorphosis, and determine whether it controls lipid or sterol metabolism. We will follow up on the observation that DHR96 co-purifies with cholesterol and that DHR96 null mutants require cholesterol for their survival on minimal medium. Finally, we will characterize the expression and function of dHNF4 to define its roles in lipid metabolism and development. Metabolic profiling and microarrays will be used to gain a more complete understanding of the molecular mechanisms of dERR, DHR96, and dHNF4 function. Selected genes will be defined as direct regulatory targets. These studies will expand our understanding of NR signaling pathways with direct implications for how the orthologous NRs function in humans, as well as their contributions to critical human diseases associated with NR dysfunction, including cardiovascular disease, diabetes, and obesity.