Regulation and Function of Drosophila Nuclear Receptors

描述(申请人提供)：果蝇有18个核受体(NR)基因，明显少于人类发现的48个基因，跨越所有脊椎动物NR亚类，编码关键人类受体的同源基因，包括RXR(果蝇中的USP)、NGFI-B/NurR(DHR38)、ErR(DERR)、SXR(DHR96)和HNF4(DHNF4)。果蝇NRS的这些特点，结合大量的遗传和基因组工具，建立了果蝇作为研究NR调节和功能的分子机制的理想模型系统。在这个提案中，我们关注两个主要的NR调节的生物途径：类固醇触发的成熟和脂类代谢。像脊椎动物一样，果蝇的成熟是由类固醇激素及其受体通过在果蝇中识别和表征的复杂转录级联来触发的。相比之下，到目前为止还没有研究表明果蝇NRs在脂类代谢中的作用。我们将研究类固醇对发生在最后幼虫阶段的一个鲜为人知的转变的调节，当时动物致力于终止其幼体生长阶段，并通过变态启动成熟。我们将确定由α-蜕皮激素(E，果蝇主要分泌的类固醇，活性激素20-羟基蜕皮激素的前体，或20E)调控的基因，并询问这些影响是否通过DHR38E受体及其RXR伙伴USP。我们将确定DHR38和ECR是否作为启动成熟的部分多余的类固醇受体发挥作用。我们将确定DERR是否受20E的转录控制，研究它在启动变态过程中的可能作用，并确定它是否控制脂肪或类固醇代谢。我们将跟踪观察到的DHR96与胆固醇共纯化，以及DHR96缺失突变株需要胆固醇才能在最低限度的培养液中生存。最后，我们将对dHNF4的表达和功能进行鉴定，以确定其在脂质代谢和发育中的作用。将使用代谢图谱和微阵列来更全面地了解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，直接影响NRs在人类中的功能，以及它们在与NR功能障碍相关的关键人类疾病中的作用，包括心血管疾病、糖尿病和肥胖症。

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.