Regulation and Function of Drosophila Nuclear Receptors

描述(申请人提供)：代谢平衡在生活的方方面面都发挥着核心作用，使动物能够平衡饮食摄入量和日常生存所需的能量需求。相反，代谢调节不当会导致肥胖和2型糖尿病，这是人类疾病的关键风险因素，包括心血管疾病和癌症。我们的研究目标是使用果蝇作为一个简单的模式系统来定义控制包括人类在内的所有高等生物体新陈代谢的中央调控途径。我们研究的分子背景是核受体(NRs)-配体调节的转录因子，它们在感知小的亲脂信号和维持代谢平衡方面发挥核心作用。果蝇有18个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，编码关键人类受体的同源基因，包括HNF4(DHNF4)、LXR/FXR(DHR96)、LRH-1(DHR39)、NR4A受体(DHR38)和ERR(DERR)。我们最近对dHNF4、DHR96、DHR38和DERR的研究首次表明，这些NRs的基本调节和代谢功能在进化过程中是保守的。此外，我们使用遗传学来剖析果蝇NR信号通路，为了解它们的作用机制提供了新的见解，并为理解它们的哺乳动物同行提供了新的方向。在这一新的应用中，我们建议进一步描述果蝇NRS在代谢中的特征，重点放在脂类代谢途径上。我们将在我们对dHNF4和DHR96-NRs的初步研究的基础上，分别控制饥饿和进食状态。此外，我们将对果蝇LRH-1同源基因DHR39进行分析，目的是确定它如何与DHR96相互作用来控制甘油三酯和胆固醇的动态平衡。这个提议有三个特定的目的：(1)确定dHNF4在发育过程中的代谢功能，(2)确定DHR96协调脂代谢的机制，(3)表征NR调节相互作用在脂代谢中的作用。通过结合代谢物测量、代谢组谱、微阵列研究、组织特异性拯救、RNAi实验、选定目标基因的功能表征、转基因动物中的启动子研究、受体的配体调节和芯片序列实验，我们将在更复杂的生物中难以实现的详细水平上定义NR信号转导的机制。这些实验将为同源哺乳动物受体HNF4、LXR/FXR和LRH-1如何通过调节特定的下游转录程序而促进代谢动态平衡提供深入的见解。这些研究还对了解同源人类NRs如何导致与NR功能障碍相关的关键疾病，包括心血管疾病、糖尿病和肥胖症具有直接意义。

DESCRIPTION (provided by applicant): Metabolic homeostasis plays a central role in all aspects of life, allowing animals to balance their dietary intake with the energy needs required for day-to-day survival. Conversely, misregulation of metabolism can lead to obesity and type 2 diabetes, which are critical risk factors for human disease, including cardiovascular disorders and cancer. The goal of our research is to use the fruit fly, Drosophila melanogaster, as a simple model system to define the central regulatory pathways that control metabolism in all higher organisms, including humans. The molecular context for our studies is nuclear receptors (NRs) - ligand-regulated transcription factors that play a central role in sensing small lipophilic signals and maintaining metabolic homeostasis. Drosophila has 18 NR genes, significantly fewer than the 48 genes found in humans, spanning all vertebrate NR subclasses and encoding homologs of key human receptors, including HNF4 (dHNF4), LXR/FXR (DHR96), LRH-1 (DHR39), NR4A receptors (DHR38), and ERR (dERR). Our recent studies of dHNF4, DHR96, DHR38, and dERR, have shown, for the first time, that the basic regulation and metabolic functions of these NRs have been conserved through evolution. In addition, our use of genetics to dissect Drosophila NR signaling pathways has provided new insights into their mechanism of action and new directions for understanding their mammalian counterparts. In this renewal application, we propose further characterization of Drosophila NRs in metabolism, with a focus on lipid metabolic pathways. We will build off our initial studies of dHNF4 and DHR96 - NRs that control the starved and fed state, respectively. In addition, we will undertake an analysis of the Drosophila LRH-1 homolog, DHR39, with the goal of defining how it interacts with DHR96 to control triglyceride and cholesterol homeostasis. There are three specific aims to this proposal: (1) To define the metabolic functions of dHNF4 during development, (2) To define the mechanisms by which DHR96 coordinates lipid metabolism, and (3) To characterize the role of NR regulatory interactions in lipid metabolism. By combining metabolite measurements, metabolomic profiling, microarray studies, tissue- specific rescue, RNAi experiments, functional characterization of select target genes, promoter studies in transgenic animals, ligand regulation of the receptor, and ChIP-seq experiments, we will define the mechanisms of NR signaling at a level of detail that is difficult to achieve in more complex organisms. These experiments will provide insights into how the orthologous mammalian receptors, HNF4, LXR/FXR, and LRH-1 contribute to metabolic homeostasis through their regulation of specific downstream transcriptional programs. These studies also have direct implications for understanding how the orthologous human NRs contribute to critical diseases associated with NR dysfunction, including cardiovascular disease, diabetes, and obesity.