Regulation of Energy Balance in Drosophila

摘要 禁食会引发行为、身体活动和新陈代谢的协调变化， 在进化过程中保存得非常好在哺乳动物中，这种反应通常是 由转录辅激活因子协调，转录辅激活因子是环境线索调节的靶点。 CREB转录因子家族参与多种细胞功能，包括 能量平衡最近，一个新的关键CREB共活化剂家族，称为TORC，已经被发现。 鉴定在激活后，TORC蛋白易位到细胞核，在那里它们增强基因表达。 通过与CREB的直接相互作用激活。果蝇只有一个TORC家族成员， dTORC，其在禁食时被诱导，并且在进食时被磷酸化和降解， 胰岛素依赖的方式dTORC突变果蝇对饥饿敏感，并且具有显著的 与野生型相比，糖原和脂质储存更低。dTORC在大脑中发挥作用， 在神经内分泌细胞的一个子集中起作用，调节一种未识别的神经元的释放， 指示脂肪体（能量储存器官）储存糖原和脂质的信号。这 一项提案旨在利用果蝇来了解TORC蛋白如何调节能量 平衡使用dTORC突变体表型的拯救测定， 细胞培养试验中激活、核转位和与CREB结合所需的dTORC 将被突变并在体内进行功能测试。假设dTORC在细胞中起作用， 将通过提供dTORC来测试神经内分泌细胞产生信号到脂肪体 特别是在这些细胞中，并测定突变表型的拯救。体内核 dTORC在神经内分泌细胞内响应进食和禁食的穿梭， 考察从一个基因筛选，以确定新的组成部分的dTORC途径，4离散 已经发现基因组区域增强或抑制dTORC功能，因此被 含有编码dTORC新组分的基因的极好候选物 通路这些区域内的基因将使用单基因突变和RNA鉴定。 干扰筛选影响胰岛素依赖性dTORC磷酸化的基因， 将进行降解，以确定dTORC调节剂，从而了解如何 胰岛素信号传导调节dTORC活性。考虑到TORC蛋白结构的保守性， 果蝇和哺乳动物之间的功能，我们希望我们的结果提供关键的见解， 哺乳动物TORC蛋白对能量平衡的调节。

ABSTRACT Fasting triggers concerted changes in behavior, physical activity and metabolism that are remarkably well conserved through evolution. In mammals, such responses are often coordinated by transcriptional coactivators that are targets for regulation by environmental cues. The CREB family of transcription factors participates in a variety of cellular functions including energy homeostasis. Recently, a new family of key CREB coactivators, called TORCs, has been identified. Upon activation, TORC proteins translocate to the nucleus where they potentiate gene activation via a direct interaction with CREB. Drosophila has a single TORC family member, dTORC, which is induced upon fasting, and phosphorylated and degraded upon feeding in an insulin-dependent manner. dTORC mutant flies are sensitive to starvation and have significantly lower glycogen and lipid stores compared to wild type. dTORC functions in the brain, where it is active in a subset of neuroendocrine cells, to regulate the release of an unidentified neuronal signal that instructs the fat body, the energy storage organ, to store glycogen and lipids. This proposal aims to use Drosophila to understand how TORC proteins function to regulate energy balance. Using a rescuing assay of the dTORC mutant phenotype, the specific domains of dTORC required for activation, nuclear translocation and binding to CREB in cell culture assays will be mutated and tested for function in vivo. The hypothesis that dTORC functions in the neuroendocrine cells to produce the signal to the fat body will be tested by supplying dTORC specifically in these cells and assaying for rescue of the mutant phenotype. In vivo nuclear shuttling of dTORC within the neuroendocrine cells in response to feeding and fasting will be examined. From a genetic screen to identify new components of the dTORC pathway, 4 discrete genomic regions have been found to enhance or suppress dTORC function, and thus are excellent candidates for containing genes that encode novel components of the dTORC pathway. The genes within these regions will be identified using single-gene mutations and RNA interference. A screen for genes that affect insulin-dependent dTORC phosphorylation and degradation will be carried out to identify dTORC regulators, leading to an understanding of how insulin signaling regulates dTORC activity. Given the conservation of TORC protein structure and function between Drosophila and mammals, we expect our results to provide key insights into the regulation of energy balance by mammalian TORC proteins.