Role of Myc in the Growth Regulation Pathways

描述(申请人提供)：控制生长、大小和器官形成的多功能过程，包括内分泌调节和生长因子和营养物质的产生。IGFS/DILPs(果蝇胰岛素样多肽)和TOR(雷帕霉素靶标)信号通路是这些过程的重要调节因子，也是Myc转录因子。这一应用旨在了解DILPs和TOR/养分信号调节dMyc表达的分子机制，并确定体内控制dMyc生长的关键事件。在我们的实验室中，我们已经发现dMyc，人类myc原癌基因的同源物，作为DILPs和TOR活性的下游效应因子，表明dMyc可能在这些信号通路中作为生长的传感器。此外，dMyc在体内特定代谢组织中的表达增加了组织的大小。这最后一组信息提供了一个重要的迹象，表明dMyc不仅能够通过在表达dMyc的细胞中诱导核糖体生物合成(MASS)来自主调节生长，而且还可能刺激控制有机体生长的“因子”的产生，其机制不是细胞自主的。第一个目的是研究DIPLs和TOR通路的激活如何调节dMyc的表达。我们将结合使用果蝇S2细胞或体内有丝分裂克隆的幼虫成像盘的生化实验来评估氨基酸或胰岛素/DILPs或TOR信号的组成部分对dMyc蛋白和RNA表达的相对贡献。由于IGFS/DILPs和TOR信号通路受磷酸化事件的调节，我们的第二个目标是研究通过磷酸化来调节dMyc蛋白稳定性的事件。我们已经在dMyc蛋白中发现了对其稳定性很重要的新的磷酸化结构域。我们将通过以下方式进一步确定这些突变体的特征：a)体外分析它们被特定激酶磷酸化的机制；b)在体内表征它们通过DILPs、TOR信号的调节。这些实验有望为c-Myc定义新的功能域。我们的第三个具体目标是通过以下方式识别dMyc对生物生长的贡献：a)识别响应dMyc自主和非细胞自主效应而激活的下游信号；b)识别dMyc在这些代谢组织中激活的靶点。总之，获得的信息不仅有助于理解Myc‘S在生理生长中的作用，也有助于理解脊椎动物的代谢性疾病和癌症等病理疾病，并从长远来看为治疗干预提供有用的新靶点。 与公共卫生相关：产生胰岛素和生长因子的遗传或病理条件可能会导致代谢紊乱，如糖尿病、生长紊乱或癌症。在我们的实验室里，我们正在使用果蝇作为动物模型来研究调节这些疾病的过程。自从发现60%的人类疾病基因在果蝇中有同源基因以来，果蝇已经成为研究人类疾病的流行模式生物。我们最近证实，胰岛素途径的激活诱导了一种名为Myc的基因的表达。MYC在人类细胞中非常重要，因为它是我们细胞生长和增殖所必需的基因之一。Myc基因也与人类的病理状况有关，因为它的过度表达是人类癌症的主要原因之一。利用果蝇作为模型系统来研究Myc及其受胰岛素和生长因子的调节的可能性，为了解其功能提供了一个很好的替代小鼠遗传学的方法。通过我们的研究，我们希望找出控制果蝇生长的机制，以便更好地了解人类的新陈代谢和癌症。

DESCRIPTION (provided by applicant): Multifunctional processes that include endocrine regulation and production of growth factors and nutrients control growth, size and organ formation. IGFs/DILPs (Drosophila Insulin-like Peptides) and TOR (Target of Rapamycin) signaling pathways are important regulators of these processes as well as the Myc transcription factor. This application is directed towards understanding the molecular mechanisms that regulate dMyc expression in response to DILPs and TOR/Nutrient signaling and to identify the key events that control growth by dMyc in vivo. In our laboratory we have identified dMyc, the Drosophila homologue of the human myc proto-oncogene, as a down-stream effector in response to DILPs and TOR activity suggesting that dMyc may function as a sensor for growth in these signaling pathways. In addition, expression of dMyc in vivo, in specific metabolic tissues, increases organismal size. This last set of information provides a significant indication that dMyc may be able to regulate growth not only autonomously by inducing ribosomal biogenesis (mass) in the cells where it is expressed, but also that it may stimulate the production of "factors" that control growth of the organism, with a mechanism that is non cell-autonomous. The first aim is focused on studying how the activation of the DIPLs and TOR pathways regulates dMyc expression. We will use a combination of biochemical experiments using Drosophila S2 cells or in vivo in mitotic clones in larval imaginal discs to assess the relative contribution of amino acids or components of the insulin/DILPs or TOR signaling to dMyc protein and RNA expression. As IGFs/DILPs and TOR signaling pathways are regulated by phosphorylation events, our second aim is to study the events that regulate dMyc protein stability by its phosphorylation. We have identified, novel phosphorylation domains in dMyc protein important for its stability. We will characterize further these mutants by; a) in vitro analysis of their mechanism of phosphorylation by specific kinases; b) in vivo characterization of their regulation by DILPs, TOR signaling. These experiments are expected to define new functional domains for also for c-Myc. Our third specific aim is directed to identify the contribution of dMyc to organismal growth by; a) identification of the downstream signals which are activated in response to the autonomous and non-cell autonomous effects of dMyc; b) to identify the targets that are activated by dMyc in these metabolic tissues. In conclusion, the information obtained should greatly help in understanding not only Myc' s role in physiological growth, but also in pathological disorders such as metabolic diseases and cancer in vertebrates and in the long run provide useful new targets for therapeutic intervention. Public Health Relevance: Genetic or pathological conditions in the production of insulin and Growth Factors may cause metabolic disorders, such as diabetes, growth disorders or cancer. In our laboratory we are using the fruitfly Drosophila melanogaster as an animal model to study the processes that regulate these diseases. Drosophila has become a popular model organism for studying human disease since the discovery that 60% of these human disease genes have homologues in the fruitfly. We recently demonstrated that activation of the insulin pathway induces the expression of a gene named Myc. Myc is very important in human cells as it is one of the genes necessary for our cells to grow and proliferate. The Myc gene is also responsible for human pathological condition as its over-expression is one the major causes of human cancer. The possibility to use Drosophila as a model system to study Myc and its regulation by insulin and Growth Factors, offers an excellent alternative to mouse genetic to understand its function. With our research we expect to identify the mechanism that control growth in Drosophila in order to better understand metabolism and cancer in humans.