Role of Myc in the Growth Regulation Pathways

描述（由申请人提供）：多功能过程，包括内分泌调节和生长因子和营养素的产生，控制生长、大小和器官形成。IGFs/DILPs（果蝇胰岛素样肽）和TOR（雷帕霉素靶蛋白）信号通路是这些过程的重要调节因子，Myc转录因子也是如此。本申请旨在理解响应DILP和TOR/营养信号调节dMyc表达的分子机制，并鉴定通过dMyc在体内控制生长的关键事件。在我们的实验室中，我们已经确定了dMyc，果蝇同源的人myc原癌基因，作为下游效应器在响应DILPs和TOR活性，这表明dMyc可能作为传感器在这些信号通路的增长。此外，dMyc在特定代谢组织中的体内表达增加了生物体大小。这最后一组信息提供了一个重要的指示，即dMyc可能不仅能够通过诱导其表达的细胞中的核糖体生物合成（质量）来自主调节生长，而且它还可以刺激控制生物体生长的“因子”的产生，其机制是非细胞自主的。第一个目的是研究DIPLs和TOR通路的激活如何调节dMyc表达。我们将使用果蝇S2细胞或在幼虫成虫盘中的有丝分裂克隆中的体内生物化学实验的组合来评估胰岛素/DILP或TOR信号传导的氨基酸或组分对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调节，我们的第二个目的是研究通过磷酸化调节dMyc蛋白稳定性的事件。我们已经确定了dMyc蛋白中对其稳定性重要的新的磷酸化结构域。我们将通过以下方式进一步表征这些突变体：a）通过特异性激酶对其磷酸化机制的体外分析; B）通过DILP、TOR信号传导对其调节的体内表征。这些实验预期也为c-Myc定义新的功能结构域。我们的第三个具体目标是通过以下方式鉴定dMyc对生物体生长的贡献：a）鉴定响应于dMyc的自主和非细胞自主效应而被激活的下游信号; B）鉴定在这些代谢组织中被dMyc激活的靶标。总之，所获得的信息不仅有助于理解Myc在生理生长中的作用，而且有助于理解Myc在脊椎动物代谢疾病和癌症等病理性疾病中的作用，并从长远来看为治疗干预提供有用的新靶点。 公共卫生相关性：胰岛素和生长因子生产中的遗传或病理条件可能导致代谢紊乱，如糖尿病，生长障碍或癌症。在我们的实验室中，我们使用果蝇作为动物模型来研究调节这些疾病的过程。果蝇已成为研究人类疾病的流行模式生物，因为发现这些人类疾病基因的60%在果蝇中具有同源物。我们最近证明，胰岛素途径的激活诱导了一个名为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基因也是人类病理状态的原因，因为它的过度表达是人类癌症的主要原因之一。使用果蝇作为模型系统来研究Myc及其通过胰岛素和生长因子的调节的可能性，提供了一个很好的替代小鼠遗传学来了解其功能。通过我们的研究，我们希望确定控制果蝇生长的机制，以便更好地了解人类的代谢和癌症。

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.