Regulation of UV-induced apoptosis

描述(申请人提供)：为了确保多细胞生物体的组织动态平衡，因环境伤害(如紫外线照射)而损坏的细胞必须修复或消除。细胞修复和细胞死亡之间的错误调节在视网膜退行性疾病中起着重要作用，如老年性黄斑变性，以及更广泛的癌症。对细胞损伤、防御和细胞死亡的调控的洞察将提高我们预防和/或治疗此类疾病的能力。 目前的模型表明，细胞存活信号和促凋亡刺激之间的平衡控制着细胞的修复和死亡的决定。这些相互竞争的信号如何被整合和解释，以实现对体内细胞命运的准确控制，目前还不完全清楚。需要使用遗传可及模型系统进行研究，以进一步深入了解这一监管系统。 申请人已经进行了初步研究，以分析视网膜中细胞生死决定的调节。这些研究表明，在发育中的果蝇视网膜中，Jun-N末端激酶信号通路下游需要Forkhead Box O转录因子FOXO和AP-1转录因子DFOS，以实现对紫外线诱导的DNA损伤的凋亡反应。重要的是，这些研究表明，紫外线诱导的细胞凋亡受到受体酪氨酸激酶通路发出的生存信号的抑制，受体酪氨酸激酶通路是已知的灭活FOXO的途径。这些数据表明，通过FOXO整合压力和生存信号推动了体内细胞死亡和受损细胞修复之间的决定。这一模型将通过实验解决以下特定目标进行测试：(I)分析紫外线诱导的视网膜转录反应的调节。利用表达谱方法，将分析视网膜中促凋亡和促生存基因表达程序的调节。(Ii)测试JNK信号的双相激活是否控制细胞对紫外线的反应。申请人提出，JNK对紫外线胁迫的反应经历了两个阶段：促进细胞恢复的初始阶段，以及当DNA损伤持续存在时，诱导促凋亡基因表达的第二阶段。基因实验将被用来检验这个模型。(3)使用遗传方法确定视网膜紫外线反应的调节器。果蝇系统的一个优势是能够使用遗传筛选来快速识别信号通路的新组成部分。在这里，这种方法将被用来识别新的基因，这些基因将允许解决关于控制细胞命运和信号特异性的特定问题。 这些实验有望极大地提高我们对完整组织中细胞生命/死亡决定的调控的理解，因此将对未来退行性疾病的合理治疗方法具有重要意义。

DESCRIPTION (provided by applicant): To ensure tissue homeostasis in multicellular organisms, cells damaged by environmental insults (such as UV irradiation) have to be either repaired or eliminated. Misregulation of the decision between cell repair and cell death plays an important role in degenerative diseases of the retina, such as age-related macular degeneration, as well as more generally in cancer. Insight into the regulation of cellular damage defense and cell death will increase our ability to prevent and/or treat such diseases. Current models suggest that the balance between cell survival signals and pro-apoptotic stimuli controls the decision between repair and death of a cell. How these competing signals are integrated and interpreted to achieve accurate control over cell fate in vivo is incompletely understood. Studies using genetically accessible model systems are required to gain further insight into this regulatory system. The applicant has performed preliminary studies to analyze the regulation of cellular life-death decisions in the retina. These studies show that the Forkhead Box O transcription factor Foxo as well as the AP-1 transcription factor DFos are required downstream of the Jun-N-terminal Kinase signaling pathway for the apoptotic response to UV-induced DNA damage in the developing Drosophila retina. Importantly, these studies show that UV-induced apoptosis is repressed by survival signals emanating from Receptor Tyrosine Kinase pathways, which are known to inactivate Foxo. These data suggest that integrating stress and survival signals through Foxo drives the decision between cell death and repair of damaged cells in vivo. This model will be tested by addressing the following specific aims experimentally: (i) Analyze the regulation of UV-induced transcriptional responses in the retina. Using expression profiling approaches, the regulation of pro-apoptotic and pro-survival gene expression programs will be analyzed in the retina. (ii) Test whether biphasic activation of JNK signaling governs the cellular response to UV. The applicant proposes that JNK activation in response to UV stress occurs in two phases: an initial phase that promotes cell recovery and, when DNA damage persists, a second phase that induces pro-apoptotic gene expression. Genetic experimentation will be used to test this model. (iii) Identify regulators of the retinal UV response using genetic approaches. One advantage of the Drosophila system is the ability to use genetic screens to rapidly identify new components of signaling pathways. Here, such approaches will be used to identify new genes that will allow addressing specific questions regarding the control of cell fate and signaling specificity. The experiments proposed here are expected to significantly advance our understanding of the regulation of cellular life/death decisions in intact tissues and will therefore be of relevance to future rational therapeutic approaches for degenerative diseases.