Coordination of Apoptosis and Cell Proliferation in Drosophila

描述（由申请人提供）：我们的长期目标是了解细胞凋亡和细胞增殖在动物发育过程中是如何协调的。增殖细胞容易发生损伤引起的凋亡，而有丝分裂后细胞获得对许多凋亡刺激的抗性。抗凋亡对于防止不可替代的重要有丝分裂后细胞的损失是重要的。相反，增殖组织中的易化细胞死亡被认为是科普细胞损伤的有效方式，因为细胞损失可以通过补偿性增殖来替代。因此，细胞增殖和细胞凋亡的协调对于维持动物健康是必不可少的，并且不能协调这些过程导致由过度细胞增殖引起的疾病，如癌症，或过度细胞凋亡，如在神经退行性疾病中所见。在这项提案中，我们将测试的假设，即Apoptosome，一个全酶复合物，由引发剂caspase Drone和衔接蛋白Apafl，作为一个关键的协调员凋亡和细胞增殖。为了测试这一点，我们将利用简单的果蝇细胞死亡范例，其中Diapl（果蝇凋亡蛋白1抑制剂）直接抑制活细胞中的凋亡体，并且Diapl拮抗剂Reaper、Hid和Grim的表达先于凋亡以减轻对凋亡体的这种抑制。一旦凋亡小体激活效应器半胱天冬酶，细胞就完全致力于细胞死亡。我们将追求三个具体目标。首先，我们将研究Diapl如何抑制Apoptosome。特别地，我们将测试Diapl直接泛素化Apafl以在活细胞中降解的假设，而Diapl在注定死亡的细胞中的失活允许稳定的凋亡体形成。其次，我们将研究凋亡细胞触发增殖组织代偿性增殖的机制。具体来说，我们将集中在有丝分裂的信号通路的机制启动的活性Apoptosomes，并确定这是否是补偿性增殖的基础。最后，我们将研究有丝分裂后细胞获得抗凋亡的机制。在这里，我们将测试的假设，即细胞周期退出增强凋亡体不稳定性通过泛素介导的蛋白质降解。我们在果蝇组织中的遗传方法将与生化测定相补充，以进行进一步的机制研究。这项研究的进展可能有助于制定对抗癌症和神经退行性疾病的新策略。

DESCRIPTION (provided by applicant): Our long-term goal is to understand how apoptosis and cell proliferation are coordinated during animal development. Proliferating cells readily undergo injury-provoked apoptosis, while postmitotic cells acquire resistance to many apoptotic stimuli. Resistance to apoptosis is important to prevent the loss of vital postmitotic cells that cannot be replaced. Conversely, facilitated cell death in proliferating tissues is thought to be an effective way to cope with cellular injury, as cell loss can be replaced through compensatory proliferation. Accordingly, coordination of cell proliferation and apoptosis is essential for maintaining animal health, and inability to coordinate these processes leads to diseases caused by excess cell proliferation as in cancer, or excess apoptosis as seen in neurodegenerative disorders. In this proposal, we will test the hypothesis that the Apoptosome, a holoenzyme complex that consists of the initiator caspase Drone and the adaptor protein Apafl, serve as a critical coordinator of apoptosis and cell proliferation. To test this, we will exploit the simple Drosophila cell death paradigm, in which Diapl (Drosophila Inhibitor of Apoptosis Protein 1) directly inhibits the Apoptosome in living cells, and the expression of Diapl antagonists Reaper, Hid and Grim precedes apoptosis to relieve this inhibition of the Apoptosome. Once Apoptosomes activate effector caspases, cells become fully committed to cell death. We will pursue three specific aims. First, we will investigate how Diapl inhibits the Apoptosome. In particular, we will test the hypothesis that Diapl directly ubiquitylates Apafl for degradation in living cells, while inactivation of Diapl in cells destined to die allow stable Apoptosome formation. Second, we will investigate the mechanism by which apoptotic cells trigger compensatory proliferation in proliferating tissues. Specifically, we will focus on the mechanism of a mitogenic signaling pathway initiated by active Apoptosomes and determine whether this underlies compensatory proliferation. Finally, we will investigate the mechanism by which postmitotic cells acquire resistance to apoptosis. Here, we will test the hypothesis that cell cycle exit enhances Apoptosome instability through ubiquitin-mediated protein degradation. Our genetic approaches in Drosophila tissues will be complemented with biochemical assays for further mechanistic studies. Progress from this research may help devise new strategies against cancer and neurodegenerative disorders.