Coordination of Apoptosis and Cell Proliferation in Drosophila

描述（申请人提供）：我们的长期目标是了解在动物发育过程中细胞凋亡和细胞增殖是如何协调的。增殖细胞容易发生损伤引起的凋亡，而有丝分裂后细胞对许多凋亡刺激具有抗性。对细胞凋亡的抵抗对于防止有丝分裂后不能被替换的重要细胞的损失是重要的。相反，在增殖组织中促进细胞死亡被认为是应对细胞损伤的有效方法，因为细胞损失可以通过代偿性增殖来弥补。因此，细胞增殖和细胞凋亡的协调对维持动物健康至关重要，如果这些过程无法协调，就会导致细胞过度增殖（如癌症）或神经退行性疾病（如神经退行性疾病）引起的疾病。在本研究中，我们将验证一个假说，即凋亡蛋白是一种由启动物caspase Drone和接头蛋白Apafl组成的全酶复合物，在细胞凋亡和细胞增殖中起着关键的协调作用。为了验证这一点，我们将利用简单的果蝇细胞死亡模式，其中Diapl（果蝇凋亡抑制蛋白1）直接抑制活细胞中的凋亡，并且Diapl拮抗剂Reaper， Hid和Grim的表达先于凋亡来缓解这种对凋亡的抑制。一旦凋亡体激活效应半胱天冬酶，细胞就会完全死亡。我们将努力实现三个具体目标。首先，我们将研究Diapl如何抑制细胞凋亡。特别是，我们将验证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失活则允许稳定的凋亡体形成。其次，我们将研究凋亡细胞在增殖组织中触发代偿性增殖的机制。具体来说，我们将关注由活性凋亡体启动的有丝分裂信号通路的机制，并确定这是否构成代偿性增殖的基础。最后，我们将探讨有丝分裂后细胞获得细胞凋亡抗性的机制。在这里，我们将验证细胞周期退出通过泛素介导的蛋白质降解增强凋亡不稳定性的假设。我们在果蝇组织中的遗传方法将与生化分析相辅相成，以进一步进行机制研究。这项研究的进展可能有助于设计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.