Death and Destruction: How the Ubiquitin Proteasome System Executes Linker Cell-type Death

项目摘要 拟议研究的长期目标是了解细胞生物学机制， 执行非凋亡性细胞死亡。程序性细胞死亡对生物体发育至关重要， 体内平衡，其破坏与许多人类疾病相关，包括癌症和 神经变性细胞凋亡是一种主要的细胞死亡形式，然而，仅在关键的细胞凋亡调节因子中发生突变， 会导致轻微的发育缺陷因此，也存在非凋亡程序，但它们的分子基础是 不太了解。Linker细胞型死亡（LCD）是一种非凋亡和非半胱天冬酶依赖的细胞死亡过程 在C.在脊椎动物中也观察到了线虫的发育及其形态学特征 发展和疾病。泛素蛋白酶体系统（UPS）是C.优雅，但 它是如何导致细胞死亡的尚不清楚。在这里，我将使用强大的遗传和分子工具在C。elegans 以鉴定和表征LCD期间UPS的蛋白水解靶点，并确定它们如何 降解触发细胞死亡。与细胞凋亡相反，细胞凋亡使用半胱天冬酶瞬时结合它们的受体。 尽管UPS与底物的相互作用非常小，并且值得注意的是，UPS仍然知之甚少，但UPS稳定地与其底物相互作用。因此，我们认为， 我发现的导致细胞死亡的蛋白质可能揭示了细胞破坏的一般机制， 也在细胞凋亡和疾病中起作用。事实上，我们的初步数据表明，一种候选底物 UPS降解的是一种维持异染色质所需的酶，这与我们的研究结果一致。 先前的观察表明，垂死的连接细胞表现出开放的染色质状态。因此，这项建议将 研究令人兴奋的假设，即由UPS引起的染色质重塑， 杀伤性我还将发现其他蛋白水解靶点和机制，执行非凋亡细胞 用酵母双杂交和RNAi筛选死亡。因为UPS和染色质状态的失调也是 与肿瘤发生和神经退行性疾病有关，我的研究可以提供对细胞 疾病中的死亡程序中断，可以指向新的治疗目标。

Project Summary The long-term goal of the proposed research is to understand the cell biological mechanisms that execute non-apoptotic cell death. Programmed cell death is essential for organismal development and homeostasis, and its disruption is associated with many human diseases including cancer and neurodegeneration. Apoptosis is a prominent cell death form, however mutations in key apoptotic regulators only cause minor developmental defects. Non-apoptotic programs, therefore, also exist, but their molecular basis is poorly understood. Linker Cell-type Death (LCD) is a non-apoptotic and caspase-independent cell death process operating in C. elegans development, and its morphological hallmarks have also been observed in vertebrate development and disease. The Ubiquitin Proteasome System (UPS) is a key effector of LCD in C. elegans, but how it executes cell death is unknown. Here I will use powerful genetic and molecular tools in C. elegans to identify and characterize the proteolytic targets of the UPS during LCD and determine how their degradation trigger cell demise. In contrast to apoptosis, which uses caspases that transiently bind their substrates and, remarkably, remain poorly understood, the UPS stably interacts with its substrates. Therefore, the proteins I discover that precipitate cell death may unearth general mechanisms of cellular destruction that also function during apoptosis and disease. Indeed, our preliminary data suggest that one candidate substrate degraded by the UPS is an enzyme required for the maintenance of heterochromatin, which is in line with our previous observations that dying linker cells exhibit an open chromatin state. Therefore, this proposal will investigate the exciting hypothesis that chromatin remodeling, precipitated by the UPS, triggers cellular destruction. I will also discover additional proteolytic targets and mechanisms that execute non-apoptotic cell death with yeast 2-hybrid and RNAi screens. Because dysregulation of the UPS and chromatin state are also linked to tumorigenesis and neurodegenerative diseases, my studies can provide greater understanding of cell death programs disrupted in disease that can point towards new therapeutic targets.