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

项目摘要 这项拟议研究的长期目标是了解 执行非凋亡性细胞死亡。程序性细胞死亡对生物体发育和 动态平衡，它的破坏与许多人类疾病有关，包括癌症和 神经退行性变。细胞凋亡是一种重要的细胞死亡形式，但仅在关键的凋亡调节因子中发生突变。 造成轻微的发育缺陷。因此，非凋亡程序也存在，但它们的分子基础是 人们对此知之甚少。连接型细胞死亡(Linker Cell-type Death，LCD)是一种非凋亡性、caspase非依赖性的细胞死亡过程 在线虫发育过程中运作，其形态特征也在脊椎动物中观察到 发展和疾病。泛素蛋白酶体系统(UPS)是线虫LCD的关键效应因子，但 它是如何执行细胞死亡的尚不清楚。在这里，我将使用强大的基因和分子工具来研究线虫 识别和表征LCD期间UPS的蛋白水解靶，并确定其 退化会引发细胞死亡。与细胞凋亡不同的是，细胞凋亡使用的半胱氨酸天冬氨酸酶能短暂地结合它们的细胞 值得注意的是，UPS与基材之间的相互作用仍然很少，但UPS与基材之间的相互作用非常稳定。因此， 我发现的导致细胞死亡的蛋白质可能揭示细胞破坏的一般机制 也在细胞凋亡和疾病中发挥作用。事实上，我们的初步数据表明，一种候选底物 被UPS降解的是维持异染色质所需的一种酶，这与我们的 先前的观察表明，死亡的连接细胞呈现开放的染色质状态。因此，这项提议将 研究一种令人兴奋的假设，即由UPS沉淀的染色质重塑触发细胞 毁灭。我还将发现更多的蛋白分解靶点和执行非凋亡细胞的机制 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的更多了解 在疾病中中断的死亡计划可能指向新的治疗目标。

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.