Survival Mechanisms for Apoptotic Caspase

描述（由申请人提供）：自从近20年前发现半胱天冬酶以来，已有关于凋亡半胱天冬酶非凋亡作用的报道。也许最清晰的范例是caspase-8 (casp8)，尽管它对触发外源性凋亡通路至关重要，但在发育过程中某些细胞群的存活也是必需的。例如，小鼠的缺失研究表明，casp8及其适配器FADD和调节因子FLIPL可能驱动淋巴细胞、心肌细胞和一些上皮细胞类型的克隆扩增/增殖或凋亡。这一提议旨在为生存与死亡之间的选择提供生化证据，同时也有可能揭示生存途径的下游目标。因此，我们提供了概念验证工具和知识，可以导致化合物的开发，以治疗性地干扰增殖疾病（如癌症）的生存/死亡轴。“进入增殖程序的细胞的存活取决于casp8活性，这在很大程度上取决于casp8酶的构象和有限数量的下游靶标的切割”这一首要假设将在本研究中被剖析。我们提出三个相互关联的目标来检验这一假设

DESCRIPTION (provided by applicant): Ever since the discovery of the caspases almost 20 years ago there have been reports of non-apoptotic roles for apoptotic caspases. Perhaps the clearest paradigm is caspase-8 (casp8), which although essential for triggering the extrinsic apoptotic pathway, is also required for the survival of certain cell populations during development. For example, deletion studies in mice reveal that casp8, its adapter FADD, and its regulator FLIPL may drive either clonal expansion/proliferation or apoptosis of lymphocytes, cardiomyocytes, and some epithelial cell types. This proposal seeks to provide biochemical evidence for the choice between survival and death, while also having the potential to reveal downstream targets of the survival pathway. Thus we provide proof-of-concept tools and knowledge that can lead to the development of compounds to interfere therapeutically in the survival/death axis of proliferative diseases such as cancer. The overarching hypothesis "The survival of cells entering the proliferation program that depends on casp8 activity relies criticaly on the conformation of the casp8 enzyme and cleavage of a limited number of downstream targets" will be dissected in this study. We propose three interlinked aims to test this hypothesis by defining the biochemical nature of the casp8 enzyme that drives the survival events, defining the targets of this enzyme, and understanding how casp8 promotes survival, and not apoptosis, in specific experimental cellular contexts. Each aim can be accomplished independently, and the outcome of each aim will substantially further knowledge of the mechanisms of cell survival mediated by casp8. However, the full power of this project is realized when the data from Aim 1 (fundamental mechanisms of casp8 specificity) is coupled to Aim 2 (endogenous pro-survival casp8 targets), and the outcomes of Aims 1 and 2 used to inform the appropriate experimental paradigms for defining the cell's decision between survival and apoptosis (Aim 3). This proposal is significant because it seeks to reveal the molecular mechanism used by casp8 to delineate survival from death, and a successful outcome may impact directly on the selection of protein and small molecule pharmacologic tools that are under clinical development as cancer therapeutics. PUBLIC HEALTH RELEVANCE: A balance of cell survival and cell death is required to maintain the proliferative pathways in normal cells during development and during education of the immune system. This balance is disrupted in tumor cells, leading towards cancer growth. This proposal takes state-of-the-art biochemical approaches to dissect the intersection of cell survival and apoptosis, and thus gain understanding of how to therapeutically intervene to favor one fate over another.