Establishing Apoptotic Thresholds: Insights from Neurons and Stem Cells to Cancer

 描述（由申请人提供）：尽管鉴定了哺乳动物细胞凋亡途径的主要组分，但各种原代细胞中细胞凋亡调节的差异仍然令人惊讶地未被探索。我们对细胞凋亡领域的独特持续贡献是定义不同细胞类型如何设置细胞凋亡阈值，以最佳地匹配其生理功能并适应不断变化的环境。事实上，我们相信，新的模式的细胞凋亡调控仍有待发现在生理上不同的细胞类型。我们的实验室已经发现，与有丝分裂细胞如成纤维细胞相比，凋亡途径在有丝分裂后细胞如神经元、心肌细胞和肌管中受到高度限制。虽然严格调节细胞凋亡对于有丝分裂后细胞的长期存活至关重要， 有丝分裂细胞需要保持其快速激活凋亡的能力，因为它们可能处于持续的癌变风险中。因此，细胞必须有效地平衡具有引发的凋亡途径的需要与与细胞死亡相关的风险。事实上，我们已经在胚胎干细胞（ES）中看到了最好的例子，这些细胞参与了既启动细胞凋亡途径以响应DNA损伤而快速死亡的机制，同时也参与了响应线粒体损伤的细胞存活机制。因此，ES细胞似乎具有灵敏的能力来响应特定的损伤刺激，其机制确保基因组完整性和最佳存活。 在这个MIRA提案中，我们希望使用有针对性的和广泛的综合方法来研究细胞凋亡调控的不同机制，并确定其在健康和疾病中的生理重要性。我们的重点是我们确定的细胞凋亡控制的两个极端：1）抵抗细胞凋亡和促进线粒体损伤后存活的机制（例如，我们发现E3连接酶PARC介导细胞溶质细胞色素c的降解），以及2）引发细胞快速凋亡的机制（例如，我们发现Bax在干细胞中保持活性状态）。我们将使用原代神经元和人类胚胎干细胞（hES），进行创新的筛选，并在癌症和神经退行性疾病模型中研究疾病的影响。特别是，我们感到兴奋的是，MIRA的机会将使我们的雄心勃勃的计划，使用hES细胞的强大能力，以确定如何凋亡机制经历动态变化与细胞分化。

 DESCRIPTION (provided by applicant): Despite the identification of the main components of the mammalian apoptotic pathway, the differences in the regulation of apoptosis in various primary cells remain surprisingly unexplored. Our unique ongoing contribution to the apoptosis field has been to define how different cell types set the apoptosis threshold to optimally matche their physiological functions and adapt to changing environments. Indeed, we believe that new paradigms of apoptosis regulation remain to be discovered in physiologically distinct cell types. Our lab has discovered that the apoptotic pathway is highly restricted in postmitotic cells such as neurons, cardiomyocytes, and myotubes, as compared to mitotic cells such as fibroblasts. While a strict regulation of apoptosis is critical for the long-term survival of postmitotic cells, mitotic cells need to maintain their ability to activate apoptosis rapidly as they can be at continual risk of becoming cancerous. Therefore, cells must efficiently balance the need for having a primed apoptotic pathway versus the risks associated with cell death. In fact, we have seen this best exemplified in embryonic stem (ES) cells which engage mechanisms that both prime the apoptotic pathway for rapid death in response to DNA damage, while also engaging cell survival mechanisms in response to mitochondrial damage. Thus, ES cells appear to have an exquisite capability to respond to the specific damage stimuli with mechanisms that ensure both genomic integrity and optimal survival. In this MIRA proposal, we wish to use both targeted and broad integrative approaches to examine the distinct mechanisms of apoptosis regulation and define their physiological importance in health and disease. Our focus is on the two extremes of the apoptosis control we identified: 1) Mechanisms that resistant apoptosis and promote survival after mitochondrial damage (e.g. our findings that the E3 ligase PARC mediates the degradation of cytosolic cytochrome c), and 2) Mechanisms that prime cells for rapid apoptosis (e.g. our discovery that Bax is maintained in an active state in stem cells). We will use primary neurons and human embryonic stem (hES) cells, conduct innovative screens and examine disease implications in models of cancer and neurodegeneration. In particular, we are excited that the MIRA opportunity would enable our ambitious plans to use the powerful capability of hES cells to define how the apoptotic machinery undergoes dynamic changes with cellular differentiation.