Regulation of cytosolic pattern recognition receptor signaling in macrophages

描述(申请人提供)：入侵病原体被先天免疫系统的模式识别受体(PRR)识别为第一道防线。在巨噬细胞中，来自核苷酸结合和富含亮氨酸重复序列(NLR)蛋白家族的PRRs被激活，而在黑色素瘤2(AIM2)中缺失，导致炎症体的形成。炎性小体是激活炎性Caspase并随后成熟和释放促炎细胞因子IL-1所必需的蛋白质平台吗？和IL-18。炎性小体的组装依赖于吡咯结构域(PYD)介导的接头蛋白ASC与激活的PRRs的募集，然后募集到前Caspase-1。此外，Caspase-4、-5和-8也参与其中。然而，胞质PRRs激活炎性小体的分子机制，特别是调控和终止这一过程的分子机制还知之甚少。我们发现了一个仅由PYD组成的小蛋白家族，称为含PYD(PYDC或POP)蛋白。我们发现PYDC通过阻断PYD-PYD相互作用来抑制炎性小体的激活，这些相互作用是炎性小体形成所必需的。然而，它们在体内宿主防御和炎症性疾病中的确切作用和贡献仍不清楚。炎性小体对于宿主防御是必不可少的；然而，不适当的炎性小体激活也会导致过度和慢性炎症、组织破坏和日益增长的自体炎症性疾病的衰弱症状。因此，平衡的炎症体反应，在急性感染期间允许病原体清除，同时通过及时终止来预防全身炎症，对于体内平衡至关重要。我们假设是PYDC蛋白通过负反馈机制维持这种平衡的炎症体反应。由于小鼠缺乏PYDC蛋白，我们建立了新的小鼠模型来模拟人类进化中更复杂的炎症体调节。我们建议在所有已知的炎症体激活场景中确定PYDC介导的炎症体调节和终止：病原体感染/病原体相关分子模式(PAMP)、组织损伤/损害相关分子模式(DAMP)以及巨噬细胞和体内遗传性PRR突变。我们将重点介绍部分激活炎症的PRRs。在目标1中，我们将确定每个PYDC在体外巨噬细胞中调节和终止炎症体的分子机制，在目标2中，我们建议在体内确定PYDC介导的炎症体调节。总而言之，我们的研究旨在建立PYDC家族在感染和炎症性疾病期间的特定炎症体调节功能，我们预计这将显著促进我们对先天性免疫、宿主防御和炎症性疾病的基本生物学原理以及这些反应的调节机制的理解。

DESCRIPTION (provided by applicant): Invading pathogens are recognized by pattern recognition receptors (PRRs) of the innate immune system as a first line of defense. Activation of PRRs from the Nucleotide-binding and leucine-rich repeat containing (NLR) protein family and Absent in melanoma 2 (AIM2) in macrophages results in inflammasome formation. Inflammasomes are protein platforms that are essential for the activation of inflammatory Caspases and subsequently for the maturation and release of the pro-inflammatory cytokines interleukin (IL)-1? and IL-18. Assembly of inflammasomes depends on PYRIN domain (PYD)-mediated recruitment of the adaptor protein ASC to activated PRRs, which then recruits pro-Caspase-1. In addition, Caspase-4, -5 and -8 participate. However, the molecular mechanism of inflammasome activation by cytosolic PRRs and in particular, regulation and termination of this process is poorly understood. We discovered a family of small proteins composed of only a PYD, called PYD-containing (PYDC or POP) proteins. We show that PYDCs function to inhibit inflammasome activation by blocking the PYD-PYD interactions essential for inflammasome formation. However, their precise role and contribution to in vivo host defense and inflammatory disease is still unknown. Inflammasomes are essential for host defense; however, inappropriate inflammasome activation also causes excessive and chronic inflammation, tissue destruction and the debilitating symptoms of the growing autoinflammatory diseases. Therefore, a balanced inflammasome response to allow pathogen clearance during acute infection, while preventing systemic inflammation through timely termination, is essential for homeostasis. We hypothesize that it is the role of the PYDC proteins to maintain this balanced inflammasome response through a negative feedback mechanism. Since PYDC proteins are lacking from mice, we generated novel mouse models to simulate the more complex inflammasome regulation evolved in humans. We propose to determine PYDC-mediated inflammasome regulation and termination during all known scenarios of inflammasome activation: pathogen infection/pathogen-associated molecular pattern (PAMP), tissue damage/damage associated molecular pattern (DAMP) and hereditary PRR mutation in macrophages and in vivo. We will focus on select inflammasome-activating PRRs. In aim 1 we will determine the molecular mechanism of inflammasome regulation and termination for each PYDC ex vivo in macrophages and in aim 2 we propose to determine PYDC-mediated inflammasome regulation in vivo. Collectively, our study is designed to establish the specific inflammasome regulatory function of the PYDC family during infection and inflammatory disease, which we expect will significantly advance our understanding of fundamental biological principles underlying innate immunity, host defense and inflammatory disease and the mechanism by which these responses are regulated.