Human NLRP11 function in non-canonical inflammasome activation by bacterial pathogen LPS

革兰氏阴性细菌外膜糖脂脂多糖(LPS)被两种细菌识别 细胞表面TLR4复合体和胞浆感受器。胞浆中细菌内毒素的识别诱导 激活caspase-4/caspase-5(人，CASP4/5)或CASP11(小鼠)炎症体，发出信号 引发嗜热性细胞死亡的平台。识别细菌内毒素的教条，基于最简单的 非生理学数据的解释表明CASP4/11在体外与细菌内毒素结合，是胞质的 细菌内毒素是通过CASP4/11直接感受的，而不是通过模式识别受体。我们最近发现 NLRP11是模式识别受体家族中一个特征不佳的灵长类特异性成员，是一种 胞质细菌脂多糖的模式识别受体。 我们发现，胞浆细菌内毒素诱导的人巨噬细胞有效死亡依赖于 NLRP11在CASP4炎症体途径中发挥作用。我们最初在全基因组中发现了NLRP11 筛选人髓系细胞在感染革兰氏杆菌过程中促进细胞死亡的因素 阴性细菌病原体福氏志贺氏菌。我们建议利用我们的发现来揭示 NLRP11在细菌内毒素激活人CASP4炎症体中的作用，包括 福氏志贺氏菌内毒素变异在这一过程中的作用。 1.确定NLRP11与细菌脂多糖和半胱氨酸天冬氨酸蛋白酶相互作用的决定因素(S) 和NLRP11对caspase的特异性(S)。我们将定义分子结构域和序列， 介导细菌内毒素与NLRP11和NLRP11与CASP4的相互作用。 2.确定宿主NLRP11介导的CASP4激活响应胞浆的机制 细菌病原体和胞质细菌内毒素。我们将测试休息状态NLRP11为 自身抑制和激活的NLRP11通过邻近诱导的二聚反应触发CASP4激活，并将测试 NLRP11激活对细菌内毒素的要求。 3.测试宿主NLRP11识别是否受特定的内毒素修饰或模式的调制 内毒素由革兰氏阴性细菌致病菌传递。我们将确定选定的修改的作用 福氏志贺氏菌的脂多糖对NLRP11识别和依赖NLRP11激活CASP4的影响 我们的假设是，当福氏志贺氏菌内毒素处于胶束减少时，NLRP11对CASP4反应最关键 条件。 我们的重点是确定胞浆细菌内毒素触发NLRP11介导的激活的机制。 人类CASP4炎症体。我们处于实现这些目标的得天独厚的地位。我们的见解是 可能对革兰氏阴性菌的发病机制有广泛的影响，因此引起了人们的极大兴趣 病机社区。

The gram-negative bacterial outer membrane glycolipid lipopolysaccharide (LPS) is recognized by both the cell surface TLR4 complex and cytosolic sensors. Recognition of bacterial LPS in the cytosol induces the activation of the caspase-4/caspase-5 (CASP4/5, human) or CASP11 (mouse) inflammasome, signaling platforms that trigger pyroptotic cell death. The dogma for recognition of bacterial LPS, based on the simplest interpretation of non-physiological data showing that CASP4/11 bind bacterial LPS in vitro, is that cytosolic bacterial LPS is directly sensed by CASP4/11 rather than by a pattern recognition receptor. We recently found that NLRP11, a poorly characterized primate-specific member of a family of pattern recognition receptors, is a pattern recognition receptor for cytosolic bacterial LPS. We found that efficient cell death induced by cytosolic bacterial LPS in human macrophages depends on NLRP11 function in the CASP4 inflammasome pathway. We initially identified NLRP11 in a genome-wide screen of human myeloid-derived cells for factors that promote cell death during infection with the gram- negative bacterial pathogen Shigella flexneri. We propose to leverage our findings to uncover mechanisms of NLRP11 function in cytosolic bacterial LPS-triggered activation of the human CASP4 inflammasome, including the role of variants of S. flexneri LPS in this process. 1. Define determinants of host-pathogen interaction of NLRP11 with bacterial LPS and caspase(s) and of NLRP11 specificity for caspase(s). We will define the molecular domains and sequences that mediate bacterial LPS interaction with NLRP11 and NLRP11 with CASP4. 2. Determine mechanisms of host NLRP11-mediated activation of CASP4 in response to cytosolic bacterial pathogens and cytosolic bacterial LPS. We will test our hypothesis that resting state NLRP11 is autoinhibited and activated NLRP11 triggers CASP4 activation by proximity-induced dimerization and will test the requirements for bacterial LPS in NLRP11 activation. 3. Test whether host NLRP11 recognition is modulated by specific LPS modifications or modes of LPS delivery by gram-negative bacterial pathogens. We will determine the role of selected modifications of LPS from S. flexneri on its recognition by NLRP11 and on NLRP11-dependent CASP4 activation and will test our hypothesis that NLRP11 is most critical to CASP4 responses when S. flexneri LPS is in micelle-reducing conditions. Our focus is to determine mechanisms of cytosolic bacterial LPS-triggered NLRP11-mediated activation of the human CASP4 inflammasome. We are uniquely positioned to accomplish these goals. Our insights are likely to have broad implications for gram-negative pathogenesis and thus be of great interest to the pathogenesis community.