Modulation of Inflammasome Activation by Yersinia

描述（由申请人提供）：本项目的总体目标是了解先天免疫系统如何感知和响应细菌病原体的分子机制，以及细菌病原体为避免免疫检测而使用的逃避策略。特别地，我们使用假结核耶尔森氏菌（Yersinia pseudotuberculosis）作为模型来理解宿主-病原体界面并发现宿主对革兰氏阴性细菌病原体的先天免疫应答的共有特征，所述假结核耶尔森氏菌表达许多与其近亲和鼠疫病原体鼠疫耶尔森氏菌相同的毒力因子。革兰氏阴性菌多重耐药性的快速扩展增加了开发新的抗菌治疗方法的重要性，并且了解先天免疫系统最初如何检测细菌病原体以及相应的病原体逃避策略有望用于识别新型抗菌剂。III型分泌系统（T3 SS）是一个广泛保守的毒力决定因子，是许多革兰氏阴性菌致病力所必需的。coli转化为Y.鼠疫杆菌，并将毒力因子注入宿主细胞，破坏细胞信号传导途径。然而，T3 SS活性也可以被Nod样受体（NLR）家族的胞质模式识别受体感知并诱导宿主免疫应答。以往的研究表明，Y. pseudotuberculosis和Y.鼠疫T3 SS诱导NLRP 3依赖性炎性体的活化，导致细胞死亡和半胱天冬酶-1依赖性细胞因子分泌。此外，研究表明，必需的耶尔森氏菌毒力因子YopK，其调节T3 SS的孔形成活性并限制其他Yop效应蛋白的易位，防止炎性小体活化。炎性体激活在宿主防御耶尔森氏菌中起重要作用，因为YopK缺陷型细菌的毒力缺陷在缺乏炎性体组分的小鼠中得到恢复。然而，细胞如何感知耶尔森氏菌T3 SS活性以及YopK如何阻止这种感知的分子基础尚不清楚。我们提出了三个具体目标，以解决我们知识中的这一重要差距。首先，我们将测试转运子组分递送到宿主细胞胞质溶胶中通过破坏细胞内区室激活NLRP 3炎性体的假设。第二，我们将测试YopK通过结合到易位子并限制易位子组分注射到细胞中来防止NLRP 3炎性小体活化的假设。第三，我们将测试体内炎性小体激活通过产生半胱天冬酶-1依赖性细胞因子来控制耶尔森氏菌感染的假设，所述细胞因子诱导促进细菌清除的特异性免疫细胞亚群的激活。

DESCRIPTION (provided by applicant): The overall goal of this project is to understand molecular mechanisms of how the innate immune system senses and responds to bacterial pathogens and the evasion strategies utilized by bacterial pathogens to avoid immune detection. In particular we use Yersinia pseudotuberculosis, which expresses many of the same virulence factors as its close relative and plague pathogen Yersinia pestis, as a model to understand the host- pathogen interface and discover shared features of host innate immune responses to Gram-negative bacterial pathogens. The rapid expansion of multi-drug resistance among Gram-negative bacteria has increased the importance of developing new approaches to antimicrobial therapeutics, and understanding how the innate immune system initially detects bacterial pathogens and the corresponding pathogen evasion strategies holds promise for identifying novel antimicrobials. The Type III secretion system (T3SS) is a broadly conserved virulence determinant that is essential for virulence of many Gram-negative bacterial pathogens from E. coli to Y. pestis, and injects virulence factors into host cells that disrupt cellular signling pathways. However, T3SS activities can also be sensed by cytosolic pattern recognition receptors of the Nod-like receptor (NLR) family and induce host immune responses. Previous studies demonstrated that the Y. pseudotuberculosis and Y. pestis T3SS induces activation of an NLRP3-dependent inflammasome, resulting in cell death and caspase-1 dependent cytokine secretion. Furthermore, studies demonstrated that the essential Yersinia virulence factor YopK, which modulates the pore-forming activity of the T3SS and limits translocation of other Yop effector proteins, prevents inflammasome activation. Inflammasome activation plays an important role in host defense against Yersinia, as the virulence defect of YopK-deficient bacteria is restored in mice that lack inflammasome components. However, the molecular basis for how cells sense the activity of Yersinia's T3SS and how YopK prevents this sensing is not known. We propose three Specific Aims to address this important gap in our knowledge. First we will test the hypothesis that delivery of translocon components into the host cell cytosol activates the NLRP3 inflammasome through disruption of intracellular compartments. Second we will test the hypothesis that YopK prevents NLRP3 inflammasome activation by binding to the translocon and limiting injection of translocon components into the cell. Third, we will test te hypothesis that inflammasome activation in vivo controls Yersinia infection via production of caspase-1 dependent cytokines that induce activation of specific immune cell subsets that promote bacterial clearance.