Molecular Genetics of Innate Immunity in C. elegans

描述（由申请人提供）：最近的研究表明，哺乳动物先天免疫的关键信号通路具有古老的进化起源，这在昆虫和线虫等无脊椎生物的免疫反应级联中很明显。本项目的长期目标是对秀丽隐杆线虫的先天免疫进行全面分析，期望对这种遗传易感的宿主生物的免疫系统研究将阐明哺乳动物先天免疫中病原识别和防御的进化保守机制。我们已经启动了一种多管齐下的功能基因组方法来研究秀丽隐杆线虫的免疫。我们发现了一个保守的PMK-1 p38 MARK通路和一个保守的toll -白细胞介素-1受体（TIR）结构域衔接蛋白TIR-1的需求，该蛋白似乎在PMK-1通路上游起作用。我们使用全基因组微阵列分析来鉴定PMK-1通路调控下的候选免疫效应物。我们已经从基于rnai的系统筛选中确定了可能会聚在PMK-1上的其他候选免疫信号组件。基于这些数据，我们提出了这一建议的具体假设，即病原体感染激活了TIR-1-PMK-1信号级联，通过调节感染部位分泌的抗菌因子来赋予免疫。我们提出了三个具体目标来定义TIR-1-PMK-1途径赋予免疫的机制。首先，我们将确定PMK-1 MAPK通路是局部作用于感染部位的细胞还是系统作用于病原体防御。其次，我们将通过PMK-1转录靶点的功能分析，确定PMK-1调控的赋予病原体抗性的机制。第三，我们将明确TIR-1激活PMK-1 MAPK通路以应对病原体的机制。我们将解剖TIR-1蛋白的功能域并表征相互作用蛋白，通过遗传相互作用分析将RNAi筛选的候选基因分配到TIR-1-PMK-1途径，并使用互补遗传方法系统地识别TIR-1激活PMK-1途径所需的其他基因。总之，p38 MAPK通路构成了从蠕虫到人类的先天免疫的关键介质。我们预计，p38 MAPK同源物PMK-1介导的免疫机制的遗传解剖，将为哺乳动物先天免疫机制提供重要的见解，包括哺乳动物TIR-1同源物SARM的作用。

DESCRIPTION (provided by applicant): Recent studies have revealed that key signaling pathways of mammalian innate immunity have ancient evolutionary origins evident in the immune response cascades of invertebrate organisms such as insects and nematodes. The long-term goal of this project is to carry out the comprehensive analysis of innate immunity in C. elegans, with the anticipation that the systematic study of immunity in this genetically tractable host organism will illuminate evolutionarily conserved mechanisms of pathogen recognition and defense in mammalian innate immunity. We have initiated a multi-pronged functional genomic approach to the study of C. elegans immunity. We identified a requirement for a conserved PMK-1 p38 MARK pathway and TIR-1, a conserved Toll-lnterleukin-1-Receptor (TIR) domain adaptor protein that appears to function upstream of the PMK-1 pathway. We have used genome-wide microarray analysis to identify candidate immune effectors under the regulation of the PMK-1 pathway. We have identified additional candidate immune signaling components that may converge on PMK-1 from a systematic RNAi-based screen. Based on these data, we have developed the specific hypothesis of this proposal, which is that pathogen infection activates a TIR-1-PMK-1 signaling cascade that confers immunity through the regulation of secreted antimicrobial factors at the site of infection. We propose three specific aims to define the mechanisms by which the TIR-1-PMK-1 pathway confers immunity. First, we will determine whether the PMK-1 MAPK pathway acts locally in cells at the site of infection or systemically in pathogen defense. Second, we will define the mechanisms regulated by PMK-1 that confer pathogen resistance by functional analysis of PMK-1 transcriptional targets. Third, we will define the mechanism of TIR-1 activation of the PMK-1 MAPK pathway in response to pathogen. We will dissect the functional domains of the TIR-1 protein and characterize interacting proteins, assign candidate genes from our RNAi screen to the TIR-1-PMK-1 pathway by genetic interaction analysis, and systematically identify additional genes required for TIR-1 activation of the PMK-1 pathway using complementary genetic methods. In summary, the p38 MAPK pathway constitutes a critical mediator of innate immunity that has been conserved from worms to humans. We anticipate that the genetic dissection, of the mechanisms of immunity mediated by the p38 MAPK ortholog, PMK-1, will provide important insights into the mechanisms of mammalian innate immunity, including the role of the mammalian TIR-1 ortholog, SARM.