Molecular Genetics of Innate Immunity in C. elegans

描述(申请人提供)：最近的研究表明，哺乳动物天然免疫的关键信号通路具有古老的进化起源，在昆虫和线虫等无脊椎动物的免疫反应级联中很明显。该项目的长期目标是对线虫的天然免疫进行全面的分析，以期对这种遗传易感性的宿主的免疫进行系统的研究，以揭示哺乳动物天然免疫中病原体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线虫的免疫。我们发现需要一个保守的PMK-1 p38Mark通路和TIR-1，TIR-1是一种保守的Toll-IL-1受体(TIR)结构域适配蛋白，似乎在PMK-1通路的上游发挥作用。我们已经使用全基因组微阵列分析来确定PMK-1途径调控下的候选免疫效应器。我们已经从基于RNAi的系统筛查中确定了可能会聚在PMK-1上的其他候选免疫信号成分。基于这些数据，我们提出了这一假设的具体假设，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实现免疫。我们提出了三个特定的目标来确定TIR-1-PMK-1途径产生免疫的机制。首先，我们将确定PMK-1 MAPK通路是在感染部位的细胞中局部发挥作用，还是在病原体防御中发挥系统作用。其次，我们将通过对PMK-1转录靶标的功能分析来确定PMK-1调控病原菌抗性的机制。第三，我们将明确TIR-1激活PMK-1 MAPK通路以响应病原体的机制。我们将剖析TIR-1蛋白的功能结构域并鉴定相互作用的蛋白质，通过遗传交互作用分析将RNAi筛选的候选基因分配到TIR-1-PMK-1途径，并使用互补遗传学方法系统地鉴定TIR-1激活PMK-1途径所需的其他基因。综上所述，p38MAPK通路构成了从蠕虫到人类的天然免疫的关键介体。我们预计，对p38MAPK同源基因PMK-1介导的免疫机制的遗传解剖将为研究哺乳动物天然免疫的机制提供重要的见解，包括哺乳动物TIR-1同源基因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.