Microbial Pattern Recognition by the Social Amoeba Dictyostelium discoideum - Mod

描述（由申请人提供）：先天免疫细胞作为对抗致病病原体的第一道防线，在检测到广泛的细菌、病毒和真菌上保守的微生物结构模式时产生反应。有效的先天反应清除了大量入侵病原体的个体，对B和T淋巴细胞记忆反应的最佳刺激也显得至关重要。另一方面，过度活跃的先天反应与过敏性和自身免疫性疾病有关。因此，对先天免疫反应和这些反应背后的微生物模式识别机制的基本了解对于开发感染性和自身免疫性疾病的新疗法至关重要。此外，了解记忆淋巴细胞的先天免疫刺激可以帮助开发有效的疫苗。先天免疫系统用于检测病原体的微生物模式识别机制似乎高度保守，因此，对简单动物（如果蝇）的免疫研究导致了许多微生物模式识别机制的发现和表征，特别是toll样受体。利用简单的真核细胞系统和强大的遗传分析工具，可以促进对先天免疫系统识别微生物的分子基础的研究。在这里，我们建议探索社会性阿米巴使用相同类型的微生物模式识别机制来检测细菌猎物和防御细菌病原体的可能性，就像哺乳动物的先天免疫细胞一样，从而提供这样一个模型。事实上，盘状棘球虫已被证明是研究哺乳动物免疫细胞趋化反应的有用模型，并且在这些进化多样的细胞中介导趋化的信号通路的相似性是显著的。几条线索的证据表明，盘状棘球蚴使用保守的模式识别机制。它的基因组编码与已知模式识别分子同源的蛋白质，对其中一些蛋白质的分析表明，这些蛋白质在细菌识别中起作用。此外，我们的初步结果表明，盘状棘球蚴在检测到特定的微生物模式时启动细胞反应。为了验证我们的假设，即微生物模式识别机制在盘状盘虱中是保守的，我们计划1)进一步分析盘状盘虱对细菌模式的反应，2)使用敲除和过表达技术来表征盘状盘虱对已知模式识别分子的同源蛋白，3)使用突变体筛选和酵母双杂交技术来鉴定盘状盘虱参与细菌识别的新蛋白。我们的研究结果应该允许进一步表征微生物模式识别盘状棘球蚴。鉴于微生物模式识别机制在多种物种中的保守性，我们的发现也应该为哺乳动物先天免疫系统的模式识别提供见解。

DESCRIPTION (provided by applicant): Innate immune cells, which act as a first line of defense against disease-causing pathogens, mount responses upon detection of microbial structural patterns conserved on a wide array of bacteria, viruses and fungi. Effective innate responses rid an individual of a vast number of invading pathogens and also appear vital for optimal stimulation of B and T lymphocyte memory responses. On the other hand, overactive innate responses are correlated with allergic and autoimmune diseases. Thus, a basic understanding of innate immune responses and the microbial pattern recognition machinery underlying these responses is crucial to development of new therapies for infectious and autoimmune diseases. In addition, insights into innate immune stimulation of memory lymphocytes can assist in development of effective vaccines. The microbial pattern recognition machinery used by innate immune systems to detect pathogens appears highly conserved, and for this reason, the study of immunity in simple animals such as Drosophila has led to the discovery and characterization of many microbial pattern recognition mechanisms, notably the Toll-like receptors. The study of the molecular basis of the innate immune system's recognition of microbes would be facilitated by the use of a simple eukaryotic cell system with powerful tools for genetic analysis. Here we propose to explore the possibility that the social amoeba uses the same types of microbial pattern recognition machinery to detect bacterial prey and defend against bacterial pathogens as do mammalian innate immune cells and would thus provide such a model. Indeed, D. discoideum has proven to be a useful model for the study of chemotactic responses by mammalian immune cells, and the parallels in the signaling pathways that mediate chemotaxis in these evolutionary diverse cells are remarkable. Several lines of evidence suggest that D. discoideum uses conserved pattern recognition mechanisms. Its genome encodes for proteins homologous to known pattern recognition molecules, and analysis of some of these proteins has indicated a role in bacterial recognition. In addition, our preliminary results show that D. discoideum initiates cellular responses upon detection of particular microbial patterns. To test our hypothesis that microbial pattern recognition machinery is conserved in D. discoideum we plan to 1) further analyze D. discoideum responses to bacterial patterns, 2) use knockout and overexpression technologies to characterize D. discoideum proteins homologous to known pattern recognition molecules, and 3) employ mutant screening and yeast-two-hybrid techniques to identify new D. discoideum proteins involved in bacterial recognition. The results from our studies should allow further characterization of microbial pattern recognition in D. discoideum. Given the conservation of microbial pattern recognition mechanisms among a wide array of species, our findings should also give insight into pattern recognition in mammalian innate immune systems. PUBLIC HEALTH RELEVANCE: Innate immune responses are critical both for the quick and efficient removal of most pathogens and for the stimulation of effective long-term memory responses from T and B lymphocytes. Conversely, overactive innate responses are associated with allergic and autoimmune diseases. A greater understanding of the molecular mechanisms underlying microbial recognition by innate immune systems could allow for the regulation of innate immune responses in infectious and autoimmune diseases and allergies. Insights into the stimulation of long-term memory responses by innate immune systems should also allow for design of more effective vaccine strategies. Our proposal here to use the social amoeba Dictyostelium discoideum as a model system to study the molecular mechanisms underlying microbial pattern recognition in innate immunity should lend insight into mechanisms that may be conserved in mammalian immune systems and may inform development of new therapeutics for infectious and autoimmune diseases.