Protein Secretion Pathways of Mycobacterium tuberculosis

总结/摘要 结核病仍然是一个严重的全球健康问题。更好地了解结核分枝杆菌， 导致这种疾病的细菌，将促进新的抗结核病战略的发展。如在 其他细菌病原体，M.结核病在 毒力和宿主免疫力的发展。这项研究的长期目标是确定 负责将这些蛋白质输出到其适当位置的系统，并决定它们在M. 结核病发病机制我们的研究有助于显示分枝杆菌具有保守的蛋白质输出 途径：一般分泌（Sec）途径和双精氨酸易位（达特）途径。我们也 确定了一个专门的系统，致力于分泌和表面蛋白的选择子集。这 SecA 2依赖的输出系统对M. 在巨噬细胞和小鼠中的结核病secA 2突变体。用secA 2突变体感染的巨噬细胞产生 更高水平的促炎细胞因子和效应物。我们假设SecA 2在致病性中的作用 限制宿主免疫反应，可能通过调节MyD 88依赖性途径。具体 这项建议的目的如下。1)研究SecA 2在限制宿主反应中的作用， 通过对SecA 2改变的巨噬细胞反应进行全面分析来促进巨噬细胞的生长 并在巨噬细胞和小鼠中测试免疫调节的意义。2)确定SecA 2依赖性 通过定量蛋白质组学的方法，研究SecA 2与新发现的Dos之间的关系， 调节的细胞包膜蛋白。3)通过确定靶向，表征SecA 2输出机制 结构域的SecA 2输出的蛋白质，并确定蛋白质的工作SecA 2在出口。研究 本提案中的内容将有助于我们理解SecA 2出口系统在M中所起的作用。 结核病的发病机制，它将阐明这种新型的专门出口的机制基础 通路这些结果可能为疾病干预提供新的途径，并促进生命周期的构建。 具有增强的输出和呈递保护性抗原能力的分枝杆菌疫苗。

SUMMARY/ABSTRACT Tuberculosis remains a severe global health problem. A better understanding of Mycobacterium tuberculosis, the bacterium responsible for this disease, will facilitate development of new anti-tuberculosis strategies. As in other bacterial pathogens, the secreted and surface-localized proteins of M. tuberculosis have important roles in virulence and in the development of host immunity. The long-term objective of this research is to define the systems responsible for exporting these proteins to their proper location and determine the role they play in M. tuberculosis pathogenesis. Our research has helped show mycobacteria to possess conserved protein export pathways: the general secretion (Sec) pathway and the twin-arginine translocation (Tat) pathway. We also identified a specialized system that is dedicated to a select subset of secreted and surface proteins. This SecA2-dependent export system is important to virulence as shown by the attenuated phenotype of a M. tuberculosis secA2 mutant in macrophages and mice. Macrophages infected with the secA2 mutant produce higher levels of pro-inflammatory cytokines and effectors. We hypothesize that the role of SecA2 in virulence is to limit host immune responses, possibly through modulation of MyD88-dependent pathways. The specific aims of this proposal are the following. 1) Investigate the role of SecA2 in limiting host responses and promoting growth in macrophages by performing a global analysis of macrophage responses altered by SecA2 and testing the significance of the immunomodulation in macrophages and mice. 2) Identify SecA2-dependent proteins by quantitative proteomics and study the relationship between SecA2 and newly identified Dos regulated cell envelope proteins. 3) Characterize the mechanism of SecA2 export by identifying targeting domains in SecA2-exported proteins and by identifying proteins that work with SecA2 in export. The research in this proposal will improve our understanding of the role played by the SecA2 export system in M. tuberculosis pathogenesis and it will clarify the mechanistic basis of this new type of specialized export pathway. The results may reveal new approaches for disease intervention and facilitate construction of live mycobacterial vaccines with enhanced ability to export and present protective antigens.