Modulation of Host Cell Environment by Mycobacterial PE/PPE Proteins

摘要 自噬是宿主防御的一个重要途径，在天然免疫和适应性免疫中起着重要作用。然而，在这方面， 许多微生物已经进化出逃避、破坏或利用自噬的机制。细菌和病毒 病原体可以阻断自噬体与溶酶体的融合以逃避降解，或者利用自噬体中的营养物质。 囊泡已经证明，刺激巨噬细胞中的自噬途径导致 分枝杆菌吞噬体成熟为吞噬溶酶体，然后可以克服运输障碍 由结核分枝杆菌引起的。因此，自噬的诱导可以抑制细胞内存活， 分枝杆菌我们假设分枝杆菌毒力因子介导自噬逃避， 确保在受感染的巨噬细胞内存活。这种毒性的鉴定和表征 这些因素将使我们了解自噬影响宿主-微生物结果的机制。 相互作用和免疫反应。通过使用转座子筛选分枝杆菌的功能丧失 突变体筛选，我们能够确定十三个染色体区域负责操纵 分枝杆菌感染诱导的自噬。值得注意的是，这些区域中有六个含有属于 PE/PPE蛋白家族在致病性分枝杆菌中特别丰富，并已被证明在致病性分枝杆菌中起作用。 在分枝杆菌发病机制和调节关键先天免疫途径中的不同作用。但没有 已知PE/PPE蛋白与自噬途径相关。因此，本项目的目标是 研究PE/PPE蛋白质子集的作用和机制，并确定 分枝杆菌的自噬降解对先天性和获得性免疫的影响。增加了对M. 结核病感染诱导的自噬为发现新的有前途的治疗方法提供了机会 针对结核病，以防止分枝杆菌感染和宿主内的存活。此外，亲- 本研究中产生的自噬突变体可能在开发有效的， 安全和持久的结核病疫苗。

Abstract Autophagy, a key host defense pathway, has an essential role in both innate and adaptive immunity. However, many microbes have evolved mechanisms to evade, subvert, or exploit autophagy. Bacterial and viral pathogens can block autophagosome fusion with lysosomes to evade degradation, or utilize nutrients in such vesicles. It has been demonstrated that stimulation of autophagic pathways in macrophages causes mycobacterial phagosomes to mature into phagolysosomes, which can then overcome the trafficking block imposed by Mycobacterium tuberculosis. Thus, induction of autophagy can suppress intracellular survival of mycobacteria. We hypothesize that mycobacterial virulence factors mediate autophagy evasion in order to ensure survival within the infected macrophages. The identification and characterization of such virulence factors will allow us to understand the mechanisms by which autophagy affects the outcome of host-microbe interactions and immune responses. Through loss-of-function screening of mycobacteria using transposon mutant screening, we were able to identify thirteen chromosomal regions responsible for manipulating mycobacterial infection-induced autophagy. Remarkably, six of these regions contain genes belonging to the PE/PPE protein family that are especially abundant in pathogenic mycobacteria and have been shown to play diverse roles in mycobacterial pathogenesis and in modulating critical innate immune pathways. However, no PE/PPE proteins are known to be associated with autophagy pathways. Thus, the goals of this project are to investigate the roles and mechanisms of a subset of PE/PPE proteins and to determine the consequences of autophagic degradation of mycobacteria on innate and adaptive immunity. Increased knowledge of M. tuberculosis infection-induced autophagy presents an opportunity to uncover new and promising therapeutics against tuberculosis to prevent mycobacterial infection and survival within the host. Additionally, the pro- autophagic mutants generated in this study may have significant application in the development of effective, safe and persistent TB vaccines.