Modulation of Host Cell Environment by Mycobacterial PE/PPE Proteins

摘要 自噬是一种关键的宿主防御途径，在先天免疫和适应性免疫中都具有重要作用。然而， 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 病原体可以阻止自噬体与溶酶体融合以逃避降解，或利用此类物质中的营养物质 囊泡。已经证明，刺激巨噬细胞中的自噬途径会导致 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。因此，自噬的诱导可以抑制细胞内的存活 分枝杆菌。我们假设分枝杆菌毒力因子介导自噬逃避，以便 确保受感染的巨噬细胞内的存活。这种毒力的鉴定和表征 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。使用转座子对分枝杆菌进行功能丧失筛查 通过突变体筛选，我们能够识别出 13 个负责操纵的染色体区域 分枝杆菌感染诱导的自噬。值得注意的是，其中六个区域包含属于 PE/PPE 蛋白家族在致病性分枝杆菌中含量特别丰富，并已被证明发挥作用 在分枝杆菌发病机制和调节关键先天免疫途径中发挥不同作用。然而，没有 已知 PE/PPE 蛋白与自噬途径相关。因此，该项目的目标是 研究 PE/PPE 蛋白子集的作用和机制，并确定其后果 分枝杆菌的自噬降解对先天性和适应性免疫的影响。增加了M的知识。 结核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 抗结核病，防止分枝杆菌感染和在宿主体内存活。此外，亲 本研究中产生的自噬突变体可能在开发有效的、 安全且持久的结核病疫苗。

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.