Regulation of Legionella pneumophila pathogenesis by the central eukaryotic metabolic checkpoint kinase Mechanistic Target of Rapamycin (MTOR)

本文提出的工作旨在研究哺乳动物 巨噬细胞抑制代谢检查点激酶 （MTOR）促进免疫防御和抵消空泡蛋白的合成代谢重编程 病原体嗜肺军团菌MTOR是一种普遍保守的主开关调节 在真核细胞中的催化剂到催化剂的转变。嗜热病原体依赖于宿主 代谢物不仅用于细菌复制，而且用于维持其细胞内的 壁龛人类呼吸道病原体嗜肺军团菌是一种典型的空泡状 在哺乳动物巨噬细胞内感染和复制的病原体。我们发现 军团菌通过破坏MTOR刺激宿主细胞膜生物合成以扩大其生态位。 然而，宿主抑制途径抵消了L。嗜肺菌诱导的MTOR激活， 靶向MTOR进行泛素依赖性蛋白水解。在巨噬细胞中， 促进细胞内在（自噬）和细胞外在（炎症）宿主防御。具体地说， 致病性L.表达IVb型分泌系统（T4bSS）但不表达 缺乏功能性T4bSS的无毒突变体引起宿主MTOR抑制应答。 因此，我们假设，在哺乳动物巨噬细胞中，MTOR的功能下游的 自我平衡机制，感知入侵微生物的致病潜力， 宿主防御这些机制通过检测由以下基因编码的毒力适应来起作用： 细菌病原体（如专门的分泌系统和分泌的毒素）， 经常产生病原体特异性信号。在第一个目标中，我们将确定 当宿主抑制途径被破坏时，军团菌破坏MTOR功能的机制 灭活在第二个目标中，我们将使用生物化学和遗传学方法， 确定军团菌细胞内生态位如何受宿主代谢调节因子控制。我们 第三个目的是阐明eliminant MTOR抑制的病原体特征如何与 生成的.为此，我们将对军团菌细胞内生态位进行系统分析 使用各种成像方法来确定触发MTOR的早期事件 镇压

The work proposed here seeks to investigate the mechanism by which mammalian macrophages suppress the metabolic checkpoint kinase Mechanistic target of rapamycin (MTOR) to promote immune defenses and counteract anabolic reprogramming by the vacuolar pathogen Legionella pneumophila. MTOR is a universally conserved master switch regulating catabolism to anabolism transition in eukaryotic cells. Vacuolar pathogens rely on host metabolites not only for bacterial replication but also for maintenance of their intracellular niches. The human respiratory pathogen Legionella pneumophila is a prototypical vacuolar pathogen that infects and replicates within mammalian macrophages. We uncovered that Legionella stimulates host membrane biosynthesis to expand its niche by subverting MTOR. However, a host suppression pathway counteracts L. pneumophila-induced MTOR activation by targeting MTOR for ubiquitin-dependent proteolysis. In macrophages, MTOR suppression promotes cell intrinsic (autophagy) and cell extrinsic (inflammation) host defenses. Specifically, pathogenic L. pneumophila expressing the type IVb secretion system (T4bSS) but not the avirulent mutants lacking a functional T4bSS elicited the host MTOR suppression response. Thus, we hypothesize that in mammalian macrophages MTOR functions downstream of homeostatic mechanisms that sense the pathogenic potential of invading microbes to potentiate host defenses. Such mechanisms operate by detecting virulence adaptations encoded by bacterial pathogens (such as specialized secretion systems and secreted toxins), which frequently produce pathogen-specific signatures. In the first aim we will determine the mechanism by which Legionella subverts MTOR function, when the host suppression pathway is inactivated. In the second aim we are going to use biochemical and genetic approaches to determine how the Legionella intracellular niche is controlled by host metabolic regulators. Our third aim is to elucidate how the pathogen signature that elicits MTOR suppression is generated. To this end, we will perform a systematic analysis of the Legionella intracellular niche using a variety of imaging approaches to define the early events that trigger MTOR suppression.