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

这里提出的工作试图调查哺乳动物通过什么机制 巨噬细胞抑制雷帕霉素代谢检查点激酶机制靶点 (MTOR)促进免疫防御和对抗空泡的合成代谢重编程 病原体嗜肺军团菌。MTOR是一种普遍保守的主开关调节 真核细胞中分解代谢向合成代谢的转变。空泡病原体依赖寄主 代谢物不仅用于细菌复制，还用于维持其细胞内 利基市场。人类呼吸道病原体嗜肺军团菌是一种典型的空泡 在哺乳动物巨噬细胞内感染和复制的病原体。我们发现了 军团菌通过颠覆MTOR来刺激宿主膜生物合成以扩大其生态位。 然而，宿主抑制途径通过以下方式抵消嗜肺乳杆菌诱导的MTOR激活 针对泛素依赖的蛋白分解的MTOR。巨噬细胞中MTOR抑制 促进细胞内在(自噬)和细胞外源性(炎症)宿主防御。具体来说， 致病性嗜肺乳杆菌表达IVb型分泌系统(T4bSS)，但不表达 缺乏功能性T4bSS的无毒突变体可引起宿主MTOR抑制反应。 因此，我们假设在哺乳动物巨噬细胞中，MTOR在下游发挥作用 感知入侵微生物的致病潜力以增强其致病能力的动态平衡机制 主机防御。这种机制通过检测编码的毒力适应来运行 细菌病原体(如专门的分泌系统和分泌的毒素)， 经常产生病原体特有的特征。在第一个目标中，我们将确定 军团菌在宿主抑制途径被抑制时颠覆MTOR功能的机制 已停用。在第二个目标中，我们将使用生化和遗传方法来 确定军团菌胞内生态位如何受到宿主代谢调节剂的控制。我们的 第三个目的是阐明引起MTOR抑制的病原体信号是如何 已生成。为此，我们将对军团菌胞内生态位进行系统分析 使用各种成像方法来定义触发MTOR的早期事件 压制。

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.