Effector-mediated Ubiquitin Manipulation in Legionella Pneumophila Pathogenesis

项目摘要 宿主功能的主动调节对于细菌病原体的成功是必不可少的。泛素 网络几乎调节真核生物中的每一个细胞过程，特别是那些参与检测的过程， 识别和应对感染。因此，许多病原体靶向宿主并不意外 泛在化的好处。早期的研究表明，嗜肺军团菌， 军团病通过使用至少9种其Dot/Icm效应物干扰宿主泛素信号传导。我们 最近的研究已经鉴定了SidE效应子家族的成员作为独特的泛素操纵酶。 首先，这些蛋白质含有去泛素化酶基序，攻击泛素化蛋白质。二是这些 蛋白质通过一种不寻常的机制催化泛素化：该反应不需要E1，E2 酶或ATP，是所有描述的泛素化事件所必需的因子。此外，这些小说 泛素操纵效应子是最大细胞内细菌复制所必需的，这与 与大多数IV型军团菌效应子明显相关。通过生物化学和结构分析，我们将首先 研究这些蛋白质的作用机制。我们还将研究通过以下方式对它们的活动进行调节： 因子，并确定这种活性如何有助于吞噬体的生物发生 支持细胞内细菌复制。这些研究不仅将揭示新的宿主机制， 功能开发的细胞内病原体，而且也将有可能修改目前的 理解泛素化，一个非常重要的信号机制。

Project Summary Active modulation of host function is essential for the success of bacterial pathogens. The ubiquitin network regulates virtually every cellular process in eukaryote, particularly those involved in the detection, recognition and response to infection. It is thus not unexpected that many pathogens target host ubiquitination for their benefits. Earlier studies revealed that Legionella pneumophila, the causative agent of Legionnaires' disease, interferes with host ubiquitin signaling by using at least 9 of its Dot/Icm effectors. Our recent study has identified members of the SidE effector family as unique ubiquitin manipulation enzymes. First, these proteins contain a deubiquitinase motif that attacks ubiquitinated proteins. Second, these proteins catalyze ubiquitination by an unusual mechanism: the reaction does not require the E1, E2 enzymes or ATP, factor that are essential for all described ubiquitination events. Furthermore, these novel ubiquitin manipulating effectors are required for maximal intracellular bacterial replication, which differs sharply with the majority of Legionella type IV effectors. By biochemical and structural analyses, we will first study the mechanisms of action of these proteins. We will also study the regulation of their activity by factors from the bacterium and determine how such activity contributes to the biogenesis of the phagosome supportive of intracellular bacterial replication. These studies will not only reveal novel mechanisms of host function exploitation by intracellular pathogens, but also will have the potential to revise the current understanding of ubiquitination, an enormously important signaling mechanism.