Characterization of Legionella virulence mechanisms

我们研究的目的是破译允许细菌嗜肺军团菌感染人体细胞并导致称为军团菌病的严重肺炎的分子机制。 自L.嗜肺菌普遍存在于淡水栖息地，如饮水机、空调系统或淋浴喷头和淋浴器中，美国人口经常暴露于这种生物体。当老年人或免疫功能低下的人吸入L。嗜肺菌可感染肺泡巨噬细胞，导致潜在致命的呼吸道感染。根据疾病控制和预防中心（CDC）的数据，在过去十年中，诊断出的军团病病例数量翻了一番，这解释了为什么这种疾病是一种新出现的公共卫生威胁。 L. pneumophla在感染细胞内建立复制空泡是其毒力的关键，但该过程的细节还没有很好地表征。在过去的资助期间，我们继续研究了L。pneumophila，以确定哪些细菌分子有助于疾病的发展，它们的功能是什么，以及我们如何干预它们的活动。我们发现L. pneumophila使用蛋白质，即所谓的效应物，将其注射到受感染的人类细胞中，在那里它们操纵人类信号蛋白如GTP酶的活性。通过这样做，细菌控制了受感染的细胞，并以宿主细胞现在支持细菌复制而不是对抗入侵微生物的方式对其进行重新编程。 值得注意的是，L.在进化过程中，嗜肺菌从宿主细胞自身获得了操纵我们细胞的能力，现在正被细菌用来对付宿主。例如，我们和其他人发现L.嗜肺菌具有一组效应蛋白，其连接或去除人GT3的翻译后修饰以控制其活性。在与西班牙的一个小组的合作中，我们成功地解决了其中一种效应物的三维结构，这为了解这种细菌蛋白在分子水平上的功能提供了重要的见解。这些数据现在为开发小分子抑制剂提供了一个框架，这些抑制剂可以阻断酶的活性，从而抑制其控制人类细胞中信号蛋白的能力。 我们的工作不仅对L.它不仅可以解释嗜肺菌和相关病原体，而且还提供了有关我们自身细胞内微妙平衡的信号网络以及它们如何促进或抵消细菌感染的重要线索。

The purpose of our research is to decipher the molecular mechanisms that allow the bacterium Legionella pneumophila to infect human cells and cause a severe pneumonia known as Legionnaires disease. Since L. pneumophila is ubiquitously found in freshwater habitats such as water fountains, air conditioning systems, or shower heads and faucets, the American population is frequently exposed to this organism. When inhaled by elderly or immunocompromised individuals, L. pneumophila can infect alveolar macrophages resulting in a potentially fatal respiratory infection. According to the Center for Disease Control and Prevention (CDC), the number of diagnosed Legionnaires' disease cases has doubled over the past decade, explaining why this disease is an emerging public health threat. The ability of L. pneumophla to establish a replication vacuole within infected cells is key to its virulence, yet the details of this process are not very well characterized. Over the past funding period, we have continued our study of the intracellular replication cycle of L. pneumophila in order to determine which bacterial molecules contribute to disease development, what their functions are, and how we can interfere with their activity. We have discovered that L. pneumophila uses proteins, so called effectors, that are injected into infected human cells where they manipulate the activity of human signaling proteins such as GTPases. By doing so, the bacterium takes control of the infected cell and reprograms it in a way that the host cell now supports bacterial replication instead of fighting the invading microbe. Remarkably, some of the effectors that are used by L. pneumophila to manipulate our cells have been been acquired during evolution from the host cell itself and are now being used by the bacterium against the host. For instance, we and others discovered that L. pneumophila has a set of effector proteins that attach or remove a post-translational modification to human GTPase in order to control its activity. In collaboration with a group in Spain, we successfully solved the three-dimensional structure of one of these effectors which provided important insight into how this bacterial protein functions at a molecular level. These data now provide a framework for the development of small molecule inhibitors that block the enzymes activity and, thus, its ability to control signaling proteins in human cells. Our work not only yields much-needed insight into the virulence strategies of L. pneumophila and related pathogens, but it also provides important clues about the delicately balanced signaling networks within our own cells and how they contribute to or counteract bacterial infections.