Deciphering microbial virulence mechanisms during Legionella pneumophila infection

破译嗜肺军团菌感染期间微生物的毒力机制

• 批准号: 10266518
• 负责人: Matthias Machner
• 金额: $ 119.55万
• 依托单位: EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH & HUMAN DEVELOPMENT
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10266518
• 关键词: Affect; Alveolar Macrophages; Antibiotics; Bacteria; Cell physiology; Cells; Clinical; Contracts; Coxiella burnetii; Dangerousness; Development; Disease; Disease Outbreaks; Economic Burden; Elderly; Event; Fresh Water; Funding; Goals; Growth; Habitats; Head; Health; Human; Immune; Immune system; Individual; Infant; Infection; Infection prevention; Inhalation; Knowledge; Legionella; Legionella pneumophila; Legionnaires' Disease; Life; Lung; Membrane; Molecular; Molecular Mimicry; Pathway interactions; Personal Satisfaction; Pharmacology; Phosphotransferases; Play; Pneumonia; Process; Proteins; Research; Respiratory Tract Infections; Risk; Role; Route; Signal Pathway; Signal Transduction; Source; Structure; Therapeutic; Type IV Secretion System Pathway; Virulence; Water; aerosolized; commensal bacteria; contaminated water; human microbiota; human pathogen; improved; macrophage; microbial; multi-drug resistant pathogen; novel therapeutics; pathogen; pathogenic bacteria; pathogenic microbe; precision medicine; prevent; protein complex; small molecule; therapeutic development

The bacterium Legionella pneumophila is the causative agent of a potentially life-threatening pneumonia called Legionnaires' disease. Upon inhalation by humans, L. pneumophila enters the human lung where it can infect and replicate within alveolar macrophages, specialized immune cells. Instead of being degraded by macrophages, L. pneumophila uses the infected cell for its intracellular replication cycle. If not treated promptly, this respiratory infection ends fatal in up to 30 percent of all cases. The number of Legionnaires' disease cases in the U.S. has increased four-fold over the past 15 years, making L. pneumophila a significant health threat and a considerable economic burden. We are committed to studying how Legionella can escape our immune system so that we can develop better ways to prevent this from happening. Legionella is ubiquitously found in freshwater habitats such as cooling towers, faucets and shower heads, or water fountains. Major outbreaks of Legionnaires' disease occur when water from contaminated sources is aerosolized and subsequently inhaled by humans. Immune-compromised individuals, infants, or the elderly are at an elevated risk of contracting an infection. Like many other microbial pathogens, L. pneumophila have developed a variety of strategies to infect their human host and to cause disease. They use a specialized protein complex called Type IV Secretion System to inject an abundance of proteins, or effectors, into the infected host cell. The effectors modulate signaling events within the host in order to create conditions favorable for L. pneumophila. Obtaining a detailed understanding of Legionella's effectors and itsvirulence strategies is essential for the development of novel therapeutics capable of preventing and treating this dangerous pneumonia and will profoundly improve people's lives and wellbeing. Over the past funding period, we have made significant progress in deciphering some of the virulence strategies of L. pneumophila. One intriguing finding was that L. pneumophila exploits the human Hippo signaling pathway. The Hippo pathway is highly conserved in all eukaryotic life forms where it is best known for its role in controlling cell development and differentiation. Yet, our finding now suggests that this pathway also plays an important role during microbial infection. Specifically, we discovered that L. pneumophila encodes an effector called LegK7 that mimics the human Hippo kinase, thereby taking control of the Hippo signaling route with the goal of causing changes in host cell physiology that promotes intracellular bacterial growth. Pharmacological interference with this molecular mimicry rendered human cells less susceptible to L. pneumophila growth, providing us with a new way to treat infections by this pathogen. Another notable finding was the existence of a previously undescribed membrane targeting domain in one of the Legionella effectors. This protein, called SidD, localizes to a specific membranes within infected cells in order to properly execute its function. Not only did we reveal at a mechanistic and structural level how this domain can accomplish membrane targeting of SidD, but we also developed strategies to interfere with the targeting process and thus with the function of the Legionella effector. In a third project, we have taken the first step towards the development of smarter antibiotics that selectively target pathogens. Multi-drug-resistant pathogens are an emerging threat to human health. Since conventional antibiotics target not only the pathogen but also eradicate the beneficial human microbiota, they often cause additional clinical complications. Thus, there is an urgent need for the development of therapeutics that selectively target pathogens without affecting beneficial commensals. The bacterial type IV secretion system (T4SS) is essential for the virulence of a variety of pathogens but dispensable for bacterial viability in general and can, thus, be considered a pathogens Achilles heel. By identifying small molecules that interfere with the function of the T4SS from Legionella pneumophila and another important human pathogen, Coxiella burnetii, our study represents the first step in our pursuit towards precision medicine by developing pathogen-selective therapeutics capable of treating the infections without causing harm to commensal bacteria.

嗜肺军团菌是一种可能危及生命的肺炎的病原体，称为军团病。当人类吸入时，L。嗜肺菌进入人肺，在那里它可以感染肺泡巨噬细胞（特化的免疫细胞）并在其中复制。L.嗜肺菌利用受感染的细胞进行其细胞内复制循环。如果不及时治疗，这种呼吸道感染的死亡率高达30%。 在过去的15年里，美国的军团病病例增加了四倍，使L。嗜肺菌是严重的健康威胁和相当大的经济负担。 我们致力于研究军团菌如何逃脱我们的免疫系统，以便我们能够开发更好的方法来预防这种情况的发生。 军团菌普遍存在于淡水栖息地，如冷却塔，水箱和淋浴喷头，或喷泉。军团病的大规模爆发发生在污染水源的水被雾化并随后被人类吸入时。免疫功能低下的个体、婴儿或老年人感染的风险较高。 与许多其他微生物病原体一样，L.嗜肺菌已经发展出多种策略来感染它们的人类宿主并引起疾病。他们使用一种称为IV型分泌系统的特殊蛋白质复合物将大量蛋白质或效应物注入受感染的宿主细胞。效应子调节宿主内的信号事件，以便为L创造有利条件。嗜肺菌详细了解军团菌的效应子及其毒力策略对于开发能够预防和治疗这种危险的肺炎的新疗法至关重要，并将深刻改善人们的生活和福祉。 在过去的资助期内，我们在破译L.嗜肺菌 一个有趣的发现是L.嗜肺菌利用人类Hippo信号通路。Hippo通路在所有真核生物中高度保守，其中最为人所知的是其在控制细胞发育和分化中的作用。然而，我们现在的发现表明，这一途径在微生物感染过程中也起着重要作用。 具体地说，我们发现L.嗜肺菌编码称为LegK7的效应子，其模拟人Hippo激酶，从而控制Hippo信号传导途径，目的是引起宿主细胞生理学的变化，从而促进细胞内细菌生长。药理学对这种分子模拟的干扰使人类细胞对L. pneumophila生长，为我们提供了一种新的方法来治疗这种病原体的感染。 另一个值得注意的发现是在军团菌效应子之一中存在以前未描述的膜靶向结构域。这种被称为SidD的蛋白质定位于受感染细胞内的特定膜，以正确执行其功能。我们不仅在机制和结构水平上揭示了该结构域如何实现SidD的膜靶向，而且我们还开发了干扰靶向过程的策略，从而干扰军团菌效应子的功能。 在第三个项目中，我们朝着开发选择性靶向病原体的更智能抗生素迈出了第一步。多重耐药病原体是对人类健康的一个新威胁。由于传统抗生素不仅针对病原体，而且还根除有益的人类微生物群，因此它们通常会导致额外的临床并发症。因此，迫切需要开发选择性靶向病原体而不影响有益生物的治疗剂。细菌IV型分泌系统（T4SS）对于多种病原体的毒力是必不可少的，但通常对细菌存活力不利，因此可以被认为是病原体的阿喀琉斯之踵。 通过鉴定干扰嗜肺军团菌和另一种重要的人类病原体贝氏柯克斯体的T4SS功能的小分子，我们的研究代表了我们通过开发能够治疗感染而不对肠道细菌造成伤害的病原体选择性疗法来追求精准医学的第一步。