Molecular mechanisms underlying the promotion of antibacterial immunity by LC3-associated phagocytosis

LC3相关吞噬作用促进抗菌免疫的分子机制

• 批准号: 432240111
• 负责人: Professor Dr. Olaf Utermöhlen, since 4/2021
• 金额: --
• 依托单位: Institut für Medizinische Mikrobiologie, Immunologie und Hygiene
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/432240111?language=en
• 关键词: Molecular; mechanisms; underlying; promotion; antibacterial

Phagocytosis of invading bacteria by neutrophils and macrophages is a key component of antibacterial immunity. In the phagosome, the bacteria are inactivated, killed and degraded. Some pathogens, such as Mycobacterium tuberculosis or Listeria monocytogenes, however, have evolved mechanisms that prevent their killing in conventional phagosomes. We have recently identified a non-canonical autophagy pathway called LC3-associated phagocytosis (LAP) that allows macrophages to effectively kill phagocytosed L. monocytogenes (Gluschko et al., Cell Host & Microbe 2018). LAP also is crucial for elimination of other microbial pathogens, such as M. tuberculosis or Aspergillus fumigatus, indicating that it generally represents a particularly microbicidal pathway. During LAP, phagosomes are decorated by the protein LC3, which enhances the fusion with lysosomes and thus the killing of the phagocytosed pathogen. However, only a subpopulation of pathogen-containing phagosomes is targeted by LAP and decorated with LC3. Hence, the high antimicrobial potential of LAP is not fully retrieved. Therapeutic approaches based on increasing the targeting of phagocytosed pathogens by LAP would therefore potentially markedly enhance cell-mediated antibacterial defense.The objective of this project is to further elucidate the molecular mechanisms of LAP induction and thereby identify potential starting-points for using the superior microbicidal activity of this cellular mechanism in the treatment of microbial infections.Illustrating that promoting LAP may be a promising strategy for enhancing cell-mediated antibacterial defense, our preliminary data show that the targeting and killing of L. monocytogenes by LAP is substantially increased by the proinflammatory cytokine tumor necrosis factor (TNF). Thus, TNF is an endogenous promotor of LAP and, thereby, antibacterial defense. The first specific aim of this project is to decipher the molecular mechanisms through which TNF promotes LAP induction.Regarding the induction of LAP, we and others have shown that reactive oxygen species (ROS) produced by the NADPH oxidase Nox2 are critically required. In addition to their well-known direct function in killing of phagocytosed pathogens, ROS also exert regulatory functions. How the ROS induce the recruitment of LC3 to phagosomes by LAP, however, remains completely elusive. The second specific aim of this project therefore is to unravel the molecular mechanism through which ROS induce LAP.The insights gained by this project into how macrophages bring to use the particularly microbicidal mechanism of LAP will substantially further our understanding of cell-mediated antimicrobial immunity and identify potential starting-points for novel therapeutic approaches based on increasing the targeting of phagocytosed pathogens by LAP.

嗜中性粒细胞和巨噬细胞吞噬入侵细菌是抗菌免疫的关键组成部分。在吞噬体中，细菌被灭活、杀死和降解。然而，一些病原体，如结核分枝杆菌或单核细胞增生李斯特菌，已经进化出阻止它们在常规吞噬体中被杀死的机制。我们最近发现了一种非经典的自噬途径，称为LC 3相关吞噬作用（LC 3-associated phagocytosis，简称LPS），它允许巨噬细胞有效地杀死吞噬的LC 3。单核细胞增多症（Gluschko等人，Cell Host & Microbe 2018）。它对消除其他微生物病原体也是至关重要的，如M。结核病或烟曲霉，表明它通常代表一种特别的杀微生物途径。在吞噬过程中，吞噬体被蛋白质LC 3修饰，这增强了与溶酶体的融合，从而杀死被吞噬的病原体。然而，只有一个亚群的病原体含有吞噬体的目标是由LC 3和装饰。因此，没有完全恢复ESTA的高抗菌潜力。因此，基于增加靶向吞噬病原体的治疗方法可能会显着增强细胞介导的抗菌防御。本项目的目的是进一步阐明诱导的分子机制，从而确定潜在的起始点。在微生物感染的治疗中使用这种细胞机制的上级杀微生物活性的要点。说明促进细胞内的微生物可能是一种有前途的策略对于增强细胞介导的抗菌防御，我们的初步数据显示，L.促炎性细胞因子肿瘤坏死因子（TNF）显著增加了单核细胞增多症。因此，TNF是一种内源性的启动子，因此，抗菌防御。该项目的第一个具体目标是破译TNF促进TNF诱导的分子机制。关于TNF的诱导，我们和其他人已经表明，NADPH氧化酶Nox 2产生的活性氧（ROS）是至关重要的。除了它们众所周知的在杀死吞噬的病原体中的直接功能之外，ROS还发挥调节功能。然而，ROS如何诱导LC 3被吞噬体募集，仍然完全难以捉摸。因此，该项目的第二个具体目标是解开ROS诱导的分子机制。通过该项目获得的见解如何巨噬细胞带来使用特别是杀微生物的机制的ROS将大大促进我们的细胞介导的抗微生物免疫的理解，并确定潜在的起点，新的治疗方法的基础上增加靶向吞噬病原体的ROS。