Division of Infectious Diseases, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.
mBio. 2018 Nov 27;9(6):e01765-18. doi: 10.1128/mBio.01765-18.
Intracellular pathogens have varied strategies to breach the endolysosomal barrier so that they can deliver effectors to the host cytosol, access nutrients, replicate in the cytoplasm, and avoid degradation in the lysosome. In the case of , the bacterium perforates the phagosomal membrane shortly after being taken up by macrophages. Phagosomal damage depends upon the mycobacterial ESX-1 type VII secretion system (T7SS). Sterile insults, such as silica crystals or membranolytic peptides, can also disrupt phagosomal and endolysosomal membranes. Recent work revealed that the host endosomal sorting complex required for transport (ESCRT) machinery rapidly responds to sterile endolysosomal damage and promotes membrane repair. We hypothesized that ESCRTs might also respond to pathogen-induced phagosomal damage and that could impair this host response. Indeed, we found that ESCRT-III proteins were recruited to phagosomes in an -dependent manner. We previously demonstrated that the mycobacterial effectors EsxG/TB9.8 and EsxH/TB10.4, both secreted by the ESX-3 T7SS, can inhibit ESCRT-dependent trafficking of receptors to the lysosome. Here, we additionally show that ESCRT-III recruitment to sites of endolysosomal damage is antagonized by EsxG and EsxH, both within the context of infection and sterile injury. Moreover, EsxG and EsxH themselves respond within minutes to membrane damage in a manner that is independent of calcium and ESCRT-III recruitment. Thus, our study reveals that T7SS effectors and ESCRT participate in a series of measures and countermeasures for control of phagosome integrity. causes tuberculosis, which kills more people than any other infection. grows in macrophages, cells that specialize in engulfing and degrading microorganisms. Like many intracellular pathogens, in order to cause disease, damages the membrane-bound compartment (phagosome) in which it is enclosed after macrophage uptake. Recent work showed that when chemicals damage this type of intracellular compartment, cells rapidly detect and repair the damage, using machinery called the endosomal sorting complex required for transport (ESCRT). Therefore, we hypothesized that ESCRT might also respond to pathogen-induced damage. At the same time, our previous work showed that the EsxG-EsxH heterodimer of can inhibit ESCRT, raising the possibility that impairs this host response. Here, we show that ESCRT is recruited to damaged phagosomes and that EsxG-EsxH undermines ESCRT-mediated endomembrane repair. Thus, our studies demonstrate a battle between host and pathogen over endomembrane integrity.
细胞内病原体有各种各样的策略来突破内体溶酶体屏障,以便将效应器输送到宿主细胞质中,获取营养物质,在细胞质中复制,并避免在溶酶体中降解。在 的情况下,细菌在被巨噬细胞摄取后不久就穿透吞噬体膜。吞噬体的损伤取决于分枝杆菌 ESX-1 型 VII 型分泌系统(T7SS)。非感染性刺激,如硅晶体或膜溶肽,也可以破坏吞噬体和内体溶酶体膜。最近的工作表明,宿主内体分选复合物所需的运输(ESCRT)机制会迅速对非感染性内体损伤做出反应,并促进膜修复。我们假设 ESCRTs 也可能对病原体诱导的吞噬体损伤做出反应,并且 可能会损害这种宿主反应。事实上,我们发现 ESCRT-III 蛋白以依赖于 的方式被募集到 吞噬体上。我们之前证明,分枝杆菌效应物 EsxG/TB9.8 和 EsxH/TB10.4,均由 ESX-3 T7SS 分泌,可以抑制受体向溶酶体的 ESCRT 依赖性运输。在这里,我们还表明,ESCRT-III 募集到内体溶酶体损伤部位受到 EsxG 和 EsxH 的拮抗,无论是在 感染还是非感染性损伤的情况下。此外,EsxG 和 EsxH 本身在几分钟内就会对膜损伤做出反应,这种反应不依赖于钙和 ESCRT-III 的募集。因此,我们的研究揭示了 T7SS 效应物和 ESCRT 参与了一系列控制吞噬体完整性的措施和对策。 引起结核病,它比任何其他感染都杀死更多的人。 在巨噬细胞中生长,巨噬细胞专门吞噬和降解微生物。像许多细胞内病原体一样,为了引起疾病, 在被巨噬细胞摄取后,会破坏其所在的膜结合隔室(吞噬体)。最近的工作表明,当化学物质损伤这种类型的细胞内隔室时,细胞会使用称为内体分选复合物所需的运输(ESCRT)的机制来快速检测和修复损伤。因此,我们假设 ESCRT 也可能对病原体诱导的损伤做出反应。与此同时,我们之前的工作表明, 的 EsxG-EsxH 异二聚体可以抑制 ESCRT,这增加了 破坏这种宿主反应的可能性。在这里,我们表明 ESCRT 被募集到受损的 吞噬体上,并且 EsxG-EsxH 破坏了 ESCRT 介导的内膜修复。因此,我们的研究表明,宿主和病原体之间存在着对内质网完整性的争夺。
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