Henry Brittany, Sibley L David, Rosenberg Alex
Department of Infectious Diseases, Center for Tropical and Emerging Infectious Diseases, University of Georgia, Athens, Georgia, USA.
Department of Molecular Microbiology, Washington University School of Medicine, St Louis, Missouri, USA.
bioRxiv. 2023 Dec 25:2023.12.24.573224. doi: 10.1101/2023.12.24.573224.
In both mice and humans, Type II interferon-gamma (IFNγ) is crucial for regulation of () infection, during acute or chronic phases. To thwart this defense, secretes protein effectors hindering the hosťs immune response. For example, relies on the MYR translocon complex to deploy soluble dense granule effectors (GRAs) into the host cell cytosol or nucleus. Recent genome-wide loss-of-function screens in IFNγ-primed primary human fibroblasts identified MYR translocon components as crucial for parasite resistance against IFNγ driven vacuole clearance. However, these screens did not pinpoint specific MYR-dependent GRA proteins responsible for IFNγ signaling blockade, suggesting potential functional redundancy. Our study reveals that depends on the MYR translocon complex to prevent host cell death and parasite premature egress in human cells stimulated with IFNγ postinfection, a unique phenotype observed in various human cell lines but not in murine cells. Intriguingly, inhibiting parasite egress did not prevent host cell death, indicating this mechanism is distinct from those described previously. Genome-wide loss-of-function screens uncovered TgIST, GRA16, GRA24, and GRA28 as effectors necessary for a complete block of IFNγ response. GRA24 and GRA28 directly influenced IFNγ driven transcription, GRA24's action depended on its interaction with p38 MAPK, while GRA28 disrupted histone acetyltransferase activity of CBP/p300. Given the intricate nature of the immune response to , it appears that the parasite has evolved equally elaborate mechanisms to subvert IFNγ signaling, extending beyond direct interference with the JAK/STAT1 pathway, to encompass other signaling pathways as well.
在小鼠和人类中,II型干扰素-γ(IFNγ)在急性或慢性阶段对()感染的调节至关重要。为了对抗这种防御,(病原体)分泌蛋白质效应物来阻碍宿主的免疫反应。例如,(病原体)依靠MYR转运体复合物将可溶性致密颗粒效应物(GRAs)部署到宿主细胞胞质溶胶或细胞核中。最近在IFNγ预处理的原代人成纤维细胞中进行的全基因组功能丧失筛选确定,MYR转运体成分对于寄生虫抵抗IFNγ驱动的液泡清除至关重要。然而,这些筛选并未确定负责IFNγ信号传导阻断的特定MYR依赖性GRA蛋白,这表明可能存在功能冗余。我们的研究表明,(病原体)依靠MYR转运体复合物来防止感染后用IFNγ刺激的人细胞中的宿主细胞死亡和寄生虫过早逸出,这是在各种人类细胞系中观察到的独特表型,但在鼠细胞中未观察到。抑制寄生虫逸出并不能防止宿主细胞死亡,这表明这种机制与先前描述的机制不同。全基因组功能丧失筛选发现TgIST、GRA16、GRA24和GRA28是完全阻断IFNγ反应所必需的效应物。GRA24和GRA28直接影响IFNγ驱动的转录,GRA24的作用取决于其与p38丝裂原活化蛋白激酶的相互作用,而GRA28破坏了CBP/p300的组蛋白乙酰转移酶活性。鉴于对(病原体)免疫反应的复杂性,看来寄生虫已经进化出同样复杂的机制来破坏IFNγ信号传导,不仅包括对JAK/STAT1途径的直接干扰,还包括其他信号传导途径。
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