作为γ干扰素下游免疫机制的类LAP过程在控制人类疟疾间日疟原虫肝期的作用

LAP-like process as an immune mechanism downstream of IFN-γ in control of the human malaria Plasmodium vivax liver stage.

作者信息

Boonhok Rachasak, Rachaphaew Nattawan, Duangmanee Apisak, Chobson Pornpimol, Pattaradilokrat Sittiporn, Utaisincharoen Pongsak, Sattabongkot Jetsumon, Ponpuak Marisa

机构信息

Department of Microbiology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand; Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand;

Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand;

出版信息

Proc Natl Acad Sci U S A. 2016 Jun 21;113(25):E3519-28. doi: 10.1073/pnas.1525606113. Epub 2016 May 16.

Abstract

IFN-γ is a major regulator of immune functions and has been shown to induce liver-stage Plasmodium elimination both in vitro and in vivo. The molecular mechanism responsible for the restriction of liver-stage Plasmodium downstream of IFN-γ remains uncertain, however. Autophagy, a newly described immune defense mechanism, was recently identified as a downstream pathway activated in response to IFN-γ in the control of intracellular infections. We thus hypothesized that the killing of liver-stage malarial parasites by IFN-γ involves autophagy induction. Our results show that whereas IFN-γ treatment of human hepatocytes activates autophagy, the IFN-γ-mediated restriction of liver-stage Plasmodium vivax depends only on the downstream autophagy-related proteins Beclin 1, PI3K, and ATG5, but not on the upstream autophagy-initiating protein ULK1. In addition, IFN-γ enhanced the recruitment of LC3 onto the parasitophorous vacuole membrane (PVM) and increased the colocalization of lysosomal vesicles with P. vivax compartments. Taken together, these data indicate that IFN-γ mediates the control of liver-stage P. vivax by inducing a noncanonical autophagy pathway resembling that of LC3-associated phagocytosis, in which direct decoration of the PVM with LC3 promotes the fusion of P. vivax compartments with lysosomes and subsequent killing of the pathogen. Understanding the hepatocyte response to IFN-γ during Plasmodium infection and the roles of autophagy-related proteins may provide an urgently needed alternative strategy for the elimination of this human malaria.

摘要

干扰素-γ是免疫功能的主要调节因子,已证实在体外和体内均可诱导肝期疟原虫的清除。然而,干扰素-γ下游负责限制肝期疟原虫的分子机制仍不明确。自噬是一种新描述的免疫防御机制,最近被确定为在控制细胞内感染时响应干扰素-γ而激活的下游途径。因此,我们推测干扰素-γ对肝期疟原虫的杀伤涉及自噬诱导。我们的结果表明,虽然用干扰素-γ处理人肝细胞可激活自噬,但干扰素-γ介导的间日疟原虫肝期限制仅依赖于下游自噬相关蛋白Beclin 1、PI3K和ATG5,而不依赖于上游自噬起始蛋白ULK1。此外,干扰素-γ增强了LC3在寄生泡膜(PVM)上的募集,并增加了溶酶体囊泡与间日疟原虫区室的共定位。综上所述,这些数据表明,干扰素-γ通过诱导一种类似于LC3相关吞噬作用的非经典自噬途径来介导对间日疟原虫肝期的控制,其中LC3直接修饰PVM促进间日疟原虫区室与溶酶体融合并随后杀死病原体。了解疟原虫感染期间肝细胞对干扰素-γ的反应以及自噬相关蛋白的作用,可能为消除这种人类疟疾提供迫切需要的替代策略。

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