The Human Fungal Pathogen Cryptococcus neoformans Escapes Macrophages by a Phagosome Emptying Mechanism That Is Inhibited by Arp2/3 Complex-Mediated Actin Polymerisation
The Human Fungal Pathogen Cryptococcus neoformans Escapes Macrophages by a Phagosome Emptying Mechanism That Is Inhibited by Arp2/3 Complex-Mediated Actin Polymerisation
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DOI：
10.1371/journal.ppat.1001041
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发表时间：
2010-08-01
期刊：
影响因子：
6.7
通讯作者：
May, Robin C.
中科院分区：
文献类型：
--
作者：
Johnston, Simon A.;May, Robin C.
致病微生物裂解感染细胞是一种有效但危险的传播性感染策略，因为它使病原体暴露于宿主免疫系统的全部库中。新型隐球菌是一种广泛存在的真菌病原体，可导致HIV和其他免疫功能低下患者的致命性脑膜炎。在细胞内生长后，隐球菌能够通过非溶解性排出机制逃离其宿主细胞，这可能有助于侵入中枢神经系统。一些细菌病原体也表现出非裂解性逃逸，并且可能在潜伏期期间促进对宿主免疫系统的长期回避。在这里，我们表明，含有细胞内隐球菌的吞噬体经历肌动蛋白聚合的重复循环。这些肌动蛋白“闪光”发生在鼠和人巨噬细胞中，并且依赖于经典的WASP-Arp 2/3复合物介导的肌动蛋白丝成核。三维共聚焦成像时间推移显示，这种闪光是高度动态的肌动蛋白笼，形成周围的吞噬体。使用荧光葡聚糖作为吞噬体膜完整性探针，我们发现隐球菌的非溶解性驱逐通过吞噬体和质膜的融合发生，并且在驱逐之前，95%的吞噬体变得透化，这是紧接着肌动蛋白闪光的事件。通过使用药理学试剂来调节肌动蛋白动力学和上游信号传导事件，我们发现闪光的发生与隐球菌的驱逐呈负相关，这表明闪光可能起到暂时抑制从感染的吞噬细胞驱逐的作用。总之，我们的数据揭示了存在一种新的肌动蛋白依赖性的过程中含有隐球菌，作为一个潜在的块驱逐隐球菌的吞噬体，并可能有显着的影响，这种生物体的传播和中枢神经系统的入侵。
The lysis of infected cells by disease-causing microorganisms is an efficient but risky strategy for disseminated infection, as it exposes the pathogen to the full repertoire of the host's immune system. Cryptococcus neoformans is a widespread fungal pathogen that causes a fatal meningitis in HIV and other immunocompromised patients. Following intracellular growth, cryptococci are able to escape their host cells by a non-lytic expulsive mechanism that may contribute to the invasion of the central nervous system. Non-lytic escape is also exhibited by some bacterial pathogens and is likely to facilitate long-term avoidance of the host immune system during latency. Here we show that phagosomes containing intracellular cryptococci undergo repeated cycles of actin polymerisation. These actin 'flashes' occur in both murine and human macrophages and are dependent on classical WASP-Arp2/3 complex mediated actin filament nucleation. Three dimensional confocal imaging time lapse revealed that such flashes are highly dynamic actin cages that form around the phagosome. Using fluorescent dextran as a phagosome membrane integrity probe, we find that the non-lytic expulsion of Cryptococcus occurs through fusion of the phagosome and plasma membranes and that, prior to expulsion, 95% of phagosomes become permeabilised, an event that is immediately followed by an actin flash. By using pharmacological agents to modulate both actin dynamics and upstream signalling events, we show that flash occurrence is inversely related to cryptococcal expulsion, suggesting that flashes may act to temporarily inhibit expulsion from infected phagocytes. In conclusion, our data reveal the existence of a novel actin-dependent process on phagosomes containing cryptococci that acts as a potential block to expulsion of Cryptococcus and may have significant implications for the dissemination of, and CNS invasion by, this organism.