Pneumolysin activates macrophage lysosomal membrane permeabilization and executes apoptosis by distinct mechanisms without membrane pore formation.
Pneumolysin activates macrophage lysosomal membrane permeabilization and executes apoptosis by distinct mechanisms without membrane pore formation.
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DOI：
10.1128/mbio.01710-14
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发表时间：
2014-10-07
期刊：
影响因子：
6.4
通讯作者：
Dockrell DH
中科院分区：
文献类型：
--
作者：
Bewley MA;Naughton M;Preston J;Mitchell A;Holmes A;Marriott HM;Read RC;Mitchell TJ;Whyte MK;Dockrell DH
肺炎链球菌的细胞内杀伤通过诱导巨噬细胞凋亡来补充。在这里，我们表明，毒素肺炎球菌溶血素（pneumolysin）有助于溶酶体/吞噬溶酶体膜透化（LMP），上游事件编程的细胞凋亡的易感性，并通过线粒体途径，通过不同的机制凋亡执行。对于LMP和细胞凋亡的最大诱导而言，E2是必要的，但不是充分的。LMP和细胞凋亡的诱导能力与其形成溶细胞孔的能力无关，并且仅需要LMP的前三个结构域。LMP涉及TLR（Toll样受体），但不涉及NLRP 3/ASC（核苷酸结合寡聚化结构域[Nod]样受体家族，含pyrin结构域的蛋白3/含半胱天冬酶募集结构域的凋亡相关斑点样蛋白）信号传导，并且是PLY依赖性但非吞噬作用依赖性宿主应答的一部分，包括细胞因子（包括白细胞介素-1 β（IL-1β））的产生。LMP涉及对40-kDa但不对250-kDa异硫氰酸荧光素（FITC）标记的葡聚糖的渐进性和选择性渗透，因为葡聚糖在细胞质中积累。相比之下，PLY依赖性的细胞凋亡的执行需要吞噬作用，并且是宿主对细胞内细菌的反应的一部分，其还包括NO的产生。在用PLY缺陷型细菌挑战的细胞中，使用溶肌营养型洗涤剂LeuLeuOMe重建LMP有利于细胞坏死，而LMP则有利于细胞凋亡的重建。结果表明，LMP有助于巨噬细胞活化和细胞因子产生，但也参与LMP。在细菌吞噬作用后，作为广泛的抗微生物策略的一个组成部分，抗菌素触发细胞凋亡并防止巨噬细胞坏死。这说明了一个关键的毒力因子如何成为巨噬细胞的多层和协调的先天反应的焦点，优化病原体清除和限制炎症。肺炎链球菌是细菌性肺炎最常见的病因，它表达的毒素肺炎链球菌溶血素可以在细胞表面穿孔，导致组织损伤。巨噬细胞是对组织中的细菌做出反应所必需的常驻免疫细胞，它激活一种称为细胞凋亡的细胞自杀程序，最大限度地清除细菌并限制有害的炎症。我们研究了肺炎链球菌溶血素在激活这种反应中的作用。我们证明肺炎球菌溶血素没有直接在细胞中形成孔来触发细胞凋亡，并且表明肺炎球菌溶血素具有两种不同的作用，其仅需要分子的一部分。由未被巨噬细胞吞噬的细菌释放的巨噬细胞溶血素和其他细菌因子激活巨噬细胞以释放炎性因子，但也使含有摄入细菌的细胞区室泄漏。一旦进入细胞，肺炎球菌溶血素确保细菌激活巨噬细胞凋亡，而不是坏死，增强细菌杀伤和限制炎症。这种对肺炎链球菌溶血素的双重应答对于对肺炎链球菌的有效免疫应答至关重要。
Intracellular killing of Streptococcus pneumoniae is complemented by induction of macrophage apoptosis. Here, we show that the toxin pneumolysin (PLY) contributes both to lysosomal/phagolysosomal membrane permeabilization (LMP), an upstream event programing susceptibility to apoptosis, and to apoptosis execution via a mitochondrial pathway, through distinct mechanisms. PLY is necessary but not sufficient for the maximal induction of LMP and apoptosis. PLY’s ability to induce both LMP and apoptosis is independent of its ability to form cytolytic pores and requires only the first three domains of PLY. LMP involves TLR (Toll-like receptor) but not NLRP3/ASC (nucleotide-binding oligomerization domain [Nod]-like receptor family, pyrin domain-containing protein 3/apoptosis-associated speck-like protein containing a caspase recruitment domain) signaling and is part of a PLY-dependent but phagocytosis-independent host response that includes the production of cytokines, including interleukin-1 beta (IL-1β). LMP involves progressive and selective permeability to 40-kDa but not to 250-kDa fluorescein isothiocyanate (FITC)-labeled dextran, as PLY accumulates in the cytoplasm. In contrast, the PLY-dependent execution of apoptosis requires phagocytosis and is part of a host response to intracellular bacteria that also includes NO generation. In cells challenged with PLY-deficient bacteria, reconstitution of LMP using the lysomotrophic detergent LeuLeuOMe favored cell necrosis whereas PLY reconstituted apoptosis. The results suggest that PLY contributes to macrophage activation and cytokine production but also engages LMP. Following bacterial phagocytosis, PLY triggers apoptosis and prevents macrophage necrosis as a component of a broad-based antimicrobial strategy. This illustrates how a key virulence factor can become the focus of a multilayered and coordinated innate response by macrophages, optimizing pathogen clearance and limiting inflammation. Streptococcus pneumoniae, the commonest cause of bacterial pneumonia, expresses the toxin pneumolysin, which can make holes in cell surfaces, causing tissue damage. Macrophages, resident immune cells essential for responses to bacteria in tissues, activate a program of cell suicide called apoptosis, maximizing bacterial clearance and limiting harmful inflammation. We examined pneumolysin’s role in activating this response. We demonstrate that pneumolysin did not directly form holes in cells to trigger apoptosis and show that pneumolysin has two distinct roles which require only part of the molecule. Pneumolysin and other bacterial factors released by bacteria that have not been eaten by macrophages activate macrophages to release inflammatory factors but also make the cell compartment containing ingested bacteria leaky. Once inside the cell, pneumolysin ensures that the bacteria activate macrophage apoptosis, rather than necrosis, enhancing bacterial killing and limiting inflammation. This dual response to pneumolysin is critical for an effective immune response to S. pneumoniae.