Proteomic characterization of the interplay of Staphylococcus aureus and human alveolar epithelial cells during infection - host cell proteins

Since infectious diseases caused by Staphylococcus aureus are still a major threat for human health we aimed to gain a detailed understanding of the molecular interplay of pathogen and host upon internalization by proteome analyses. In the present study we infected human alveolar epithelial A549 cells with S. aureus HG001 pMV158GFP and separated intact bacteria from host cell debris or infected from non-infected A549 cells prior to proteome analysis by cell sorting thus facilitating detailed analyses. During the first 6.5 h in the intracellular milieu S. aureus displayed reduced growth rate, induction of the stringent response, and adaptation to microaerobic conditions as well as cell wall stress. Interestingly, both truly infected host cells and those only potentially exposed to secreted S. aureus proteins but not infected displayed differences in the proteome pattern compared to A549 cells which had never been in contact with S. aureus. However, adaptation reactions were more pronounced in infected compared to non-infected A549 cells. Additional cytokine measurements revealed elaborated levels of pro-inflammatory cytokines in supernatants of the infection setting compared to pure host cell cultures which might mediate communication among the host cells and trigger adaptation even in cells not infected with S. aureus.

鉴于金黄色葡萄球菌（Staphylococcus aureus）引发的传染病仍是威胁人类健康的重大威胁，本研究旨在通过蛋白质组分析，深入解析病原菌侵入宿主细胞后二者间的分子互作机制。本研究中，我们使用金黄色葡萄球菌HG001 pMV158GFP感染人肺泡上皮A549细胞，并通过细胞分选将完整细菌与宿主细胞碎片分离，或是将感染与未感染的A549细胞分开，以便开展后续精细的蛋白质组分析。在侵入宿主细胞后的前6.5小时内，金黄色葡萄球菌的生长速率显著降低，同时激活严紧反应（stringent response），并对微需氧环境与细胞壁应激产生适应性调整。值得注意的是，与从未接触过金黄色葡萄球菌的A549细胞相比，无论是真正被感染的宿主细胞，还是仅潜在接触过分泌型金黄色葡萄球菌蛋白但未被感染的宿主细胞，其蛋白质组谱均存在显著差异。但相较于未感染的A549细胞，真正被感染的细胞的适应性反应更为显著。额外的细胞因子检测结果显示，与纯宿主细胞培养体系相比，感染模型体系的上清液中促炎细胞因子（pro-inflammatory cytokine）水平显著升高，这类细胞因子或可介导宿主细胞间的信号通讯，甚至在未被金黄色葡萄球菌感染的细胞中也能触发适应性反应。