DFG Membrane, Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Versbacherstr. 9, 97078 Würzburg, Germany.
Toxins (Basel). 2011 Jan;3(1):43-62. doi: 10.3390/toxins3010043. Epub 2011 Jan 7.
Streptococcus pneumoniae is a common pathogen that causes various infections, such as sepsis and meningitis. A major pathogenic factor of S. pneumoniae is the cholesterol-dependent cytolysin, pneumolysin. It produces cell lysis at high concentrations and apoptosis at lower concentrations. We have shown that sublytic amounts of pneumolysin induce small GTPase-dependent actin cytoskeleton reorganization and microtubule stabilization in human neuroblastoma cells that are manifested by cell retraction and changes in cell shape. In this study, we utilized a live imaging approach to analyze the role of pneumolysin's pore-forming capacity in the actin-dependent cell shape changes in primary astrocytes. After the initial challenge with the wild-type toxin, a permeabilized cell population was rapidly established within 20-40 minutes. After the initial rapid permeabilization, the size of the permeabilized population remained unchanged and reached a plateau. Thus, we analyzed the non-permeabilized (non-lytic) population, which demonstrated retraction and shape changes that were inhibited by actin depolymerization. Despite the non-lytic nature of pneumolysin treatment, the toxin's lytic capacity remained critical for the initiation of cell shape changes. The non-lytic pneumolysin mutants W433F-pneumolysin and delta6-pneumolysin, which bind the cell membrane with affinities similar to that of the wild-type toxin, were not able to induce shape changes. The initiation of cell shape changes and cell retraction by the wild-type toxin were independent of calcium and sodium influx and membrane depolarization, which are known to occur following cellular challenge and suggested to result from the ion channel-like properties of the pneumolysin pores. Excluding the major pore-related phenomena as the initiation mechanism of cell shape changes, the existence of a more complex relationship between the pore-forming capacity of pneumolysin and the actin cytoskeleton reorganization is suggested.
肺炎链球菌是一种常见的病原体，可引起各种感染，如败血症和脑膜炎。肺炎链球菌的一个主要致病因素是胆固醇依赖性细胞溶解素，肺炎溶素。它在高浓度下产生细胞溶解，在低浓度下产生细胞凋亡。我们已经表明，亚致死量的肺炎溶素诱导人神经母细胞瘤细胞中小 GTPase 依赖性肌动蛋白细胞骨架重排和微管稳定，表现为细胞回缩和细胞形状变化。在这项研究中，我们利用活细胞成像方法分析了肺炎溶素的孔形成能力在原代星形胶质细胞中依赖肌动蛋白的细胞形状变化中的作用。在用野生型毒素进行初始攻击后，在 20-40 分钟内迅速建立了一个通透性细胞群体。在初始快速通透后，通透群体的大小保持不变并达到一个平台。因此，我们分析了非通透（非溶胞）群体，该群体表现出收缩和形状变化，而肌动蛋白解聚抑制了这种变化。尽管肺炎溶素处理是非溶胞性的，但毒素的溶胞能力对于启动细胞形状变化仍然至关重要。非溶胞性肺炎溶素突变体 W433F-肺炎溶素和 delta6-肺炎溶素与野生型毒素结合细胞膜的亲和力相似，不能诱导形状变化。野生型毒素诱导的细胞形状变化和细胞回缩的起始与钙和钠离子内流以及膜去极化无关，这些现象已知在细胞受到刺激后会发生，并被认为是由于肺炎溶素孔的离子通道样特性所致。排除作为细胞形状变化起始机制的主要孔相关现象，表明肺炎溶素的孔形成能力与肌动蛋白细胞骨架重排之间存在更复杂的关系。
