Gouin E, Gantelet H, Egile C, Lasa I, Ohayon H, Villiers V, Gounon P, Sansonetti P J, Cossart P
Unité des Interactions Bactéries-Cellules, Station Centrale de Microscopie Electronique, Institut Pasteur, 75724 Paris Cedex 15, France.
J Cell Sci. 1999 Jun;112 ( Pt 11):1697-708. doi: 10.1242/jcs.112.11.1697.
Listeria monocytogenes, Shigella flexneri, and Rickettsia conorii are three bacterial pathogens that are able to polymerize actin into 'comet tail' structures and move within the cytosol of infected cells. The actin-based motilities of L. monocytogenes and S. flexneri are known to require the bacterial proteins ActA and IcsA, respectively, and several mammalian cytoskeleton proteins including the Arp2/3 complex and VASP (vasodilator-stimulated phosphoprotein) for L. monocytogenes and vinculin and N-WASP (the neural Wiskott-Aldrich syndrome protein) for S. flexneri. In contrast, little is known about the motility of R. conorii. In the present study, we have analysed the actin-based motility of this bacterium in comparison to that of L. monocytogenes and S. flexneri. Rickettsia moved at least three times more slowly than Listeria and Shigella in both infected cells and Xenopus laevis egg extracts. Decoration of actin with the S1 subfragment of myosin in infected cells showed that the comet tails of Rickettsia have a structure strikingly different from those of L. monocytogenes or S. flexneri. In Listeria and Shigella tails, actin filaments form a branching network while Rickettsia tails display longer and not cross-linked actin filaments. Immunofluorescence studies revealed that the two host proteins, VASP and (&agr;)-actinin colocalized with actin in the tails of Rickettsia but neither the Arp2/3 complex which we detected in the Shigella actin tails, nor N-WASP, were detected in Rickettsia actin tails. Taken together, these results suggest that R. conorii may use a different mechanism of actin polymerization.
单核细胞增生李斯特菌、福氏志贺菌和康氏立克次体是三种能够将肌动蛋白聚合成“彗尾”结构并在受感染细胞的胞质溶胶中移动的细菌病原体。已知单核细胞增生李斯特菌和福氏志贺菌基于肌动蛋白的运动分别需要细菌蛋白ActA和IcsA，以及几种哺乳动物细胞骨架蛋白，包括单核细胞增生李斯特菌的Arp2/3复合物和VASP（血管舒张刺激磷蛋白）以及福氏志贺菌的纽蛋白和N-WASP（神经维斯科特-奥尔德里奇综合征蛋白）。相比之下，关于康氏立克次体的运动知之甚少。在本研究中，我们分析了这种细菌与单核细胞增生李斯特菌和福氏志贺菌相比基于肌动蛋白的运动。在受感染细胞和非洲爪蟾卵提取物中，立克次体的移动速度比李斯特菌和志贺菌至少慢三倍。在受感染细胞中用肌球蛋白的S1亚片段对肌动蛋白进行标记显示，立克次体的彗尾结构与单核细胞增生李斯特菌或福氏志贺菌的彗尾结构明显不同。在李斯特菌和志贺菌的彗尾中，肌动蛋白丝形成分支网络，而立克次体的彗尾则显示出更长且未交联的肌动蛋白丝。免疫荧光研究表明，两种宿主蛋白VASP和（α）-辅肌动蛋白与立克次体彗尾中的肌动蛋白共定位，但在立克次体肌动蛋白彗尾中既未检测到我们在福氏志贺菌肌动蛋白彗尾中检测到的Arp2/3复合物，也未检测到N-WASP。综上所述，这些结果表明康氏立克次体可能使用不同的肌动蛋白聚合机制。
