Adam T, Arpin M, Prévost M C, Gounon P, Sansonetti P J
Unité de Pathogénie Microbienne Moléculaire, Institut Pasteur, Paris, France.
J Cell Biol. 1995 Apr;129(2):367-81. doi: 10.1083/jcb.129.2.367.
Shigella flexneri is an enteroinvasive bacterium which causes bacillary dysentery in humans. A major feature of its pathogenic potential is the capacity to invade epithelial cells. Shigella entry into epithelial cells is considered a parasite-induced internalization process requiring polymerization of actin. Here we describe the cytoskeletal rearrangements during S. flexneri invasion of HeLa cells. After an initial contact of the bacterium with the cell surface, distinct nucleation zones of heavy chain actin polymerization appear in close proximity to the contact site underneath the parasite with long filaments being polymerized. These structures then push cellular protrusions that rise beside the entering bacterium, being sustained by tightly bundled long actin filaments organized in parallel orientation with their positive ends pointing to the cytoplasmic membrane. Finally, the cellular projections coalesce above the bacterial body, leading to its internalization. In addition, we found the actin-bundling protein plastin to be concentrated in these protrusions. Since plastin is known to bundle actin filaments in parallel orientation, colocalization of parallel actin filaments and plastin in the cellular protrusions strongly suggested a functional role of this protein in the architecture of parasite-induced cellular projections. Using transfection experiments, we show the differential recruitment of the two plastin isoforms (T- and L-) into Shigella entry zones. By transient expression of a truncated T-plastin which is deprived of one of its actin-binding sites, we also demonstrate the functional role of T-plastin in Shigella entry into HeLa cells.
福氏志贺菌是一种侵袭性肠道细菌，可引起人类细菌性痢疾。其致病潜力的一个主要特征是侵入上皮细胞的能力。志贺菌进入上皮细胞被认为是一种寄生虫诱导的内化过程，需要肌动蛋白聚合。在此，我们描述了福氏志贺菌侵袭HeLa细胞过程中的细胞骨架重排。细菌与细胞表面初次接触后，重链肌动蛋白聚合的明显成核区出现在寄生虫下方紧邻接触位点的位置，同时有长丝在聚合。这些结构随后推动在进入细菌旁边升起的细胞突起，这些突起由紧密束状的长肌动蛋白丝维持，这些肌动蛋白丝以平行方向排列，其正端指向细胞质膜。最后，细胞突起在菌体上方合并，导致菌体内化。此外，我们发现肌动蛋白结合蛋白丝束蛋白集中在这些突起中。由于已知丝束蛋白以平行方向捆绑肌动蛋白丝，因此平行肌动蛋白丝与丝束蛋白在细胞突起中的共定位强烈表明该蛋白在寄生虫诱导的细胞突起结构中具有功能作用。通过转染实验，我们展示了两种丝束蛋白异构体（T-和L-）在志贺菌进入区域的差异募集。通过瞬时表达缺失一个肌动蛋白结合位点的截短T-丝束蛋白，我们还证明了T-丝束蛋白在志贺菌进入HeLa细胞中的功能作用。
