Goldberg M B, Theriot J A
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Proc Natl Acad Sci U S A. 1995 Jul 3;92(14):6572-6. doi: 10.1073/pnas.92.14.6572.
Shigella flexneri is a Gram-negative bacterial pathogen that can grow directly in the cytoplasm of infected host cells and uses a form of actin-based motility for intra- and intercellular spread. Moving intracellular bacteria are associated with a polarized "comet tail" composed of actin filaments. IcsA, a 120-kDa outer membrane protein necessary for actin-based motility, is located at a single pole on the surface of the organism, at the junction with the actin tail. Here, we demonstrate that stable expression of IcsA on the surface of Escherichia coli is sufficient to allow actin-dependent movement of E. coli in cytoplasmic extracts, at rates comparable to the movement of S. flexneri in infected cells. Thus, IcsA is the sole Shigella-specific factor required for actin-based motility. Continuous protein synthesis and polarized distribution of the protein are not necessary for actin tail formation or movement. Listeria monocytogenes is an unrelated bacterial pathogen that exhibits similar actin-based intracytoplasmic motility. Actin filament dynamics in the comet tails associated with the two different organisms are essentially identical, which indicates that they have independently evolved mechanisms to interact with the same components of the host cytoskeleton.
福氏志贺菌是一种革兰氏阴性细菌病原体，它能够直接在受感染宿主细胞的细胞质中生长，并利用一种基于肌动蛋白的运动方式进行细胞内和细胞间传播。移动的细胞内细菌与由肌动蛋白丝组成的极化“彗尾”相关联。IcsA是一种基于肌动蛋白的运动所必需的120 kDa外膜蛋白，位于菌体表面与肌动蛋白尾相连的单极处。在此，我们证明IcsA在大肠杆菌表面的稳定表达足以使大肠杆菌在细胞质提取物中进行依赖肌动蛋白的移动，其移动速度与福氏志贺菌在受感染细胞中的移动速度相当。因此，IcsA是基于肌动蛋白的运动所必需的唯一志贺菌特异性因子。肌动蛋白尾的形成或移动并不需要持续的蛋白质合成和蛋白质的极化分布。单核细胞增生李斯特菌是一种不相关的细菌病原体，它表现出类似的基于肌动蛋白的胞质内运动。与这两种不同生物体相关的彗尾中的肌动蛋白丝动力学基本相同，这表明它们独立进化出了与宿主细胞骨架相同成分相互作用的机制。
