Giardini P A, Theriot J A
Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, USA.
Biophys J. 2001 Dec;81(6):3193-203. doi: 10.1016/S0006-3495(01)75955-3.
How does subcellular architecture influence the intracellular movements of large organelles and macromolecular assemblies? To investigate the effects of mechanical changes in cytoplasmic structure on intracellular motility, we have characterized the actin-based motility of the intracellular bacterial pathogen Listeria monocytogenes in normal mouse fibroblasts and in fibroblasts lacking intermediate filaments. The apparent diffusion coefficient of L. monocytogenes was two-fold greater in vimentin-null fibroblasts than in wild-type fibroblasts, indicating that intermediate filaments significantly restrict the Brownian motion of bacteria. However, the mean speed of L. monocytogenes actin-based motility was statistically identical in vimentin-null and wild-type cells. Thus, environmental drag is not rate limiting for bacterial motility. Analysis of the temporal variations in speed measurements indicated that bacteria in vimentin-null cells displayed larger fluctuations in speed than did trajectories in wild-type cells. Similarly, the presence of the vimentin meshwork influenced the turning behavior of the bacteria; in the vimentin-null cells, bacteria made sharper turns than they did in wild-type cells. Taken together, these results suggest that a network of intermediate filaments constrains bacterial movement and operates over distances of several microns to reduce fluctuations in motile behavior.
亚细胞结构如何影响大型细胞器和大分子聚集体的细胞内运动？为了研究细胞质结构的机械变化对细胞内运动性的影响，我们已对细胞内细菌病原体单核细胞增生李斯特菌在正常小鼠成纤维细胞和缺乏中间丝的成纤维细胞中的基于肌动蛋白的运动性进行了表征。在缺乏波形蛋白的成纤维细胞中，单核细胞增生李斯特菌的表观扩散系数比野生型成纤维细胞中的大两倍，这表明中间丝显著限制了细菌的布朗运动。然而，在缺乏波形蛋白的细胞和野生型细胞中，单核细胞增生李斯特菌基于肌动蛋白的运动平均速度在统计学上是相同的。因此，环境阻力不是细菌运动性的限速因素。对速度测量的时间变化分析表明，缺乏波形蛋白的细胞中的细菌速度波动比野生型细胞中的轨迹更大。同样，波形蛋白网络的存在影响了细菌的转向行为；在缺乏波形蛋白的细胞中，细菌的转弯比在野生型细胞中更尖锐。综上所述，这些结果表明，中间丝网络限制细菌运动，并在几微米的距离上起作用以减少运动行为的波动。
