Curvature and torsion in growing actin networks.
Curvature and torsion in growing actin networks.
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生长中的肌动蛋白网络的曲率和扭转。
DOI：
10.1088/1478-3975/5/2/026006
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发表时间：
2008
期刊：
影响因子：
2
通讯作者：
Fletcher,DanielA
中科院分区：
文献类型：
--
作者：
Shaevitz,JoshuaW;Fletcher,DanielA
细胞内病原体，如单核细胞增生李斯特菌和立克次氏体在宿主细胞内移动，通过聚合肌动蛋白纤维的彗星尾，最终推动细胞向前。这种交联肌动蛋白聚合物的密集网络通常表现出惊人的曲率，导致细菌以温和的环状路径移动。从理论上讲，尾部弯曲已经联系到运动的细节，考虑力和扭矩平衡从有限数量的聚合丝。在这里，我们跟踪珠包被原核激活剂的肌动蛋白聚合的三维直接量化珠运动路径的曲率和扭转。我们发现，珠路径更可能有低，而不是高曲率在任何给定的时间。此外，路径曲率随时间变化非常缓慢，自相关衰减时间为200 s。因此，曲率半径小的路径在较长的时间内保持不变，当被限制在二维时，会形成环路。当允许探索三维（3D）空间时，路径循环不太明显。最后，我们量化的扭转珠路径，并表明珠不表现出显着的左手或右手的偏见，他们的运动在3D。这些结果表明，肌动蛋白推进物体的路径可能是由于曲率的缓慢变化，可能与细丝脱支，而不是一个固定的扭矩。
Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left-or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque.