Department of Bio-Systems Engineering, Graduate School of Science and Engineering, Yamagata University, Yonezawa 992-8510, Japan.
Department of Bio-Systems Engineering, Graduate School of Science and Engineering, Yamagata University, Yonezawa 992-8510, Japan.
Biochim Biophys Acta Gen Subj. 2017 Nov;1861(11 Pt A):2717-2725. doi: 10.1016/j.bbagen.2017.07.016. Epub 2017 Jul 25.
Cellular dynamics depend on cytoskeletal filaments and motor proteins. Collective movements of filaments driven by motor proteins are observed in the presence of dense filaments in in vitro systems. As multiple macromolecules exist within cells and the physiological ionic conditions affect their interactions, crowding might contribute to ordered cytoskeletal architecture because of collective behavior.
Using an in vitro reconstituted system, we observed the emergence of stripe patterns resulting from collective actin filament streaming driven by myosin motors in the presence of the crowding agent, methylcellulose (MC).
Although at high KCl concentrations (150mM), actin filaments tended to dissociate from a myosin-coated surface, 1% MC prevented this dissociation and enabled filament movement on myosin molecules. At concentrations of actin filaments above 0.2mg/mL, the moving filaments accumulated and progressively formed long, dense bands. The bands were spaced at about 10-μm intervals. Increasing the KCl concentration up to 300mM resulted in narrowing of the spacing between the aligned bands. On the other hand, low KCl concentrations (≤25mM) induced broad streams, where actin filaments exhibited bidirectional movement.
These results suggest that crowded environments can promote spatial patterning of the actin cytoskeleton, depending on the intensity of the myosin driving force and filament velocity, both modulated by the ionic strength.
The mutual contribution of packing and driving forces provides insight into cytoskeleton organization in living cells, in which various macromolecules mingle.
细胞动力学依赖于细胞骨架丝和马达蛋白。在体外系统中，存在密集丝的情况下，可以观察到马达蛋白驱动的丝集体运动。由于细胞内存在多种大分子，并且生理离子条件会影响它们的相互作用，拥挤可能会由于集体行为而有助于有序的细胞骨架结构。
我们使用体外重建系统，观察到在存在拥挤剂甲基纤维素（MC）的情况下，肌球蛋白驱动的肌动蛋白丝集体流动导致条纹图案的出现。
尽管在高 KCl 浓度（150mM）下，肌动蛋白丝倾向于从肌球蛋白涂覆的表面解离，但 1% MC 阻止了这种解离，并使丝在肌球蛋白分子上移动。在高于 0.2mg/mL 的肌动蛋白丝浓度下，移动的丝会积累并逐渐形成长而密集的带。这些带的间隔约为 10-μm。增加 KCl 浓度至 300mM 会导致对齐带之间的间隔变窄。另一方面，低 KCl 浓度（≤25mM）会诱导宽流，其中肌动蛋白丝表现出双向运动。
这些结果表明，拥挤的环境可以促进肌动蛋白细胞骨架的空间模式形成，这取决于肌球蛋白驱动力和丝速度的强度，而这两者都受离子强度的调节。
包装力和驱动力的相互贡献为了解活细胞中的细胞骨架组织提供了思路，其中存在各种大分子的混合。
