Backouche F, Haviv L, Groswasser D, Bernheim-Groswasser A
Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Phys Biol. 2006 Dec 4;3(4):264-73. doi: 10.1088/1478-3975/3/4/004.
The actin cytoskeleton is an active gel which constantly remodels during cellular processes such as motility and division. Myosin II molecular motors are involved in this active remodeling process and therefore control the dynamic self-organization of cytoskeletal structures. Due to the complexity of in vivo systems, it is hard to investigate the role of myosin II in the reorganization process which determines the resulting cytoskeletal structures. Here we use an in vitro model system to show that myosin II actively reorganizes actin into a variety of mesoscopic patterns, but only in the presence of bundling proteins. We find that the nature of the reorganization process is complex, exhibiting patterns and dynamical phenomena not predicted by current theoretical models and not observed in corresponding passive systems (excluding motors). This system generates active networks, asters and even rings depending on motor and bundling protein concentrations. Furthermore, the motors generate the formation of the patterns, but above a critical concentration they can also disassemble them and even totally prevent the polymerization and bundling of actin filaments. These results may suggest that tuning the assembly and disassembly of cytoskeletal structures can be obtained by tuning the local myosin II concentration/activity.
肌动蛋白细胞骨架是一种动态凝胶，在诸如运动和分裂等细胞过程中不断重塑。肌球蛋白II分子马达参与这一动态重塑过程，从而控制细胞骨架结构的动态自组织。由于体内系统的复杂性，很难研究肌球蛋白II在决定最终细胞骨架结构的重组过程中的作用。在此，我们使用体外模型系统表明，肌球蛋白II能将肌动蛋白主动重组为多种介观模式，但前提是存在成束蛋白。我们发现重组过程的本质很复杂，呈现出当前理论模型未预测到且在相应被动系统（不含马达蛋白）中未观察到的模式和动力学现象。该系统根据马达蛋白和成束蛋白的浓度产生动态网络、星状体甚至环。此外，马达蛋白促使这些模式的形成，但在超过临界浓度时，它们也会使其解体，甚至完全阻止肌动蛋白丝的聚合和成束。这些结果可能表明，通过调节局部肌球蛋白II的浓度/活性，可以调控细胞骨架结构的组装和解聚。
