Murrell Michael, Gardel Margaret L
Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637.
Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637Department of Physics and James Franck Institute, University of Chicago, Chicago, IL 60637
Mol Biol Cell. 2014 Jun 15;25(12):1845-53. doi: 10.1091/mbc.E13-08-0450. Epub 2014 Apr 23.
Myosin II motors embedded within the actin cortex generate contractile forces to modulate cell shape in essential behaviors, including polarization, migration, and division. In sarcomeres, myosin II-mediated sliding of antiparallel F-actin is tightly coupled to myofibril contraction. By contrast, cortical F-actin is highly disordered in polarity, orientation, and length. How the disordered nature of the actin cortex affects actin and myosin movements and resultant contraction is unknown. Here we reconstitute a model cortex in vitro to monitor the relative movements of actin and myosin under conditions that promote or abrogate network contraction. In weakly contractile networks, myosin can translocate large distances across stationary F-actin. By contrast, the extent of relative actomyosin sliding is attenuated during contraction. Thus actomyosin sliding efficiently drives contraction in actomyosin networks despite the high degree of disorder. These results are consistent with the nominal degree of relative actomyosin movement observed in actomyosin assemblies in nonmuscle cells.
嵌入肌动蛋白皮层的肌球蛋白II马达产生收缩力，以调节细胞在包括极化、迁移和分裂等基本行为中的形状。在肌节中，肌球蛋白II介导的反平行F-肌动蛋白滑动与肌原纤维收缩紧密耦合。相比之下，皮层F-肌动蛋白在极性、方向和长度上高度无序。肌动蛋白皮层的无序性质如何影响肌动蛋白和肌球蛋白的运动以及由此产生的收缩尚不清楚。在这里，我们在体外重建了一个模型皮层，以监测在促进或消除网络收缩的条件下肌动蛋白和肌球蛋白的相对运动。在弱收缩网络中，肌球蛋白可以在静止的F-肌动蛋白上远距离移位。相比之下，在收缩过程中，肌动球蛋白相对滑动的程度会减弱。因此，尽管存在高度无序，肌动球蛋白滑动仍能有效地驱动肌动球蛋白网络中的收缩。这些结果与在非肌肉细胞的肌动球蛋白组装体中观察到的相对肌动球蛋白运动的标称程度一致。
