Key result
In a reconstituted biomimetic cortex, relative actomyosin sliding is attenuated during contraction, demonstrating that actomyosin sliding efficiently drives contraction despite a high degree of disorder.
In a reconstituted biomimetic cortex, actomyosin sliding efficiently drives contraction despite a high degree of disorder, with relative sliding attenuated during active contraction.
Findings on cortical contractility do not alter clinical practice; leaves open translation to cardiac myocyte mechanics.
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.
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Murrell et al. (2014) studied this question. Myosin II thick filament density variation vs. Low myosin density / weakly contractile networks was evaluated on F-actin network contraction and relative actomyosin sliding. In a reconstituted biomimetic cortex, relative actomyosin sliding is attenuated during contraction, demonstrating that actomyosin sliding efficiently drives contraction despite a high degree of disorder.
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