Why the study?
Self-assembly and force generation are usually considered separately, despite signals activating nonmuscle myosin II molecular motors simultaneously leading to both minifilament self-assembly and cross-bridge cycle progression.
Theoretical modeling suggests that coupling myosin II assembly with force generation lowers the critical aggregation concentration, making minifilaments more responsive to varying conditions.
Model predictions imply tunable myosin assembly under load; extends biophysical theory but leaves open validation in cardiac myocytes.
Self-assembly and force generation are two central processes in biological systems that usually are considered in separation. However, the signals that activate nonmuscle myosin II molecular motors simultaneously lead to self-assembly into myosin II minifilaments as well as progression of the motor heads through the cross-bridge cycle. Here we investigate theoretically the possible effects of coupling these two processes. Our assembly model, which builds on a consensus architecture of the minifilament, predicts a critical aggregation concentration at which the assembly kinetics slows down dramatically. The combined model predicts that increasing actin filament concentration and force both lead to a decrease in the critical aggregation concentration. We suggest that due to these effects, myosin II minifilaments in a filamentous context might be in a critical state that reacts faster to varying conditions than in solution. We finally compare our model to experiments by simulating fluorescence recovery after photobleaching.
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Grewe et al. (2020) studied this question.
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