Mechanosensitive Self-Assembly of Myosin II Minifilaments

TL;DR

This paper presents a theoretical model linking the self-assembly of myosin II minifilaments with force generation, predicting critical behaviors influenced by actin concentration and force, and compares these predictions with experimental fluorescence recovery data.

Contribution

It introduces a coupled model of myosin II minifilament assembly and force generation, revealing critical concentration effects and dynamic responses in filamentous environments.

Findings

Critical aggregation concentration causes slow-down in assembly kinetics.

Increased actin and force decrease the critical concentration.

Model aligns with fluorescence recovery experiments.

Abstract

Self-assembly and force generation are two central processes in biological systems that usually are considered in separation. However, the signals that activate non-muscle myosin II molecular motors simultaneously lead to self-assembly into myosin II minifilaments as well as progression of the motor heads through the crossbridge cycle. Here we investigate theoretically the possible effects of coupling these two processes. Our assembly model, which builds upon 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.