Geometrical origins of contractility in disordered actomyosin networks

Abstract

Movement within eukaryotic cells largely originates from localized forces exerted by myosin motors on scaffolds of actin filaments. Although individual motors locally exert both contractile and extensile forces, large actomyosin structures at the cellular scale are overwhelmingly contractile, suggesting that the scaffold serves to favor contraction over extension. While this mechanism is well understood in highly organized striated muscle, its origin in disordered networks such as the cell cortex is unknown. Here we develop a mathematical model of the actin scaffold's local two- or three-dimensional mechanics and identify four competing contraction mechanisms. We predict that one mechanism dominates, whereby local deformations of the actin break the balance between contraction and extension. In this mechanism, contractile forces result mostly from motors plucking the filaments transversely rather than buckling them longitudinally. These findings sheds light on recent $\text{in vitro}$ experiments, and provides a new geometrical understanding of contractility in the myriad of disordered actomyosin systems found $\text{in vivo}$.

arXiv comment9 pages, 5 figures, 5-page supplement

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Cited by in corpus (11)

• Broken detailed balance and non-equilibrium dynamics in living systems
• Nonequilibrium Physics in Biology
• Role of turn-over in active stress generation in a filament network
• Multiscale modeling and simulation of microtubule/motor protein assemblies
• Nonequilibrium dynamics of probe filaments in actin-myosin networks
• Stochastic Ratcheting on a Funneled Energy Landscape is Necessary for Highly Efficient Contractility of Actomyosin Force Dipoles
• Active restructuring of cytoskeleton composites leads to increased mechanical stiffness, memory, and heterogeneity
• Maximal fluctuations of confined actomyosin gels: dynamics of the cell nucleus
• Dynamics in Steady State In Vitro Acto-Myosin Networks
• Elasticity of randomly diluted honeycomb and diamond lattices with bending forces
• Percolation with trapping mechanism drives active gels to the critically connected state