Scaling behavior in steady-state contractile actomyosin network flow

TL;DR

This study investigates how actomyosin network remodeling influences cellular flow by analyzing in vitro networks, revealing that contraction rate scales with turnover rate and is regulated by network geometry and viscosity.

Contribution

It demonstrates that actomyosin network contraction is governed by turnover rate and network geometry, providing insights into cellular flow regulation mechanisms.

Findings

Contraction is density-independent across physiological conditions.

Contraction rate scales with network turnover rate.

Excessive crosslinking or branching disrupts this scaling.

Abstract

Contractile actomyosin network flows are crucial for many cellular processes including cell division and motility, morphogenesis and transport. How local remodeling of actin architecture tunes stress production and dissipation and regulates large-scale network flow remains poorly understood. Here, we generate contractile actomyosin networks with rapid turnover in vitro, by encapsulating cytoplasmic Xenopus egg extracts into cell-sized 'water-in-oil' droplets. Within minutes, the networks reach a dynamic steady-state with continuous inward flow. The networks exhibit homogenous, density-independent contraction for a wide range of physiological conditions, indicating that the myosin-generated stress driving contraction is proportional to the effective network viscosity. We further find that the contraction rate approximately scales with the network turnover rate, but this relation breaks down in the presence of excessive crosslinking or branching. Our findings suggest that cells use diverse biochemical mechanisms to generate robust, yet tunable, actin flows by regulating two parameters: turnover rate and network geometry.