Contraction of cross-linked actomyosin bundles

TL;DR

This paper models the contraction dynamics of cross-linked actomyosin bundles as a viscoelastic process driven by internal protein friction, estimating the contraction timescale consistent with experimental observations.

Contribution

It introduces a hydrodynamic model that describes bundle retraction as a viscoelastic process and estimates active stress magnitude from experimental data.

Findings

Contraction time scale tau estimated as 10-100 seconds.

Model aligns with experimental data on microfilament bundles.

Active stress magnitude inferred from the model.

Abstract

Cross-linked actomyosin bundles retract when severed in vivo by laser ablation, or when isolated from the cell and micromanipulated in vitro in the presence of ATP. We identify the time scale for contraction as a viscoelastic time tau, where the viscosity is due to (internal) protein friction. We obtain an estimate of the order of magnitude of the contraction time tau ~ 10-100 s, consistent with available experimental data for circumferential microfilament bundles and stress fibers. Our results are supported by an exactly solvable, hydrodynamic model of a retracting bundle as a cylinder of isotropic, active matter, from which the order of magnitude of the active stress is estimated.