Requirements for contractility in disordered cytoskeletal bundles

TL;DR

This paper investigates the mechanisms of actomyosin contractility in disordered cytoskeletal bundles, highlighting the necessity of non-identical motors and filament buckling for force generation, which differs from organized muscle models.

Contribution

It identifies the microscopic symmetry conditions and force requirements for contraction in disordered actomyosin bundles, emphasizing the role of filament buckling.

Findings

Contractility requires non-identical motors with sufficient force.

Filament buckling plays a key role in contraction.

Disordered bundles can contract without organized structure.

Abstract

Actomyosin contractility is essential for biological force generation, and is well understood in highly organized structures such as striated muscle. Additionally, actomyosin bundles devoid of this organization are known to contract both in vivo and in vitro, which cannot be described by standard muscle models. To narrow down the search for possible contraction mechanisms in these systems, we investigate their microscopic symmetries. We show that contractile behavior requires non-identical motors that generate large enough forces to probe the nonlinear elastic behavior of F-actin. This suggests a role for filament buckling in the contraction of these bundles, consistent with recent experimental results on reconstituted actomyosin bundles.