Constriction of actin rings by passive crosslinkers

TL;DR

This paper presents a model demonstrating how passive crosslinkers can generate sufficient force to constrict actin rings during cell division, challenging the belief that motor proteins are necessary for this process.

Contribution

The study introduces a new model incorporating passive crosslinker forces and predicts their ability to drive actin ring constriction without motor proteins.

Findings

Passive crosslinkers can generate enough force for ring constriction.

Actin-filament sliding results from filament rotation and crosslinker hopping.

Frictional forces are lower compared to microtubule sliding with crosslinkers.

Abstract

In many organisms, cell division is driven by the constriction of a cytokinetic ring, which consists of actin filaments and crosslinking proteins. While it has long been believed that the constriction is driven by motor proteins, it has recently been discovered that passive crosslinkers that do not turn over fuel are able to generate enough force to constrict actin filament rings. To study the ring constriction dynamics, we develop a model that includes the driving force of crosslinker condensation and the opposing forces of friction and filament bending. We analyze the constriction force as a function of ring topology and crosslinker concentration, and predict forces that are sufficient to constrict an unadorned plasma membrane. Our model also predicts that actin-filament sliding arises from an interplay between filament rotation and crosslinker hopping, producing frictional forces that are low compared to those of crosslinker-mediated microtubule sliding.