Collective Dynamics of Active Cytoskeletal Networks

Simone Köhler,Volker Schaller,Andreas R. Bausch,Daniel J. Muller

doi:10.1371/journal.pone.0023798

Abstract

Self organization mechanisms are essential for the cytoskeleton to adapt to the requirements of living cells. They rely on the intricate interplay of cytoskeletal filaments, crosslinking proteins and molecular motors. Here we present an in vitro minimal model system consisting of actin filaments, fascin and myosin-II filaments exhibiting pulsatile collective dynamics and superdiffusive transport properties. Both phenomena rely on the complex competition of crosslinking molecules and motor filaments in the network. They are only observed if the relative strength of the binding of myosin-II filaments to the actin network allows exerting high enough forces to unbind actin/fascin crosslinks. This is shown by varying the binding strength of the acto-myosin bond and by combining the experiments with phenomenological simulations based on simple interaction rules.

Highlights

The cytoskeleton of eukaryotic cells is a highly flexible and adaptable scaffold that undergoes constant remodeling to meet their changing needs
To shed light on the principles underlying the physics of such active gels, to examine their microscopic dynamics and to classify the thereby resulting dynamic structures, we study a reconstituted actin network that is actively set under stress by molecular motors [7]
Active gels composed of 1 M actin filaments, 1 M fascin crosslinker and 0.1 M skeletal muscle myosin-II filaments in presence of ATP undergo drastic structural rearrangements

Summary

Introduction

The cytoskeleton of eukaryotic cells is a highly flexible and adaptable scaffold that undergoes constant remodeling to meet their changing needs. Similar self organization mechanisms are of outmost importance in many aspects of cellular development [3] All these processes rely on the intricate interplay between three major components: actin filaments, molecular motors and crosslinking proteins. While a polymer network consisting of filaments and crosslinkers result in a viscoelastic physical gel, molecular motors exert local forces and turn it into an active gel [4]. The dynamics in these active actomyosin gels can be coordinated in time and space as has been observed for the pulsed constrictions during dorsal closure giving rise to a collective behavior in vivo [5]

Methods

Results

Conclusion