Myosin 1b flattens and prunes branched actin filaments.

Julien Pernier,Valentina Caorsi,Evelyne Coudrier,Antoine Morchain,Patricia Bassereau,Aurélie Bertin,Hugo Bousquet

doi:10.1242/jcs.247403

Abstract

ABSTRACTMotile and morphological cellular processes require a spatially and temporally coordinated branched actin network that is controlled by the activity of various regulatory proteins, including the Arp2/3 complex, profilin, cofilin and tropomyosin. We have previously reported that myosin 1b regulates the density of the actin network in the growth cone. Here, by performing in vitro F-actin gliding assays and total internal reflection fluorescence (TIRF) microscopy, we show that this molecular motor flattens (reduces the branch angle) in the Arp2/3-dependent actin branches, resulting in them breaking, and reduces the probability of new branches forming. This experiment reveals that myosin 1b can produce force sufficient enough to break up the Arp2/3-mediated actin junction. Together with the former in vivo studies, this work emphasizes the essential role played by myosins in the architecture and dynamics of actin networks in different cellular regions.This article has an associated First Person interview with the first author of the paper.

Highlights

Many motile and morphological processes involve spatially and temporally coordinated branching of filamentous actin (F-actin) networks
We have recently reported that single F-actins depolymerize when they slide on immobilized Myosin 1b (Myo1b) (Pernier et al, 2019), but how mammalian myosin 1 acts to reorganize branched actin network architecture remains to be explored
The branch density of stabilized F-actin decreases when sliding on Myo1b We first polymerized F-actin in solution in the presence of the constitutively active C-terminal domain of N-WASP (VCA) and the Arp2/3 complex (Pernier et al, 2016), to generate branched filaments and stabilized them with phalloidin

Summary

Introduction

Many motile and morphological processes involve spatially and temporally coordinated branching of filamentous actin (F-actin) networks. We have recently reported that single F-actins depolymerize when they slide on immobilized Myo1b (Pernier et al, 2019), but how mammalian myosin 1 acts to reorganize branched actin network architecture remains to be explored.

Results

Conclusion