Myosin 1b is an actin depolymerase

Julien Pernier,Patricia Bassereau,Thibaut Lagny,Jean-François Joanny,Remy Kusters,Hugo Bousquet,Antoine Morchain,Evelyne Coudrier

doi:10.1038/s41467-019-13160-y

Abstract

The regulation of actin dynamics is essential for various cellular processes. Former evidence suggests a correlation between the function of non-conventional myosin motors and actin dynamics. Here we investigate the contribution of myosin 1b to actin dynamics using sliding motility assays. We observe that sliding on myosin 1b immobilized or bound to a fluid bilayer enhances actin depolymerization at the barbed end, while sliding on myosin II, although 5 times faster, has no effect. This work reveals a non-conventional myosin motor as another type of depolymerase and points to its singular interactions with the actin barbed end.

Highlights

The regulation of actin dynamics is essential for various cellular processes
In contrast to muscle Myosin II (MyoII), this particular myosin 1b (Myo1b) is a catch-bound motor, it remains attached to the filament for a time that depends on the applied force[8]
We first measured the sliding velocity vf of single stabilized Factin on Myo1b immobilized on a glass coverslip (Supplementary Fig. 1a, top and Supplementary Movie 1), the sliding velocity vf and the polymerization rate vp of single Factin (Supplementary Fig. 1a, bottom and Supplementary Movie 1) (“Methods”), both in the presence and in the absence of 0.3% methylcellulose for keeping the filaments in the total internal reflection fluorescence (TIRF) field, by image analysis

Summary

Introduction

The regulation of actin dynamics is essential for various cellular processes. Former evidence suggests a correlation between the function of non-conventional myosin motors and actin dynamics. Beside the involvement of myosin 1 proteins in a large variety of cellular processes including cell migration and membrane trafficking[3], manipulation of myosin 1 expression has revealed a correlation between these myosins and actin network architecture[4,5,6,7]. We use in vitro F-actin gliding assays (Fig. 1b–e) and total internal reflection fluorescence (TIRF) microscopy to study the effect of full-length Myo1b on actin polymerization dynamics, with the motors either immobilized on a solid substrate (Fig. 1b, d) or bound to a fluid supported bilayer, which mimics cell membranes (Fig. 1c, e)

Methods

Results

Conclusion