Coupled Myosin VI Motors Facilitate Unidirectional Movement on an F-actin Network

Abstract

Unconventional myosins interact with the dense cortical actin network during processes such as membrane trafficking, cell migration and mechanotransduction. Our understanding of unconventional myosin function is derived largely from assays that examine the interaction of a single myosin with a single actin filament. In this study we have developed a model system to study the interaction between multiple tethered unconventional myosins and a model F-actin cortex, namely the lamellipodium of a migrating fish epidermal keratocyte. Using myosin VI, which moves towards the pointed-end of actin filaments, we directly determine the polarity of the extracted keratocyte lamellipodium, from the cell periphery to the cell nucleus. We use a combination of experiment and simulation to demonstrate that multiple myosin VI molecules can coordinate to efficiently transport vesicle-size cargo over 10 microns of the dense interlaced actin network. Furthermore, several molecules of monomeric myosin VI, which are non-processive in single molecule assays, can coordinate to transport cargo with similar speeds as dimers.