Reconstitution of an Actin Cortex Inside a Liposome

Abstract

The composite and versatile structure of the cytoskeleton confers complex mechanical properties on cells. Actin filaments sustain the cell membrane and their dynamics insure cell shape changes. For example, the lamellipodium moves by actin polymerization, a mechanism that has been studied using simplified experimental systems. Much less is known about the actin cortex, a shell-like structure underneath the membrane that contracts for cell movement. We have designed an experimental system that mimicks the cell cortex by allowing actin polymerization to nucleate and assemble at the inner membrane of a liposome. Actin shell growth can be triggered inside the liposome, which offers a useful system for a controlled study. The observed actin shell thickness and estimated mesh size of the actin structure are in good agreement with cellular data. Such a system paves the way for a thorough characterization of cortical dynamics and mechanics.

Cell-sized liposomes reveal how actomyosin cortical tension drives shape change

“…The thickness of the actin shells increases with liposome radius, indicating that the amount of membrane-adsorbed actin is proportional to the volume-to-surface ratio, consistent with previous reports (Fig. S5) (32). In about 10% of the liposomes, the actin forms a space-filling "bulk" network.…”

Motor-mediated Cortical versus Astral Microtubule Organization in Lipid-monolayered Droplets

“…Lipid-monolayered droplets can then be transformed into liposomes (14). This method has been used recently for the reconstitution of an active actin cortex inside liposomes consisting of a defined set of purified proteins of the actin cytoskeleton (15,16). Comparable experiments for encapsulated active motor/microtubule assemblies produced with purified proteins are lacking.…”

Divided we stand: splitting synthetic cells for their proliferation

“…For example, assembly of either actin or tubulin inside vesicles resulted in their deformation and the growth of protrusions (Fygenson et al 1997;Miyata et al 1999). More recently, protein cortices made up of actin and its associated proteins were reconstituted inside vesicles (Liu and Fletcher 2006;Merkle et al 2008;Pontani et al 2009;Tsai et al 2011;López-Montero et al 2012). These cortices increase the mechanical stability of vesicles.…”