Rearrangement of GUV-confined actin networks in response to micropipette aspiration.

Abstract

Studies have shown that actin networks to be force sensing, force generating and endowing the mechanical property of cells. Actin networks are capable of these specialized tasks due to their ability to rearrange and assemble into diverse networks via numerous actin binding proteins. However, how different actin networks reorganize under applied forces is not entirely understood. Recently, bottom-up reconstitution has enabled studies where dynamic and phenotypical characteristics of various actin networks can be recreated in an isolated cell-like environment. Here, by creating a giant unilamellar vesicle (GUV)-based cell model encapsulating actin networks, we aim to understand how actin networks rearrange in response to stresses in confined spaces. We reconstitute actin cortex and actin bundles separately and use micropipette aspiration to mechanically perturb and induce stress. Interestingly, we find that, when aspirated, protrusive actin bundles that are otherwise randomly oriented in the GUV lumen collapse and align along the axis of pipette. Furthermore, when uniform cortex-GUVs are aspirated, bleb-like cortex-free membrane is aspirated in the micropipette. These results reveal diverse responses in the rearrangement of actin networks subject to physical forces.