Differential regulation of GUV mechanics via actin network architectures

Actin networks polymerize and depolymerize to construct highly organized structures, thereby, endowing the mechanical phenotypes found in a cell. It is generally believed that the amount of filamentous actin and actin network architecture determine cytoplasmic viscosity and elasticity of the whole cell. However, the intrinsic complexity of a cell and numerous other endogenous cellular components make it difficult to study the differential role of distinct actin networks in regulating cell mechanics. Here, we model a cell by using giant unilamellar vesicles (GUVs) encapsulating actin filaments and networks assembled by various actin crosslinker proteins. Perturbation of these cytoskeletal vesicles using AC electric fields revealed that deformability depends on lumenal viscosity and actin network architecture. While actin-free vesicles exhibited large electromechanical deformations, deformations of GUVs encapsulating actin filaments were significantly dampened. The suppression of electrodeformation of actin-GUVs can be similarly recapitulated by using aqueous PEG 8000 solutions at different concentrations to modulate viscosity. Furthermore, alpha actinin-crosslinked actin networks resulted in decreased GUV deformability in comparison to actin filament-encapsulating GUVs, and membrane-associated actin networks through the formation of dendritic actin cortex greatly dampened electrodeformation of GUVs. These results highlight the organization of actin networks regulates the mechanics of GUVs and shed insights into the origin of differential deformability of cells.