Wrinkling of a spherical lipid interface induced by actomyosin cortex

Abstract

Actomyosin actively generates contractile forces that provide the plasma membrane with the deformation stresses essential to carry out biological processes. Although the contractile property of purified actomyosin has been extensively studied, to understand the physical contribution of the actiomyosin contractile force on a deformable membrane is still a challenging problem and of great interest in the field of biophysics. Here, we reconstituted a model system with a cell-sized deformable interface that exhibits anomalous curvature dependent wrinkling caused by actomyosin cortex underneath the spherical closed interface. Through the shape analysis of the wrinkling deformation, we found that the dominant contributor on the wrinkled shape changes from bending elasticity to stretching elasticity of the reconstituted cortex by increasing the droplet curvature radius of the order of the cell-size, i.e., tens of micrometer. The observed curvature dependence was explained by the theoretical description of the cortex elasticity and contractility. Our present results provide a fundamental insight on the deformation of a curved membrane induced by the actomyosin cortex.

Actin shells control buckling and wrinkling of biomembranes

“…1C). Cup shapes are reminiscent of the ones of buckled spherical capsules under an osmotic shock (5,9) and the wrinkled shapes are reminiscent of that of a liposome under acto-myosin contraction (19,20). Again, we confirm that naked liposomes subjected to a decrease in volume (osmotic shock) display dynamical thermal shape undulations (Supplementary movie 2).…”

“…1C, the surface of a wrinkled liposome displays small spatial undulations around the average radius R, which remain unchanged over time and are therefore clearly distinct from thermal fluctuations. The wrinkling undulation occurs at wavelengths much smaller than the radius of the liposome, an observation that is similar to mimics of actomyosin cortices (19) . Local bending is favored into a buckling shape whereas wrinkling implies deformations all along the actin shell.…”

“…As a consequence, wrinkled shapes are only found if the actin thickness is larger than the wavelength. Experimentally, wrinkling of acto-myosin shells within incompressible oil droplets happens after a critical time that depends on the presence of a compressive stress energy term, due to acto-myosin contraction (19). In our system, the change in volume due to the osmotic shock may create compressive stresses of the thick actin layer in the absence of myosin, a phenomenon that would slow down localized shell buckling, and therefore favor wrinkling we observe here for thick actin shells.…”

Non-periodic oscillatory deformation of an actomyosin microdroplet encapsulated within a lipid interface

“…After the oscillations ceased together with the depletion of the actomyosin bundles bridging the aster core and the interface, the tangential tension of the lipid interface leads to regain its original spherical shape. Thereafter, (ii) wrinkle development started on the lipid interface, where the remaining actomyosin fraction exhibited a cortical shell ( Movie S2 ) 44 .…”

Coarse-grained molecular dynamics simulation of binary charged lipid membranes: Phase separation and morphological dynamics

“…Some ions or charged biomolecules can also trigger dynamic morphological changes through adsorption onto the lipid monolayers or bilayers via the electrostatic interactions. For example, locally injected HCl drives cristae-like deformation [33], BAR (Bin/amphiphysin/Rvs) domain family proteins induce the formation of tubular structures on the membranes [34], and actin cytoskeletons with myosin motor proteins cause concave deformations of oppositely charged lipid membranes [35,36].…”