Bioinspired Membrane Interfaces: Controlling Actomyosin Architecture and Contractility

Abstract

The creation of biologically inspired artificial lipid bilayers on planar supports provides a unique platform to study membrane-confined processes in a well-controlled setting. At the plasma membrane of mammalian cells, the linkage of the filamentous (F)-actin network is of pivotal importance leading to cell-specific and dynamic F-actin architectures, which are essential for the cell's shape, mechanical resilience, and biological function. These networks are established through the coordinated action of diverse actin-binding proteins and the presence of the plasma membrane. Here, we established phosphatidylinositol-4,5-bisphosphate (PtdIns[4,5]P 2 )-doped supported planar lipid bilayers to which contractile actomyosin networks were bound via the membrane−actin linker ezrin. This membrane system, amenable to high-resolution fluorescence microscopy, enabled us to analyze the connectivity and contractility of the actomyosin network. We found that the network architecture and dynamics are not only a function of the PtdIns[4,5]P 2 concentration but also depend on the presence of negatively charged phosphatidylserine (PS). PS drives the attached network into a regime, where low but physiologically relevant connectivity to the membrane results in strong contractility of the actomyosin network, emphasizing the importance of the lipid composition of the membrane interface.

Spatial Control of Arp2/3-Induced Actin Polymerization on Phase-Separated Giant Unilamellar Vesicles

“…A simple model to reconstitute this heterogeneity in vitro is phase-separated GUVs that form Ld (liquid disordered) and Lo (liquid ordered) domains. Some articles reported the effect of actin or actomyosin on phase-separated SLBs ,− or of the prokaryotic tubulin homologue FtsZ on phase-separated GUVs . So far, only one seminal study has addressed the interplay between lipid domains and actin networks on GUVs .…”