Bioinspired Membrane Interfaces: Controlling Actomyosin Architecture and Contractility

Area of Science:

• Biophysics
• Cell Biology
• Materials Science

Background:

• The plasma membrane's interaction with the filamentous (F)-actin network is crucial for cell shape, mechanics, and function.
• Actin networks are assembled by actin-binding proteins and influenced by the membrane environment.
• Supported planar lipid bilayers offer a controlled system to study membrane-protein interactions.

Purpose of the Study:

• To investigate how lipid composition in artificial bilayers affects actomyosin network connectivity and contractility.
• To understand the role of phosphatidylinositol-4,5-bisphosphate (PtdIns[4,5]P2) and phosphatidylserine (PS) in modulating membrane-actin interactions.
• To establish a model system for studying membrane-confined biological processes.

Main Methods:

• Development of phosphatidylinositol-4,5-bisphosphate (PtdIns[4,5]P2)-doped supported planar lipid bilayers.
• Binding of contractile actomyosin networks to the bilayers via the ezrin linker.
• High-resolution fluorescence microscopy to analyze network architecture and dynamics.

Main Results:

• Actomyosin network architecture and dynamics are dependent on PtdIns[4,5]P2 concentration.
• The presence of negatively charged phosphatidylserine (PS) significantly impacts network behavior.
• Low, physiologically relevant PS concentrations promote strong actomyosin contractility due to specific membrane connectivity.

Conclusions:

• Membrane lipid composition, particularly the interplay between PtdIns[4,5]P2 and PS, is a key determinant of actomyosin network contractility.
• This study emphasizes the importance of the lipid interface in regulating cellular mechanical properties.
• The developed artificial membrane system provides a valuable platform for future studies on membrane-confined processes.