Hydrostatic pressure in the ocean increases with depth by approximately 10 MPa per km. Complex life has adapted to occupy oceanic depths as far as 11 km where pressure reaches 110 MPa. High hydrostatic pressure alters cellular structure and function, including actin depolymerization and modification of lipid membrane properties. At the cell periphery, membrane-actin interactions are crucial for maintaining shape and mechanical integrity under external forces, making their responses key to understanding deep-sea cellular adaptation. Previous studies have investigated pressure effects on bulk actin and confinement effect on actin by lipid vesicles. However, little is known about the effect of pressure on encapsulated actin and membrane-actin dynamics. Our research aims to explain how membrane-actin coupled systems respond to pressurization. Specifically, we hypothesize that physically anchoring actin to lipid membranes will produce more pressure-stable membranes and actin networks. To demonstrate this, we developed a high-pressure and confocal microscopy compatible experimental platform. This system integrates a pump with a square cross-section glass capillary able to withstand pressures up to 100 MPa while remaining thin enough to allow high numerical aperture imaging like confocal microscopy. Our model system consists of 20–50 micrometer sized giant unilamellar vesicles (GUVs) containing polymerized actin filaments, where streptavidin-biotin linkers or actin binding proteins anchor the F-actin network to the GUV. Current progress includes successful encapsulation and confocal imaging of actin inside vesicles of desirable sizes. Ongoing work with this system will quantify pressure-dependent changes in filament density and distribution through fluorescent imaging. The findings will extend prior studies on actin and membrane separately and reveal how deep-sea organisms preserve their membrane and cytoskeletal actin functionality under extreme pressures.
Amin et al. (Sun,) studied this question.