Heterogeneous nanoscopic lipid diffusion in the live cell membrane and its dependency on cholesterol

Area of Science:

• Membrane biophysics
• Cellular dynamics
• Nanoscale lipid behavior

Background:

• Cholesterol regulates membrane organization and dynamics by influencing nanoscale phase transitions.
• Cholesterol-mediated membrane nanodomains' effects on membrane dynamics are not well understood due to their small size and dynamic nature.

Purpose of the Study:

• To investigate nanoscale phospholipid diffusion in live cell plasma membranes.
• To determine the dependency of lipid diffusion on cholesterol concentration and temperature.

Main Methods:

• Utilized ultrahigh-speed single-molecule tracking with advanced optical microscopy.
• Analyzed diffusive motion of single phospholipids in live cell plasma membranes at the nanoscale.

Main Results:

• Observed anomalous subdiffusion for both saturated and unsaturated phospholipids (10-100 nm scale).
• Found highly heterogeneous lipid diffusion in space and time, with apparent dual-mobility subdiffusion.
• Cholesterol depletion and temperature reduction decreased lipid mobility, suggesting smaller compartments and stronger confinement.

Conclusions:

• Cholesterol depletion induces formation of gel-phase, solid-like nanodomains that restrict diffusion.
• These nanodomains act as obstacles, excluding other membrane molecules and altering dynamics.
• Nanoscale lipid diffusion is heterogeneous, sensitive to cholesterol and temperature, revealing key regulation mechanisms.