Actin cortex rearrangement caused by coupling with the lipid bilayer-modeling considerations

Area of Science:

• Cell Biology
• Biophysics
• Materials Science

Background:

• Cell membrane mechanics are crucial for cellular functions.
• The actin cortex plays a significant role in cell membrane viscoelasticity.
• Micro rheological measurements provide insights into cell membrane dynamics.

Purpose of the Study:

• To investigate the impact of actin cortex-lipid bilayer coupling on cell membrane viscoelasticity.
• To analyze the rearrangement dynamics of the actin cortex in various cell types.
• To correlate cortex properties with cell stiffness and energy dissipation.

Main Methods:

• Utilized micro rheological measurements to study cell membrane fluctuations.
• Analyzed storage and loss moduli against angular velocity for different cell types.
• Quantified actin cortex rearrangement time and micro domain size.

Main Results:

• Coupling between the actin cortex and lipid bilayer affects energy dissipation.
• Softer cells (erythrocytes, Jurkat cells, fibroblasts) show actin cortex rearrangement at low angular velocities.
• Jurkat cells and fibroblasts exhibit longer rearrangement times (2.70-7.53 s) and smaller micro domains (~0.20-0.22 μm and ~36 nm) than erythrocytes (3.0-5.3 μm).
• Stiffer cells (epithelial lung, muscle cells) did not show observable cortex rearrangement.

Conclusions:

• Actin cortex rearrangement dynamics vary significantly across cell types.
• Smaller micro domain size and longer rearrangement time correlate with a stiffer cortex.
• The study provides a quantitative understanding of cell membrane mechanics and cortex behavior.