Mapping correlated membrane pulsations and fluctuations in human cells

Area of Science:

• Biophysics
• Cell Biology
• Mechanobiology

Background:

• Cell membranes and cytoskeletons are dynamic structures.
• Thermo-mechanical forces and biological processes influence cell mechanics.
• Understanding cell membrane motion is crucial for cell biology.

Purpose of the Study:

• To measure local cell membrane motion in human foreskin fibroblasts (HFFs) using atomic force microscopy (AFM).
• To investigate the influence of cytoskeletal dynamics and physiological state on cell membrane mechanics.
• To analyze the random and non-random correlated mechanical processes governing membrane motion.

Main Methods:

• Utilized atomic force microscopy (AFM) to measure local membrane motion of HFFs.
• Applied actin and microtubule (MT) destabilizing drugs to observe effects on membrane pulsations.
• Induced early apoptosis in cells to assess changes in membrane mechanics.
• Performed correlation analysis to identify random and non-random processes and their time constants.
• Mapped correlation time constants over a 10 µm² area above the nucleus.

Main Results:

• Interphase HFFs exhibited distinct membrane pulsations (20-100 pN) and random fluctuations (<20 pN).
• Actin or MT depolymerization did not prevent pulsations, but early apoptosis abolished them.
• Correlation analysis revealed largely random motion with non-random processes (time constants 2-35 s).
• Compared to highly correlated cardiomyocyte motion, HFF motion showed distinct correlation patterns.
• Spatial mapping indicated variability in membrane correlation time constants.

Conclusions:

• Cell membrane pulsations and fluctuations are linked to the cell's physiological state and cytoskeletal dynamics.
• Distinct correlation time constants characterize different mechanical processes in human cells.
• AFM is a valuable tool for probing cell membrane mechanics and its relation to cellular state.