Cell-sized liposome doublets reveal active tension build-up driven by acto-myosin dynamics

Area of Science:

• Cell Biology
• Biophysics

Background:

• Cells change shape for specific functions, regulated by the cell cortex, an actin network beneath the plasma membrane.
• Cortical tension, crucial for cell mechanics, arises from myosin motor activity and actin dynamics.

Purpose of the Study:

• To investigate the distinct and combined roles of actin polymerization and myosin activity in modulating cell cortex tension.
• To develop a non-invasive method for quantifying tension changes in a cell-sized system.

Main Methods:

• Utilized cell-sized liposome doublets coated with either stabilized preformed actin filaments or dynamic branched actin networks.
• Introduced myosin II minifilaments to observe shape changes indicative of tension variations.
• Employed a non-invasive assay to measure tension alterations driven by actin polymerization and myosin activity.

Main Results:

• Myosin II addition induced shape changes, confirming tension increases in both preformed and dynamic actin cortices.
• Isolated the effect of myosin activity using preformed actin filaments.
• Demonstrated the synergistic action of actin polymerization and myosin motors in dynamic actin cortices.

Conclusions:

• The study successfully quantified the contributions of actin polymerization and myosin activity to cortical tension.
• The developed assay offers a platform for evaluating tension modulation by various actin-associated proteins in a cell-sized context.
• Provides insights into the biophysical mechanisms governing cell shape and mechanics.