Actin protein inside DMPC GUVs and its mechanical response to AC electric fields

Area of Science:

• Biophysics
• Cellular Mechanics
• Biomaterials Science

Background:

• Cells possess complex mechanical properties governed by protein assembly and disassembly.
• Giant unilamellar vesicles (GUVs) serve as simplified cell models for studying mechanical responses to stimuli.
• Actin, a key protein, exists in monomeric (G-actin) and filamentous (F-actin) forms, influencing cellular structure and function.

Purpose of the Study:

• To investigate the impact of actin polymerization state on the mechanical properties of DMPC-based GUVs.
• To quantify changes in membrane bending stiffness induced by the presence of G-actin versus F-actin within GUVs.
• To understand how internal protein dynamics affect the mechanical resilience of model cell membranes.

Main Methods:

• Rabbit skeletal muscle G-actin was introduced into DMPC GUVs via electroformation.
• Actin polymerization within GUVs was induced using MgCl2 and the ion carrier A23187.
• GUVs were subjected to AC electric fields to induce deformation, and shape changes were analyzed using optical microscopy.
• Membrane bending stiffness was calculated from the observed deformation responses.

Main Results:

• Monomeric G-actin did not significantly alter the bending stiffness of DMPC GUVs.
• Polymerized F-actin significantly increased the rigidity and deformation resistance of the GUVs.
• Evidence suggests F-actin filaments accumulate near the GUV membrane, contributing to increased stiffness.

Conclusions:

• The mechanical properties of model cell membranes (GUVs) are significantly influenced by the polymerization state of internal actin.
• F-actin polymerization enhances membrane rigidity, suggesting a role in cellular structural integrity and mechanical response.
• These findings highlight the importance of protein structural dynamics in modulating cellular mechanical behavior.