Voltage-induced membrane movement

Area of Science:

• Biophysics
• Cellular Electrophysiology

Background:

• Thermodynamics predicts transmembrane voltage affects membrane tension, leading to cell movement.
• Cell stiffness and surface potentials govern the direction and magnitude of this movement.

Purpose of the Study:

• To experimentally confirm thermodynamic predictions of voltage-induced cell movement.
• To quantify the relationship between voltage, cell properties, and movement.
• To investigate the role of surface charge and the effect of salicylate on electromotility.

Main Methods:

• Utilized atomic force microscopy (AFM) to track movement of voltage-clamped HEK293 cells.
• Performed experiments in solutions of varying ionic strengths.
• Applied a physical model to estimate surface charge densities.

Main Results:

• Confirmed voltage-induced cell movement (electromotility) in HEK293 cells.
• Observed outward movement in normal saline and inward movement in low ionic strength solutions.
• Movement amplitude correlated with voltage (~1 nm/100 mV) and indentation depth.
• Estimated external and internal surface charge densities.
• Salicylate inhibited electromotility by increasing external charge, suggesting a potential reassessment of prestin's role.

Conclusions:

• Experimental evidence supports thermodynamic predictions of transmembrane voltage-driven cell movement.
• Cellular electromotility is dependent on ionic strength, voltage, and cell mechanical properties.
• Surface charge plays a critical role in modulating electromotility, with implications for mechanosensitive proteins like prestin.