2021 Theses Doctoral

Electromechanical Coupling in Cells and Its Effects on Membrane Tension and Conductance

Jones Molina, John Anthony

Electromechanical (EM) coupling in cells and the cell membrane is the product of basic electrical forces acting on the cell membrane and has been shown to produce voltage-driven membrane movements. While this type of EM coupling phenomenon has been observed in several cell types, including cultured neurons, its precise mechanism and physiological significance remain unclear. We have developed a novel platform that combines Atomic force microscopy (AFM) and patch clamp to measure voltage driven mechanical changes in the membranes of cultured HEK 293T cells. Using this technique, we have measured the mechanical effects of changes in membrane potential, determining the force and displacement at the membrane surface, as a function of voltage. Using our experimental data and basic physical principles, we developed a model of the effects of electrical forces on the membrane, which correlates highly with our observations. Importantly, our model predicts that the sum of electrical forces acting on the AFM tip and lipid bilayer will be different, suggesting that the membrane will experience a much larger tension change from EM coupling than was previously thought. The voltage driven tension is difficult to measure directly, but is predicted to act on mechanosensitive ion channels, resulting in a conductance profile that scales with the square of membrane potential. Conductance measurements exhibited a non-linear change in conductance that agreed with the predicted effects of EM coupling forces, as well as a mechanosensitive response to AFM induced tension. Our findings suggest that EM coupling could have a significant physiological role that had previously been underestimated.