Voltage-induced membrane movement

Abstract

Thermodynamics predicts that transmembrane voltage modulates membrane tension and that this will cause movement. The magnitude and polarity of movement is governed by cell stiffness and surface potentials. Here we confirm these predictions using the atomic force microscope to dynamically follow the movement of voltage-clamped HEK293 cells in different ionic-strength solutions. In normal saline, depolarization caused an outward movement, and at low ionic strength an inward movement. The amplitude was proportional to voltage (about 1 nm per 100 mV) and increased with indentation depth. A simple physical model of the membrane and tip provided an estimate of the external and internal surface charge densities (-5 x 10(-3) C x m(-2) and -18 x 10(-3) C x m(-2), respectively). Salicylate (a negative amphiphile) inhibited electromotility by increasing the external charge density by -15 x 10(-3) C x m(-2). As salicylate blocks electromotility in cochlear outer hair cells at the same concentration, the role of prestin as a motor protein may need to be reassessed.

Solitary electromechanical pulses in lobster neurons

“…The origin of the deviation of the early mechanical data from other recordings is not quite clear. Later direct recordings of mechanical changes induced by voltage include (28), who determined movement of membranes induced by voltage changes across HEK cell membranes by AFM (they find a displacement proportional to voltage), and (29), who measured mechanical changes in the soma of rat PC12 cells with a piezo-electric ribbon (reporting a force generated by a membrane proportional to voltage). The latter publication pointed out that AFM experiments on single neurons are in fact very difficult.…”

An historical perspective on cell mechanics

“…Although the major observable in AFM studies is the Young's modulus or elasticity (which is a related but fundamentally different parameter from viscosity), similar measurements have been performed in cells over the last two decades with AFM. These include the effects of anti-cytoskeletal drugs [41, 125,126], chemotherapy reagents [114,127] and electrical stimulation [27,128].…”

Finite element analysis of microelectrotension of cell membranes

“…Electric fields interact with lipid bilayer dielectric properties to induce compressive forces sufficient to deform membranes (Helfrich 1974;Kummrow and Helfrich 1991;Riske and Dimova 2006;Sens and Isambert 2002;Zhang et al 2001). Because the membrane is incompressible, electrocompression leads to electrotension (ET) (Needham and Hochmuth 1989;Riske and Dimova 2005), which forms the basis of electroporation, a widely-used method by which molecules are inserted into cells through electric field-induced membrane pores (Weaver 1993(Weaver , 1995.…”