On cell surface deformation during an action potential

TL;DR

This study demonstrates that plant cells undergo reversible surface deformations during action potentials, with mechanical pulses propagating alongside electrical signals, suggesting a physical component to cellular excitability.

Contribution

It provides experimental and theoretical evidence of mechanical deformations during action potentials in plant cells, highlighting a physical aspect of cellular excitability.

Findings

Cell surface displaces 1-10 microns during AP

Mechanical pulse propagates at ~10 mm/s, matching electrical pulse speed

Deformations are reversible and mostly biphasic

Abstract

The excitation of many cells and tissues is associated with cell mechanical changes. The evidence presented herein corroborates that single cells deform during an action potential (AP). It is demonstrated that excitation of plant cells (Chara braunii internodes) is accompanied by out-of-plane displacements of the cell surface in the micrometer range (1-10 micron). The onset of cellular deformation coincides with the depolarization phase of the AP. The mechanical pulse (i) propagates with the same velocity as the electrical pulse (within experimental accuracy; 10 mm/s), (ii) is reversible, (iii) in most cases of biphasic nature (109 out of 152 experiments) and (iv) presumably independent of actin-myosin-motility. The existence of transient mechanical changes in the cell cortex is confirmed by micropipette aspiration experiments. A theoretical analysis demonstrates that this observation can be explained by a reversible change in the mechanical properties of the cell surface (transmembrane pressure, surface tension and bending rigidity). Taken together, these findings contribute to the ongoing debate about the physical nature of cellular excitability.