Ionic Wave Propagation along Actin Filaments

Abstract

We investigate the conditions enabling actin filaments to act as electrical transmission lines for ion flows along their lengths. We propose a model in which each actin monomer is an electric element with a capacitive, inductive, and resistive property due to the molecular structure of the actin filament and viscosity of the solution. Based on Kirchhoff's laws taken in the continuum limit, a nonlinear partial differential equation is derived for the propagation of ionic waves. We solve this equation in two different regimes. In the first, the maximum propagation velocity wave is found in terms of Jacobi elliptic functions. In the general case, we analyze the equation in terms of Fisher-Kolmogoroff modes with both localized and extended wave characteristics. We propose a new signaling mechanism in the cell, especially in neurons.

Electrodiffusion phenomena in neuroscience: a neglected companion

“…While featuring a high surface charge density (nominally exceeding 200 mM on the nanoscale) such structures appear to occupy only a small fraction of the cytosol volume 91 , thus permitting relatively free diffusion of small molecules in between 92 . Similar logic applies to the effects of intracellular organelles bearing a surface charge: for instance, in physiological conditions, actin filaments of the cytoskeleton bear the charge at a linear density of ~4·10 3 e/µm 93 . It has recently been estimated 94 that in such cases the charge-screening ion layers are formed around the densely accumulated surface charges while the bulk of intracellular electrolyte remains in an equilibrium with free-diffusing ions such as chloride (Fig.…”

Electrical dimensions in cell science

“…Both actin filaments and microtubules conduct electricity, with roughly the same conduction velocity along filamentous actin as in nerves (20 m/s) (Tuszynski et al, 2004;Priel et al, 2006). Actin filaments and microtubules are intimately associated with the anchoring of voltage-sensitive membrane receptors and channels, and intact microtubules and actinfilament networks are required for directional EF responses (Rajnicek et al, 2006b).…”

A new list of functions of the cytoskeleton

“…Information transport can be achieved by means of autocooperative conformational changes described above (3,7,17). They may be based on a number of coherent (superconducting) mechanisms explained in (1), including Davydov solitons, electrosolitons, protonic solitons (42 -44), surface bound ionic solitons (25,26) and Fro¨hlich waves (14). The latter correspond (1) to Ling's rest-to-action/action-to-rest transitions (3), to Pollack's gel-sol/sol-gel phase transitions (7) and to Del Giudice's Bose-decondensation/condensation mechanism (15).…”