Model of ionic currents through microtubule nanopores and the lumen

TL;DR

This paper models microtubules as electrical circuits with nanopores to understand ionic conductance and current amplification, revealing asymmetries and internal voltage effects that could influence cellular signaling and nano-bioelectronics.

Contribution

It introduces a novel circuit model of microtubules incorporating nanopore asymmetries and internal voltage sources, advancing understanding of their electrical properties.

Findings

Nanopores exhibit asymmetric conductance leading to nonlinear IV curves.

Internal voltage sources from C-terminal tail motion can pump net current.

The model suggests microtubules can amplify endogenous ionic currents.

Abstract

It has been suggested that microtubules and other cytoskeletal filaments may act as electrical transmission lines. An electrical circuit model of the microtubule is constructed incorporating features of its cylindrical structure with nanopores in its walls. This model is used to study how ionic conductance along the lumen is affected by flux through the nanopores when an external potential is applied across its two ends. Based on the results of Brownian dynamics simulations, the nanopores were found to have asymmetric inner and outer conductances, manifested as nonlinear IV curves. Our simulations indicate that a combination of this asymmetry and an internal voltage source arising from the motion of the C-terminal tails causes a net current to be pumped across the microtubule wall and propagate down the microtubule through the lumen. This effect is demonstrated to enhance and add directly to the longitudinal current through the lumen resulting from an external voltage source, and could be significant in amplifying low-intensity endogenous currents within the cellular environment or as a nano-bioelectronic device.