Tubulin as a sensitive target of nanosecond-scale intense electric field: quantitative insights from molecular dynamics simulations

Abstract

Intense pulsed electric fields are known to act at the cell membrane level and are already being exploited in biomedical and biotechnological applications. However, it is not clear if intra-cellular components such as cytoskeletal proteins could be directly influenced by electric pulses within biomedically-attainable parameters. If so, a molecular mechanism of action could be uncovered for therapeutic applications of such electric fields. To help clarify this question, we first identified that a tubulin heterodimer is a natural biological target for intense electric fields due to its exceptional electric properties and crucial roles played in cell division. Using molecular dynamics simulations, we then demonstrated that an intense - yet experimentally attainable - electric field of nanosecond duration can affect the {beta}-tubulins C-terminus conformations and also influence local electrostatic properties at the GTPase as well as the binding sites of major tubulin drugs site. Our results suggest that intense nanosecond electric pulses could be used for physical modulation of microtubule dynamics. Since a nanosecond pulsed electric field can penetrate the tissues and cellular membranes due to its broadband spectrum, our results are also potentially significant for the development of novel therapeutic protocols. Author summary/{beta}-tubulin heterodimers are the basic building blocks of microtubules, that form diverse cellular structures responsible for essential cell functions such as cell division and intracellular transport. The ability of tubulin protein to adopt distinct conformations contributes to control the architecture of microtubule networks, microtubule-associated proteins, and motor proteins; moreover, it regulates microtubule growth, shrinkage, and the transitions between these states. Previous recent molecular dynamics simulations demonstrated that the interaction of the tubulin protein macrodipole with external electric field modifies orientation and conformations of key loops involved in lateral contacts: as a result, the stability of microtubules can be modulated by such fields. In this study, we seek to exploit these findings by investigating the possibility of fine-tuning the dipolar properties of binding sites of major drugs, by means of the action of electric fields. This may open the way to control tubulin-drug interactions using electric fields, thus modulating and altering the biological functions relative to the molecular vectors of microtubule assembly or disassembly. The major finding of our study reveals that intense (> 20 MV/m) ultra-short (30 ns) electric fields induce changes in the major residues of selected binding sites in a field strength-dependent manner.