Nonlinear calcium ion waves along actin filaments control active hair-bundle motility.

Calcium ions (Ca) tune and control numerous diverse aspects of cochlear and vestibular physiological processes. This paper is focused on the Ca control of mechanotransduction in sensory hair cells in the context of polyelectrolyte properties of actin filaments within the hair-bundles of inner ear. These actin filaments appear to serve as efficient pathways for the flow of Ca ions inside stereocilia. We showed how this can be utilized for tuning of force-generating myosin motors. In an established model, we unified the Ca nonlinear dynamics involved in the control of myosin adaptation motors with mechanical displacements of hair-bundles. The model shows that the characteristic time scales fit reasonably well with the available experimental data for spontaneous oscillations in the inner ear. This scenario promises to fill a gap in our understanding of the role of Ca ions in the regulation of processes in the auditory cells of the inner ear.