A model for amplification of hair-bundle motion by cyclical binding of Ca2+ to mechanoelectrical-transduction channels
AUTOR(ES)
Choe, Yong
FONTE
The National Academy of Sciences
RESUMO
Amplification of auditory stimuli by hair cells augments the sensitivity of the vertebrate inner ear. Cell-body contractions of outer hair cells are thought to mediate amplification in the mammalian cochlea. In vertebrates that lack these cells, and perhaps in mammals as well, active movements of hair bundles may underlie amplification. We have evaluated a mathematical model in which amplification stems from the activity of mechanoelectrical-transduction channels. The intracellular binding of Ca2+ to channels is posited to promote their closure, which increases the tension in gating springs and exerts a negative force on the hair bundle. By enhancing bundle motion, this force partially compensates for viscous damping by cochlear fluids. Linear stability analysis of a six-state kinetic model reveals Hopf bifurcations for parameter values in the physiological range. These bifurcations signal conditions under which the system’s behavior changes from a damped oscillatory response to spontaneous limit-cycle oscillation. By varying the number of stereocilia in a bundle and the rate constant for Ca2+ binding, we calculate bifurcation frequencies spanning the observed range of auditory sensitivity for a representative receptor organ, the chicken’s cochlea. Simulations using prebifurcation parameter values demonstrate frequency-selective amplification with a striking compressive nonlinearity. Because transduction channels occur universally in hair cells, this active-channel model describes a mechanism of auditory amplification potentially applicable across species and hair-cell types.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=28041Documentos Relacionados
- The selectivity of the hair cell’s mechanoelectrical-transduction channel promotes Ca2+ flux at low Ca2+ concentrations
- Negative hair-bundle stiffness betrays a mechanism for mechanical amplification by the hair cell
- Effects of extracellular Ca2+ concentration on hair-bundle stiffness and gating-spring integrity in hair cells
- Active hair-bundle movements can amplify a hair cell’s response to oscillatory mechanical stimuli
- Detection of Ca2+ entry through mechanosensitive channels localizes the site of mechanoelectrical transduction in hair cells.