Positive feedback by a potassium-selective inward rectifier enhances tuning in vertebrate hair cells.
AUTOR(ES)
Goodman, M B
RESUMO
Electrical resonance in vertebrate hair cells shapes receptor potentials and tunes each cell to a narrow band of frequencies. We have investigated the contribution of a potassium-selective inward rectifier (IR) to electrical resonance, isolating outward current carried by IR from other ionic currents active in the physiological voltage range (-75 to -30 mV) using a combination of potassium and calcium channel antagonists. IR expression is tightly regulated in the turtle's auditory epithelium, as revealed by the observation that its size declines systematically with resonant frequency. A critical feature of IR is the rapid inhibition produced by depolarization, which results in a negative slope in the steady-state current-voltage relation in the vicinity of the resting potential (-50 mV). The increasing block of outward current produced by depolarization is functionally equivalent to activating an inward current, suggesting that IR provides positive feedback and, in hair cells, serves an electrical function ordinarily reserved for voltage-dependent sodium and calcium currents. Additional support for this idea comes from the observation that superfusion with cesium selectively reduces IR and eliminates resonance in cells tuned to low frequencies and degrades resonant quality in cells tuned to more than 50 Hz.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1233494Documentos Relacionados
- ORK1, a potassium-selective leak channel with two pore domains cloned from Drosophila melanogaster by expression in Saccharomyces cerevisiae
- Inositol polyphosphate receptor and clathrin assembly protein AP-2 are related proteins that form potassium-selective ion channels in planar lipid bilayers.
- Calcium-activated potassium channels in goldfish hair cells.
- Calcium-binding sites on sensory processes in vertebrate hair cells.
- Position-dependent expression of potassium currents by chick cochlear hair cells.