Ca2+ Changes the Force Sensitivity of the Hair-Cell Transduction Channel

¹ Harvard Medical School

^* To whom correspondence should be addressed. E-mail: dcorey{at}hms.harvard.edu.

Submitted on February 16, 2005
Revised on March 23, 2005
Accepted on 8 July 2005

	Abstract

The mechanically gated transduction channels of vertebrate hair cells tend to close in ~1 ms following their activation by hair bundle deflection. This fast adaptation is correlated with a quick negative movement of the bundle (a "twitch"), which can exert force and may mediate an active mechanical amplification of sound stimuli in hearing organs. We used an optical trap to deflect bullfrog hair bundles and to measure bundle movement while controlling Ca2+ entry with voltage clamp. The twitch elicited by repolarization of the cell varied with force applied to the bundle, going to zero where channels were all open or closed. The force dependence is quantitatively consistent with a model in which a Ca2+-bound channel requires ~3 pN more force to open, and rules out other models for the site of Ca2+ action. In addition, we characterized a faster, voltage-dependent "flick," which requires intact tip links but not current through transduction channels.

Key Words: cochlea, force, optical trap, sacculus, stereocilia, tuning

This article has been cited by other articles:

				K. A. Montgomery Multifrequency Forcing of a Hopf Oscillator Model of the Inner Ear Biophys. J., August 1, 2008; 95(3): 1075 - 1079. [Abstract] [Full Text] [PDF]

				W. M. Roberts and M. A. Rutherford Linear and nonlinear processing in hair cells J. Exp. Biol., June 1, 2008; 211(11): 1775 - 1780. [Abstract] [Full Text] [PDF]

				M. Beurg, J.-H. Nam, A. Crawford, and R. Fettiplace The Actions of Calcium on Hair Bundle Mechanics in Mammalian Cochlear Hair Cells Biophys. J., April 1, 2008; 94(7): 2639 - 2653. [Abstract] [Full Text] [PDF]

				T. A. Ghanem, K. D. Breneman, R. D. Rabbitt, and H. M. Brown Ionic Composition of Endolymph and Perilymph in the Inner Ear of the Oyster Toadfish, Opsanus tau Biol. Bull., February 1, 2008; 214(1): 83 - 90. [Abstract] [Full Text] [PDF]

				J. Ashmore Cochlear Outer Hair Cell Motility Physiol Rev, January 1, 2008; 88(1): 173 - 210. [Abstract] [Full Text] [PDF]

				J.-Y. Tinevez, F. Julicher, and P. Martin Unifying the Various Incarnations of Active Hair-Bundle Motility by the Vertebrate Hair Cell Biophys. J., December 1, 2007; 93(11): 4053 - 4067. [Abstract] [Full Text] [PDF]

				J.-H. Nam, J. R. Cotton, and W. Grant A Virtual Hair Cell, I: Addition of Gating Spring Theory into a 3-D Bundle Mechanical Model Biophys. J., March 15, 2007; 92(6): 1918 - 1928. [Abstract] [Full Text] [PDF]

				J.-H. Nam, J. R. Cotton, and W. Grant A Virtual Hair Cell, II: Evaluation of Mechanoelectric Transduction Parameters Biophys. J., March 15, 2007; 92(6): 1929 - 1937. [Abstract] [Full Text] [PDF]

				R. Fettiplace Active hair bundle movements in auditory hair cells J. Physiol., October 1, 2006; 576(1): 29 - 36. [Abstract] [Full Text] [PDF]

				D. P. Corey What is the hair cell transduction channel? J. Physiol., October 1, 2006; 576(1): 23 - 28. [Abstract] [Full Text] [PDF]

				J.-H. Nam, J. R. Cotton, E. H. Peterson, and W. Grant Mechanical Properties and Consequences of Stereocilia and Extracellular Links in Vestibular Hair Bundles Biophys. J., April 15, 2006; 90(8): 2786 - 2795. [Abstract] [Full Text] [PDF]