Adaptation and Regulation of the Transduction Mechanism in Vestibular Hair Cells
Abstract
The research objectives are to characterize the time and displacement dependence of adaptation in hair cells; to localize the site of action of calcium and determine its calcium specificity; to identify and localize calcium- binding and structural proteins in stereocilia that may mediate calcium's effect. The results indicate that the adaptation process involves the movement of the attachment point of the spring attached to transduction channels; this may be a movement of one end of the morphologically-defined 'tip links'. They also suggest that there are two separate processes in the adaptation: One is a slipping or relaxing process that is linearly proportional in rate to the displacement, indicating that the rate may depend on tension in the tip link. The other is a climbing or tensioning process that is largely independent of displacement, suggesting an intrinsic climbing rate. Incidentally, the rate and final tension of the element are nearly identical to that of myosin moving on actin. We also have a good measure of the calcium dependence, using the microphonic preparation, and have made simple measurements of the cation specificity. The binding site appears to be specific for calcium, as magnesium, strontium or barium inhibit calcium's action. Patch clamp experiments have suggested that the site of calcium action is inside the tips of the stereocilia. Results are consistent with some molecular motor intimately associated with the transduction apparatus at the tips of the stereocilia. Immunohistochemical experiments have indicated that calmodulin is inside the tips of the stereocilia, as well as in the cell body. There is also calbindin throughout the cell.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 15, 1988
- Accession Number
- ADA203582
Entities
People
- David P. Corey
- John A. Assad
- Nir Hacohen
- Wendy J. Smith
Organizations
- Massachusetts General Hospital