The studies proposed here continue work on the molecular mechanism of sensory transduction by hair cells. A great deal of physiological evidence indicates that the transduction channels in vertebrate hair cells are directly activated by mechanical stimuli: that the tip links on stereocilia convey the displacement of the hair bundle to the channels, and that the stress causes channels to open. Similarly, adaptation of the transduction channels in the presence of a steady displacement is thought to come about by a decline in the stress reaching channels, by a movement of the tip link attachment. A particular myosin, type Ibeta, has been cloned from hair cells and is thought to be the motor protein that drives this movement. An additional phase of adaptation has been proposed to result from Ca++ binding directly to a site associated with the channel so as to close it. Both of these adaptation mechanisms can serve to regulate the set point for transduction. In this study, three aspects of the molecular apparatus mediating adaptation will be investigated. In the first part, the forces exerted by the hair bundle will be measured by the gradient-force light trap during adaptation. In this way, the contributions of a motor and a Ca++-dependent channel closure can be separated. In the second, the modulation of myosin-Ibeta by the second messenger cAMP will be studied. Myosin-Ibeta may be a substrate for protein kinase A, as part of a slower regulation of set point, and enzymes involved in cAMP metabolism may be part of the transduction apparatus. In the third, the yeast two-hybrid system will be used to find other proteins that bind to myosin- Ibeta, as a way of starting to identify all the proteins of the transduction complex. This understanding of hair bundle structures and the proteins associated with adaptation may elucidate certain pathological conditions of the auditory system. For instance, one of the myosins we cloned from hair cells is defective in Usher Syndrome, the most common inherited deafness in humans. Identification of the motor protein and proteins that bind to it may provide genetic tests for other inherited deafness.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC000304-19
Application #
6650801
Study Section
Special Emphasis Panel (ZRG1-IFCN-6 (01))
Program Officer
Donahue, Amy
Project Start
1984-09-01
Project End
2005-03-31
Budget Start
2003-04-01
Budget End
2004-03-31
Support Year
19
Fiscal Year
2003
Total Cost
$319,328
Indirect Cost
Name
Harvard University
Department
Biology
Type
Schools of Medicine
DUNS #
047006379
City
Boston
State
MA
Country
United States
Zip Code
02115
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Corey, David P; Akyuz, Nurunisa; Holt, Jeffrey R (2018) Function and Dysfunction of TMC Channels in Inner Ear Hair Cells. Cold Spring Harb Perspect Med :
Pan, Bifeng; Askew, Charles; Galvin, Alice et al. (2017) Gene therapy restores auditory and vestibular function in a mouse model of Usher syndrome type 1c. Nat Biotechnol 35:264-272
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Vogl, Christian; Panou, Iliana; Yamanbaeva, Gulnara et al. (2016) Tryptophan-rich basic protein (WRB) mediates insertion of the tail-anchored protein otoferlin and is required for hair cell exocytosis and hearing. EMBO J 35:2536-2552
Wu, Xudong; Indzhykulian, Artur A; Niksch, Paul D et al. (2016) Hair-Cell Mechanotransduction Persists in TRP Channel Knockout Mice. PLoS One 11:e0155577
Christensen, Adam P; Akyuz, Nurunisa; Corey, David P (2016) The Outer Pore and Selectivity Filter of TRPA1. PLoS One 11:e0166167
Kwan, Kelvin Y; Shen, Jun; Corey, David P (2015) C-MYC transcriptionally amplifies SOX2 target genes to regulate self-renewal in multipotent otic progenitor cells. Stem Cell Reports 4:47-60

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