The purpose of this proposal is to further our understanding of outer hair cell (OHC) function. Since these sensory receptor cells are required for normal sensitivity and frequency selectivity, it is important to define the protein networks involved in establishing these essential features of peripheral signal processing. It is known that OHC physiology is modulated by efferent signals originating in the medial olivocochlear (MOC) pathway (Guinan, 1996). In response to the release of acetylcholine (ACh), intracellular calcium increases and the subsequent outflow of potassium hyperpolarizes the cell. This change in membrane potential is thought to adjust the cochlear amplifier. Additional calcium-associated events and protein phosphorylation are likely to underlie changes in the cytoskeleton and in prestin, the OHC's motor protein. An influence on mechanoelectrical transduction (MET) in the stereocilia is also implicated. Speculation suggests that slow aspects of these changes are important for protecting OHCs at high sound levels. The fast changes, however, are thought to improve hearing in noise. Although studied for well over 50 years (Rasmussen, 1946;Galambos, 1956), the mechanisms underlying these changes are largely hypothetical. We are, therefore using various genetically altered mice to define the protein networks comprising this mechanical feedback loop. The use of mice with altered cytoskeleton, missing or nonfunctional prestin, defects in calcium-binding proteins and malfunction in various aspects of MET, will allow us to characterize cellular components associated with both fast and slow aspects of OHC modulation associated with activation of the MOC pathway. By combining measurements of basilar membrane mechanics and cochlear potentials with in vitro OHC and molecular analysis, it is possible to learn which mechanisms are required for changes in OHC function on both fast and slow time scales.

Public Health Relevance

Of the well over 30 million people in the US with auditory problems, the vast majority have defects in outer hair cell (OHC) function. These sensory receptor cells within the cochlea are required for normal sensitivity and frequency selectivity. Because their loss or malfunction results in major processing difficulties, our work on both normal and genetically altered OHCs is required in order to improve clinical outcomes.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Auditory System Study Section (AUD)
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Freeman, Nancy
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Northwestern University at Chicago
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Schools of Arts and Sciences
United States
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Takahashi, Satoe; Cheatham, Mary Ann; Zheng, Jing et al. (2016) The R130S mutation significantly affects the function of prestin, the outer hair cell motor protein. J Mol Med (Berl) 94:1053-62
Takahashi, Satoe; Homma, Kazuaki; Zhou, Yingjie et al. (2016) Susceptibility of outer hair cells to cholesterol chelator 2-hydroxypropyl-β-cyclodextrine is prestin-dependent. Sci Rep 6:21973
Cheatham, Mary Ann; Edge, Roxanne M; Homma, Kazuaki et al. (2015) Prestin-Dependence of Outer Hair Cell Survival and Partial Rescue of Outer Hair Cell Loss in PrestinV499G/Y501H Knockin Mice. PLoS One 10:e0145428
Keller, Jacob Pearson; Homma, Kazuaki; Duan, Chongwen et al. (2014) Functional regulation of the SLC26-family protein prestin by calcium/calmodulin. J Neurosci 34:1325-32
Homma, Kazuaki; Duan, Chongwen; Zheng, Jing et al. (2013) The V499G/Y501H mutation impairs fast motor kinetics of prestin and has significance for defining functional independence of individual prestin subunits. J Biol Chem 288:2452-63
Guinan Jr, John J; Salt, Alec; Cheatham, Mary Ann (2012) Progress in cochlear physiology after Bekesy. Hear Res 293:12-20
Homma, Kazuaki; Dallos, Peter (2011) Evidence that prestin has at least two voltage-dependent steps. J Biol Chem 286:2297-307
Zheng, Jing; Miller, Katharine K; Yang, Tao et al. (2011) Carcinoembryonic antigen-related cell adhesion molecule 16 interacts with alpha-tectorin and is mutated in autosomal dominant hearing loss (DFNA4). Proc Natl Acad Sci U S A 108:4218-23
Sengupta, Soma; Miller, Katharine K; Homma, Kazuaki et al. (2010) Interaction between the motor protein prestin and the transporter protein VAPA. Biochim Biophys Acta 1803:796-804
Homma, Kazuaki; Miller, Katharine K; Anderson, Charles T et al. (2010) Interaction between CFTR and prestin (SLC26A5). Biochim Biophys Acta 1798:1029-40

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