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 acetycholine (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.
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.
|Cheatham, Mary Ann; Low-Zeddies, Sharon; Naik, Khurram et al. (2009) A chimera analysis of prestin knock-out mice. J Neurosci 29:12000-8|
|Dallos, Peter (2008) Cochlear amplification, outer hair cells and prestin. Curr Opin Neurobiol 18:370-6|
|Dallos, Peter; Wu, Xudong; Cheatham, Mary Ann et al. (2008) Prestin-based outer hair cell motility is necessary for mammalian cochlear amplification. Neuron 58:333-9|
|Wu, Xudong; Wang, Xiang; Gao, Jiangang et al. (2008) Glucose transporter 5 is undetectable in outer hair cells and does not contribute to cochlear amplification. Brain Res 1210:20-8|
|Jia, Shuping; Dallos, Peter; He, David Z Z (2007) Mechanoelectric transduction of adult inner hair cells. J Neurosci 27:1006-14|
|He, David Z Z; Jia, Shuping; Dallos, Peter (2003) Prestin and the dynamic stiffness of cochlear outer hair cells. J Neurosci 23:9089-96|
|Zheng, Jing; Richter, Claus-Peter; Cheatham, Mary Ann (2003) Prestin expression in the cochlea of the reeler mouse. Neurosci Lett 347:13-6|
|Cheatham, M A; Dallos, P (2001) Inner hair cell response patterns: implications for low-frequency hearing. J Acoust Soc Am 110:2034-44|
|Cheatham, M A; Dallos, P (2000) The dynamic range of inner hair cell and organ of Corti responses. J Acoust Soc Am 107:1508-20|
|Cheatham, M A; Dallos, P (1999) Response phase: a view from the inner hair cell. J Acoust Soc Am 105:799-810|
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