Studies in cochlear hair cell transduction

描述(申请人提供)：本建议的目的是加深我们对外毛细胞(OHC)功能的了解。由于这些感觉感受器细胞是正常灵敏度和频率选择性所必需的，因此确定与建立这些外周信号处理的基本特征有关的蛋白质网络是很重要的。众所周知，OHC的生理学是由起源于内侧橄榄耳蜗(MOC)通路的传出信号调制的(Guinan，1996)。作为对乙酰胆碱(ACh)释放的反应，细胞内钙增加，随后钾的外流使细胞超极化。这种膜电位的变化被认为是对耳蜗放大器的调节。额外的钙相关事件和蛋白磷酸化很可能是细胞骨架和OHC的运动蛋白Prestin变化的基础。也牵涉到在立体纤毛中对机械电转导(MET)的影响。推测表明，这些变化的缓慢方面对于保护处于高声音水平的OHC很重要。然而，快速的变化被认为可以改善噪音中的听力。尽管研究了50多年(拉斯穆森，1946；加拉博斯，1956)，但这些变化背后的机制在很大程度上是假设的。因此，我们正在使用各种基因改变的小鼠来定义组成这个机械反馈循环的蛋白质网络。利用细胞骨架改变、Prestin缺失或不起作用、钙结合蛋白缺陷以及MET各个方面的故障的小鼠，将使我们能够表征与MOC途径激活相关的OHC调节的快和慢方面的细胞成分。通过将基底膜力学和耳蜗电的测量与体外OHC和分子分析相结合，可以了解OHC功能在快时间尺度和慢时间尺度上的变化需要哪些机制。 与公共健康相关：在美国3000多万听力有问题的人中，绝大多数人的外毛细胞(OHC)功能存在缺陷。耳蜗内的这些感觉感受器细胞是正常灵敏度和频率选择性所必需的。由于它们的丢失或故障会导致严重的处理困难，因此我们在正常和基因改变的内囊细胞上的工作是必要的，以改善临床结果。

DESCRIPTION (provided by applicant): 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.