Studies in cochlear hair cell transduction

摘要 这项建议的目的是加深我们对外毛细胞(OHC)功能的了解。因为这些 感觉受体细胞是正常灵敏度和频率选择性所必需的，重要的是定义 蛋白质网络参与建立这些外周信号处理的基本特征。这是众所周知的 OHC生理受源于内侧橄榄耳蜗区(MOC)通路的传出信号的调制 (Guinan，1996)。作为对乙酰胆碱(ACh)释放的反应，细胞内钙离子增加，并 随后钾的外流使细胞超极化。这种膜电位的变化被认为是 调整耳蜗放大器。更多的钙相关事件和蛋白质磷酸化可能会 细胞骨架和OHC的运动蛋白Prestin的变化是其根本原因。对…的影响 还涉及到立体纤毛中的机电转导(MET)。猜测表明，缓慢的 这些变化的某些方面对于在高声电平下保护OHC非常重要。然而，快速的变化， 被认为可以改善在噪音中的听力。尽管研究了50多年(拉斯穆森，1946； 加拉博斯，1956)，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环路的蛋白质网络。这个 使用细胞骨架改变、缺少或不起作用的prestin、钙结合蛋白缺陷和 MET不同方面的故障，将使我们能够表征与两者相关的细胞组件 与MOC通路激活相关的OHC调节的快慢方面。通过组合 用体外OHC和分子检测技术测量基底膜力学和耳蜗电 分析，可以了解FAST和OHC功能的变化需要哪些机制 缓慢的时间尺度。

Abstract 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.