Mechanisms of Self-Tuning in Inner Ear Hair Cells

内耳毛细胞的自我调节机制

基本信息

批准号：
8488426
负责人：
Dolores Bozovic
金额：
$ 36.58万
依托单位：
UNIVERSITY OF CALIFORNIA LOS ANGELES
依托单位国家：
美国
项目类别：
财政年份：
2011
资助国家：
美国
起止时间：
2011-07-01 至 2016-06-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): The inner ear is capable of mechanical detection at sub-nanometer scale, while displaying remarkable dynamic range. If the system could modulate its sensitivity of detection in response to the acoustic surroundings, it could reduce its gain of amplification or de-tune its frequency selectivity upon strong external stimulus, thus protecting itself from damage. Subsequent recovery to the original state would maintain optimal sensitivity of operation. The goal of the proposed research is to determine whether self-tuning occurs already at the sensory level, and determine its impact on the responsiveness of hair cells. Theoretical models have proposed that a hair cell contains an internal control parameter that determines its sensitivity of detection. Modulation of this parameter would control the gain of active amplification, and could cause the cell to exhibit instability by oscillating spontaneously. We aim to experimentally demonstrate crossing of this proposed bifurcation and explore potential biological mechanisms behind this phenomenon. Prolonged high-amplitude displacements will be applied to individual cells to mimic the effects of acoustic over-stimulation. Changes in active oscillation profiles and sensitivity of detection will be observed in real time, and the subsequent recovery recorded. Experimental demonstration of self-tuning of the mechanical response will allow us to establish a closer connection between the mathematical modeling and biologically relevant phenomena. In the first set of experiments, we will use mechanical manipulation to induce self-tuning in hair cells. The subsequent measurements will explore cellular mechanisms whereby a hair cell could self-adjust an internal parameter and thus modulate its dynamic state. Two potential biological parameters that we propose as control knobs for self-tuning in the hair cell are somatic membrane potential and internal calcium level. Simultaneous electrophysiological recordings and mechanical motility measurements will allow us to determine how the system of somatic ion channels interacts with the active mechanical amplifier. Sensitivity, frequency selectivity, and gain will be measured at different voltage-clamped levels. Pharmacological manipulation will be used to interfere with elements of the somatic circuit, and thus probe its impact on mechanical response. The effects of calcium on active bundle motility will be probed at multiple timescales. Fluorescence imaging will be combined with mechanical manipulation to extract the dynamics of calcium influx, accumulation, and extrusion from the stereocilia. Custom-designed instrumentation will be constructed to improve the temporal resolution currently accessible by confocal fluorescent imaging. The new technology will enable us to directly observe calcium signaling in biologically functional hair cells.

描述（由申请人提供）：内耳能够在亚纳米尺度上进行机械检测，同时显示出显着的动态范围。如果该系统可以根据声学环境调节其对检测的敏感性，则可以在强大的外部刺激下降低其扩增的增益或降低其频率选择性，从而保护自己免受损害。随后恢复到原始状态将保持最佳操作敏感性。拟议研究的目的是确定自我调整是否已经在感觉水平上发生，并确定其对毛细胞反应性的影响。理论模型提出，毛细胞包含一个决定其检测敏感性的内部控制参数。该参数的调节将控制主动扩增的增益，并可能通过自发振荡而使细胞表现出不稳定。我们的目标是实验证明这种提出的分叉的穿越，并探索这种现象背后的潜在生物学机制。长时间的高振幅位移将应用于单个细胞，以模仿声学过度刺激的影响。主动振荡轮廓的变化和检测的灵敏度将实时观察到，并记录了随后的恢复。机械响应进行自调的实验证明将使我们能够在数学建模和生物学相关现象之间建立更紧密的联系。在第一组实验中，我们将使用机械操作来诱导毛细胞中的自我调整。随后的测量结果将探索细胞机制，从而使毛细胞可以自我调整内部参数，从而调节其动态状态。我们提出的两个潜在的生物学参数作为对照旋钮进行自我调整，是体细胞膜的潜力和内部钙水平。同时进行电生理记录和机械运动测量将使我们能够确定体细胞离子通道系统如何与主动机械放大器相互作用。灵敏度，频率选择性和增益将在不同的电压钳位水平下测量。药理操作将用于干扰体电路的元素，从而探测其对机械反应的影响。钙对活动束运动性的影响将在多个时间尺度上进行探测。荧光成像将与机械操作结合使用，以从立体尾核中提取钙涌入，积累和挤出的动力学。将构建定制设计的仪器，以改善通过共聚焦荧光成像访问的时间分辨率。这项新技术将使我们能够直接观察到生物学功能性毛细胞中的钙信号传导。