Investigating the molecular mechanism of slow adaptation

项目摘要/摘要 机械-电转换(MET)过程允许机械信息从 声音和头部的运动转化为电信号，是耳蜗和前庭的基本步骤 系统功能。MET发生在发束水平，由尖端连接、细胞外调节 连接较短的立体纤毛和相邻的较高的立体纤毛的蛋白质。发束的正偏转 (朝向最高的一排立体纤毛)增加顶端-连接部的张力，这增加了MET的打开概率 频道。在持续的移位过程中，受体电流的峰值随后衰减，表明 MET信道打开概率降低。这一特殊的过程被称为“适应”，这一过程极其复杂 这一点很重要，因为它改变了仪表过程的工作范围，以保持系统的灵敏度。 一个有几十年历史的假说提出，慢适应是以时间常数的方式在 10毫秒或更长的数量级，需要通过MET通道的钙离子进入和肌球蛋白马达的活动 调节较高的立体纤毛上的尖端连接位置。汽车模型的主要证据是 在刺激过程中，存在蠕动(沿着阶梯式力量方向的持续运动 刺激)在发束运动中，具有与慢适应类似的时间进程。然而，在方法论上 测试运动模型假说的实验有限，困难也是原因之一。使用人工耳蜗术 以及小鼠、大鼠和沙土鼠的前庭毛细胞，我们证实在哺乳动物中，缓慢适应需要 钙离子和肌球蛋白马达，我们评估了调节适应不影响发束蠕动。 因此，适应并不涉及挑战关键部件的上尖端连接件的移动 支持汽车模型的证据。 利用前庭和耳蜗毛细胞的电生理记录，我将检验一个新的假说 其中磷脂对于缓慢适应是必不可少的。特别是，对老鼠和青蛙的研究表明， 磷脂PIP2影响MET通道的特性，最近的数据表明TMIE是一个必不可少的 MET通道的亚基，并调节与PIP2的相互作用，以调节通道功能。我将测试PIP2是否 对于耳蜗毛细胞和前庭毛细胞的缓慢适应是必需的，我将测试它与肌球蛋白的相互作用 摩托公司。我的结果将使我能够确定慢适应的潜在分子机制 哺乳动物，这一关键过程保持了系统的敏感性，并允许我们检测到广泛的 具有极高精确度的声音强度。

Project Summary/Abstract The mechano-electrical transduction (MET) process allows the transduction of mechanical information from sound and head movements into electrical signals, and it is a fundamental step in cochlear and vestibular system function. MET takes place at the level of the hair bundle and is mediated by tip links, extracellular proteins connecting shorter stereocilia to adjacent taller stereocilia. A positive deflection of the hair bundle (toward the tallest row of stereocilia) increases tip-link tension, which increases the open probability of MET channels. During a sustained displacement, the receptor current peaks then decays, indicating a gradual decrease in MET channel open probability. This particular process is called "adaptation" and is extremely important because it shifts the operating range of the MET process to preserve the sensitivity of the system. A decades-old hypothesis proposed that slow adaptation, which operates with a time constant on the order of 10 ms or more, requires Ca2+ entry through the MET channels and the activity of myosin motors to modulate the tip-link position on taller stereocilia. The major piece of evidence for the motor model is the presence, during the stimulation, of a creep (a continued movement in the direction of a step-like force stimulus) in the hair bundle motion with a similar time course as slow adaptation. However, methodological difficulties have contributed to the limited experiments that test the motor model hypothesis. Using cochlear and vestibular hair cells of mice, rats, and gerbils, we confirmed that in mammals, slow adaptation requires Ca2+ and myosin motors, and we assessed that modulating adaptation does not affect hair-bundle creep. Therefore, adaptation does not involve the movement of the upper tip-link insertion challenging a critical piece of evidence upholding the motor model. Using electrophysiological recording in vestibular and cochlear hair cells, I will test a new hypothesis where phospholipids are essential for slow adaptation. In particular, studies in rats and frogs have shown that the phospholipid PIP2 affects MET channel proprieties, and recent data demonstrate that TMIE is an essential subunit of the MET channel and mediates interactions with PIP2 to modulate channel function. I will test if PIP2 is necessary for slow adaptation in cochlear and vestibular hair cells, and I will test its interplay with myosin motors. My results will allow me to determine the underlying molecular mechanism of slow adaptation in mammals, the key process that preserves the sensitivity of the system and allows us to detect a wide range of sound intensities with extremely high precision.