Investigating the molecular mechanism of slow adaptation

研究缓慢适应的分子机制

• 批准号: 10291590
• 负责人: Giusy A Caprara
• 金额: $ 15.55万
• 依托单位: UNIVERSITY OF COLORADO DENVER
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10291590
• 关键词: Actins; Affect; Auditory; Auditory system; Binding; C-terminal; Calcium; Cochlea; Data; Electrophysiology (science); Extracellular Protein; Gerbils; Goals; Hair; Hair Cells; Head Movements; Height; Ions; Link; Mammals; Mechanics; Mediating; Medical; Methodology; Modeling; Molecular; Motion; Motor; Movement; Mus; Mutation; Myosin ATPase; Organelles; Persons; Phosphatidylinositol 4,5-Diphosphate; Phospholipids; Point Mutation; Positioning Attribute; Probability; Process; Publishing; Rana; Rana catesbeiana; Rattus; Regulation; Rest; Role; Signal Transduction; Stereocilium; Stimulus; System; Testing; Time; Vestibular Hair Cells; cofactor; deafness; essential phospholipids; experimental study; hearing impairment; link protein; mechanotransduction; preservation; receptor; sound

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.

项目总结/摘要 机械-电转换（MET）过程允许机械信息的转换， 声音和头部运动转化为电信号，这是耳蜗和前庭神经系统的基本步骤。 系统功能MET发生在毛束水平，由尖端连接、细胞外 连接短静纤毛和相邻的高静纤毛的蛋白质。发束的正偏转 （朝向静纤毛的最高行）增加尖端连接张力，从而增加MET的开放概率 渠道在持续的位移过程中，受体电流峰值然后衰减，表明逐渐的 MET通道开放概率降低。这个特殊的过程被称为“适应”， 这一点很重要，因为它改变了MET过程的操作范围，以保持系统的灵敏度。 一个几十年前的假设提出，缓慢的适应，这与一个时间常数的运作， 约10 ms或更长时间，需要Ca 2+通过MET通道进入和肌球蛋白马达的活性， 调节较高静纤毛上的尖端连接位置。电动机模型的主要证据是 在刺激过程中，存在蠕变（在阶梯状力的方向上的连续运动 刺激）在发束运动中具有与缓慢适应类似的时间过程。然而，方法论 困难导致了测试运动模型假设的有限实验。使用耳蜗 以及小鼠、大鼠和沙鼠的前庭毛细胞，我们证实，在哺乳动物中，缓慢的适应需要 Ca 2+和肌球蛋白电机，我们评估，调制适应不影响毛束蠕变。 因此，适应性调整不涉及挑战关键件的上尖端连杆插入的移动 支持电动机模型的证据 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设 其中磷脂是缓慢适应所必需的。特别是，对大鼠和青蛙的研究表明， 磷脂PIP 2影响MET通道特性，最近的数据表明，TMIE是一个重要的通道， 它是MET通道的亚基，并介导与PIP 2的相互作用以调节通道功能。我将测试PIP 2是否 是耳蜗和前庭毛细胞缓慢适应所必需的，我将测试它与肌球蛋白的相互作用 电动机.我的研究结果将使我能够确定慢性适应的潜在分子机制， 哺乳动物，保持系统灵敏度的关键过程，使我们能够检测到广泛的 声音强度具有极高的精度。