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Role of myosin 1c in adaptation in the inner ear

肌球蛋白 1c 在内耳适应中的作用

基本信息

批准号：
8610435
负责人：
LYNNE M COLUCCIO
金额：
$ 36.65万
依托单位：
BOSTON UNIVERSITY MEDICAL CAMPUS
依托单位国家：
美国
项目类别：
财政年份：
2008
资助国家：
美国
起止时间：
2008-07-01 至 2014-06-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8610435
关键词：
Role myosin 1c adaptation inner

项目摘要

DESCRIPTION (provided by applicant): The broad, long-range goal of this study is to determine the molecular mechanism of hearing and balance. Actin-filled projections, or stereocilia, on the sensory hair cells of the inner ear convert force produced by sounds and mechanical vibrations into nerve impulses. The prevailing model for mechanotransduction, thought to be well-conserved for both cochlear and vestibular hair cells, is one in which neighboring stereocilia connected by extracellular filaments called tip links, deflect in response to stimuli, thereby causing the opening or closing of transduction channels. The channels are attached to an adaptation-motor complex, which controls tip-link tension. During an excitatory stimulus, tension is initially high, opening channels; the motor complex then slips down the actin cytoskeleton, reducing tip-link tension and allowing the channels to close. By contrast, during a negative stimulus, tension is initially low and channels close; the motor complex then ascends the cytoskeleton, restoring the resting tension and reopening the channels. Localization of the molecular motor, myosin 1c (Myo1c) at strategic places in the stereocilia; and studies using mice expressing a mutant Myo1c that can be selectively inhibited have shown Myo1c's involvement in this process known as adaptation (Holt et al., 2002; Stauffer et al., 2005). Adaptation allows hair cells under prolonged stimuli to remain sensitive to new stimuli. The goal of this proposal is to determine how Myo1c supports specific aspects of adaptation by measuring adaptation in mice expressing Myo1c mutants with defined molecular properties. Myo1c mutants will include (i) those that affect the ability of Myo1c to adapt to mechanical load, a property predicted for Myo1c from previous studies in this laboratory (Batters et al., 2004a; 2004b); and (ii) those with aberrant sensitivity to Ca2+, which regulates Myo1c and adaptation. The specific aims are: to express in vitro and characterize the biochemical and mechanical properties of Myo1c mutants using ATPase assays, motility assays, kinetic analyses and single-molecule mechanical studies. Next, knock-in mice expressing these mutant Myo1c molecules will be generated and adaptation will be measured in hair cells from the knock-in mice. The combined in vitro and animal studies are expected to provide critical, new insight into the molecular mechanism of Myo1c and its role in adaptation. This knowledge could ultimately lead to the design of rational diagnostics and therapies to treat diseases of hearing and/or balance. The proposed study focuses on the molecular motor protein, Myo1c, which is implicated as the adaptation-motor complex in the hair cells of the inner ear. Determining the biochemical and biophysical properties of key components of the transduction apparatus in hair cells, like Myo1c, and its role in adaptation are of fundamental importance to revealing the molecular mechanisms of hearing and balance, so that new and appropriate diagnostics and therapies to prevent or treat hearing loss and vertigo can be developed.

描述（由申请人提供）：本研究的广泛、长期目标是确定听力和平衡的分子机制。内耳感觉毛细胞上充满肌动蛋白的突起或静纤毛将声音和机械振动产生的力转化为神经冲动。普遍的机械转导模型被认为对于耳蜗和前庭毛细胞来说都是非常保守的，其中相邻的静纤毛通过称为尖端链接的细胞外细丝连接，响应刺激而偏转，从而导致转导通道的打开或关闭。这些通道连接到一个适应运动复合体，该复合体控制尖端连杆的张力。在兴奋性刺激期间，张力最初很高，打开通道；然后，运动复合体沿着肌动蛋白细胞骨架滑落，减少尖端连接张力并允许通道关闭。相比之下，在负面刺激期间，张力最初较低并且通道关闭；然后运动复合体沿着细胞骨架上升，恢复静息张力并重新打开通道。分子马达肌球蛋白 1c (Myo1c) 在静纤毛的重要位置定位；使用表达可选择性抑制的突变型 Myo1c 的小鼠进行的研究表明，Myo1c 参与了这一称为适应的过程（Holt 等人，2002 年；Stauffer 等人，2005 年）。适应使毛细胞在长时间刺激下仍能对新刺激保持敏感。该提案的目标是通过测量表达具有明确分子特性的 Myo1c 突变体的小鼠的适应来确定 Myo1c 如何支持适应的特定方面。 Myo1c 突变体将包括 (i) 那些影响 Myo1c 适应机械负荷能力的突变体，这是根据本实验室之前的研究预测的 Myo1c 的特性（Batters 等人，2004a；2004b）； (ii) 对 Ca2+ 异常敏感的人，Ca2+ 调节 Myo1c 和适应。具体目标是：使用 ATP 酶测定、运动测定、动力学分析和单分子机械研究来体外表达 Myo1c 突变体并表征其生化和机械特性。接下来，将产生表达这些突变型 Myo1c 分子的敲入小鼠，并在敲入小鼠的毛细胞中测量适应性。体外和动物研究相结合，有望为 Myo1c 的分子机制及其在适应中的作用提供重要的新见解。这些知识最终可能导致设计合理的诊断和疗法来治疗听力和/或平衡疾病。拟议的研究重点关注分子运动蛋白 Myo1c，它与内耳毛细胞中的适应运动复合体有关。确定毛细胞转导装置关键成分（如 Myo1c）的生化和生物物理特性及其在适应中的作用对于揭示听力和平衡的分子机制至关重要，以便开发新的、适当的诊断和疗法来预防或治疗听力损失和眩晕。