Role of myosin 1c in adaptation in the inner ear

这项研究的广泛，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，或称静纤毛， 声音和机械振动转化为神经冲动。机械传导的流行模型， 被认为是耳蜗和前庭毛细胞都很保守，是一个，其中相邻的 静纤毛由细胞外丝连接，称为尖端链接，响应刺激而偏转，从而引起 传导通道的打开或关闭。通道与自适应电机相关联 当张力很高时，复合物被拉下静纤毛的肌动蛋白细胞骨架，减少了尖端连接 张力，并打开通道;当张力低时，移位到肌动蛋白细胞骨架，恢复 静息张力，关闭Ca 2+通道。分子马达肌球蛋白1c（Myolc）的定位 在静纤毛的关键位置;以及使用表达突变Myolc的转基因小鼠的研究， 被选择性地抑制已经表明Myolc 1参与了这一称为适应的过程（Holt等， 2002; Stauffer等人，2005年）。适应使毛细胞在长时间的刺激下对新的刺激保持敏感。 刺激。该提案的目标是通过以下方式确定Myolc在适应的特定方面的作用： 测量表达具有确定分子特性的Myolc突变体的小鼠的适应性。具体 目的是：通过体外表达来表征Myolc突变体的生物化学和机械特性 然后通过ATP酶测定、运动测定、动力学分析和单分子生物学分析进行表征。 机械研究。突变体将包括那些影响Myo 1 c适应机械负荷能力的突变体，即 根据本实验室先前的研究预测的Myolc的性质（Batters等人，2004 a; 2004 b）。接下来， 这些突变对适应的影响将在来自敲入小鼠的前庭毛细胞中进行测试。 表达突变Myolc。结合体外和动物研究，预计将提供关键的，新的 Myolc的分子机制及其在适应中的作用。这些知识最终可以 导致设计合理的诊断和治疗方法来治疗平衡和/或听力疾病。

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 associated with an adaptation-motor complex, which when tension is high, is pulled down the actin cytoskeleton of the stereocilia, reducing tip link tension, and opening the channels; and when tension is low, translocates up the actin cytoskeleton, restoring the resting tension, and closing the Ca2* channels. Localization of the molecular motor, myosin 1c (Myolc) at strategic places in the stereocilia; and studies using transgenic mice expressing a mutant Myolc that can be selectively inhibited have shown Myolc1 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 the role of Myolc in specific aspects of adaptation by measuring adaptation in mice expressing Myolc mutants with defined molecular properties. The specific aims are: to characterize the biochemical and mechanical properties of Myolc mutants by in vitro expression followed by characterization by ATPase assays, motility assays, kinetic analyses and single-molecule mechanical studies. Mutants will include those that affect the ability of Myo1 c to adapt to mechanical load, a property predicted for Myolc from previous studies in this laboratory (Batters et al., 2004a; 2004b). Next, the effects of these mutations on adaptation will be tested in vestibular hair cells from knockin mice expressing mutant Myolc. The combined in vitro and animal studies are expected to provide critical, new insight into the molecular mechanism of Myolc and its role in adaptation. This knowledge could ultimately lead to the design of rational diagnostics and therapies to treat diseases of balance and/or hearing.