Role of myosin 1c in adaptation in the inner ear

这项研究的广泛、长期的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投射或立体纤毛，由 声音和机械振动转化为神经冲动。机械转导的流行模型， 被认为对耳蜗毛细胞和前庭毛细胞都很保守的是一种 立体纤毛由称为尖端连接的细胞外细丝连接，对刺激作出反应而偏转，从而引起 转导通道的打开或关闭。这些通道与适应马达相关联 复合体，当张力较高时，被拉下立体纤毛的肌动蛋白细胞骨架，减少尖端连接 张力，打开通道；当张力较低时，向上移位肌动蛋白细胞骨架，恢复 静息张力，关闭钙离子通道。分子马达肌球蛋白1c(Myolc)的定位 在立体纤毛的关键位置；以及使用表达突变Myolc的转基因小鼠进行的研究 选择性地被抑制已经表明Myolc1 S参与了这个被称为适应的过程(Holt等， 2002年；Stauffer等人，2005年)。适应使毛细胞在长期刺激下保持对新的 刺激物。这项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 检测表达具有特定分子特性的Myolc突变体的小鼠的适应性。具体的 目的：通过体外表达来表征Myolc突变体的生物化学和力学性质 然后通过ATPase分析、运动分析、动力学分析和单分子分析进行表征 机械研究。突变将包括那些影响Myo1c适应机械负荷的能力的突变，a 根据该实验室以前的研究预测Myolc的性质(Batters等人，2004a；2004b)。下一首, 这些突变对适应的影响将在敲门小鼠的前庭毛细胞中进行测试。 表达突变体Myolc。体外和动物研究的结合有望提供关键的、新的 深入了解Myolc的分子机制及其在适应中的作用。这一知识最终可能 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.