Analysis of the function of the protein motor within the outer hair cell motility

虽然当我们低声说话时，鼓膜振动的幅度只有几个纳米，但我们可以清楚地理解所说的话。这可能是由于基于外毛细胞(OHC)运动性的耳蜗放大，而运动性估计是由于细胞质膜内马达蛋白的构象变化。然而，运动蛋白的功能尚不清楚，质膜下的细胞骨架对细胞运动的影响也不清楚，因此，为了了解细胞的功能，本研究分析了细胞对低张刺激的变形和细胞对电刺激的运动。此外，用原子力显微镜(AFM)观察了细胞侧壁的超微结构，并探讨了外毛细胞运动的机制。当细胞轴上的位置用距基端的归一化距离表示，基端和顶端的位置分别用0.0%和1.0%表示时，可以得出以下结论：(1)细胞的纵向硬度在距基端0.0%-0.881的区域内是恒定的，在距基端0.881-1.0%的区域内细胞的硬度高于其他区域。(2)蛋白质马达沿细胞轴的分布在0.142-0.893之间的区域是恒定的。AFM观察到细胞顶端和基底部的环状细丝为肌动蛋白，细胞顶端刚性较高的环状细丝密度高于基底部。

Although the amplitude of the tympanic membrane vibrations is only a few nanometers when we speak in a low voice, we can understand clearly what is being said. This is speculated to be due to the cochlear amplification which is based on the outer hair cell (OHC) motility, and the motility is estimated to be due to the conformational change of motor proteins within the plasma membrane of the cell. However, the function of the motor protein is unclear, and the effect of the cytoskeleton, which underlies the plasma membrane, on the motility of the cell has not been clarified yet.Therefore, in this study, in order to understand the function of the cell, the deformations of the cell in response to the hypotonic stimulation and the motility of the cell in response to the electrical stimulation are analyzed. Moreover, the ultrastructure of the cell lateral wall is investigated by atomic force microscopy (AFM), and the mechanism of the outer hair cell motility is studied. When the position along the cell axis is represented by the normalized distance from the basal end and the positions of the basal and apical ends are expressed by 0.0 and 1.0, respectively, the following conclusions can be drawn.(1) The longitudinal stiffness of the cell is constant in the region between 0.0 and 0.881 from the basal end, and the stiffness of the cell in the region between 0.881 and 1.0 from the basal end is higher than that in other regions.(2) The distribution of the protein motor along the cell axis is constant in the region between 0.142 and 0.893, and in the other regions at the apical and basal parts of the cell, the protein motor does not exist.(3) The circumferential filaments, which would be actins in the cortical lattice, are observed by AFM, and the density of the circumferential filaments at the apical part, where the stiffness is high, is higher than that at the basal part.