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

虽然当我们低声说话时，鼓膜振动的振幅只有几纳米，但我们可以清楚地理解所说的话。推测这是由于耳蜗的放大作用，耳蜗的放大作用是基于外毛细胞（OHC）的运动性，而这种运动性估计是由于细胞质膜内运动蛋白的构象改变。然而，运动蛋白的功能尚不清楚，细胞骨架（位于质膜之下）对细胞运动的影响也尚未阐明。因此，在本研究中，为了了解细胞的功能，我们分析了细胞在低渗刺激下的变形和细胞在电刺激下的运动。利用原子力显微镜观察了细胞外侧壁的超微结构，探讨了外毛细胞运动的机制。当细胞沿轴的位置用归一化距离表示，基端和顶端位置分别用0.0和1.0表示时，可以得出以下结论：(1)单体的纵向刚度在基端距离0.0 ~ 0.881范围内保持不变，基端距离0.881 ~ 1.0范围内单体的刚度高于其他区域。(2)蛋白质马达沿细胞轴的分布在0.142 ~ 0.893之间是恒定的，在细胞的顶端和基部的其他区域不存在蛋白质马达。(3)原子力显微镜观察到皮层晶格中的周向纤维，其密度在刚性较高的根尖处高于基部。

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.