Electromechanics of the Cochlear Outer Hair Cell

描述(申请人提供)：哺乳动物正常听力所需的外毛细胞(OHC)。它们将电能转化为机械能，并为耳蜗放大器做出贡献，后者放大和细化内耳的声音振动。干扰它们的机电作用力产生机制会导致听力损失。负责产生这种力量的机制存在于OHC的质膜中。所有的薄膜似乎都能将电转化为机械力。OHC膜含有一种名为prestin的蛋白质，可以增强这一过程。此外，圆柱形的气泡能够有效地利用薄膜产生的力，并使其平行于其纵轴。这是通过一种优雅的、三层的复合纳米结构实现的，这种结构在生物学上是独一无二的，就像它在听力中所起的作用一样。1这项建议的目标是了解Prestin和侧壁的纳米级机械解剖如何促进OHC机电作用力的产生，特别是在声频。Prestin的作用是通过检测它的存在或不存在如何改变机电转导来确定的。对于所有的实验操作，都评估了药物的效果和细胞内氯离子浓度的变化可以改变OHC中的机电转导，从而调节听力。协调的实验、数学和计算方法将确定侧壁的组织如何引导质膜产生的机电作用力。3个特定目标从细胞膜开始，到整个细胞，在逐步更大的范围内研究OHC的机械特性和机电转导。在所有三个特定的目标中，电压钳位和光学镊子一起使用。特定目的1通过研究膜系绳对跨膜电位变化的机械反应来研究质膜中的机电转导。这些实验将单独确定膜的机电转换系数。特殊目标2探测侧壁的响应，特殊目标3检查整个细胞的力学和机电特性。最终的结果将是对OHC机电作用力产生及其在听力中的作用的完整描述。

DESCRIPTION (provided by applicant): Outer hair cells (OHC) are required for normal mammalian hearing. They convert electrical to mechanical energy and contribute to the cochlear amplifier that magnifies and refines sound vibrations in the inner ear. Interfering with their electromechanical force generating mechanism results in hearing loss. The mechanism responsible for this force production resides in the OHC's plasma membrane. All membranes appear able to convert electrical into mechanical force. The OHC membrane contains a protein called prestin that enhances the process. In addition, the cylindrical OHCs are effective at taking the membrane generated force and directing it parallel to their longitudinal axis. This is achieved by an elegant, 3 layered, composite nanostructure that is as biologically unique as the role it plays in hearing. 1 goal of this proposal is to understand how prestin and the nanoscale mechanical anatomy of the lateral wall facilitate OHC electromechanical force production, particularly at acoustic frequencies. The role of prestin is determined by examining how its presence or absence alters electromechanical transduction. The effect of drugs and changes in the intracellular chloride concentration known to alter electromechanical transduction in the OHC and thereby modulate hearing are assessed for all experimental manipulations. Coordinated experimental, mathematical and computational approaches will determine how the organization of the lateral wall directs the electromechanical force generated by the plasma membrane. 3 specific aims investigate OHC mechanical properties and electromechancial transduction at progressively larger scales beginning with the cell membrane and ending with the whole cell. Voltage-clamp and optical tweezers are used together in all 3 specific aims. Specific Aim 1 examines electromechanical transduction in the plasma membrane by investigating the mechanical response of membrane tethers to changes in the transmembrane potential. These experiments will determine the electromechanical transduction coefficient for the membrane alone. Specific Aim 2 probes the response of the lateral wall and Specific Aim 3 examines the mechanics and electromechanics of the whole cell. The final result will be a complete description of OHC electromechanical force production and its role in hearing.