MOLECULAR BASIS OF TRANSDUCTION IN AUDITORY SENSORY ORGANS

听觉感觉器官传导的分子基础

• 批准号: 6289629
• 负责人: BECHARA KACHAR
• 金额: --
• 依托单位: NATIONAL INSTITUTE ON DEAFNESS AND OTHER COMMUNICATION DISORDERS
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6289629
• 关键词: biological signal transduction; cell motility; cell type; cochlea; cochlear microphonic potentials; conditioning; depolarizing neuromuscular blocking agent; ear hair cell; electric field; electrostimulus; guinea pigs; neural transmission; organ of Corti; sound frequency; sulfhydryl reagents; voltage gated channel

We used a high-performance fluorescence imaging system to visualize rapid changes in intracellular free Ca2+ concentration ([Ca2+]i) evoked by focal applications of extracellullar ATP to the hair bundle of outer hair cells (OHCs) - the sensory-motor receptors of the cochlea. Simultaneous recordings of the whole-cell current and Calcium Green-1 fluorescence showed a two-component increase in [Ca2+]i. After an initial entry of Ca2+ through the apical membrane, a second and larger, InsP3-gated, [Ca2+]i surge occurred at the base of the hair bundle. Electron microscopy of this intracellular Ca2+ release site showed that it coincides with the localization of a unique system of endoplasmic reticulum (ER) membranes and mitochondria known as Hensens body. Using confocal immunofluorescence microscopy, we showed that InsP3 receptors share this location. Consistent with a Ca2+-mobilizing second messenger system linked to ATP- P2 receptors we also determined that an isoform of G proteins is present in the stereocilia. Voltage-driven cell shape changes and nonlinear capacitance were monitored before and after ATP application, showing that the ATP-evoked [Ca2+]i rise did not interfere with the OHC electromotility mechanism. This second messenger signaling mechanism bypasses the Ca2+- clearance power of the stereocilia and transiently elevates [Ca2+]i at the base of the hair bundle, where it can potentially modulate the action of unconventional myosin isozymes involved in maintaining the hair bundle integrity and potentially influence mechano-transduction. - hair sensory cells, mechano transduction, electromotility, cochlear amplifier, organ of Corti, outer hair cells, purinergic receptors.

我们使用了高性能的荧光成像系统来可视化细胞内游离Ca 2+浓度（[Ca 2 +]i）的快速变化引起的局灶性应用程序的细胞外ATP的外毛细胞（OHC）-耳蜗的感觉运动受体的毛束。全细胞电流和钙绿色-1荧光的同时记录显示[Ca 2 +]i的双组分增加。在Ca 2+最初通过顶膜进入后，在毛束底部发生了第二次更大的InsP 3门控[Ca 2 +]i激增。电子显微镜下的细胞内Ca 2+释放位点表明，它与一个独特的内质网（ER）膜和线粒体系统（称为亨森体）的定位相吻合。使用共聚焦免疫荧光显微镜，我们发现InsP 3受体共享这个位置。与连接到ATP-P2受体的Ca 2+动员第二信使系统一致，我们还确定G蛋白的同种型存在于静纤毛中。电压驱动的细胞形状的变化和非线性电容进行监测之前和之后的ATP应用程序，表明ATP诱发的[Ca 2 +]i上升不干扰OHC电运动机制。这种第二信使信号传导机制绕过静纤毛的Ca 2+清除能力，并瞬时升高毛束基部的[Ca 2 +]i，在那里它可以潜在地调节参与维持毛束完整性的非常规肌球蛋白同工酶的作用，并潜在地影响机械转导。- 毛感觉细胞，机械传导，电运动，耳蜗放大器，Corti器，外毛细胞，嘌呤受体。