MECHANISMS OF SENSORY HAIR CELL DEATH

脊椎动物感觉毛细胞对多种遗传和环境因素的损伤敏感，包括暴露于氨基糖苷类抗生素。接触这些抗生素会导致感觉毛细胞死亡。在哺乳动物中，毛细胞的损失可导致永久性听力损失和/或平衡障碍。最近的证据表明，暴露于氨基糖苷类激活毛细胞的内在细胞死亡途径。该级联反应涉及称为半胱天冬酶的半胱氨酸蛋白酶家族的激活。半胱天冬酶激活是其他系统中程序性细胞死亡的标志，并且不同的半胱天冬酶响应于不同的细胞死亡促进刺激而被激活。拟议研究的总体目标是利用哺乳动物感觉毛细胞耳毒性的体外模型来确定氨基糖苷类药物诱导的毛细胞死亡中特定半胱天冬酶的参与。在第一组实验中，我将确定哪些半胱天冬酶在感觉毛细胞中被激活以响应氨基糖苷类药物暴露，并评估激活半胱天冬酶的细胞是否随后死亡。第二组实验将集中于确定哪些上游半胱天冬酶介导暴露于氨基糖苷类的毛细胞中特定下游半胱天冬酶的激活。这样一个了解的顺序半胱天冬酶激活是一个重要的步骤，了解发生在受损的毛细胞的信号级联。第三组实验旨在确定氨基糖苷类诱导的毛细胞程序性细胞死亡所必需的单个半胱天冬酶。综上所述，这些实验旨在提供对毛细胞中半胱天冬酶激活级联反应的首次检查，该级联反应从细胞死亡触发开始并通过细胞的实际执行进行。

Vertebrate sensory hair cells are sensitive to damage from a variety of genetic and environmental factors, including exposure to aminoglycoside antibiotics. Exposure to these antibiotics results in death of sensory hair cells. In mammals the loss of hair cells can result in permanent hearing loss and/or balance disturbances. Recent evidence indicates that exposure to aminoglycosides activates an intrinsic cell death pathway in hair cells. This cascade involves activation of a family of cysteine proteases called caspases. Caspase activation is the hallmark of programmed cell death in other systems, and different caspases are activated in response to different cell death-promoting stimuli. The overall goal of the proposed research is to utilize an in vitro model of mammalian sensory hair cell ototoxicity to determine the involvement of specific caspases in aminoglycoside-induced hair cell death. In the first set of experiments, I will determine which caspases are activated in sensory hair cells in response to aminoglycoside exposure and evaluate whether the cells activating caspases are subsequently dying. The second set of experiments will focus on determining which upstream caspases mediate activation of specific downstream caspases in hair cells exposed to aminoglycosides. Such an understanding of the order of caspase activation is an essential step toward understanding the signaling cascade that takes place in a damaged hair cell. The third set of experiments is designed to determine which individual caspases are necessary for aminoglycoside-induced programmed cell death in hair cells. Taken together, the experiments are designed to provide the first examination of the cascade of caspase activation in hair cells beginning with the cell death trigger and proceeding through the actual execution of the cell.