MECHANISMS OF SENSORY HAIR CELL DEATH

脊椎动物的感觉毛细胞对各种遗传和环境因素的损害很敏感，包括接触氨基糖苷类抗生素。接触这些抗生素会导致感觉毛细胞死亡。在哺乳动物中，毛细胞的丧失可能导致永久性听力损失和/或平衡障碍。最近的证据表明，暴露于氨基糖苷类化合物会激活毛细胞内固有的细胞死亡途径。这一级联反应涉及半胱氨酸蛋白酶家族的激活，该家族被称为caspase。在其他系统中，caspase激活是细胞程序性死亡的标志，不同的caspase被激活以响应不同的细胞死亡促进刺激。这项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特定的半胱氨酸酶在氨基糖苷类药物诱导的毛细胞死亡中的作用。在第一组实验中，我将确定感觉毛细胞中哪些半胱氨酸天冬氨酸酶被激活，以回应氨基糖苷类药物的暴露，并评估激活半胱氨酸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氨酸酶介导暴露于氨基糖苷类药物的毛细胞中特定下游半胱氨酸酶的激活。对caspase激活顺序的了解是了解受损毛细胞中发生的信号级联反应的关键一步。第三组实验旨在确定哪些单独的半胱氨酸天冬氨酸酶是氨基糖苷类药物诱导毛细胞程序性死亡所必需的。综上所述，这些实验旨在首次检查毛细胞中caspase激活的级联过程，从细胞死亡触发开始，一直到细胞的实际执行。

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.