Preventing hair cell loss by regulating prestin's function

描述（由申请人提供）：哺乳动物（包括人类）需要通过外毛细胞（OHC）进行扩增，因为它们具有高灵敏度和尖锐的频率选择性。OHC也是内耳中最脆弱的细胞，并且与大多数感音神经性听力损失有关。虽然通过干细胞替代或基因治疗的OHC再生在未来提供了一个令人兴奋的选择，但预防毛细胞损失仍然是处理毛细胞损失（包括再生毛细胞）的最直接和最现实的方法。因此，我们的建议将集中在毛细胞，特别是外毛细胞的维护上。OHC死亡与已知破坏细胞的活性氧（ROS）的产生密切相关。与Corti器官中的其他细胞相比，为什么OHC更容易受到ROS的影响还没有完全了解。OHC的主要功能是通过其躯体电运动放大机械信号。这种独有的特性由一种称为普雷斯廷的独特马达蛋白执行，该蛋白仅在OHC中表达。过去，研究OHC扩增机制和防止OHC丢失被认为是两个独立的研究领域。出乎意料的是，我们发现普雷斯廷（499-普雷斯廷突变体）的非功能性点突变导致OHC死亡。此外，普雷斯廷不仅与参与ROS生成的蛋白质相关，而且普雷斯廷本身可能具有氧化还原酶活性，这可能是OHC防御系统的一部分，以最小化ROS。这些数据表明，普雷斯廷的功能和OHC的脆弱性之间的密切联系。本建议的目的是了解这种联系，并随后寻找更好的战略，以防止OHC的损失。目的一是系统地研究普雷斯廷在体外系统中的氧化还原酶活性，以揭示为什么OHC是Corti器官中最脆弱的细胞。这些知识将使我们能够制定更好的策略来防止OHC损失。在目的II中，我们将比较表达wt-普雷斯廷和突变体499-普雷斯廷的细胞之间的细胞性质。监测普雷斯廷功能和细胞脆弱性之间的联系的系统和方法的后续开发随后将用于测试不同抗OHC损失试剂对普雷斯廷功能的影响。从AIM II获得的信息将有助于我们在细胞水平上了解普雷斯廷的功能与细胞死亡之间的关系，并为选择更好的保护OHC的方法提供指导。目标III将侧重于通过小分子化合物库筛选程序寻找新化合物。我们的目的是找到新的化合物，可能有特定的和有效的影响普雷斯廷的氧化还原酶的能力，因此可用于防止OHC的损失。将使用各种细胞、生物化学和分子生物学方法。我们的策略，以防止毛细胞损失是基于知识来自了解普雷斯廷的功能，这是独特的OHC。这种创新的方法不仅将提供有关耳蜗放大的基本机制的关键信息，而且还将导致对OHC死亡相关过程的更深入理解。后者可能导致直接治疗或预防OHC损伤。这项拟议的工作是转化研究的第一步，它将耳蜗生理学的基本机制与听力障碍的治疗联系起来。 公共卫生相关性：外毛细胞构成耳蜗放大器，对于提供听觉的高灵敏度和频率选择性至关重要。它们也是内耳中最脆弱的细胞，与大多数影响数百万人听力的感音神经性听力损失有关。普雷斯廷是耳蜗外毛细胞的运动蛋白，是耳蜗放大所必需的。这项建议的目的是调查普雷斯廷的保护作用，对氧化应激的耳朵。从这些研究中收集的数据不仅将在分子水平上扩展普雷斯廷作为基于OHC的耳蜗放大器的知识，而且还将对与外毛细胞损失相关的机制产生更深入的理解，并可能为预防OHC损伤提供新的方法。

DESCRIPTION (provided by applicant): Mammals including humans need amplification by outer hair cells (OHCs) for their high sensitivity and sharp frequency selectivity. OHCs are also the most vulnerable cells in the inner ear and are involved in a majority of sensorineural hearing loss. Although OHC regeneration through either stem cell replacement or gene therapy provides an exciting option in the future, preventing hair cell loss is still the most direct and realistic approach to deal with hair cell loss, and including regenerated ones. Therefore, our proposal will focus on the maintenance of hair cells, particularly outer hair cells. OHC death is strongly connected with the generation of reactive oxygen species (ROS) that are known to destroy cells. Why OHCs, as compared to other cells in the organ of Corti, are more vulnerable to ROS is not fully understood. The main function of OHCs is to amplify mechanical signals through their somatic electromotility. This exclusive property is executed by a unique motor protein called prestin, which is expressed only in OHCs. In the past, studying OHC amplification mechanisms and preventing OHC loss were considered as two separate research fields. Unexpectedly, we discovered that non-functional point mutations in prestin (499-prestin mutant) leads to OHC death. In addition, prestin is not only associated with proteins involved in ROS generation, but prestin itself may have redox enzymatic activity, which could be a part of the OHC defense system to minimize ROS. These data indicate a close connection between prestin's function and the vulnerability of OHCs. The goal of this proposal is to understand this link, and subsequently to search for better strategies to prevent OHCs loss. Aim I of this proposal is designed to systematically characterize prestin's redox enzymatic activity in an in vitro system in order to reveal why the OHCs are the most vulnerable cells in the organ of Corti. This knowledge will allow us to develop a better strategy to prevent OHC loss. In Aim II, we will compare cell properties between wt-prestin and mutant 499-prestin expressing cells. Subsequent development of a system and method(s) to monitor the connection between prestin's function and cell vulnerability will then be used to test the effects of different anti-OHC loss reagents on prestin's functions. The information obtained from AIM II will help us to understand the relationship between prestin's function and cell death at the cellular level and provide guidance for selecting better approaches to protect OHCs. Aim III will focus on a search for new compounds through small molecule compound library screening procedures. Our purpose is to find novel compounds that may have specific and potent effects on prestin's redox enzymatic capacity, and are therefore usable for preventing OHC loss. Various cellular, biochemical and molecular biological methods will be used. Our strategies to prevent hair cell loss are based on knowledge derived from understanding prestin's function, which is unique to OHCs. This innovative approach will not only provide crucial information about basic mechanisms of cochlear amplification but it will also lead to a deeper understanding of processes associated with OHC death. The latter may lead to direct treatments or prevention of OHC damage. The proposed work is a first-step in translational research, which bridges basic mechanisms of cochlear physiology and treatments for hearing impairment. PUBLIC HEALTH RELEVANCE: Outer hair cells constitute the cochlear amplifier, essential for providing high sensitivity and frequency selectivity of hearing. They are also the most vulnerable cells in the inner ear and are involved in a majority of sensorineural hearing loss that affects the hearing of millions of people. Prestin, the motor protein of outer hair cells, is required for cochlear amplification. The goal of this proposal is to investigate prestin's protection role against oxidative stress in the ear. Data collected from these studies will not only expand knowledge of prestin as the OHC-based cochlear amplifier at the molecular level, but also produce a deeper understanding of mechanisms associated with outer hair cells loss, and may offer new methods for the prevention of OHC damage.