Integrative Structural and Functional Characterization of Tip-Link Cadherins Deafness

耳聋是一个主要的健康问题。耳聋的一个主要原因是毛细胞的缺陷，毛细胞是一种机械感觉 将声音诱发的振动转换为电信号的耳蜗细胞，为我们提供 听证。原钙粘附素(PCDH15)和钙粘附素23(CDH23)编码基因突变导致听力 损失。这两个基因都在内耳机械感觉毛细胞的发束中表达 它们形成异嗜性的黏附复合体，对毛束的形态形成和 机械转导。值得注意的是，PCDH15和CDH23的不同突变导致不同的疾病 结果。虽然一些突变会导致严重的先天性耳聋并伴有视网膜损伤(Usher 综合征)，其他导致隐性和进行性听力损失，没有视觉受累。基因关联 研究还表明，CDH23基因多态与年龄和噪声导致的听力损失有关。这个 不同的突变导致不同疾病结果的机制还没有明确的定义。我们建议 这里将高分辨率的结构研究与毛细胞的功能研究相结合，以深入了解 PCDH15和CDH23调节毛细胞功能和定义疾病机制的机制。至 为了实现这一目标，一个拥有研究钙粘附素生物物理和结构特性的专业实验室 一家致力于研究听觉神经科学的实验室联合起来，取得了什么成就 任何一个都不能单独完成。与以往侧重于小型结构分析的研究不同 CDH23和PCDH15的单体片段在细菌中表达，该团队建议定义高- 用结晶学和低温电子显微镜研究天然组装的PCDH15-CDH23络合物的分辨结构。 结构数据将通过生物化学和突变钙粘附素的功能询问进行验证 生理上相关的机械感觉毛细胞，关注与疾病相关的突变。我们 预计我们的研究将提供任何重要蛋白质复合体的第一个高分辨率天然结构 用于机械转导，并提供对其功能特性和病理生理的机械学见解 与不同形式的听力障碍相关的机制。

Deafness is a major health problem. A major cause of deafness is defects in hair cells, the mechanosensory cells of the cochlea that convert sound induced vibrations into electrical signals to provide our sense of hearing. Mutations in the genes encoding protocadherin (PCDH15) and cadherin 23 (CDH23) cause hearing loss. Both genes are expressed in the hair bundles of the mechanosensory hair cells of the inner ear where they form heterophilic adhesion complexes that are important for hair bundle morphogenesis and mechanotransduction. Significantly, different mutation in both PCDH15 and CDH23 lead to different disease outcomes. While some mutations cause profound congenital deafness with retinal impairment (Usher Syndrome) others lead to recessive and progressive hearing loss without visual involvement. Gene-association studies also suggest a link of CDH23 polymorphisms with age- and noise-induce hearing loss. The mechanisms by which different mutations lead to distinct disease outcomes are poorly defined. We propose here to combine high-resolution structural studies with functional studies in hair cells to gain insights into the mechanisms by which PCDH15 and CDH23 regulate hair cell function and to define disease mechanisms. To achieve this goal, a laboratory with expertise in studying the biophysical and structural properties of cadherins and a laboratory dedicated to the study of auditory neuroscience have combined their efforts to achieve what either could not accomplish alone. Unlike previous studies that have focused on structural analysis of small monomeric fragments of CDH23 and PCDH15 expressed in bacteria, the team proposed to define the high- resolution structure of natively assembled PCDH15-CDH23 complexes using crystallography and cryo-EM. Structural data will be validated biochemically and by functional interrogation of mutant cadherins in the physiologically relevant mechanosensory hair cells paying attention to mutations associated with disease. We anticipate that our studies will provide the first high-resolution native structure of any protein complex important for mechanotransduction and provide mechanistic insights into its functional properties and pathophysiological mechanisms that are associated with different forms of hearing impairment.