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， 耳蜗细胞将声音引起的振动转化为电信号， 听证会编码原钙粘蛋白（PCDH 15）和钙粘蛋白23（CDH 23）的基因突变导致听力 损失这两种基因都在内耳的机械感觉毛细胞的毛束中表达， 它们形成对毛束形态发生重要的嗜异性粘附复合物， 机械传导值得注意的是，PCDH 15和CDH 23的不同突变导致不同的疾病 结果。虽然一些突变导致严重的先天性耳聋伴视网膜损伤（Usher 综合征），其他导致隐性和进行性听力损失没有视觉参与。基因关联 研究还表明，CDH 23多态性与年龄和噪音引起的听力损失有关。的 不同的突变导致不同疾病结果的机制定义不清。我们提出 在这里，联合收割机结合高分辨率的结构研究与毛细胞的功能研究，以深入了解 PCDH 15和CDH 23调节毛细胞功能的机制以及确定疾病机制。到 为了实现这一目标，一个专门研究钙粘蛋白生物物理和结构特性的实验室 和一个专门研究听觉神经科学的实验室共同努力， 任何一方都无法单独完成。与以前的研究不同，这些研究侧重于小分子结构分析， 在细菌中表达的CDH 23和PCDH 15的单体片段中，研究小组提出定义高- 使用晶体学和cryo-EM的天然组装的PCDH 15-CDH 23复合物的解析结构。 结构数据将通过生物化学和功能询问的突变钙粘蛋白， 生理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物的第一个高分辨率天然结构 并提供其功能特性和病理生理机制的见解 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.