Structural basis of the gating mechanism of connexin 26 and related hearing loss

总结 连接蛋白26作为间隙连接通道，直接调节细胞间的离子交换， 代谢物和第二信使。连接蛋白26的突变会导致严重的听力损失。 然而，连接蛋白26的结构基础上的分子门控机制仍然不清楚， 尤其是连接蛋白26突变的闭合状态和功能障碍。我们开发了 用于高分辨率单颗粒冷冻EM的天然细胞膜纳米颗粒（NCMN）系统 膜蛋白结构测定及其生理功能研究 条件我们最近解决了连接蛋白26的冷冻电镜结构， 在2.3 μ m和2.9 μ m的开放状态下，钙离子与约36个脂质分子通过 NCMN系统。然而，高分辨率的连接蛋白26的闭合状态仍然未被揭示。 我们假设我们的NCMN系统在Cx 26结构测定中的应用， Cx 26-R75 W在钙和钙调蛋白存在和不存在下可以提供独特的 结构信息。目的1：研究门控机制的闭合构象 CX 26的目的2：阐明Cx 26基因单点突变R75 W的分子基础 导致严重的听力损失拟议的实验结果将提供见解， 详细的结构信息和生化分析，以了解门控机制， 还提供了在该听证会中检测到的异常通道门控功能的机制细节 disorder.结构信息可能会导致一些新的策略来调节故障 CX 26-R75 W用于治疗听力损失。

SUMMARY Connexin 26, as a gap junction channel, directly regulates the cell-to-cell exchange of ion, metabolites, and second messengers. Mutations of connexin 26 can cause severe hearing loss. However, the molecular gating mechanism on the structural basis of connexin 26 is still unclear, especially the closed state and malfunction of connexin 26 mutations. We have developed the native cell membrane nanoparticle (NCMN) system for high-resolution single-particle cryo-EM structure determination and functional studies of membrane proteins within their physiological conditions. We recently solved the cryo-EM structures of connexin 26 in the absence or presence of calcium ions in an open state at 2.3 Å and 2.9 Å associated with about 36 lipid molecules via the NCMN system. However, the close state of connexin 26 with high resolution is still uncovered. We hypothesize that our NCMN system's application to structure determination of Cx26 and Cx26-R75W in the presence and absence of calcium and calmodulin can provide unique structural information. Aim 1: To investigate the CLOSED conformation of the gating mechanism of Cx26. Aim 2: To elucidate the molecular basis of how the single point mutation R75W in Cx26 leads to profound hearing loss. The proposed experimental results will provide insights into detailed structural information and biochemical analysis in understanding the gating mechanism, also provide mechanistic details on abnormal channel gating function detected in this hearing disorder. The structural information may lead to some novel strategy to modulate the malfunction CX26-R75W for hearing loss.