Jarodsky Joshua M, Myers Janette B, Reichow Steve L
Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR 97239, USA.
Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA.
bioRxiv. 2025 Feb 14:2025.02.12.637953. doi: 10.1101/2025.02.12.637953.
Gap junctions, formed by connexin proteins, establish direct electrical and metabolic coupling between cells, enabling coordinated tissue responses. These channels universally respond to intracellular pH changes, closing under acidic conditions to limit the spread of cytotoxic signals during cellular stress, such as ischemia. Using cryo-electron microscopy (cryo-EM), we uncover insights into the structural mechanism of pH-gating in native lens connexin-46/50 (Cx46/50) gap junctions. Mild acidification drives lipid infiltration into the channel pore, displacing the N-terminal (NT) domain and stabilizing pore closure. Lipid involvement is both essential and fully reversible, with structural transitions involving an ensemble of gated-states formed through non-cooperative NT domain movement as well as minor populations of a distinct destabilized open-state. These findings provide molecular insights into pH-gating dynamics, illustrating how structural changes may regulate gap junction function under cellular stress and linking Cx46/50 dysregulation to age-related cataract formation.
由连接蛋白形成的间隙连接在细胞间建立直接的电和代谢偶联，实现组织的协调反应。这些通道普遍对细胞内pH变化做出反应，在酸性条件下关闭，以限制细胞应激（如局部缺血）期间细胞毒性信号的扩散。利用冷冻电子显微镜（cryo-EM），我们揭示了天然晶状体连接蛋白46/50（Cx46/50）间隙连接中pH门控的结构机制。轻度酸化促使脂质渗入通道孔，取代N端（NT）结构域并稳定孔的关闭。脂质的参与既是必需的，也是完全可逆的，结构转变涉及通过非协同NT结构域运动形成的一系列门控状态以及少量不同的不稳定开放状态。这些发现为pH门控动力学提供了分子见解，阐明了结构变化如何在细胞应激下调节间隙连接功能，并将Cx46/50失调与年龄相关性白内障形成联系起来。
