Molecular basis of ClC-6 function and its impairment in human disease
Bing Zhang, Sensen Zhang, Maya M. Polovitskaya, Jingbo Yi, Binglu Ye, Ruochong Li, Xueying Huang, Jian Yin, Sebastian Neuens, Tom Balfroid, Julie Soblet, Daphné Vens, Alec Aeby, X Li, Jinjin Cai, Yingcai Song, Yuanxi Li, Yuanxi Li, Marco Tartaglia, Yang Li, Yang Li, Thomas J. Jentsch, Maojun Yang, Zhiqiang Liu
Abstract
ClC-6 is a late endosomal voltage-gated chloride-proton exchanger that is predominantly expressed in the nervous system. Mutated forms of ClC-6 are associated with severe neurological disease. However, the mechanistic role of ClC-6 in normal and pathological states remains largely unknown. Here, we present cryo-EM structures of ClC-6 that guided subsequent functional studies. Previously unrecognized ATP binding to cytosolic ClC-6 domains enhanced ion transport activity. Guided by a disease-causing mutation (p.Y553C), we identified an interaction network formed by Y553/F317/T520 as potential hotspot for disease-causing mutations. This was validated by the identification of a patient with a de novo pathogenic variant p.T520A. Extending these findings, we found contacts between intramembrane helices and connecting loops that modulate the voltage dependence of ClC-6 gating and constitute additional candidate regions for disease-associated gain-of-function mutations. Besides providing insights into the structure, function, and regulation of ClC-6, our work correctly predicts hotspots for CLCN6 mutations in neurodegenerative disorders.