CFTR function, pathology and pharmacology at single-molecule resolution

The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel that regulates salt and fluid homeostasis across epithelial membranes(1). Alterations in CFTR cause cystic fibrosis, a fatal disease without a cure(2,3). Electrophysiological properties of CFTR have been analysed for decades(4-6). The structure of CFTR, determined in two globally distinct conformations, underscores its evolutionary relationship with other ATP-binding cassette transporters. However, direct correlations between the essential functions of CFTR and extant structures are lacking at present. Here we combine ensemble functional measurements, single-molecule fluorescence resonance energy transfer, electrophysiology and kinetic simulations to show that the two nucleotide-binding domains (NBDs) of human CFTR dimerize before channel opening. CFTR exhibits an allosteric gating mechanism in which conformational changes within the NBD-dimerized channel, governed by ATP hydrolysis, regulate chloride conductance. The potentiators ivacaftor and GLPG1837 enhance channel activity by increasing pore opening while NBDs are dimerized. Disease-causing substitutions proximal (G551D) or distal (L927P) to the ATPase site both reduce the efficiency of NBD dimerization. These findings collectively enable the framing of a gating mechanism that informs on the search for more efficacious clinical therapies.

Automated summary

The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel that regulates salt and fluid homeostasis across epithelial membranes. Alterations in CFTR cause cystic fibrosis, a fatal disease without a cure. In this study, the authors investigate the structure and function of CFTR, specifically focusing on the dimerization of its nucleotide-binding domains (NBDs) and the allosteric gating mechanism that regulates chloride conductance. They also explore the effects of disease-causing substitutions on NBD dimerization and propose implications for potential clinical therapies.