Influence of Disease-Causing Mutations and Ivacaftor on the Dynamics of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Protein

Abstract

Cystic fibrosis (CF), one of the most common life-shortening autosomal recessive diseases, arises from mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and leads to severe respiratory and digestive dysfunction. CFTR-targeting therapies such as ivacaftor have transformed CF care by directly modulating CFTR function. However, the precise mechanism by which ivacaftor alters CFTR’s conformational dynamics remains incompletely understood. In this study, we refined and employed a CFTR model derived from the phosphorylated, ATP- and ivacaftor-bound cryo-EM structure (PDB ID 6O2P). Through 32.5 μs of molecular dynamics simulations, we investigated the structural and dynamic effects of the common F508del mutation and the gating mutations G551D, G1349D and S549N. Our results show that mutations within the ATP-binding regions cause local rearrangements at the nucleotide-binding sites, affecting the interface between the nucleotide-binding domains (NBDs) relative to wild-type CFTR, rather than abolishing ATP binding entirely. We further indicate that, for the NBDs to approach one another productively, protonation of the aspartate side chains in G551D and G1349D CFTR is necessary to mitigate charge repulsion. The F508del mutation induces increased rigidity within the protein core, impeding the rearrangement of transmembrane helices required for channel opening. Ivacaftor does not directly perturb the ATP-binding sites, consistent with emerging evidence that it exerts its effects allosterically on regions distal to the nucleotide-binding sites. Collectively, our findings enhance our understanding of CFTR dynamics and provide a versatile framework for exploring the molecular effects of disease-causing mutations and evaluating potential therapeutic agents.