Functional Analysis of Common and Rare Cystic Fibrosis-causing Mutations
Závoti Olivér
Molekuláris Orvostudományi Tagozat
Dr. Várnai Péter
Semmelweis Egyetem Elméleti Orvostudományi Központ Hári Pál Előadóterem
2026-09-10 12:00:00
Celluláris és molekuláris élettan
Dr. Hunyady László
Dr. Csanády László
Dr. Czirják Gábor
Dr. Szántó Gábor Tibor
Dr. Enyedi Péter
Dr. Szeri Flóra
Dr. Hegedűs Tamás
This thesis examines the mechanisms by which CFTR maturation, PKA-dependent channel activation, gating, and permeation are impaired by common and rare CFTR mutations, as well as pharmacological rescue of these phenotypes. By integrating biochemical, kinetic, and pharmacological analyses, the work links molecular defects to mutation-specific responses to clinically approved modulators.
In the first study, we dissected catalytic and noncatalytic components of PKA-induced CFTR activation for WT channels and for the common disease-causing mutants ΔF508 and G551D. Although both mutants exhibit severely reduced open probability, both components of PKA-dependent activation remain present. However, catalytic activation is disproportionately impaired, resulting in channel activity being dominated by the noncatalytic component. Slowed activation kinetics were not caused by reduced PKA binding affinity but instead reflect impaired post-binding conformational transitions. Structural considerations implicate destabilisation of the NBD dimer and the NBD1-TMD interfaces as a shared mechanism. Stabilisation of these interfaces by the ATP analogue P-ATP alleviated both gating and activation defects, whereas the clinically used modulators elexacaftor and ivacaftor preferentially enhanced catalytic activation, reducing the relative contribution of reversible PKA-dependent stimulation.
In the second study, we characterised five rare CFTR mutations (G126D, I336K, T465I, T582I, and D984V) identified in Hungarian CF patients. All variants formed functional channels but displayed complex, multi-class defects involving impaired maturation, altered gating, and reduced conductance. Maturation defects were corrected by the corrector combination tezacaftor + elexacaftor, and all variants responded robustly to potentiation by ivacaftor + elexacaftor. PKA-dependent activation was preserved for all mutants, although catalytic activation was selectively reduced, consistent with findings from the first study. None of the mutations impaired ATP binding at Site 2, but each altered gating kinetics in a manner consistent with its structural location. By linking molecular mechanisms to mutation-specific drug responses, this work supports expanded eligibility for ETI therapy and contributes to the development of more precise, mechanism-based treatments for cystic fibrosis.
