Modulation of CFTR gating by permeant ions

Area of Science:

• Biophysics
• Molecular Biology
• Ion Channel Physiology

Background:

• Cystic fibrosis transmembrane conductance regulator (CFTR) gating is unique, involving ATP hydrolysis and violating microscopic reversibility.
• Recent models propose coupling between transmembrane domain gate and nucleotide-binding domain (NBD) dynamics.

Purpose of the Study:

• To investigate the effects of permeant ions, specifically nitrate, on CFTR gating mechanisms.
• To compare nitrate's effects with the known CFTR potentiator VX-770.

Main Methods:

• Single-channel electrophysiology on wild-type (WT) and mutant CFTR.
• Utilized a CFTR construct lacking NBD2 (ΔNBD2).
• Assessed effects of nitrate and VX-770 on gating kinetics and open probability (Po).

Main Results:

• Nitrate increases WT CFTR open probability (Po) by accelerating opening and slowing closing rates.
• Nitrate's effects are independent of PKA-dependent phosphorylation.
• Nitrate mimics VX-770's potentiation of WT and G551D mutant CFTR, and activity of ΔNBD2-CFTR.
• Nitrate primarily acts from the cytoplasmic side, unlike VX-770.

Conclusions:

• Nitrate modulates CFTR ATP-dependent gating through mechanisms similar to VX-770.
• Gating modulation can occur independently of NBD dimerization.
• Nitrate and VX-770 may share a common gating modulation pathway acting at distinct sites.