Molecular Action Of CFTR Potentiators On The Kca3.1 Channel

Abstract

Airway epithelial cells are the site of Cl- secretion through the cystic fibrosis transmembrane regulator (CFTR). Cystic fibrosis (CF) is a fatal genetic disease caused by mutations in CFTR. The most frequent mutation consists of a deletion of the phenylalanine at position 508 (ΔF508-CFTR) that impairs protein maturation and alters channel gating. In the last years, several small molecules were identified by high throughput screening that could restore ΔF508-CFTR function. Compounds addressing ΔF508-CFTR gating defects are referred to as potentiators and have been documented to increase the activity of ΔF508-CFTR to a level similar to wild-type CFTR. The basolateral K+ channel KCa3.1 has been documented to play a prominent role in establishing a suitable driving force for CFTR-mediated Cl- secretion in airway epithelial cells. Thus, in a global approach of transepithelial transport, the research for physiologically relevant ΔF508-CFTR potentiators should also consider their effects on the KCa3.1 channel. A characterization of the effect of different ΔF508-CFTR potentiators on the KCa3.1 channel was undertaken using inside-out patch clamp measurements on cDNA injected xenopus oocytes and on transformed HEK-293 cells that express the KCa3.1 channel. In this work we present preliminary results on the effects of different ΔF508-CFTR potentiators on KCa3.1. Our inside-out patch-clamp measurements show that VRT-532 has a state independent inhibitory effect on KCa3.1, but very little action on the V282G mutant of KCa3.1, which is constitutively active. In contrast, CBIQ succeded to activate KCa3.1, through a mechanism likely to involve an action on the channel gate. These effects were observed at concentrations known to activate ΔF508-CFTR. Supported by CCFF.