CFTR: Effect of ICL2 and ICL4 amino acids in close spatial proximity on the current properties of the channel

Background: CFTR is the only ABC transporter functioning as a chloride (CI) channel. We studied molecular determinants, which might distinguish CFTR from standard ABC transporters, and focused on the interface fanned by the intracellular loops from the membrane spanning domains. Methods: Residues from ICL2 and ICL4 in close proximity were targeted, and their involvement in the functioning of CFTR was studied by whole cell patch clamp recording. Results: We identified 2 pairs of amino acids, at the extremity of the bundle formed by the four intracellular loops, whose mutation i) decreases the CF current of CFTR (couple E267 K1060) or increases it with a change of the electrophysiological signature (couple S263 V1056). Conclusions: These results highlight the critical role of these ICL residues in the assembly of the different domains and/or in the CF permeation pathway of CFTR. (C) 2013 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.