Impact of the F508del mutation on ovine CFTR, a Cl- channel with enhanced conductance and ATP-dependent gating

Cai, Zhiwei and Palmai-Pallag, Timea and Khuituan, Pissared and Mutolo, Michael J and Boinot, Clément and Liu, Beihui and Scott-Ward, Toby S and Callebaut, Isabelle and Harris, Ann and Sheppard, David N (2015) Impact of the F508del mutation on ovine CFTR, a Cl- channel with enhanced conductance and ATP-dependent gating. Journal of Physiology, 593 (11). pp. 2427-2446. ISSN 0022-3751

Full content URL: http://dx.doi.org/10.1113/JP270227

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Abstract

Cross-species comparative studies are a powerful approach to understand the epithelial Cl- channel cystic fibrosis transmembrane conductance regulator (CFTR), which is defective in the genetic disease cystic fibrosis (CF). Here, we investigate the single-channel behaviour of ovine CFTR and the impact of the most common CF mutation, F508del-CFTR, using excised inside-out membrane patches from transiently transfected CHO cells. Like human CFTR, ovine CFTR formed a weakly inwardly rectifying Cl- channel regulated by PKA-dependent phosphorylation, inhibited by the open-channel blocker glibenclamide. However, for three reasons, ovine CFTR was noticeably more active than human CFTR. First, single-channel conductance was increased. Second, open probability was augmented because the frequency and duration of channel openings were increased. Third, with enhanced affinity and efficacy, ATP more strongly stimulated ovine CFTR channel gating. Consistent with these data, the CFTR modulator phloxine B failed to potentiate ovine CFTR Cl- currents. Like its impact on human CFTR, the F508del mutation caused a temperature-sensitive folding defect, which disrupted ovine CFTR protein processing and reduced membrane stability. However, the F508del mutation had reduced impact on ovine CFTR channel gating in contrast to its marked effects on human CFTR. We conclude that ovine CFTR forms a regulated Cl- channel with enhanced conductance and ATP-dependent channel gating. This phylogenetic analysis of CFTR structure and function demonstrates that subtle changes in structure have pronounced effects on channel function and the consequences of the CF mutation F508del. This article is protected by copyright. All rights reserved.

Keywords:CFTR, chloride channels, cystic fibrosis, JCOpen
Subjects:C Biological Sciences > C440 Molecular Genetics
C Biological Sciences > C130 Cell Biology
C Biological Sciences > C700 Molecular Biology, Biophysics and Biochemistry
Divisions:College of Science > School of Life Sciences
ID Code:17022
Deposited On:09 Apr 2015 10:13

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