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Updated: Jul 14, 2026

Functional Reconstitution and Channel Activity Measurements of Purified Wildtype and Mutant CFTR Protein
Published on: March 9, 2015
CFTR inhibition by glibenclamide requires a positive charge in cytoplasmic loop three
Patricia Melin1, Eric Hosy, Michel Vivaudou
1Institut de Physiologie et Biologie Cellulaires, Université de Poitiers, CNRS UMR 6187, 86022 Poitiers cedex, France. patricia.melin@univ-poitiers.fr
Abstract:
The sulfonylurea glibenclamide is widely used as an open-channel blocker of the CFTR chloride channel. Here, we used site-directed mutagenesis to identify glibenclamide site of interaction: a positively charged residue K978, located in the cytoplasmic loop 3. Charge-neutralizing mutations K978A, K978Q, K978S abolished the inhibition of forskolin-activated CFTR chloride current by glibenclamide but not by CFTR(inh)-172. The charge-conservative mutation K978R did not alter glibenclamide sensitivity of CFTR current. Mutations of the neighbouring R975 (R975A, R975S, R975Q) did not affect electrophysiological and pharmacological properties of CFTR. No alteration of halide selectivity was observed with any of these CFTR mutant channels. This study identifies a novel potential inhibitor site within the CFTR molecule, and suggests a novel role of cytoplasmic loop three, within the second transmembrane domain of CFTR protein. This work is the first to report on the role of a residue in a cytoplasmic loop in the mechanism of action of the channel blocker glibenclamide.
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