Rapid Publication Identification and Regulation of the Cystic Fibrosis Transmembrane Conductance Regulator-Generated Chloride Channel

Cystic fibrosis tnsmembrane conductance regulator (CFTR) generates cAMP-regulated channels; mutations in CFFR cause defective Cl- channel function in cystic fibrosis epithelia. We used the patch-chmp technique to determine the single channel properties ofCl- channels in cells expressing recombi-nant CFIR. In cell-attached patches, an increase in cellular cAMP reversibly activated low conductance Cl- channels. cAMP-dependent regulation is due to phosphorylation, be-cause the catalytic subunit of cAMP-dependent protein kinase plus ATP reversibly activated the channel in excised, cell-free patches of membrane. In symmetrical a- solutions, the chan-nel had a channel conductance of 10.4±0.2 (a = 7) pS and a linear current-voltage relation. The channel was more perme-able to Cla than to I- and showed no appreciable time-depen-dent voltage effects. These biophysical properties are consis-tent with macroscopic studies of a- channels in single cells expressing CFTR and in the apical membrane of secretory epi-thelia. Identification of the single channel characteristics of CFIR-generated channels allows further studies oftheir regula-tion and the mechanism of ion permeation. (J. Cli,. Invest