Expression of cftr controls camp-dependent activation of epithelial
k+ currents.
Loussouarn, Gildas, Sophie Demolombe, Raha Mohammad-Pannah, Denis
Escande, and Isabelle Bar[grave]u.
Laboratoire de Physiopathologie et de Pharmacologie Cellulaires et
Mol[umlaut]aculaires, H[diaeresis]opital G & R Laaennec, 44035
Nantes, France, Phone: (33).40.16.54.86; FAX: (33).40.16.54.91.
APStracts 3:0162C, 1996.
The perforated-patch configuration of the patch-clamp technique was
used to record whole-cell currents from human epithelial CFPAC-1
cells defective for functional cystic fibrosis transmembrane
conductance regulator (CFTR). In CFPAC-1 cells, cAMP stimulation with
forskolin (10 M) plus CPT-cAMP (400 M) activated neither Cl- nor K+
currents. In the same cells transfected with wild-type CFTR gene,
cAMP stimulation produced activation of both Cl- and K+ currents. In
Cl- depleted medium (gluconate as a substitute), cAMP stimulation
evoked a K+ current in CFTR-transfected but not in untransfected
CFPAC-1 cells. This cAMP-evoked K+ current was the sum of two
components: (i) a time-independent inwardly rectifying component;
(ii) a slowly relaxing component activated at positive voltages.
Increasing intracellular Ca2+ with ionomycin (1 M) activated K+
currents either in transfected or in untransfected cells. In
transfected cells, blocking the CFTR conductance with high
concentration glibenclamide (100 M) reduced the K+ current when
activated by cAMP but not when activated by Ca2+. Pretreating CFTR
-transfected cells for 48 hours with interferon g downregulated CFTR
gene expression and reduced cAMP but not Ca2+ activation of the
whole-cell K+ current. From these results, we conclude that
functional membrane CFTR protein influences activation by cAMP of
epithelial K+ currents.
Received 11 February 1996; accepted in final form 7 May 1996.
APS Manuscript Number C85-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 May 96