Characterization of basolateral K+ channels underlying anion secretion in the human airway cell line Calu-3.
Transepithelial anion secretion in many tissues depends upon the activity of basolateral channels. Using monolayers of the Calu-3 cell line, a human submucosal serous cell model mounted in an Ussing chamber apparatus, we investigated the nature of the K+ channels involved in basal, cAMP- and Ca2+-stimulated anion secretion, as reflected by the transepithelial short circuit current (I(sc)). The non-specific K+ channel inhibitor Ba2+ inhibited the basal I(sc) by either 77 or 16 % when applied directly to the basolateral or apical membranes, respectively, indicating that a basolateral K+ conductance is required for maintenance of basal anion secretion. Using the K+ channel blockers clofilium and clotrimazole, we found basal I(sc) to be sensitive to clofilium, with a small clotrimazole-sensitive component. By stimulating the cAMP and Ca2+ pathways, we determined that cAMP-stimulated anion secretion was almost entirely abolished by clofilium, but insensitive to clotrimazole. In contrast, the Ca2+-stimulated response was sensitive to both clofilium and clotrimazole. Thus, pharmacologically distinct basolateral K+ channels are differentially involved in the control of anion secretion under different conditions. Isolation of the basolateral K+ conductance in permeabilized monolayers revealed a small basal and forskolin-stimulated I(sc). Finally, using the reverse transcriptase-polymerase chain reaction, we found that Calu-3 cells express the K+ channel genes KCNN4 and KCNQ1 and the subunits KCNE2 and KCNE3. We conclude that while KCNN4 contributes to Ca2+-activated anion secretion by Calu-3 cells, basal and cAMP-activated secretion are more critically dependent on other K+ channel types, possibly involving one or more class of KCNQ1-containing channel complexes.
Cowley
Elizabeth A
EA
Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7. ecowley@tupphisiol1.bp.dal.ca
Linsdell
Paul
P
D000838:Anions / Q000378:metabolism*; D001464:Barium / Q000494:pharmacology; D001562:Benzimidazoles / Q000494:pharmacology; D002120:Calcium Channel Agonists / Q000494:pharmacology; D003022:Clotrimazole / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007477:Ions; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism / Q000502:physiology*; D020033:Protein Isoforms / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012704:Serous Membrane / Q000166:cytology / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000838:Anions; D001562:Benzimidazoles; D002120:Calcium Channel Agonists; D004791:Enzyme Inhibitors; D007477:Ions; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D020033:Protein Isoforms; D000644:Quaternary Ammonium Compounds; D001464:Barium; D019284:Thapsigargin; C022799:clofilium; D000242:Cyclic AMP; D003022:Clotrimazole; C102635:1-ethyl-2-benzimidazolinone