title: K+ channels regulate ENaC expression via changes in promoter activity and control fluid clearance in alveolar epithelial cells.
abstract: Active Na+ absorption by alveolar ENaC is the main driving force of liquid clearance at birth and lung edema resorption in adulthood. We have demonstrated previously that long-term modulation of KvLQT1 and KATP K+ channel activities exerts sustained control in Na+ transport through the regulation of ENaC expression in primary alveolar type II (ATII) cells. The goal of the present study was: 1) to investigate the role of the alpha-ENaC promoter, transfected in the A549 alveolar cell line, in the regulation of ENaC expression by K+ channels, and 2) to determine the physiological impact of K+ channels and ENaC modulation on fluid clearance in ATII cells. KvLQT1 and KATP channels were first identified in A549 cells by PCR and Western blotting. We showed, for the first time, that KvLQT1 activation by R-L3 (applied for 24 h) increased alpha-ENaC expression, similarly to KATP activation by pinacidil. Conversely, pharmacological KvLQT1 and KATP inhibition or silencing with siRNAs down-regulated alpha-ENaC expression. Furthermore, K+ channel blockers significantly decreased alpha-ENaC promoter activity. Our results indicated that this decrease in promoter activity could be mediated, at least in part, by the repressor activity of ERK1/2. Conversely, KvLQT1 and KATP activation dose-dependently enhanced alpha-ENaC promoter activity. Finally, we noted a physiological impact of changes in K+ channel functions on ERK activity, alpha-, beta-, gamma-ENaC subunit expression and fluid absorption through polarized ATII cells. In summary, our results disclose that K+ channels regulate alpha-ENaC expression by controlling its promoter activity and thus affect the alveolar function of fluid clearance.
authors.affiliation: Centre de recherche, Centre hospitalier de 1'Université de Montréal (CRCHUM) - Hôtel-Dieu, Montral, Quebec, Canada. olivier.bardou@umontreal.ca
authors.forename: Olivier
authors.initials: O
authors.lastname: Bardou
authors.forename: Anik
authors.initials: A
authors.lastname: Privé
authors.forename: Francis
authors.initials: F
authors.lastname: Migneault
authors.forename: Karl
authors.initials: K
authors.lastname: Roy-Camille
authors.forename: André
authors.initials: A
authors.lastname: Dagenais
authors.forename: Yves
authors.initials: Y
authors.lastname: Berthiaume
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Brochiero
mesh_terms: D001569:Benzodiazepines / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D053503:Epithelial Sodium Channels / Q000235:genetics* / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D054086:KATP Channels / Q000235:genetics* / Q000378:metabolism; D051657:KCNQ1 Potassium Channel / Q000235:genetics* / Q000378:metabolism; D049990:Membrane Transport Modulators / Q000494:pharmacology; D020110:Pinacidil / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011650:Pulmonary Alveoli / Q000378:metabolism / Q000473:pathology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism
chemical_list: D053503:Epithelial Sodium Channels; D054086:KATP Channels; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; C113498:L 364373; D049990:Membrane Transport Modulators; D026902:Potassium Channel Blockers; D000644:Quaternary Ammonium Compounds; C092520:uK-ATP-1 potassium channel; D001569:Benzodiazepines; D020110:Pinacidil; C022799:clofilium; D012964:Sodium; D048049:Extracellular Signal-Regulated MAP Kinases; D005905:Glyburide