K⁺ channels regulate ENaC expression via changes in promoter activity and control fluid clearance in alveolar epithelial cells

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• 作者：Olivier Bardou^a ; ^b ; ^{olivier.bardou@umontreal.ca} ; Anik Privé ; ^a ; ^{anik.prive.chum@ssss.gouv.qc.ca} ; Francis Migneault^a ; ^b ; ^{francis.migneault@umontreal.ca} ; Karl Roy-Camille^a ; ^{royca82@hotmail.com} ; André ; Dagenais^a ; ^b ; ^{andre.dagenais.chum@ssss.gouv.qc.ca} ; Yves Berthiaume^a ; ^b ; ^{yves.berthiaume@umontreal.ca} ; Emmanuelle Brochiero^a ; ^b ; ^{emmanuelle.brochiero@umontreal.ca}
• 关键词：KvLQT1 channels ; kATP channels ; 伪-ENaC ; MAPK ; Alveolar cells ; Fluid clearance
• 刊名：Biochimica et Biophysica Acta (BBA)/Biomembranes
• 出版年：2012
• 期刊代码：14_00052736
• 类别：bio
• 出版时间：July, 2012
• 卷：1818
• 期：7
• 页码：1682-1690
• 文件大小：796 K

摘要

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 K_ATP 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 伪-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 K_ATP 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 伪-ENaC expression, similarly to K_ATP activation by pinacidil. Conversely, pharmacological KvLQT1 and K_ATP inhibition or silencing with siRNAs down-regulated 伪-ENaC expression. Furthermore, K⁺ channel blockers significantly decreased 伪-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 K_ATP activation dose-dependently enhanced 伪-ENaC promoter activity. Finally, we noted a physiological impact of changes in K⁺ channel functions on ERK activity, 伪-, 尾-, 纬-ENaC subunit expression and fluid absorption through polarized ATII cells. In summary, our results disclose that K⁺ channels regulate 伪-ENaC expression by controlling its promoter activity and thus affect the alveolar function of fluid clearance.