Expression of intermediate-conductance, Ca2+-activated K+ channel (KCNN4) in H441 human distal airway epithelial cells

• Published in: American journal of physiology. Lung cellular and molecular physiology 2006-11, Vol.291 (5), p.L957-L965
• Main Authors: Wilson, S. M, Brown, S. G, McTavish, N, McNeill, R. P, Husband, E. M, Inglis, S. K, Olver, R. E, Clunes, M. T
• Format: Article
• Language: English
• Subjects: Airway management; Animals; Benzimidazoles - pharmacology; Calcium Channel Agonists - pharmacology; Cell Line; Cell Lineage; Cells; Chemical elements; CHO Cells; Cloning; Cloning, Molecular; Cricetinae; Enzyme Inhibitors - pharmacology; Gene Expression - physiology; Humans; Intermediate-Conductance Calcium-Activated Potassium Channels - genetics; Intermediate-Conductance Calcium-Activated Potassium Channels - metabolism; Membrane Potentials - drug effects; Membrane Potentials - physiology; Membranes; Potassium - metabolism; Respiratory Mucosa - cytology; Respiratory Mucosa - physiology; Ribonucleic acid; RNA; RNA, Messenger - metabolism; Sodium - metabolism; Thapsigargin - pharmacology
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00065.2006

Lung Membrane Transport Group, Division of Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom Submitted 22 February 2006 ; accepted in final form 30 May 2006 Electrophysiological studies of H441 human distal airway epithelial cells showed that thapsigargin caused a Ca 2+ -dependent increase in membrane conductance ( G Tot ) and hyperpolarization of membrane potential ( V m ). These effects reflected a rapid rise in cellular K + conductance ( G K ) and a slow fall in amiloride-sensitive Na + conductance ( G Na ). The increase in G Tot was antagonized by Ba 2+ , a nonselective K + channel blocker, and abolished by clotrimazole, a KCNN4 inhibitor, but unaffected by other selective K + channel blockers. Moreover, 1-ethyl-2-benzimidazolinone (1-EBIO), which is known to activate KCNN4, increased G K with no effect on G Na . RT-PCR-based analyses confirmed expression of mRNA encoding KCNN4 and suggested that two related K + channels (KCNN1 and KCNMA1) were absent. Subsequent studies showed that 1-EBIO stimulates Na + transport in polarized monolayers without affecting intracellular Ca 2+ concentration ([Ca 2+ ] i ), suggesting that the activity of KCNN4 might influence the rate of Na + absorption by contributing to G K . Transient expression of KCNN4 cloned from H441 cells conferred a Ca 2+ - and 1-EBIO-sensitive K + conductance on Chinese hamster ovary cells, but this channel was inactive when [Ca 2+ ] i was