Molecular diversity and function of K+ channels in airway and alveolar epithelial cells

1 Centre de Recherche, Centre Hospitalier de l'Université de Montréal (CRCHUM), Hôtel-Dieu and 2 Départment de médecine, Université de Montréal, Montréal, Québec, Canada ABSTRACT Multiple K + channels are expressed in the respiratory epithelium lining airways and alveoli. Of the three main classes [ 1 ) voltage-dependent or Ca 2+ -activated, 6-transmembrane domains (TMD), 2 ) 2-pores 4-TMD, and 3 ) inward-rectified 2-TMD K + channels], almost 40 different transcripts have already been detected in the lung. The physiological and functional significance of this high molecular diversity of lung epithelial K + channels is intriguing. As detailed in the present review, K + channels are located at both the apical and basolateral membranes in the respiratory epithelium, where they mediate K + currents of diverse electrophysiological and regulatory properties. The main recognized function of K + channels is to control membrane potential and to maintain the driving force for transepithelial ion and liquid transport. In this manner, KvLQT1, KCa and K ATP channels, for example, contribute to the control of airway and alveolar surface liquid composition and volume. Thus, K + channel activation has been identified as a potential therapeutic strategy for the resolution of pathologies characterized by ion transport dysfunction. K + channels are also involved in other key functions in lung physiology, such as oxygen-sensing, inflammatory responses and respiratory epithelia repair after injury. The purpose of this review is to summarize and discuss what is presently known about the molecular identity of lung K + channels with emphasis on their role in lung epithelial physiology. Kv channels; KCa channels; Kir channels; K 2 P channels; lung; ion transport; epithelial repair; oxygen sensing; inflammation Address for reprint requests and other correspondence: E. Brochiero, Centre de recherche du CHUM, Hôtel-Dieu, 3840, Saint-Urbain, Montréal, Québec H2W 1T8, Canada (e-mail: emmanuelle.brochiero{at}umontreal.ca )