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

Bardou O, Trinh NT, Brochiero E. Molecular diversity and function of K+ channels in airway and alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 296: L145-L155, 2009. First published December 5, 2008; doi: 10.1152/ajplung.90525.2008.-Multiple K+ channels are expressed in the respiratory epithelium lining airways and alveoli. Of the three main classes [1) voltage-dependent or Ca2+-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.