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

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 KATP channels, for example, contribute to the control of airway and alveolar surface liquid composition and volume. Thus, K+ channel activation has been ide...