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REVIEW

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

¹Centre de Recherche, Centre Hospitalier de l'Université de Montréal (CRCHUM), Hôtel-Dieu and ²Départment 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 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.

Kv channels; KCa channels; Kir channels; K₂P channels; lung; ion transport; epithelial repair; oxygen sensing; inflammation