Protease-activated receptor 2 activates airway apical membrane chloride permeability and increases ciliary beating

Mucociliary clearance, driven by the engine of ciliary beating, is the primary physical airway defense against inhaled pathogens and irritants. Abetter understanding of the regulation of ciliary beating and mucociliary transport is necessary for identifying new receptor targets to stimulate improved clearance in airway diseases, such as cystic fibrosis and chronic rhinosinusitis. In this study, we examined the protease-activated receptor (PAR)-2, a GPCR previously shown to regulate airway cell cytokine and mucus secretion, and transepithelial Cl- current. PAR-2 is activated by proteases secreted by airway neutrophils and pathogens. We cultured various airway cell lines, primary human and mouse sinonasal cells, and human bronchial cells at air-liquid interface and examined them using molecular biology, biochemistry, and live-cell imaging. We found that PAR-2 is expressed basolaterally, where it stimulates both intracellular Ca2+ release and Ca2+ influx, which activates low-levelnitric oxide production, increases apical membrane Cl- permeability similar to 3-5-fold, and increases ciliary beating similar to 20-50%. No molecular or functional evidence of PAR-4 was observed. These data suggest a novel and previously overlooked role of PAR-2 in airway physiology, adding to our understanding of the role of this receptor in airway Ca2+ signaling and innate immunity.