Innate and adaptive defense mechanisms protect the respiratory system from attack by microbes. Here, we present evidence that the bitter taste receptor T2R38 regulates the mucosal innate defense of the human upper airway. Utilizing immunofluorescent and live cell imaging techniques in polarized primary human sinonasal cells, we demonstrate that T2R38 is expressed in human upper respiratory epithelium and is activated in response to acyl-homoserine lactone quorum-sensing molecules secreted by Pseudomonas aeruginosa and other gram-negative bacteria. Receptor activation regulates calcium-dependent NO production, resulting in stimulation of mucociliary clearance and direct antibacterial effects. Moreover, common polymorphisms of the TAS2R38 gene were linked to significant differences in the ability of upper respiratory cells to clear and kill bacteria. Lastly, TAS2R38 genotype correlated with human sinonasal gram-negative bacterial infection. These data suggest that T2R38 is an upper airway sentinel in innate defense and that genetic variation contributes to individual differences in susceptibility to respiratory infection.
Robert J. Lee, Guoxiang Xiong, Jennifer M. Kofonow, Bei Chen, Anna Lysenko, Peihua Jiang, Valsamma Abraham, Laurel Doghramji, Nithin D. Adappa, James N. Palmer, David W. Kennedy, Gary K. Beauchamp, Paschalis-Thomas Doulias, Harry Ischiropoulos, James L. Kreindler, Danielle R. Reed, Noam A. Cohen
T2R38 is expressed at the apical membrane and cilia of sinonasal airway epithelial cells in both human tissue explants and primary human sinonasal ALI cultures.