SLC6A14Is a Genetic Modifier of Cystic Fibrosis That Regulates Pseudomonas aeruginosaAttachment to Human Bronchial Epithelial Cells

ABSTRACTCystic fibrosis (CF) is caused by mutations in the CFTRgene and is associated with progressive and ultimately fatal infectious lung disease. There can be considerable variability in disease severity among individuals with the same CFTRmutations, and recent genome-wide association studies have identified secondary genetic factors that contribute to this. One of these modifier genes is SLC6A14, which encodes an amino acid transporter. Importantly, variants of this gene have been associated with age at first acquisition of Pseudomonas aeruginosa. In this study, we aimed to determine the function of SLC6A14 in airway epithelia and how it might affect colonization by P. aeruginosa. We show that SLC6A14is expressed in respiratory epithelial cells and transports l-arginine out of the airway surface liquid (ASL). Exposure of airway epithelia to flagellin from P. aeruginosaled to upregulation of SLC6A14expression and increased SLC6A14-dependent uptake of l-arginine from the ASL. In support of the hypothesis that l-arginine affects P. aeruginosaattachment, we showed that l-arginine supplementation promoted P. aeruginosaattachment to an abiotic surface in a dose-dependent manner. In a coculture model, we found that inhibition of SLC6A14-dependent l-arginine transport enhanced P. aeruginosaattachment. In Slc6a14−/y(knockout) mice, P. aeruginosaattachment to lung tissue was also significantly enhanced. Together, these findings suggest that SLC6A14 activity plays a role in the modification of the initial stages of airway infection by altering the level of l-arginine in the ASL, which in turn affects the attachment of P. aeruginosa.IMPORTANCECF patients with shared CFTRgene mutations show significant variability in their clinical presentation of infectious lung disease. Genome-wide association studies have been used to identify secondary genetic factors that may explain the variable susceptibility to infection by opportunistic pathogens, including P. aeruginosa, the leading cause of pathogen-induced lung damage in nonpediatric CF patients. Once identified and characterized, these secondary genetic modifiers may allow for the development of personalized medicine for patients and ultimately the extension of life. In this study, we interrogated the biological role of one of these modifiers, SLC6A14, and showed that it contributes to host defense by depleting extracellular arginine (an attachment-promoting metabolite for P. aeruginosa) from the airway surface liquid.