SLC6A14 Is a Genetic Modifier of Cystic Fibrosis That Regulates Pseudomonas aeruginosa Attachment to Human Bronchial Epithelial Cells

Abstract

Cystic fibrosis (CF) is caused by mutations in the CFTR gene and is associated with progressive and ultimately fatal infectious lung disease. There can be considerable variability in disease severity among individuals with the same CFTR mutations, 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 SLC6A14 is expressed in respiratory epithelial cells and transports l-arginine out of the airway surface liquid (ASL). Exposure of airway epithelia to flagellin from P. aeruginosa led to upregulation of SLC6A14 expression and increased SLC6A14-dependent uptake of l-arginine from the ASL. In support of the hypothesis that l-arginine affects P. aeruginosa attachment, we showed that l-arginine supplementation promoted P. aeruginosa attachment 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. aeruginosa attachment. In Slc6a14−/y (knockout) mice, P. aeruginosa attachment 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.

Functional analysis of OCTN2 and ATB0,+ in normal human airway epithelial cells

“…Indeed, it has been recently suggested that ATB 0,+ typically localizes in places where the body interfaces with microbes, such as lung and colon, where it is probably involved in reducing available nutrients to bacteria; consistently, the transporter is up-regulated in inflammatory states, such as ulcerative colitis, Crohn's disease and colon cancer [20]. Moreover, genome-wide association studies has recently identified SLC6A14/ATB 0,+ as a genetic modifier of lung disease severity in cystic fibrosis, providing a mechanism by which it regulates Pseudomonas aeruginosa attachment to human bronchial epithelial cells [40]. In that study, Di Paola et al demonstrated an enhancement of SLC6A14 expression by LPS in Calu-3 cells cultured on plasticware.…”

Lipophilicity of the Cystic Fibrosis Drug, Ivacaftor (VX-770), and Its Destabilizing Effect on the Major CF-causing Mutation: F508del

“…SLC6A14 is an apical amino acid transporter, and we have shown that it functions to remove nutrient amino acids from the surface of respiratory epithelial cells (Di Paola et al, 2017). This function is associated with reduced adherence of Pseudomonas aeruginosa to the surface of respiratory epithelial cells (Di Paola et al, 2017).…”

Functional analysis of OCTN2 and ATB0,+ in normal human airway epithelial cells

“…Accordingly, the transporter is upregulated in inflammatory states, such as ulcerative colitis, Crohn's disease and colon cancer [14]. Moreover, genome-wide association studies has been recently identified ATB 0,+ (SLC6A14) as a genetic modifier of lung disease severity in cystic fibrosis, providing a mechanism by which it regulates Pseudomonas aeruginosa attachment to human bronchial epithelial cells [24]. Compared to Calu-3 monolayers, a close similarity between the two cell models is observed only when Calu-3 layers are maintained at ALI for 8 days.…”