Augmentation of Cystic Fibrosis Transmembrane Conductance Regulator Function in Human Bronchial Epithelial Cells via SLC6A14-Dependent Amino Acid Uptake. Implications for Treatment of Cystic Fibrosis

• Published in: American journal of respiratory cell and molecular biology Vol. 61; no. 6; pp. 755 - 764
• Main Authors: Ahmadi, Saumel, Wu, Yu-Sheng, Li, Mingyuan, Ip, Wan, Lloyd-Kuzik, Andrew, Di Paola, Michelle, Du, Kai, Xia, Sunny, Lew, Alexandria, Bozoky, Zoltan, Forman-Kay, Julie, Bear, Christine E, Gonska, Tanja
• Format: Journal Article
• Language: English
• Published: United States American Thoracic Society 01.12.2019
• Subjects: Airway management; Amino Acid Transport Systems - antagonists & inhibitors; Amino Acid Transport Systems - genetics; Amino Acid Transport Systems - physiology; Amino acids; Arginine; Arginine - metabolism; Biological Transport; Bronchi - cytology; Bronchi - metabolism; Cells, Cultured; Cystic fibrosis; Cystic Fibrosis - metabolism; Cystic Fibrosis - therapy; Cystic Fibrosis Transmembrane Conductance Regulator - deficiency; Cystic Fibrosis Transmembrane Conductance Regulator - genetics; Cystic Fibrosis Transmembrane Conductance Regulator - physiology; Epithelial cells; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Genes, Reporter; Humans; Lung diseases; Nitric Oxide - metabolism; Nitric Oxide Synthase Type II - antagonists & inhibitors; Nitric Oxide Synthase Type II - metabolism; Recombinant Proteins - metabolism; Surface Properties; Transduction, Genetic; Tryptophan - analogs & derivatives; Tryptophan - pharmacology; nitric oxide pathway; F508del-CFTR; human bronchial epithelial cells; cystic fibrosis; SLC6A14
• DOI: 10.1165/rcmb.2019-0094OC
• ISSN: 1044-1549

SLC6A14-mediated l-arginine transport has been shown to augment the residual anion channel activity of the major mutant, F508del-CFTR, in the murine gastrointestinal tract. It is not yet known if this transporter augments residual and pharmacological corrected F508del-CFTR in primary airway epithelia. We sought to determine the role of l-arginine uptake via SLC6A14 in modifying F508del-CFTR channel activity in airway cells from patients with cystic fibrosis (CF). Human bronchial epithelial (HBE) cells from lung explants of patients without CF (HBE) and those with CF (CF-HBE) were used for H -flux, airway surface liquid, and Ussing chamber studies. We used α-methyltryptophan as a specific inhibitor for SLC6A14. CFBE41o , a commonly used CF airway cell line, was employed for studying the mechanism of the functional interaction between SLC6A14 and F508del-CFTR. SLC6A14 is functionally expressed in CF-HBE cells. l-arginine uptake via SLC6A14 augmented F508del-CFTR function at baseline and after treatment with lumacaftor. SLC6A14-mediated l-arginine uptake also increased the airway surface liquid in CF-HBE cells. Using CFBE41o cells, we showed that the positive SLC6A14 effect was mainly dependent on the nitric oxide (NO) synthase activity, nitrogen oxides, including NO, and phosphorylation by protein kinase G. These finding were confirmed in CF-HBE, as inducible NO synthase inhibition abrogated the functional interaction between SLC6A14 and pharmacological corrected F508del-CFTR. In summary, SLC6A14-mediated l-arginine transport augments residual F508del-CFTR channel function via a noncanonical, NO pathway. This effect is enhanced with increasing pharmacological rescue of F508del-CFTR to the membrane. The current study demonstrates how endogenous pathways can be used for the development of companion therapy in CF.