S-nitrosoglutathione increases cystic fibrosis transmembrane regulator maturation

Endogenous S-nitrosoglutathione (GSNO) is known to increase the expression of certain proteins at concentrations present in the normal human airway. We hypothesized that GSNO would increase expression and maturation of the cystic fibrosis transmembrane conductance regulator (CFTR). Cells expressing DeltaF508 and wild type CFTR were exposed to GSNO and analyzed for expression and maturation by Western blot analysis. Physiologically relevant concentrations of GSNO resulted in dose- and time-dependent increases in expression. The GSNO-induced increases were eliminated by cycloheximide, suggesting a posttranscriptional effect. Unlike proteasome inhibitors, GSNO resulted in an increase CFTR maturation. The GSNO effect could be reversed by dithiothreitol and inhibited by acivicin, a gamma glutamyl transpeptidase inhibitor. These observations suggest that GSNO leads to maturation of mutated DeltaF508 CFTR, a process associated with restoration of CFTR function. Because endogenous levels of GSNO are low in the cystic fibrosis (CF) airway, these results raise the possibility that GSNO replacement therapy could be an effective treatment for CF.