Prevention of ubiquitination at lysines in the N tail, R, ICL4, and NBD2 domains disrupts CFTR trafficking and immune response

Abstract

RationalePost‐translational modification of lysine residues in CFTR is predicted to regulate CFTR trafficking and recycling. We hypothesized that disruption of ubiquitination in lysine residues will accelerate destruction of wt CFTR and increase inflammatory responses.MethodsSite‐directed mutagenesis, Immunoblot, confocal analysis, ELISA assay, etc.ResultsWe identify seven key lysines in CFTR protein that regulate expression, maturation, poly‐ubiquitination, and trafficking of CFTR and subsequently, its role in inflammatory responses. More specifically, K14/K68/K1218 residues are important for lysosomal degradation, while the K710/K716/K1080 residues are necessary for stabilization/poly‐ubiquitination of CFTR, and the K1041 residue is critical for overall expression of CFTR. Moreover, the K710R, K716R and K710/716R mutants are inflammatory however, inhibition of lysosomal function dampens inflammatory signaling by these mutations. K14R, K68R, K1041R, K1080R and K1218R mutants are not inflammatory. Inhibition of proteasomal degradation enhances non‐inflammatory effect of K14R and K1080R mutants.ConclusionsPost‐translational modifications in CFTR lysine residues regulate maturation and trafficking of CFTR and the inflammatory responses.Supported by R01 HL 59410; Eudowood Division of Pediatric Respiratory Sciences