Removal of multiple arginine-framed trafficking signals overcomes misprocessing of ΔF508 CFTR present in most patients with cystic fibrosis

Many cystic fibrosis transmembrane conductance regulator (CFTR) mutants are recognized as aberrant by the quality control apparatus at the endoplasmic reticulum (ER) and are targeted for degradation. The mechanism whereby nascent chains are distinguished as either competent or incompetent for ER export has not been elucidated. Here we show that export-incompetent chains display multiple arginine-framed tripeptide sequences like the one recently identified in ATP-sensitive K⁺ channels. Replacement of arginine residues at positions R29, R516, R555, and R766 with lysine residues to inactivate four of these motifs simultaneously causes ΔF508 CFTR, present in ~90% of CF patients, to escape ER quality control and function at the cell surface. Interference with recognition of these signals may be helpful in the management of CF.