A mutational approach to dissect the functional role of the putative CFTR "PTM-CODE"

Deletion of Phe at position 508 (F508del) in CFTR is the commonest cause of Cystic Fibrosis; this mutation affects the fate of the protein, since most of the F508del-CFTR is retained in the endoplasmic reticulum, ubiquitylated and degraded. CFTR is subjected to different post-translational modifications (PTMs) and the possibility to modulate these PTMs has been suggested as a potential therapeutic strategy for the functional recovery of F508del-CFTR. Recently, it has been suggested the presence of a PTM signature (phosphorylation, methylation and ubiquitylation) in the regulatory insertion element of the CFTR, named PTM-code, which is associated with CFTR maturation and F508del-CFTR recovery. However, the real contribution of these PTMs is still to be deciphered. Here, by using a mutational approach, we show that the PTM-code is dispensable for the functional recovery of F508del-CFTR and therefore its regulation would not be essential in the light of a therapeutical approach.