Understanding the mechanism of modulation of CFTR by vardenafil : a new road to basic therapies for Cystic Fibrosis
(2016)
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- Authors
- Supervisors
- Leal, Teresinha
- Abstract
- Cystic Fibrosis (CF) is a fatal genetic disease caused by mutations in the gene encoding the CF Transmembrane conductance Regulator (CFTR) protein that acts mainly as a chloride channel. The most frequent mutation, causing the deletion of a phenylalanine in position 508 (F508del), leads to misfolding of the protein and to its subsequent retention in the endoplasmic reticulum (ER) and premature proteosomal degradation. The mutation results in a loss of CFTR function and a reduced localization in apical membranes of epithelial cells, where it is normally expressed. Therapeutic strategies aiming at overcoming the multiple deficiencies caused by the mutation are crucially needed to counteract physiopathological defects of the disease. In this context, the aim of this work was to characterize the effects of vardenafil, a cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5) inhibitor, on different CF target organs using a preclinical mouse model of CF, and to elucidate its site and mechanism(s) of action using relevant human- derived cellular models of CF. In CF mice, we showed that vardenafil activated the CFTR-dependent chloride transport and corrected the mislocalization of the mutant protein towards plasma membranes in severely affected CF organs. In human-derived cells, vardenafil influenced expression of the human mutant protein, even if it failed to promote insertion of the protein into plasma membranes. In addition, we demonstrated that modulating the cGMP pathway did not affect CFTR expression, suggesting that the mechanism of action of vardenafil is cGMP-independent. Interestingly, we showed here that vardenafil promoted maturation of F508del-CFTR only in the presence of co-expression of suppressive mutations or revertants such as I539T, G550E or R1070W. This finding suggests that the mechanism of action of vardenafil is distinct from those of the revertants. Finally, we confirmed that vardenafil did not rescue the folding of Nucleotide Binding Domain 1 (NBD1) within which the F508del mutation is located. This finding is supported by the fact that vardenafil and the I539T revertant exhibit a cooperative mechanism on F508del maturation. This work contributes to shed new light on the modulation of CFTR by cGMP pathway and clearly identifies vardenafil as a potential therapeutic tool for CF.
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Citations
Dhooghe, B. (2016). Understanding the mechanism of modulation of CFTR by vardenafil : a new road to basic therapies for Cystic Fibrosis. https://hdl.handle.net/2078.5/183340