Mass spectrometric analysis of ΔF508 CFTR interactome identifies new drug targets for Cystic Fibrosis

Cystic fibrosis (CF) is one of the most common genetic childhood diseases, affecting 1:2500 newborns in Europe. The disease is caused by loss-of-function mutations in the anion channel Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). Deletion of F508 in CFTR (ΔF508 CFTR) is the most prevalent mutation, occurring in more than 70% of CF patients. Children with CF suffer from unusually thick mucus in the lung, which promotes recurrent bacterial infections, causes obstruction of the airways and eventually leads to inflammation, tissue damage and respiratory failure (1).

We recently reported the complete protein-protein interaction network of wt and ΔF508 CFTR using co-immunoprecipitation and mass spectrometry (2). We showed that deletion of F508 re-organizes the CFTR protein-protein interaction network and causes CFTR to acquire new, disease-specific interactions that drive the disease for example by preventing trafficking of ΔF508 CFTR to the plasma membrane and promoting its premature degradation at different stages of biogenesis. Analysis of interactome changes upon treatment of human CF bronchial epithelial cells with HDAC inhibitors or shift to permissive temperature, both of which partially restore channel function, then allowed us to identify novel key interactors whose removal rescued ΔF508 CFTR function at least partially. These key interactors can now be used for targeted drug development.

Mass spectrometric analysis further revealed that rescuing conditions also alter appearance and abundance of post-translational modifications (PTMs) of the ΔF508 CFTR protein.

Preliminary results indicate that a specific pattern of ΔF508 CFTR PTMs might be utilized as an alternative read-out for small molecule screens aiming to rescue CFTR channel function.

In summary, in-depth analysis of the CFTR interactome as well as its post-translational modifications can guide the development of new compounds to treat Cystic Fibrosis, which is urgently needed as current therapies are mostly directed towards symptoms and no cure is available yet.

References:

[1] F. S. Collins, Cystic fibrosis: molecular biology and therapeutic implications. Science 256, 774 – 779 (1992).

[2] S. Pankow et al., F508 CFTR interactome remodelling promotes rescue of cystic fibrosis. Nature 528, 510 – 516 (2015).