Roscovitine is a proteostasis regulator that corrects the trafficking defect of F508del‐CFTR by a CDK‐independent mechanism

Abstract

BACKGROUND AND PURPOSEThe most common mutation in cystic fibrosis (CF), F508del, causes defects in trafficking, channel gating and endocytosis of the CF transmembrane conductance regulator (CFTR) protein. Because CF is an orphan disease, therapeutic strategies aimed at improving mutant CFTR functions are needed to target the root cause of CF. EXPERIMENTAL APPROACHHuman CF airway epithelial cells were treated with roscovitine 100 μM for 2 h before CFTR maturation, expression and activity were examined. The mechanism of action of roscovitine was explored by recording the effect of depleting endoplasmic reticulum (ER) Ca 2+ on the F508del-CFTR/calnexin interaction and by measuring proteasome activity. KEY RESULTSOf the cyclin-dependent kinase (CDK) inhibitors investigated, roscovitine was found to restore the cell surface expression and defective channel function of F508del-CFTR in human CF airway epithelial cells. Neither olomoucine nor (S)-CR8, two very efficient CDK inhibitors, corrected F508del-CFTR trafficking demonstrating that the correcting effect of roscovitine was independent of CDK inhibition. Competition studies with inhibitors of the ER quality control (ERQC) indicated that roscovitine acts on the calnexin pathway and on the degradation machinery. Roscovitine was shown (i) to partially inhibit the interaction between F508del-CFTR and calnexin by depleting ER Ca 2+ and (ii) to directly inhibit the proteasome activity in a Ca 2+ -independent manner. CONCLUSIONS AND IMPLICATIONSRoscovitine is able to correct the defective function of F508del-CFTR by preventing the ability of the ERQC to interact with and degrade F508del-CFTR via two synergistic but CDK-independent mechanisms. Roscovitine has potential as a pharmacological therapy for CF. Abbreviations

In silico search for modifier genes associated with pancreatic and liver disease in Cystic Fibrosis

“…Therefore, modifications in the IFI16 and/or UBC gene expression could lead to modifications of the maturation of CFTR, showing the importance of IFI16 as a modifier gene in CF, in link to immunity. CCNE2 binds to CDK2 in a catalytically active complex which modulates the cell cycle progression [97] and CDK inhibition corrects F508del-CFTR proteins [98]. Together with the role of UBC upon the proteasomal targeting of CFTR, the physical and functional complexes involving CCNE2, UBC and CFTR (Fig 7A) indicates that CCNE2 is likely a modifier gene in CF.…”

Inflammation in cystic fibrosis: An update

“…(R)‐Roscovitine is a cyclin‐dependent kinase inhibitor that restores surface expression and function of F508del mutant CFTR . In human CF cells, roscovitine partially inhibited the interaction between F508del‐CFTR and calnexin by depleting calcium in the endoplasmic reticulum, and it inhibited the proteasome activity in a calcium‐independent manner .…”

Protein misfolding diseases: Prospects of pharmacological treatment

“…PCs hold the promise of being able to reduce the severity of several genetic diseases, but it is important to note that the number of PCs described for different targets is low. For instance, in cystic fibrosis (CF), a number of PCs and PRs that might rescue CF transmembrane conductance regulator (CFTR) have recently been identified, one of which is the PR roscovitine, which is involved in calcium regulation . The use of therapeutic autophagy inducers has also been tested in CF.…”