A possible therapeutic avenue in Cystic Fibrosis

Cystic fibrosis (CF) is an inherited chronic disease that primarily affects the lungs and digestive system. CF is caused by mutations in the Cystic Fibrosis Transmembrane Regulator (CFTR) gene, a chloride channel responsible for helping conduct chloride and other ions across epithelial membranes. The loss of a functional CFTR channel disrupts ionic homeostasis resulting in mucus production that clogs the lungs and pancreas and results in a vicious cycle of chronic infection and inflammation as the disease progresses.

There are almost 2,000 different variants in the CFTR gene and 70 % of CF patients contain a mutation at position 508, which results in the loss of Phe508 and disruption of the folding pathway of CFTR. ΔF508 CFTR is a trafficking mutant that is retained in the endoplasmic reticulum (ER) and unable to reach the plasma membrane. Efforts to enhance exit of ΔF508 CFTR from the ER and improve its trafficking are of utmost importance for the development of treatment strategies. Clinically, progress has been made in recent years identifying therapeutics that target CFTR dysfunction in patients with specific mutations. However, small molecules that directly target the most common misfolded CFTR mutant, ΔF508, and improve its intracellular trafficking in vitro, have shown modest effects We performed a study aimed to identify new therapeutic targets that will help address the unmet clinical need for CF patients homozygous for  the ΔF508 mutation.We aimed to understand the protein interactions regulating CFTR transport using mass spectrometry-based proteomics. Using mass spectrometry based protein interaction profiling and global bioinformatics analysis we revealed mammalian target of rapamycin (mTOR) signalling components to be associated with ∆F508 CFTR.  Our results showed upregulated mTOR activity in ΔF508 CF bronchial epithelial cells. In addition to a well described role in several cancer subtypes, excessive activation of the mTOR pathway has been reported to be involved in age-related misfolding diseases. There are a range of inhibitors that target the PI3K/Akt/mTOR pathway and after screening a selection of inhibitors, we identified 6 different inhibitors that demonstrated an increase in CFTR stability and expression. Mechanistically, we discovered the most effective inhibitor, MK-2206 exerted a rescue effect by restoring autophagy in ΔF508 CF cells. These findings highlight this pathway as a possible therapeutic avenue worth further exploration in Cystic Fibrosis.

Judith Coppinger and her team: Mark Ward and Zivile Useckaite

We aimed to understand the protein interactions regulating CFTR transport using mass spectrometry-based proteomics. Using mass spectrometry based protein interaction profiling and global bioinformatics analysis we revealed mammalian target of rapamycin (mTOR) signalling components to be associated with ∆F508 CFTR.  Our results showed upregulated mTOR activity in ΔF508 CF bronchial epithelial cells. In addition to a well-described role in several cancer subtypes, excessive activation of the mTOR pathway has been reported to be involved in age-related misfolding diseases. There are a range of inhibitors that target the PI3K/Akt/mTOR pathway and after screening a selection of inhibitors, we identified 6 different inhibitors that demonstrated an increase in CFTR stability and expression. Mechanistically, we discovered the most effective inhibitor, MK-2206 exerted a rescue effect by restoring autophagy in ΔF508 CF cells. These findings highlight this pathway as a possible therapeutic avenue worth further exploration in Cystic Fibrosis.

This study was a collaboration between several groups at University College Dublin, Cystic Fibrosis Unit, St Vincent’s Hospital, Royal College of Surgeons in Ireland, Beaumont Hospital and the University of Mainz, Germany. Ongoing work in this area is taking place at the National Children’s Research Centre. Further details can be found here in a recent publication on this work.