Related Experiment Video
Updated: Aug 23, 2025
Functional Reconstitution and Channel Activity Measurements of Purified Wildtype and Mutant CFTR Protein
Published on: March 9, 2015
Recovery of ΔF508-CFTR Function by Citrate
Beatrice Borkenhagen1, Peter Prehm1,2
1Institute of Physiological Chemistry and Pathobiochemistry, Muenster University Hospital, Waldeyerstr. 15, 48129 Muenster, Germany.
Abstract:
Treatment of cystic fibrosis relies so far on expensive and sophisticated drugs. A logical approach to rescuing the defective ΔF508-CFTR protein has not yet been published. Therefore, virtual docking of ATP and CFTR activators to the open conformation of the CFTR protein was performed. A new ATP binding site outside of the two known locations was identified. It was located in the cleft between the nucleotide binding domains NBD1 and NBD2 and comprised six basic amino acids in close proximity. Citrate and isocitrate were also bound to this site. Citrate was evaluated for its action on epithelial cells with intact CFTR and defective ΔF508-CFTR. It activated hyaluronan export from human breast carcinoma cells and iodide efflux, and recovered ΔF508-CFTR from premature intracellular degradation. In conclusion, citrate is an activator for ΔF508-CFTR and increases export by defective ΔF508-CFTR into the extracellular matrix of epithelial cells.
Insights
Citrate activates the defective cystic fibrosis transmembrane conductance regulator (CFTR) protein, a key factor in cystic fibrosis. This finding offers a new therapeutic avenue for treating cystic fibrosis by improving protein function and export.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Current cystic fibrosis treatments involve costly and complex medications.
- A rational strategy for correcting the defective ΔF508-CFTR protein remains elusive.
Purpose of the Study:
- To identify novel binding sites and activators for the cystic fibrosis transmembrane conductance regulator (CFTR) protein using virtual screening.
- To evaluate citrate as a potential therapeutic agent for cystic fibrosis by assessing its effect on ΔF508-CFTR function.
Main Methods:
- Virtual docking simulations of ATP and known CFTR activators were performed on the open conformation of the CFTR protein.
- A novel ATP-binding site was identified between the NBD1 and NBD2 domains.
- Citrate's effects on epithelial cells with intact and defective CFTR were experimentally evaluated, including hyaluronan export and iodide efflux assays.
Main Results:
- A previously unknown ATP-binding site was discovered in the cleft between the NBD1 and NBD2 domains, characterized by six basic amino acids.
- Citrate and isocitrate were found to bind to this novel site.
- Citrate demonstrated the ability to activate hyaluronan export and iodide efflux in epithelial cells.
- Citrate treatment also prevented the premature intracellular degradation of the ΔF508-CFTR protein.
Conclusions:
- Citrate acts as a novel activator for the ΔF508-CFTR protein.
- Citrate enhances the export of molecules by defective ΔF508-CFTR in epithelial cells, suggesting therapeutic potential for cystic fibrosis.
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