Impact of cholesterol and Lumacaftor on the folding of CFTR helical hairpins

Schenkel, M.; Ravamehr-Lake, D.; Czerniak, T.; Sáenz, J. P.; Krainer, G.; Schlierf, M.; Deber, C. M. (2023) Biochimica et Biophysica Acta (BBA) - Biomembranes, 1865(1), 184078. DOI: 10.1016/j.bbamem.2022.184078

Summary

This study examined how cholesterol and the cystic fibrosis corrector drug Lumacaftor (VX-809) affect the folding of CFTR transmembrane helical hairpin constructs. Using single-molecule FRET and circular dichroism, the authors found that 30 mol% cholesterol increased helicity of all TM3/4 hairpin variants, suggesting deeper membrane insertion due to increased bilayer cross-section. The corrector VX-809 normalized mutant hairpin folding to wild-type conformation regardless of cholesterol presence, acting as a protein-folding chaperone that shields the protein from the lipid environment in a mutant-independent manner.

Key Findings

• 30 mol% cholesterol increased helicity of all CFTR TM3/4 hairpin variants (wild-type and CF-causing mutants E217G, Q220R, V232D)
• Cholesterol-induced helicity increase suggests greater depth of membrane insertion due to bilayer thickening
• VX-809 corrector normalized mutant hairpin folding to wild-type conformation independent of cholesterol
• Fluorescence spectroscopy showed VX-809 alters lipid packing and water accessibility
• The proposed model: VX-809 shields the protein from the lipid environment, allowing the wild-type scaffold to prevail

Our Contribution

Our group contributed expertise in membrane biophysics and lipid-protein interactions, supporting the characterization of cholesterol effects on membrane protein folding.

Significance

This work demonstrates that membrane lipid composition (specifically cholesterol content) directly influences transmembrane protein folding, relevant to understanding how the lipid environment modulates disease-causing mutations and pharmacological correction in cystic fibrosis.