Redefining Hypo- and Hyper-Responding Phenotypes of CFTR Mutants for Understanding and Therapy

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Cystic Fibrosis (CF) is caused by mutations in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene, leading to protein misfolding and impaired ion channel function.
• A triple-modulator combination therapy (Trikafta) is approved for many CFTR mutations, including F508del, but understanding responses in outlier mutations is crucial.

Purpose of the Study:

• To investigate the biochemical characteristics of CFTR mutants that exhibit poor or exceptional functional responses to modulator therapies.
• To determine if biochemical responses correlate with functional outcomes in CFTR mutants.

Main Methods:

• Biosynthetic radiolabeling to track CFTR protein synthesis and folding.
• Protease-susceptibility assays to assess protein stability and conformation.
• Evaluation of CFTR mutants in the presence and absence of modulator therapies.

Main Results:

• Most CFTR mutants displayed expected biochemical responses to modulators (e.g., TMD1 conformational changes, increased stability), irrespective of their functional response.
• Biochemical changes were observed even when functional improvements were minimal or absent.

Conclusions:

• CFTR modulators may exert biochemical effects on protein folding and stability even in genotypes with limited functional benefit.
• These findings support the consideration of current modulator therapies for patients with hypo-responder genotypes.
• Further understanding of outlier mutation phenotypes can refine CFTR folding insights and improve therapeutic strategies.