Identification of CFTR proximal interactome: Proximity labeling approaches Reveals new insights

Understanding the role of proteins that interact with the cystic fibrosis transmembrane conductance regulator (CFTR) has helped to shed light on processes controlling folding, transport to the plasma membrane and recycling. Conventional approaches have enabled identification of partners implicated in these critical steps, but novel methods are emerging, called proximity labeling, allowing identification of partners in a native environment within a 10-20 nanometer range. We explored proximal interactome of CFTR and CFTR mutants by using proximity labeling strategies. Identification by mass spectrometry uncovered several hundred proteins in proximity with CFTR. A comparative analysis with database reveals both known and new CFTR partners. Study of the CFTR mutants devoid of PDZ domain revealed the loss of PDZ-associated protein interaction, demonstrating the robustness of this approach. In cystic fibrosis, therapies are now available, including for patients carrying the most frequent mutation, F508del. Nevertheless, these therapies incompletely correct some molecular characteristics in comparison to WT-CFTR (ubiquitination profile, stability on the surface...). Through proximity-based interactomics, we investigated the impact of the treatment on F508del interactome. The comparative analysis with the WT-CFTR showed only a partial rescue of the F508del-CFTR proximal interactome following the treatment. SiRNA screening compaign demonstrated that the targeting of some treatment-resistant interactors can enhance the efficacy of existing therapies. The present work highlights the potential of proximity labeling to elucidate the complex CFTR interactome, and suggests potential avenues for improving cystic fibrosis therapies.