Identification of binding sites for ivacaftor on the cystic fibrosis transmembrane conductance regulator

• Published in: iScience 2021-06, Vol.24 (6), p.102542-102542, Article 102542
• Main Authors: Laselva, Onofrio, Qureshi, Zafar, Zeng, Zhi-Wei, Petrotchenko, Evgeniy V., Ramjeesingh, Mohabir, Hamilton, C. Michael, Huan, Ling-Jun, Borchers, Christoph H., Pomès, Régis, Young, Robert, Bear, Christine E.
• Format: Article
• Language: English
• Subjects: Biochemistry; Biological sciences; Biophysics; Medicine; Structural biology
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2021.102542

Ivacaftor (VX-770) was the first cystic fibrosis transmembrane conductance regulator (CFTR) modulatory drug approved for the treatment of patients with cystic fibrosis. Electron cryomicroscopy (cryo-EM) studies of detergent-solubilized CFTR indicated that VX-770 bound to a site at the interface between solvent and a hinge region in the CFTR protein conferred by transmembrane (tm) helices: tm4, tm5, and tm8. We re-evaluated VX-770 binding to CFTR in biological membranes using photoactivatable VX-770 probes. One such probe covalently labeled CFTR at two sites as determined following trypsin digestion and analysis by tandem-mass spectrometry. One labeled peptide resides in the cytosolic loop 4 of CFTR and the other is located in tm8, proximal to the site identified by cryo-EM. Complementary data from functional and molecular dynamic simulation studies support a model, where VX-770 mediates potentiation via multiple sites in the CFTR protein. [Display omitted] •A photoactivatable probe of ivacaftor specifically modifies CFTR in membranes.•The probe modifies CFTR at the fourth cytosolic loop (ICL4) and at a kink formed by tm8.•Functional and molecular dynamic stimulation studies support ICL4 as a binding site. Biochemistry; Biological sciences; Biophysics; Medicine; Structural biology