TY - JOUR T1 - Correctors of the major Cystic Fibrosis mutant interact through membrane spanning domains JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.118.111799 SP - mol.118.111799 AU - Onofrio Laselva AU - Steven Molinski AU - Valeria Casavola AU - Christine E. Bear Y1 - 2018/01/01 UR - http://molpharm.aspetjournals.org/content/early/2018/04/04/mol.118.111799.abstract N2 - The most common Cystic Fibrosis causing mutation is deletion of phenylalanine 508 (F508del), a mutation that leads to protein misassembly with defective processing. Small molecule correctors compounds: VX-809 or Corr-4a (C4) partially restore processing of the major mutant. These two prototypical corrector compounds cause an additive effect on F508del-CFTR processing and hence were proposed to act through distinct mechanisms: VX-809 stabilizing the first membrane spanning domain 1 (MSD1) and C4, acting on the second half of the molecule (consisting of MSD2 and/or nucleotide binding domain 2 (NBD2)). We confirmed the effect of VX-809 in enhancing the stability of MSD1 and showed that it also allosterically modulates MSD2 when co-expressed with MSD1. We showed for the first time that C4 stabilizes the second half of the CFTR protein through its action on MSD2. Given the allosteric effect of VX-809 on MSD2- we were prompted to test the hypothesis that the two correctors interact in the full length mutant protein. We did see evidence supporting their interaction in the full-length F508del-CFTR protein bearing secondary mutations targeting domain:domain interfaces. Disruption of the MSD1:F508del-NBD1 interaction (R170G) prevented correction by both compounds pointing to the importance of this interface in processing. On the other hand, stabilization of the MSD2: F508del-NBD1 interface (by introducing R1070W) led to a synergistic effect of the compound combination on the total abundance of both the immature and mature form of the protein. Together- these findings suggest that the two correctors interact in stabilizing the complex of MSDs in F508del-CFTR. ER -