Article ; Online: Can two wrongs make a right? F508del-CFTR ion channel rescue by second-site mutations in its transmembrane domains.
The Journal of biological chemistry
2022 Volume 298, Issue 3, Page(s) 101615
Abstract: Deletion of phenylalanine 508 (F508del) in the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel is the most common cause of cystic fibrosis. The F508 residue is located on nucleotide-binding domain 1 (NBD1) in contact with the ... ...
| Abstract | Deletion of phenylalanine 508 (F508del) in the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel is the most common cause of cystic fibrosis. The F508 residue is located on nucleotide-binding domain 1 (NBD1) in contact with the cytosolic extensions of the transmembrane helices, in particular intracellular loop 4 (ICL4). To investigate how absence of F508 at this interface impacts the CFTR protein, we carried out a mutagenesis scan of ICL4 by introducing second-site mutations at 11 positions in cis with F508del. Using an image-based fluorescence assay, we measured how each mutation affected membrane proximity and ion-channel function. The scan strongly validated the effectiveness of R1070W at rescuing F508del defects. Molecular dynamics simulations highlighted two features characterizing the ICL4/NBD1 interface of F508del/R1070W-CFTR: flexibility, with frequent transient formation of interdomain hydrogen bonds, and loosely stacked aromatic sidechains (F1068, R1070W, and F1074, mimicking F1068, F508, and F1074 in WT CFTR). F508del-CFTR displayed a distorted aromatic stack, with F1068 displaced toward the space vacated by F508, while in F508del/R1070F-CFTR, which largely retained F508del defects, R1070F could not form hydrogen bonds and the interface was less flexible. Other ICL4 second-site mutations which partially rescued F508del-CFTR included F1068M and F1074M. Methionine side chains allow hydrophobic interactions without the steric rigidity of aromatic rings, possibly conferring flexibility to accommodate the absence of F508 and retain a dynamic interface. These studies highlight how both hydrophobic interactions and conformational flexibility might be important at the ICL4/NBD1 interface, suggesting possible structural underpinnings of F508del-induced dysfunction. |
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| MeSH term(s) | Cystic Fibrosis/genetics ; Cystic Fibrosis/metabolism ; Cystic Fibrosis Transmembrane Conductance Regulator ; Humans ; Mutation ; Protein Domains ; Protein Structure, Secondary |
| Chemical Substances | CFTR protein, human ; Cystic Fibrosis Transmembrane Conductance Regulator (126880-72-6) |
| Language | English |
| Publishing date | 2022-01-21 |
| Publishing country | United States |
| Document type | Journal Article |
| ZDB-ID | 2997-x |
| ISSN | 1083-351X ; 0021-9258 |
| ISSN (online) | 1083-351X |
| ISSN | 0021-9258 |
| DOI | 10.1016/j.jbc.2022.101615 |
| Database | MEDical Literature Analysis and Retrieval System OnLINE |
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