1
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Hong JS, Tindall JM, Tindall SR, Sorscher EJ. Mutation accumulation in H. sapiens F508del CFTR countermands dN/dS type genomic analysis. PLoS One 2024; 19:e0305832. [PMID: 39024311 PMCID: PMC11257350 DOI: 10.1371/journal.pone.0305832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Accepted: 06/05/2024] [Indexed: 07/20/2024] Open
Abstract
Understanding the mechanisms that underlie de novo mutations (DNMs) can be essential for interpreting human evolution, including aspects such as rapidly diverging genes, conservation of non-coding regulatory elements, and somatic DNA adaptation, among others. DNM accumulation in Homo sapiens is often limited to evaluation of human trios or quads across a single generation. Moreover, human SNPs in exons, pseudogenes, or other non-coding elements can be ancient and difficult to date, including polymorphisms attributable to founder effects and identity by descent. In this report, we describe multigenerational evolution of a human coding locus devoid of natural selection, and delineate patterns and principles by which DNMs have accumulated over the past few thousand years. We apply a data set comprising cystic fibrosis transmembrane conductance regulator (CFTR) alleles from 2,393 individuals homozygous for the F508del defect. Additional polymorphism on the F508del background diversified subsequent to a single mutational event during recent human history. Because F508del CFTR is without function, SNPs observed on this haplotype are effectively attributable to factors that govern accumulating de novo mutations. We show profound enhancement of transition, synonymous, and positionally repetitive polymorphisms, indicating appearance of DNMs in a manner evolutionarily designed to protect protein coding DNA against mutational attrition while promoting diversity.
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Affiliation(s)
- Jeong S. Hong
- Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Janice M. Tindall
- Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Samuel R. Tindall
- Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Eric J. Sorscher
- Emory University School of Medicine, Atlanta, Georgia, United States of America
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2
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Ferreira FC, Amaral MD, Bacalhau M, Lopes-Pacheco M. PTI-801 (posenacaftor) shares a common mechanism with VX-445 (elexacaftor) to rescue p.Phe508del-CFTR. Eur J Pharmacol 2024; 967:176390. [PMID: 38336013 DOI: 10.1016/j.ejphar.2024.176390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 01/05/2024] [Accepted: 02/01/2024] [Indexed: 02/12/2024]
Abstract
The deletion of a phenylalanine at position 508 (p.Phe508del) in the CFTR anion channel is the most prevalent variant in people with Cystic Fibrosis (CF). This variant impairs folding and stability of the CF transmembrane conductance regulator (CFTR) protein, resulting in its defective trafficking and premature degradation. Over the last years, therapeutic accomplishments have been attained in developing small molecules that partially correct p.Phe508del-CFTR defects; however, the mechanism of action (MoA) of these compounds has only started to be uncovered. In this study, we employed biochemical, fluorescence microscopy, and functional assays to examine the efficacy and properties of PTI-801, a newly developed p.Phe508del-CFTR corrector. To exploit its MoA, we assessed PTI-801 effects in combination with low temperature, genetic revertants of p.Phe508del-CFTR (the in cis p.Val510Asp, p.Gly550Glu, p.Arg1070Trp, and 4RK) and other correctors. Our results demonstrated that PTI-801 rescues p.Phe508del-CFTR processing, PM trafficking, and channel function (upon agonist stimulation) with greater correction effects in combination with ABBV-2222, FDL-169, VX-661, or VX-809, but not with VX-445. Although PTI-801 exhibited no potentiator activity on low temperature- and corrector-rescued p.Phe508del-CFTR, this compound displayed similar behavior to that of VX-445 on genetic revertants. Such evidence associated with the lack of additivity when PTI-801 and VX-445 were combined indicates that they share a common binding site to correct p.Phe508del-CFTR defects. Despite the high efficacy of PTI-801 in combination with ABBV-2222, FDL-169, VX-661, or VX-809, these dual corrector combinations only partially restored p.Phe508del-CFTR conformational stability, as shown by the lower half-life of the mutant protein compared to that of WT-CFTR. In summary, PTI-801 likely shares a common MoA with VX-445 in rescuing p.Phe508del-CFTR, thus being a feasible alternative for the development of novel corrector combinations with greater capacity to rescue mutant CFTR folding and stability.
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Affiliation(s)
- Filipa C Ferreira
- Biosystems & Integrative Sciences Institute (BioISI), Faculty of Sciences, University of Lisbon, 1749-016, Lisbon, Portugal
| | - Margarida D Amaral
- Biosystems & Integrative Sciences Institute (BioISI), Faculty of Sciences, University of Lisbon, 1749-016, Lisbon, Portugal
| | - Mafalda Bacalhau
- Biosystems & Integrative Sciences Institute (BioISI), Faculty of Sciences, University of Lisbon, 1749-016, Lisbon, Portugal
| | - Miquéias Lopes-Pacheco
- Biosystems & Integrative Sciences Institute (BioISI), Faculty of Sciences, University of Lisbon, 1749-016, Lisbon, Portugal.
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3
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McKee AG, McDonald EF, Penn WD, Kuntz CP, Noguera K, Chamness LM, Roushar FJ, Meiler J, Oliver KE, Plate L, Schlebach JP. General trends in the effects of VX-661 and VX-445 on the plasma membrane expression of clinical CFTR variants. Cell Chem Biol 2023; 30:632-642.e5. [PMID: 37253358 PMCID: PMC10330547 DOI: 10.1016/j.chembiol.2023.05.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 02/17/2023] [Accepted: 05/05/2023] [Indexed: 06/01/2023]
Abstract
Cystic fibrosis (CF) is caused by mutations that compromise the expression and/or function of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. Most people with CF harbor a common misfolded variant (ΔF508) that can be partially rescued by therapeutic "correctors" that restore its expression. Nevertheless, many other CF variants are insensitive to correctors. Using deep mutational scanning, we quantitatively compare the effects of two correctors on the plasma membrane expression of 129 CF variants. Though structural calculations suggest corrector binding provides similar stabilization to most variants, it's those with intermediate expression and mutations near corrector binding pockets that exhibit the greatest response. Deviations in sensitivity appear to depend on the degree of variant destabilization and the timing of misassembly. Combining correctors appears to rescue more variants by doubling the binding energy and stabilizing distinct cotranslational folding transitions. These results provide an overview of rare CF variant expression and establish new tools for precision pharmacology.
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Affiliation(s)
- Andrew G McKee
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| | - Eli F McDonald
- Department of Chemistry, Vanderbilt University, Nashville, TN 37232, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Wesley D Penn
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| | - Charles P Kuntz
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| | - Karen Noguera
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| | - Laura M Chamness
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| | - Francis J Roushar
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| | - Jens Meiler
- Department of Chemistry, Vanderbilt University, Nashville, TN 37232, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA; Institute for Drug Development, Leipzig University, Leipzig, SAC 04109, Germany
| | - Kathryn E Oliver
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Lars Plate
- Department of Chemistry, Vanderbilt University, Nashville, TN 37232, USA; Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA
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4
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Baatallah N, Elbahnsi A, Chevalier B, Castanier S, Mornon JP, Pranke I, Edelman A, Sermet-Gaudelus I, Callebaut I, Hinzpeter A. Acting on the CFTR Membrane-Spanning Domains Interface Rescues Some Misfolded Mutants. Int J Mol Sci 2022; 23:ijms232416225. [PMID: 36555865 PMCID: PMC9780841 DOI: 10.3390/ijms232416225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/09/2022] [Accepted: 12/13/2022] [Indexed: 12/24/2022] Open
Abstract
ABC transporters are large membrane proteins sharing a complex architecture, which comprises two nucleotide-binding domains (NBDs) and two membrane-spanning domains (MSDs). These domains are susceptible to mutations affecting their folding and assembly. In the CFTR (ABCC7) protein, a groove has been highlighted in the MSD1 at the level of the membrane inner leaflet, containing both multiple mutations affecting folding and a binding site for pharmaco-chaperones that stabilize this region. This groove is also present in ABCB proteins, however it is covered by a short elbow helix, while in ABCC proteins it remains unprotected, due to a lower position of the elbow helix in the presence of the ABCC-specific lasso motif. Here, we identified a MSD1 second-site mutation located in the vicinity of the CFTR MSD1 groove that partially rescued the folding defect of cystic fibrosis causing mutations located within MSD1, while having no effect on the most frequent mutation, F508del, located within NBD1. A model of the mutated protein 3D structure suggests additional interaction between MSD1 and MSD2, strengthening the assembly at the level of the MSD intracellular loops. Altogether, these results provide insightful information in understanding key features of the folding and function of the CFTR protein in particular, and more generally, of type IV ABC transporters.
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Affiliation(s)
- Nesrine Baatallah
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Ahmad Elbahnsi
- Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France
| | - Benoit Chevalier
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Solène Castanier
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Jean-Paul Mornon
- Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France
| | - Iwona Pranke
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Aleksander Edelman
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Isabelle Sermet-Gaudelus
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
| | - Isabelle Callebaut
- Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France
- Correspondence: (I.C.); (A.H.)
| | - Alexandre Hinzpeter
- INSERM, U1151, Institut Necker Enfants Malades (INEM), Faculté de Médecine, Université Paris Cité, CNRS, UMR 8253, 75015 Paris, France
- Correspondence: (I.C.); (A.H.)
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5
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Fiedorczuk K, Chen J. Molecular structures reveal synergistic rescue of Δ508 CFTR by Trikafta modulators. Science 2022; 378:284-290. [PMID: 36264792 PMCID: PMC9912939 DOI: 10.1126/science.ade2216] [Citation(s) in RCA: 72] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The predominant mutation causing cystic fibrosis, a deletion of phenylalanine 508 (Δ508) in the cystic fibrosis transmembrane conductance regulator (CFTR), leads to severe defects in CFTR biogenesis and function. The advanced therapy Trikafta combines the folding corrector tezacaftor (VX-661), the channel potentiator ivacaftor (VX-770), and the dual-function modulator elexacaftor (VX-445). However, it is unclear how elexacaftor exerts its effects, in part because the structure of Δ508 CFTR is unknown. Here, we present cryo-electron microscopy structures of Δ508 CFTR in the absence and presence of CFTR modulators. When used alone, elexacaftor partially rectified interdomain assembly defects in Δ508 CFTR, but when combined with a type I corrector, did so fully. These data illustrate how the different modulators in Trikafta synergistically rescue Δ508 CFTR structure and function.
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Affiliation(s)
- Karol Fiedorczuk
- Laboratory of Membrane Biology and Biophysics, The Rockefeller University, New York, NY 10065, USA
| | - Jue Chen
- Laboratory of Membrane Biology and Biophysics, The Rockefeller University, New York, NY 10065, USA,Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA,Corresponding author.
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6
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Prins S, Corradi V, Sheppard DN, Tieleman DP, Vergani P. Can two wrongs make a right? F508del-CFTR ion channel rescue by second-site mutations in its transmembrane domains. J Biol Chem 2022; 298:101615. [PMID: 35065958 PMCID: PMC8861112 DOI: 10.1016/j.jbc.2022.101615] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 01/13/2022] [Accepted: 01/17/2022] [Indexed: 11/20/2022] Open
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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Affiliation(s)
- Stella Prins
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Valentina Corradi
- Department of Biological Sciences, Centre for Molecular Simulation, University of Calgary, Calgary, Alberta, Canada
| | - David N Sheppard
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - D Peter Tieleman
- Department of Biological Sciences, Centre for Molecular Simulation, University of Calgary, Calgary, Alberta, Canada
| | - Paola Vergani
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK.
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7
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Bahia MS, Khazanov N, Zhou Q, Yang Z, Wang C, Hong JS, Rab A, Sorscher EJ, Brouillette CG, Hunt JF, Senderowitz H. Stability Prediction for Mutations in the Cytosolic Domains of Cystic Fibrosis Transmembrane Conductance Regulator. J Chem Inf Model 2021; 61:1762-1777. [PMID: 33720715 DOI: 10.1021/acs.jcim.0c01207] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cystic Fibrosis (CF) is caused by mutations to the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) chloride channel. CFTR is composed of two membrane spanning domains, two cytosolic nucleotide-binding domains (NBD1 and NBD2) and a largely unstructured R-domain. Multiple CF-causing mutations reside in the NBDs and some are known to compromise the stability of these domains. The ability to predict the effect of mutations on the stability of the cytosolic domains of CFTR and to shed light on the mechanisms by which they exert their effect is therefore important in CF research. With this in mind, we have predicted the effect on domain stability of 59 mutations in NBD1 and NBD2 using 15 different algorithms and evaluated their performances via comparison to experimental data using several metrics including the correct classification rate (CCR), and the squared Pearson correlation (R2) and Spearman's correlation (ρ) calculated between the experimental ΔTm values and the computationally predicted ΔΔG values. Overall, the best results were obtained with FoldX and Rosetta. For NBD1 (35 mutations), FoldX provided R2 and ρ values of 0.64 and -0.71, respectively, with an 86% correct classification rate (CCR). For NBD2 (24 mutations), FoldX R2, ρ, and CCR were 0.51, -0.73, and 75%, respectively. Application of the Rosetta high-resolution protocol (Rosetta_hrp) to NBD1 yielded R2, ρ, and CCR of 0.64, -0.75, and 69%, respectively, and for NBD2 yielded R2, ρ, and CCR of 0.29, -0.27, and 50%, respectively. The corresponding numbers for the Rosetta's low-resolution protocol (Rosetta_lrp) were R2 = 0.47, ρ = -0.69, and CCR = 69% for NBD1 and R2 = 0.27, ρ = -0.24, and CCR = 63% for NBD2. For NBD1, both algorithms suggest that destabilizing mutations suffer from destabilizing vdW clashes, whereas stabilizing mutations benefit from favorable H-bond interactions. Two triple consensus approaches based on FoldX, Rosetta_lpr, and Rosetta_hpr were attempted using either "majority-voting" or "all-voting". The all-voting consensus outperformed the individual predictors, albeit on a smaller data set. In summary, our results suggest that the effect of mutations on the stability of CFTR's NBDs could be largely predicted. Since NBDs are common to all ABC transporters, these results may find use in predicting the effect and mechanism of the action of multiple disease-causing mutations in other proteins.
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Affiliation(s)
| | - Netaly Khazanov
- Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel
| | - Qingxian Zhou
- School of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
| | - Zhengrong Yang
- School of Medicine, Division of Hematology & Oncology, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
| | - Chi Wang
- 702 Fairchild Center, MC3423, Department of Biological Sciences, Columbia University, New York, New York 10027, United States
| | - Jeong S Hong
- Department of Paediatrics, Emory University School of Medicine, Atlanta, Georgia 30303, United States
| | - Andras Rab
- Department of Paediatrics, Emory University School of Medicine, Atlanta, Georgia 30303, United States
| | - Eric J Sorscher
- Department of Paediatrics, Emory University School of Medicine, Atlanta, Georgia 30303, United States
| | - Christie G Brouillette
- Department of Biochemistry & Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
| | - John F Hunt
- 702 Fairchild Center, MC3423, Department of Biological Sciences, Columbia University, New York, New York 10027, United States
| | - Hanoch Senderowitz
- Department of Chemistry, Bar-Ilan University, Ramat-Gan, 5290002, Israel
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8
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Uliyakina I, Botelho HM, da Paula AC, Afonso S, Lobo MJ, Felício V, Farinha CM, Amaral MD. Full Rescue of F508del-CFTR Processing and Function by CFTR Modulators Can Be Achieved by Removal of Two Regulatory Regions. Int J Mol Sci 2020; 21:ijms21124524. [PMID: 32630527 PMCID: PMC7350234 DOI: 10.3390/ijms21124524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 06/20/2020] [Accepted: 06/22/2020] [Indexed: 01/07/2023] Open
Abstract
Cystic Fibrosis (CF) is caused by mutations in the CF Transmembrane conductance Regulator (CFTR), the only ATP-binding cassette (ABC) transporter functioning as a channel. Unique to CFTR is a regulatory domain which includes a highly conformationally dynamic region—the regulatory extension (RE). The first nucleotide-binding domain of CFTR contains another dynamic region—regulatory insertion (RI). Removal of RI rescues the trafficking defect of CFTR with F508del, the most common CF-causing mutation. Here we aimed to assess the impact of RE removal (with/without RI or genetic revertants) on F508del-CFTR trafficking and how CFTR modulator drugs VX-809/lumacaftor and VX-770/ivacaftor rescue these variants. We generated cell lines expressing ΔRE and ΔRI CFTR (with/without genetic revertants) and assessed CFTR expression, stability, plasma membrane levels, and channel activity. Our data demonstrated that ΔRI significantly enhanced rescue of F508del-CFTR by VX-809. While the presence of the RI seems to be precluding full rescue of F508del-CFTR processing by VX-809, this region appears essential to rescue its function by VX-770, suggesting some contradictory role in rescue of F508del-CFTR by these two modulators. This negative impact of RI removal on VX-770-stimulated currents on F508del-CFTR can be compensated by deletion of the RE which also leads to the stabilization of this mutant. Despite both regions being conformationally dynamic, RI precludes F508del-CFTR processing while RE affects mostly its stability and channel opening.
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9
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Chen X, Zhu S, Zhenin M, Xu W, Bose SJ, Wong MPF, Leung GPH, Senderowitz H, Chen JH. A defective flexible loop contributes to the processing and gating defects of the predominant cystic fibrosis-causing mutation. FASEB J 2019; 33:5126-5142. [PMID: 30668920 DOI: 10.1096/fj.201801218rr] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
People with the genetic disease cystic fibrosis (CF) often carry a deletion mutation ΔF508 on the gene encoding the CF transmembrane conductance regulator (CFTR) Cl- channel. This mutation greatly reduces the CFTR maturation process and slows the channel opening rate. Here, we investigate whether residues near F508 contribute to these defects in ΔF508-CFTR. Most deletion mutations, but not alanine substitutions, of individual residues from positions 503 to 513 impaired CFTR maturation. Interestingly, only protein processing of ΔY512-CFTR, like that of ΔF508-CFTR, was greatly improved by low-temperature culture at 27°C or small-molecule corrector C18. The 2 mutant Cl- channels were equally slow to open, suggesting that they may share common structural flaws. Studies on the H3-H4 loop that links residues F508 and Y512 demonstrate that G509A/V510G mutations, moving G509 1 position backward in the loop, markedly enhanced ΔF508-CFTR maturation and opening rate while promoting protein stability and persistence of the H3 helix in ΔF508 nucleotide-binding domain 1. Moreover, V510A/S511A mutations noticeably increased ΔY512-CFTR maturation at 27°C and its opening rate. Thus, loop abnormalities may contribute to ΔF508- and ΔY512-CFTR defects. Importantly, correcting defects from G509 displacement in ΔF508-CFTR may offer a new avenue for drug discovery and CF treatments.-Chen, X., Zhu, S., Zhenin, M., Xu, W., Bose, S. J., Wong, M. P.-F., Leung, G. P. H., Senderowitz, H., Chen, J.-H. A defective flexible loop contributes to the processing and gating defects of the predominant cystic fibrosis-causing mutation.
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Affiliation(s)
- Xinying Chen
- School of Biomedical Sciences, University of Hong Kong, Hong Kong.,The University of Hong Kong Shenzhen Institute of Research and Innovation, Shenzhen, China
| | - Siyu Zhu
- School of Biomedical Sciences, University of Hong Kong, Hong Kong.,The University of Hong Kong Shenzhen Institute of Research and Innovation, Shenzhen, China
| | - Michael Zhenin
- Department of Chemistry, Bar Ilan University, Ramat-Gan, Israel
| | - Weiyi Xu
- School of Biomedical Sciences, University of Hong Kong, Hong Kong.,The University of Hong Kong Shenzhen Institute of Research and Innovation, Shenzhen, China
| | - Samuel J Bose
- School of Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol, United Kingdom; and
| | - Molly Pik-Fan Wong
- School of Biomedical Sciences, University of Hong Kong, Hong Kong.,The University of Hong Kong Shenzhen Institute of Research and Innovation, Shenzhen, China
| | - George P H Leung
- Department of Pharmacology and Pharmacy, University of Hong Kong, Hong Kong, China
| | | | - Jeng-Haur Chen
- School of Biomedical Sciences, University of Hong Kong, Hong Kong.,The University of Hong Kong Shenzhen Institute of Research and Innovation, Shenzhen, China
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10
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Yeh JT, Yu YC, Hwang TC. Structural mechanisms for defective CFTR gating caused by the Q1412X mutation, a severe Class VI pathogenic mutation in cystic fibrosis. J Physiol 2018; 597:543-560. [PMID: 30408177 DOI: 10.1113/jp277042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 11/06/2018] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS Electrophysiological characterization of Q1412X-CFTR, a C-terminal truncation mutation of cystic fibrosis transmembrane conductance regulator (CFTR) associated with the severe form of cystic fibrosis (CF), reveals a gating defect that has not been reported previously. Mechanistic investigations of the gating deficit in Q1412X-CFTR suggest that the reduced open probability in Q1412X-CFTR is the result of a disruption of the function of the second ATP binding site (or site 2) in the nucleotide binding domains (NBDs). Detailed comparisons of several mutations with different degrees of truncation in the C-terminal region of NBD2 reveal the importance of the last two beta-strands in NBD2 for maintaining proper gating functions. The results of the present study also show that the application of clinically-approved drugs (VX-770 and VX-809) can greatly enhance the function of Q1412X, providing in vitro evidence for a therapeutic strategy employing both reagents for patients bearing Q1412X or similar truncation mutations. ABSTRACT Cystic fibrosis (CF) is caused by loss-of-function mutations of cystic fibrosis transmembrane conductance regulator (CFTR), a phosphorylation-activated but ATP-gated chloride channel. Based on the molecular mechanism of CF pathogenesis, disease-associated mutations are categorized into six classes. Among them, Class VI, whose members include some of the C-terminal truncation mutations such as Q1412X, is defined as decreased membrane expression because of a faster turnover rate. In the present study, we characterized the functional properties of Q1412X-CFTR, a severe-form premature stop codon mutation. We confirmed previous findings of a ∼90% decrease in membrane expression but found a ∼95% reduction in the open probability (Po ). Detailed kinetic studies support the idea that the gating defect is the result of a dysfunctional ATP-binding site 2 in the nucleotide binding domains (NBDs). Because the Q1412X mutation results in a deletion of the last two beta-strands in NBD2 and the whole C-terminal region, we further characterized truncation mutations with different degrees of deletion in this segment. Mutations that completely or partially remove the C-terminus of CFTR at the same time as keeping an intact NBD2 (i.e. D1425X and S1455X) assume gating function almost identical to that of wild-type channels. However, the deletion of the last beta-strand in the NBD2 (i.e. N1419X) causes gating dysfunction that is milder than that of Q1412X. Thus, normal CFTR gating requires structural integrity of NBD2. Moreover, our observation that clinically-approved VX-809 (Lumacaftor, Vertex Pharmaceuticals, Boston, MA, USA) and VX-770 (Ivacaftor, Vertex Pharmaceuticals, Boston, MA, USA) significantly enhance the overall function of Q1412X-CFTR provides the conceptual basis for the treatment of patients carrying this mutation.
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Affiliation(s)
- Jiunn-Tyng Yeh
- Interdisciplinary Neuroscience Program.,Dalton Cardiovascular Research Center
| | - Ying-Chun Yu
- Dalton Cardiovascular Research Center.,Department of Pharmacology and Physiology, School of Medicine, University of Missouri-Columbia, MO, USA
| | - Tzyh-Chang Hwang
- Interdisciplinary Neuroscience Program.,Dalton Cardiovascular Research Center.,Department of Pharmacology and Physiology, School of Medicine, University of Missouri-Columbia, MO, USA
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11
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Wang C, Aleksandrov AA, Yang Z, Forouhar F, Proctor EA, Kota P, An J, Kaplan A, Khazanov N, Boël G, Stockwell BR, Senderowitz H, Dokholyan NV, Riordan JR, Brouillette CG, Hunt JF. Ligand binding to a remote site thermodynamically corrects the F508del mutation in the human cystic fibrosis transmembrane conductance regulator. J Biol Chem 2018; 293:17685-17704. [PMID: 29903914 PMCID: PMC6240863 DOI: 10.1074/jbc.ra117.000819] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 05/31/2018] [Indexed: 01/07/2023] Open
Abstract
Many disease-causing mutations impair protein stability. Here, we explore a thermodynamic strategy to correct the disease-causing F508del mutation in the human cystic fibrosis transmembrane conductance regulator (hCFTR). F508del destabilizes nucleotide-binding domain 1 (hNBD1) in hCFTR relative to an aggregation-prone intermediate. We developed a fluorescence self-quenching assay for compounds that prevent aggregation of hNBD1 by stabilizing its native conformation. Unexpectedly, we found that dTTP and nucleotide analogs with exocyclic methyl groups bind to hNBD1 more strongly than ATP and preserve electrophysiological function of full-length F508del-hCFTR channels at temperatures up to 37 °C. Furthermore, nucleotides that increase open-channel probability, which reflects stabilization of an interdomain interface to hNBD1, thermally protect full-length F508del-hCFTR even when they do not stabilize isolated hNBD1. Therefore, stabilization of hNBD1 itself or of one of its interdomain interfaces by a small molecule indirectly offsets the destabilizing effect of the F508del mutation on full-length hCFTR. These results indicate that high-affinity binding of a small molecule to a remote site can correct a disease-causing mutation. We propose that the strategies described here should be applicable to identifying small molecules to help manage other human diseases caused by mutations that destabilize native protein conformation.
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Affiliation(s)
- Chi Wang
- From the Departments of Biological Sciences and
| | - Andrei A. Aleksandrov
- the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Zhengrong Yang
- the Department of Chemistry, University of Alabama, Birmingham, Alabama 35294, and
| | | | - Elizabeth A. Proctor
- the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Pradeep Kota
- the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Jianli An
- the Department of Chemistry, University of Alabama, Birmingham, Alabama 35294, and
| | - Anna Kaplan
- From the Departments of Biological Sciences and
| | - Netaly Khazanov
- the Department of Chemistry, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | | | - Brent R. Stockwell
- From the Departments of Biological Sciences and ,Chemistry, Columbia University, New York, New York 10027
| | - Hanoch Senderowitz
- the Department of Chemistry, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Nikolay V. Dokholyan
- the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | - John R. Riordan
- the Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
| | | | - John F. Hunt
- From the Departments of Biological Sciences and , To whom correspondence should be addressed. Tel.:
212-854-5443; Fax:
212-865-8246; E-mail:
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12
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Correcting CFTR folding defects by small-molecule correctors to cure cystic fibrosis. Curr Opin Pharmacol 2017; 34:83-90. [PMID: 29055231 DOI: 10.1016/j.coph.2017.09.014] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 09/15/2017] [Accepted: 09/26/2017] [Indexed: 12/18/2022]
Abstract
Pharmacological intervention to treat the lethal genetic disease cystic fibrosis has become reality, even for the severe, most common folding mutant F508del CFTR. CFTR defects range from absence of the protein, misfolding that leads to degradation rather than cell-surface localization (such as F508del), to functional chloride-channel defects on the cell surface. Corrector and potentiator drugs improve cell-surface location and channel activity, respectively, and combination therapy of two correctors and a potentiator have shown synergy. Several combinations are in the drug-development pipeline and although the primary defect is not repaired, rescue levels are reaching those resembling a cure for CF. Combination therapy with correctors may also improve functional CFTR mutants and benefit patients on potentiator therapy.
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13
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Hudson RP, Dawson JE, Chong PA, Yang Z, Millen L, Thomas PJ, Brouillette CG, Forman-Kay JD. Direct Binding of the Corrector VX-809 to Human CFTR NBD1: Evidence of an Allosteric Coupling between the Binding Site and the NBD1:CL4 Interface. Mol Pharmacol 2017; 92:124-135. [PMID: 28546419 DOI: 10.1124/mol.117.108373] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 05/17/2017] [Indexed: 01/06/2023] Open
Abstract
Understanding the mechanism of action of modulator compounds for the cystic fibrosis transmembrane conductance regulator (CFTR) is key for the optimization of therapeutics as well as obtaining insights into the molecular mechanisms of CFTR function. We demonstrate the direct binding of VX-809 to the first nucleotide-binding domain (NBD1) of human CFTR. Disruption of the interaction between C-terminal helices and the NBD1 core upon VX-809 binding is observed from chemical shift changes in the NMR spectra of residues in the helices and on the surface of β-strands S3, S9, and S10. Binding to VX-809 leads to a significant negative shift in NBD1 thermal melting temperature (Tm), pointing to direct VX-809 interaction shifting the NBD1 conformational equilibrium. An inter-residue correlation analysis of the chemical shift changes provides evidence of allosteric coupling between the direct binding site and the NBD1:CL4 interface, thus enabling effects on the interface in the absence of direct binding in that location. These NMR binding data and the negative Tm shifts are very similar to those previously reported by us for binding of the dual corrector-potentiator CFFT-001 to NBD1 (Hudson et al., 2012), suggesting that the two compounds may share some aspects of their mechanisms of action. Although previous studies have shown an important role for VX-809 in modulating the conformation of the first membrane spanning domain (Aleksandrov et al., 2012; Ren et al., 2013), this additional mode of VX-809 binding provides insight into conformational dynamics and allostery within CFTR.
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Affiliation(s)
- Rhea P Hudson
- Molecular Medicine, Hospital for Sick Children, Toronto, Ontario, Canada (R.P.H, J.E.D., P.A.C., J.D.F.-K.); Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada (J.D.F.-K.); Center for Structural Biology (Z.Y., C.G.B.) and Department of Chemistry (C.G.B.), University of Alabama at Birmingham, Birmingham, Alabama; and Department of Physiology, UT Southwestern Medical Center, Dallas, Texas (L.M., P.J.T.)
| | - Jennifer E Dawson
- Molecular Medicine, Hospital for Sick Children, Toronto, Ontario, Canada (R.P.H, J.E.D., P.A.C., J.D.F.-K.); Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada (J.D.F.-K.); Center for Structural Biology (Z.Y., C.G.B.) and Department of Chemistry (C.G.B.), University of Alabama at Birmingham, Birmingham, Alabama; and Department of Physiology, UT Southwestern Medical Center, Dallas, Texas (L.M., P.J.T.)
| | - P Andrew Chong
- Molecular Medicine, Hospital for Sick Children, Toronto, Ontario, Canada (R.P.H, J.E.D., P.A.C., J.D.F.-K.); Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada (J.D.F.-K.); Center for Structural Biology (Z.Y., C.G.B.) and Department of Chemistry (C.G.B.), University of Alabama at Birmingham, Birmingham, Alabama; and Department of Physiology, UT Southwestern Medical Center, Dallas, Texas (L.M., P.J.T.)
| | - Zhengrong Yang
- Molecular Medicine, Hospital for Sick Children, Toronto, Ontario, Canada (R.P.H, J.E.D., P.A.C., J.D.F.-K.); Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada (J.D.F.-K.); Center for Structural Biology (Z.Y., C.G.B.) and Department of Chemistry (C.G.B.), University of Alabama at Birmingham, Birmingham, Alabama; and Department of Physiology, UT Southwestern Medical Center, Dallas, Texas (L.M., P.J.T.)
| | - Linda Millen
- Molecular Medicine, Hospital for Sick Children, Toronto, Ontario, Canada (R.P.H, J.E.D., P.A.C., J.D.F.-K.); Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada (J.D.F.-K.); Center for Structural Biology (Z.Y., C.G.B.) and Department of Chemistry (C.G.B.), University of Alabama at Birmingham, Birmingham, Alabama; and Department of Physiology, UT Southwestern Medical Center, Dallas, Texas (L.M., P.J.T.)
| | - Philip J Thomas
- Molecular Medicine, Hospital for Sick Children, Toronto, Ontario, Canada (R.P.H, J.E.D., P.A.C., J.D.F.-K.); Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada (J.D.F.-K.); Center for Structural Biology (Z.Y., C.G.B.) and Department of Chemistry (C.G.B.), University of Alabama at Birmingham, Birmingham, Alabama; and Department of Physiology, UT Southwestern Medical Center, Dallas, Texas (L.M., P.J.T.)
| | - Christie G Brouillette
- Molecular Medicine, Hospital for Sick Children, Toronto, Ontario, Canada (R.P.H, J.E.D., P.A.C., J.D.F.-K.); Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada (J.D.F.-K.); Center for Structural Biology (Z.Y., C.G.B.) and Department of Chemistry (C.G.B.), University of Alabama at Birmingham, Birmingham, Alabama; and Department of Physiology, UT Southwestern Medical Center, Dallas, Texas (L.M., P.J.T.)
| | - Julie D Forman-Kay
- Molecular Medicine, Hospital for Sick Children, Toronto, Ontario, Canada (R.P.H, J.E.D., P.A.C., J.D.F.-K.); Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada (J.D.F.-K.); Center for Structural Biology (Z.Y., C.G.B.) and Department of Chemistry (C.G.B.), University of Alabama at Birmingham, Birmingham, Alabama; and Department of Physiology, UT Southwestern Medical Center, Dallas, Texas (L.M., P.J.T.).
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14
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Loo TW, Clarke DM. Corrector VX-809 promotes interactions between cytoplasmic loop one and the first nucleotide-binding domain of CFTR. Biochem Pharmacol 2017; 136:24-31. [PMID: 28366727 DOI: 10.1016/j.bcp.2017.03.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 03/28/2017] [Indexed: 10/19/2022]
Abstract
A large number of correctors have been identified that can partially repair defects in folding, stability and trafficking of CFTR processing mutants that cause cystic fibrosis (CF). The best corrector, VX-809 (Lumacaftor), has shown some promise when used in combination with a potentiator (Ivacaftor). Understanding the mechanism of VX-809 is essential for development of better correctors. Here, we tested our prediction that VX-809 repairs folding and processing defects of CFTR by promoting interactions between the first cytoplasmic loop (CL1) of transmembrane domain 1 (TMD1) and the first nucleotide-binding domain (NBD1). To investigate whether VX-809 promoted CL1/NBD1 interactions, we performed cysteine mutagenesis and disulfide cross-linking analysis of Cys-less TMD1 (residues 1-436) and ΔTMD1 (residues 437-1480; NBD1-R-TMD2-NBD2) truncation mutants. It was found that VX-809, but not bithiazole correctors, promoted maturation (exited endoplasmic reticulum for addition of complex carbohydrate in the Golgi) of the ΔTMD1 truncation mutant only when it was co-expressed in the presence of TMD1. Expression in the presence of VX-809 also promoted cross-linking between R170C (in CL1 of TMD1 protein) and L475C (in NBD1 of the ΔTMD1 truncation protein). Expression of the ΔTMD1 truncation mutant in the presence of TMD1 and VX-809 also increased the half-life of the mature protein in cells. The results suggest that the mechanism by which VX-809 promotes maturation and stability of CFTR is by promoting CL1/NBD1 interactions.
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Affiliation(s)
- Tip W Loo
- Department of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - David M Clarke
- Department of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
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15
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Farinha CM, Canato S. From the endoplasmic reticulum to the plasma membrane: mechanisms of CFTR folding and trafficking. Cell Mol Life Sci 2017; 74:39-55. [PMID: 27699454 PMCID: PMC11107782 DOI: 10.1007/s00018-016-2387-7] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 09/28/2016] [Indexed: 01/10/2023]
Abstract
CFTR biogenesis starts with its co-translational insertion into the membrane of endoplasmic reticulum and folding of the cytosolic domains, towards the acquisition of a fully folded compact native structure. Efficiency of this process is assessed by the ER quality control system that allows the exit of folded proteins but targets unfolded/misfolded CFTR to degradation. If allowed to leave the ER, CFTR is modified at the Golgi and reaches the post-Golgi compartments to be delivered to the plasma membrane where it functions as a cAMP- and phosphorylation-regulated chloride/bicarbonate channel. CFTR residence at the membrane is a balance of membrane delivery, endocytosis, and recycling. Several adaptors, motor, and scaffold proteins contribute to the regulation of CFTR stability and are involved in continuously assessing its structure through peripheral quality control systems. Regulation of CFTR biogenesis and traffic (and its dysregulation by mutations, such as the most common F508del) determine its overall activity and thus contribute to the fine modulation of chloride secretion and hydration of epithelial surfaces. This review covers old and recent knowledge on CFTR folding and trafficking from its synthesis to the regulation of its stability at the plasma membrane and highlights how several of these steps can be modulated to promote the rescue of mutant CFTR.
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Affiliation(s)
- Carlos M Farinha
- BioISI-Biosystems and Integrative Sciences Institute, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisbon, Portugal.
| | - Sara Canato
- BioISI-Biosystems and Integrative Sciences Institute, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisbon, Portugal
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16
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Callebaut I, Hoffmann B, Lehn P, Mornon JP. Molecular modelling and molecular dynamics of CFTR. Cell Mol Life Sci 2017; 74:3-22. [PMID: 27717958 PMCID: PMC11107702 DOI: 10.1007/s00018-016-2385-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 09/28/2016] [Indexed: 12/11/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) protein is a member of the ATP-binding cassette (ABC) transporter superfamily that functions as an ATP-gated channel. Considerable progress has been made over the last years in the understanding of the molecular basis of the CFTR functions, as well as dysfunctions causing the common genetic disease cystic fibrosis (CF). This review provides a global overview of the theoretical studies that have been performed so far, especially molecular modelling and molecular dynamics (MD) simulations. A special emphasis is placed on the CFTR-specific evolution of an ABC transporter framework towards a channel function, as well as on the understanding of the effects of disease-causing mutations and their specific modulation. This in silico work should help structure-based drug discovery and design, with a view to develop CFTR-specific pharmacotherapeutic approaches for the treatment of CF in the context of precision medicine.
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Affiliation(s)
- Isabelle Callebaut
- UMR CNRS 7590, Museum National d'Histoire Naturelle, IRD UMR 206, IUC, Case 115, IMPMC, Sorbonne Universités, UPMC Univ Paris 06, 4 Place Jussieu, 75005, Paris Cedex 05, France.
| | - Brice Hoffmann
- UMR CNRS 7590, Museum National d'Histoire Naturelle, IRD UMR 206, IUC, Case 115, IMPMC, Sorbonne Universités, UPMC Univ Paris 06, 4 Place Jussieu, 75005, Paris Cedex 05, France
| | - Pierre Lehn
- INSERM U1078, SFR ScInBioS, Université de Bretagne Occidentale, Brest, France
| | - Jean-Paul Mornon
- UMR CNRS 7590, Museum National d'Histoire Naturelle, IRD UMR 206, IUC, Case 115, IMPMC, Sorbonne Universités, UPMC Univ Paris 06, 4 Place Jussieu, 75005, Paris Cedex 05, France
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17
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Convertino M, Das J, Dokholyan NV. Pharmacological Chaperones: Design and Development of New Therapeutic Strategies for the Treatment of Conformational Diseases. ACS Chem Biol 2016; 11:1471-89. [PMID: 27097127 DOI: 10.1021/acschembio.6b00195] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Errors in protein folding may result in premature clearance of structurally aberrant proteins, or in the accumulation of toxic misfolded species or protein aggregates. These pathological events lead to a large range of conditions known as conformational diseases. Several research groups have presented possible therapeutic solutions for their treatment by developing novel compounds, known as pharmacological chaperones. These cell-permeable molecules selectively provide a molecular scaffold around which misfolded proteins can recover their native folding and, thus, their biological activities. Here, we review therapeutic strategies, clinical potentials, and cost-benefit impacts of several classes of pharmacological chaperones for the treatment of a series of conformational diseases.
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Affiliation(s)
- Marino Convertino
- Department of Biochemistry
and Biophysics, University of North Carolina, 120 Mason Farm Road, Chapel Hill, North Carolina 27599, United States
| | - Jhuma Das
- Department of Biochemistry
and Biophysics, University of North Carolina, 120 Mason Farm Road, Chapel Hill, North Carolina 27599, United States
| | - Nikolay V. Dokholyan
- Department of Biochemistry
and Biophysics, University of North Carolina, 120 Mason Farm Road, Chapel Hill, North Carolina 27599, United States
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18
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Estácio SG, Martiniano HFMC, Faísca PFN. Thermal unfolding simulations of NBD1 domain variants reveal structural motifs associated with the impaired folding of F508del-CFTR. MOLECULAR BIOSYSTEMS 2016; 12:2834-48. [DOI: 10.1039/c6mb00193a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The deletion of phenylalanine 508 reshapes the conformational space of the NBD1 domain that populates unique intermediate states that provide insights into the molecular events that underlie the impaired folding of F508del-NBD1.
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Affiliation(s)
- Sílvia G. Estácio
- BioISI – Biosystems & Integrative Sciences Institute
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
| | - Hugo F. M. C. Martiniano
- BioISI – Biosystems & Integrative Sciences Institute
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
| | - Patrícia F. N. Faísca
- BioISI – Biosystems & Integrative Sciences Institute
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
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19
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Zhenin M, Noy E, Senderowitz H. REMD Simulations Reveal the Dynamic Profile and Mechanism of Action of Deleterious, Rescuing, and Stabilizing Perturbations to NBD1 from CFTR. J Chem Inf Model 2015; 55:2349-64. [PMID: 26418372 DOI: 10.1021/acs.jcim.5b00312] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cystic Fibrosis (CF) is a lethal, genetic disease caused by mutations to the CFTR chloride channel. The most common CF causing mutation is the deletion of F508 from the first Nucleotide Binding Domain (F508del-NBD1). This mutation leads to a thermally unstable domain and a misfolded, nonfunctioning CFTR. Replica Exchange MD simulations were used to simulate seven NBD1 constructs including wt and F508del-NBD1 both alone and in the presence of known rescuing mutations as well as F508del-NBD1 in complex with a known small (ligand) stabilizer. Analyzing the resulting trajectories suggests that differences in the biochemical properties of the constructs result from local and coupled differences in their dynamic profiles. A comparative analysis of these profiles as well as of the resulting trajectories reveals how the different perturbations exert their deleterious, rescuing, and stabilizing effects on NBD1. These simulations may therefore be useful for the design and mechanism-of-action analysis of new NBD1 stabilizers.
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Affiliation(s)
- Michael Zhenin
- Department of Chemistry, Bar Ilan University , Ramat-Gan 52900, Israel
| | - Efrat Noy
- Department of Chemistry, Bar Ilan University , Ramat-Gan 52900, Israel
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20
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Chong PA, Farber PJ, Vernon RM, Hudson RP, Mittermaier AK, Forman-Kay JD. Deletion of Phenylalanine 508 in the First Nucleotide-binding Domain of the Cystic Fibrosis Transmembrane Conductance Regulator Increases Conformational Exchange and Inhibits Dimerization. J Biol Chem 2015; 290:22862-78. [PMID: 26149808 DOI: 10.1074/jbc.m115.641134] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Indexed: 12/17/2022] Open
Abstract
Deletion of Phe-508 (F508del) in the first nucleotide-binding domain (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR) results in destabilization of the domain, intramolecular interactions involving the domain, and the entire channel. The destabilization caused by F508del manifests itself in defective channel processing and channel gating defects. Here, we present NMR studies of the effect of F508del and the I539T stabilizing mutation on NBD1 dynamics, with a view to understanding these changes in stability. Qualitatively, F508del NMR spectra exhibit significantly more peak broadening than WT spectra due to the enhanced intermediate time scale (millisecond to microsecond) motions in the mutant. Unexpectedly, studies of fast (nanosecond to picosecond) motions revealed that F508del NBD1 tumbles more rapidly in solution than WT NBD1. Whereas F508del tumbles at a rate nearly consistent with the monomeric state, the WT protein tumbles significantly more slowly. Paramagnetic relaxation enhancement experiments confirm that NBD1 homodimerizes in solution in the expected head-to-tail orientation. NMR spectra of WT NBD1 reveal significant concentration-dependent chemical shift perturbations consistent with NBD1 dimerization. Chemical shift analysis suggests that the more rapid tumbling of F508del is the result of an impaired ability to dimerize. Based on previously published crystal structures and NMR spectra of various NBD1 mutants, we propose that deletion of Phe-508 affects Q-loop conformational sampling in a manner that inhibits dimerization. These results provide a potential mechanism for inhibition of channel opening by F508del and support the dimer interface as a target for cystic fibrosis therapeutics.
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Affiliation(s)
- P Andrew Chong
- From the Molecular Structure and Function Program, Hospital for Sick Children, and
| | - Patrick J Farber
- From the Molecular Structure and Function Program, Hospital for Sick Children, and
| | - Robert M Vernon
- From the Molecular Structure and Function Program, Hospital for Sick Children, and
| | - Rhea P Hudson
- From the Molecular Structure and Function Program, Hospital for Sick Children, and
| | | | - Julie D Forman-Kay
- From the Molecular Structure and Function Program, Hospital for Sick Children, and Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1X8 and
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21
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Wang G. Interplay between Inhibitory Ferric and Stimulatory Curcumin Regulates Phosphorylation-Dependent Human Cystic Fibrosis Transmembrane Conductance Regulator and ΔF508 Activity. Biochemistry 2015; 54:1558-66. [DOI: 10.1021/bi501318h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Guangyu Wang
- Department of Physiology
and Biophysics and Gregory Fleming James Cystic Fibrosis Research
Center, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama 35294, United States
- Department of Physiology
and Membrane Biology, University of California School of Medicine, Davis, California 95616, United States
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22
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Pasyk S, Molinski S, Ahmadi S, Ramjeesingh M, Huan LJ, Chin S, Du K, Yeger H, Taylor P, Moran MF, Bear CE. The major cystic fibrosis causing mutation exhibits defective propensity for phosphorylation. Proteomics 2014; 15:447-61. [PMID: 25330774 DOI: 10.1002/pmic.201400218] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 09/24/2014] [Accepted: 10/16/2014] [Indexed: 11/11/2022]
Abstract
The major cystic fibrosis causing mutation, F508del-CFTR (where CFTR is cystic fibrosis transmembrane conductance regulator), impairs biosynthetic maturation of the CFTR protein, limiting its expression as a phosphorylation-dependent channel on the cell surface. The maturation defect can be partially rescued by low-temperature (27°C) cell culture conditions or small-molecule corrector compounds. Following its partial rescue, the open probability of F508del-CFTR is enhanced by the potentiator compound, VX-770. However, the channel activity of rescued F508del-CFTR remains less than that of the Wt-CFTR protein in the presence of VX-770. In this study, we asked if there are allosteric effects of F508del on the phosphorylation-regulated R domain. To identify defects in the R domain, we compared the phosphorylation status at protein kinase A sites in the R domain of Wt and F508del-CFTR. Here we show that phosphorylation of Ser-660, quantified by SRM-MS, is reduced in F508del-CFTR. Although the generation of a phosphomimic at this site (substituting aspartic acid for serine) did not modify the maturation defect, it did enhance F508del-CFTR channel function after pharmacological rescue with corrector VX-809, and treatment with the potentiator, VX-770. These findings support the concept that defective phosphorylation of F508del-CFTR partially accounts for its altered channel activity at the cell surface.
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Affiliation(s)
- Stan Pasyk
- Programme in Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada; Department of Biochemistry, The University of Toronto, Toronto, ON, Canada
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Caohuy H, Yang Q, Eudy Y, Ha TA, Xu AE, Glover M, Frizzell RA, Jozwik C, Pollard HB. Activation of 3-phosphoinositide-dependent kinase 1 (PDK1) and serum- and glucocorticoid-induced protein kinase 1 (SGK1) by short-chain sphingolipid C4-ceramide rescues the trafficking defect of ΔF508-cystic fibrosis transmembrane conductance regulator (ΔF508-CFTR). J Biol Chem 2014; 289:35953-68. [PMID: 25384981 DOI: 10.1074/jbc.m114.598649] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Cystic fibrosis (CF) is due to a folding defect in the CF transmembrane conductance regulator (CFTR) protein. The most common mutation, ΔF508, prevents CFTR from trafficking to the apical plasma membrane. Here we show that activation of the PDK1/SGK1 signaling pathway with C4-ceramide (C4-CER), a non-toxic small molecule, functionally corrects the trafficking defect in both cultured CF cells and primary epithelial cell explants from CF patients. The mechanism of C4-CER action involves a series of mutual autophosphorylation and phosphorylation events between PDK1 and SGK1. Detailed mechanistic studies indicate that C4-CER initially induces autophosphorylation of SGK1 at Ser(422). SGK1[Ser(P)(422)] and C4-CER coincidently bind PDK1 and permit PDK1 to autophosphorylate at Ser(241). Then PDK1[Ser(P)(241)] phosphorylates SGK1[Ser(P)(422)] at Thr(256) to generate fully activated SGK1[Ser(422), Thr(P)(256)]. SGK1[Ser(P)(422),Thr(P)(256)] phosphorylates and inactivates the E3 ubiquitin ligase Nedd4-2. ΔF508-CFTR is thus free to traffic to the plasma membrane. Importantly, C4-CER-mediated activation of both PDK1 and SGK1 is independent of the PI3K/Akt/mammalian target of rapamycin signaling pathway. Physiologically, C4-CER significantly increases maturation and stability of ΔF508-CFTR (t½ ∼10 h), enhances cAMP-activated chloride secretion, and suppresses hypersecretion of interleukin-8 (IL-8). We suggest that candidate drugs for CF directed against the PDK1/SGK1 signaling pathway, such as C4-CER, provide a novel therapeutic strategy for a life-limiting disorder that affects one child, on average, each day.
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Affiliation(s)
- Hung Caohuy
- From the Department of Anatomy, Physiology, and Genetics, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 and
| | - Qingfeng Yang
- From the Department of Anatomy, Physiology, and Genetics, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 and
| | - Yvonne Eudy
- From the Department of Anatomy, Physiology, and Genetics, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 and
| | - Thien-An Ha
- From the Department of Anatomy, Physiology, and Genetics, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 and
| | - Andrew E Xu
- From the Department of Anatomy, Physiology, and Genetics, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 and
| | - Matthew Glover
- the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15224
| | - Raymond A Frizzell
- the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15224
| | - Catherine Jozwik
- From the Department of Anatomy, Physiology, and Genetics, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 and
| | - Harvey B Pollard
- From the Department of Anatomy, Physiology, and Genetics, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814 and
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He L, Aleksandrov AA, An J, Cui L, Yang Z, Brouillette CG, Riordan JR. Restoration of NBD1 thermal stability is necessary and sufficient to correct ∆F508 CFTR folding and assembly. J Mol Biol 2014; 427:106-20. [PMID: 25083918 DOI: 10.1016/j.jmb.2014.07.026] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 07/09/2014] [Accepted: 07/11/2014] [Indexed: 11/29/2022]
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) (ABCC7), unique among ABC exporters as an ion channel, regulates ion and fluid transport in epithelial tissues. Loss of function due to mutations in the cftr gene causes cystic fibrosis. The most common cystic-fibrosis-causing mutation, the deletion of F508 (ΔF508) from the first nucleotide binding domain (NBD1) of CFTR, results in misfolding of the protein and clearance by cellular quality control systems. The ΔF508 mutation has two major impacts on CFTR: reduced thermal stability of NBD1 and disruption of its interface with membrane-spanning domains (MSDs). It is unknown if these two defects are independent and need to be targeted separately. To address this question, we varied the extent of stabilization of NBD1 using different second-site mutations and NBD1 binding small molecules with or without NBD1/MSD interface mutation. Combinations of different NBD1 changes had additive corrective effects on ∆F508 maturation that correlated with their ability to increase NBD1 thermostability. These effects were much larger than those caused by interface modification alone and accounted for most of the correction achieved by modifying both the domain and the interface. Thus, NBD1 stabilization plays a dominant role in overcoming the ΔF508 defect. Furthermore, the dual target approach resulted in a locked-open ion channel that was constitutively active in the absence of the normally obligatory dependence on phosphorylation by protein kinase A. Thus, simultaneous targeting of both the domain and the interface, as well as being non-essential for correction of biogenesis, may disrupt normal regulation of channel function.
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Affiliation(s)
- Lihua He
- Department of Biochemistry and Biophysics, Cystic Fibrosis Treatment and Research Center, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Andrei A Aleksandrov
- Department of Biochemistry and Biophysics, Cystic Fibrosis Treatment and Research Center, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Jianli An
- Center for Structural Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Liying Cui
- Department of Biochemistry and Biophysics, Cystic Fibrosis Treatment and Research Center, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Zhengrong Yang
- Center for Structural Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA; Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Christie G Brouillette
- Center for Structural Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA; Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - John R Riordan
- Department of Biochemistry and Biophysics, Cystic Fibrosis Treatment and Research Center, University of North Carolina, Chapel Hill, NC, 27599, USA.
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25
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Pranke IM, Sermet-Gaudelus I. Biosynthesis of cystic fibrosis transmembrane conductance regulator. Int J Biochem Cell Biol 2014; 52:26-38. [DOI: 10.1016/j.biocel.2014.03.020] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 03/19/2014] [Accepted: 03/20/2014] [Indexed: 01/19/2023]
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26
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Swartz D, Mok L, Botta S, Singh A, Altenberg G, Urbatsch I. Directed evolution of P-glycoprotein cysteines reveals site-specific, non-conservative substitutions that preserve multidrug resistance. Biosci Rep 2014; 34:e00116. [PMID: 24825346 PMCID: PMC4069687 DOI: 10.1042/bsr20140062] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 05/05/2014] [Accepted: 05/06/2014] [Indexed: 11/21/2022] Open
Abstract
Pgp (P-glycoprotein) is a prototype ABC (ATP-binding-cassette) transporter involved in multidrug resistance of cancer. We used directed evolution to replace six cytoplasmic Cys (cysteine) residues in Pgp with all 20 standard amino acids and selected for active mutants. From a pool of 75000 transformants for each block of three Cys, we identified multiple mutants that preserved drug resistance and yeast mating activity. The most frequent substitutions were glycine and serine for Cys427 (24 and 20%, respectively) and Cys1070 (37 and 25%) of the Walker A motifs in the NBDs (nucleotide-binding domains), Cys1223 in NBD2 (25 and 8%) and Cys638 in the linker region (24 and 16%), whereas close-by Cys669 tolerated glycine (16%) and alanine (14%), but not serine (absent). Cys1121 in NBD2 showed a clear preference for positively charged arginine (38%) suggesting a salt bridge with Glu269 in the ICL2 (intracellular loop 2) may stabilize domain interactions. In contrast, three Cys residues in transmembrane α-helices could be successfully replaced by alanine. The resulting CL (Cys-less) Pgp was fully active in yeast cells, and purified proteins displayed drug-stimulated ATPase activities indistinguishable from WT (wild-type) Pgp. Overall, directed evolution identified site-specific, non-conservative Cys substitutions that allowed building of a robust CL Pgp, an invaluable new tool for future functional and structural studies, and that may guide the construction of other CL proteins where alanine and serine have proven unsuccessful.
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Key Words
- abc transporter
- multidrug transporter
- non-conservative cysteine substitutions
- protein evolution site-saturation mutagenesis
- yeast drug resistance
- abc, atp-binding-cassette
- cftr, cystic fibrosis transmembrane conductance regulator
- cl, cys-less
- cp-mts, 7-diethylamino-3-(4′-maleimidylphenyl)-4-methylcoumarin
- ddm, n-dodecyl-β-d-maltopyranoside
- icl, intracellular loop
- nbd, nucleotide-binding domain
- pgp, p-glycoprotein
- sec, size exclusion chromatography
- tmd, transmembrane domain
- wt, wild-type
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Affiliation(s)
- Douglas J. Swartz
- *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
| | - Leo Mok
- *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
| | - Sri K. Botta
- *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
| | - Anukriti Singh
- *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
| | - Guillermo A. Altenberg
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- ‡Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
| | - Ina L. Urbatsch
- *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
- †Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, U.S.A
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27
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Farinha CM, King-Underwood J, Sousa M, Correia AR, Henriques BJ, Roxo-Rosa M, Da Paula AC, Williams J, Hirst S, Gomes CM, Amaral MD. Revertants, low temperature, and correctors reveal the mechanism of F508del-CFTR rescue by VX-809 and suggest multiple agents for full correction. ACTA ACUST UNITED AC 2014; 20:943-55. [PMID: 23890012 DOI: 10.1016/j.chembiol.2013.06.004] [Citation(s) in RCA: 140] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 05/10/2013] [Accepted: 06/09/2013] [Indexed: 11/30/2022]
Abstract
Cystic fibrosis is mostly caused by the F508del mutation, which impairs CFTR protein from exiting the endoplasmic reticulum due to misfolding. VX-809 is a small molecule that rescues F508del-CFTR localization, which recently went into clinical trial but with unknown mechanism of action (MoA). Herein, we assessed if VX-809 is additive or synergistic with genetic revertants of F508del-CFTR, other correctors, and low temperature to determine its MoA. We explored and integrated those various agents in combined treatments, showing how they add to each other to identify their complementary MoA upon correction of F508del-CFTR. Our experimental and modeling data, while compatible with putative binding of VX-809 to NBD1:ICL4 interface, also indicate scope for further synergistic F508del-CFTR correction by other compounds at distinct conformational sites/cellular checkpoints, thus suggesting requirement of combined therapies to fully rescue F508del-CFTR.
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Affiliation(s)
- Carlos M Farinha
- Faculty of Sciences, Center for Biodiversity, Functional, and Integrative Genomics, University of Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
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28
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Yang Z, Wang C, Zhou Q, An J, Hildebrandt E, Aleksandrov LA, Kappes JC, DeLucas LJ, Riordan JR, Urbatsch IL, Hunt JF, Brouillette CG. Membrane protein stability can be compromised by detergent interactions with the extramembranous soluble domains. Protein Sci 2014; 23:769-89. [PMID: 24652590 PMCID: PMC4093953 DOI: 10.1002/pro.2460] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 03/07/2014] [Accepted: 03/17/2014] [Indexed: 11/06/2022]
Abstract
Detergent interaction with extramembranous soluble domains (ESDs) is not commonly considered an important determinant of integral membrane protein (IMP) behavior during purification and crystallization, even though ESDs contribute to the stability of many IMPs. Here we demonstrate that some generally nondenaturing detergents critically destabilize a model ESD, the first nucleotide-binding domain (NBD1) from the human cystic fibrosis transmembrane conductance regulator (CFTR), a model IMP. Notably, the detergents show equivalent trends in their influence on the stability of isolated NBD1 and full-length CFTR. We used differential scanning calorimetry (DSC) and circular dichroism (CD) spectroscopy to monitor changes in NBD1 stability and secondary structure, respectively, during titration with a series of detergents. Their effective harshness in these assays mirrors that widely accepted for their interaction with IMPs, i.e., anionic > zwitterionic > nonionic. It is noteworthy that including lipids or nonionic detergents is shown to mitigate detergent harshness, as will limiting contact time. We infer three thermodynamic mechanisms from the observed thermal destabilization by monomer or micelle: (i) binding to the unfolded state with no change in the native structure (all detergent classes); (ii) native state binding that alters thermodynamic properties and perhaps conformation (nonionic detergents); and (iii) detergent binding that directly leads to denaturation of the native state (anionic and zwitterionic). These results demonstrate that the accepted model for the harshness of detergents applies to their interaction with an ESD. It is concluded that destabilization of extramembranous soluble domains by specific detergents will influence the stability of some IMPs during purification.
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Affiliation(s)
- Zhengrong Yang
- Department of Chemistry, University of Alabama at BirminghamBirmingham, Alabama
- Center for Structural Biology, University of Alabama at BirminghamBirmingham, Alabama
| | - Chi Wang
- Department of Biological Sciences, Columbia UniversityNew York, New York
| | - Qingxian Zhou
- Center for Structural Biology, University of Alabama at BirminghamBirmingham, Alabama
| | - Jianli An
- Center for Structural Biology, University of Alabama at BirminghamBirmingham, Alabama
| | - Ellen Hildebrandt
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences CenterLubbock, Texas
| | - Luba A Aleksandrov
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel HillChapel Hill, North Carolina
- Cystic Fibrosis Treatment and Research Center, The University of North Carolina at Chapel HillChapel Hill, North Carolina
| | - John C Kappes
- Department of Medicine, University of Alabama at BirminghamBirmingham, Alabama
- Birmingham Veterans Affairs Medical Center, Research ServiceBirmingham, Alabama
| | - Lawrence J DeLucas
- Center for Structural Biology, University of Alabama at BirminghamBirmingham, Alabama
- Department of Optometry, University of Alabama at BirminghamBirmingham, Alabama
| | - John R Riordan
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel HillChapel Hill, North Carolina
- Cystic Fibrosis Treatment and Research Center, The University of North Carolina at Chapel HillChapel Hill, North Carolina
| | - Ina L Urbatsch
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences CenterLubbock, Texas
- Center for Membrane Protein Research, Texas Tech University Health Sciences CenterLubbock, TX
| | - John F Hunt
- Department of Biological Sciences, Columbia UniversityNew York, New York
| | - Christie G Brouillette
- Department of Chemistry, University of Alabama at BirminghamBirmingham, Alabama
- Center for Structural Biology, University of Alabama at BirminghamBirmingham, Alabama
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29
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Xu Z, Pissarra LS, Farinha CM, Liu J, Cai Z, Thibodeau PH, Amaral MD, Sheppard DN. Revertant mutants modify, but do not rescue, the gating defect of the cystic fibrosis mutant G551D-CFTR. J Physiol 2014; 592:1931-47. [PMID: 24591578 DOI: 10.1113/jphysiol.2014.271817] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cystic fibrosis (CF) is caused by dysfunction of the epithelial anion channel cystic fibrosis transmembrane conductance regulator (CFTR). One strategy to restore function to CF mutants is to suppress defects in CFTR processing and function using revertant mutations. Here, we investigate the effects of the revertant mutations G550E and 4RK (the simultaneous disruption of four arginine-framed tripeptides (AFTs): R29K, R516K, R555K and R766K) on the CF mutant G551D, which impairs severely channel gating without altering protein processing and which affects a residue in the same α-helix as G550 and R555. Both G550E and 4RK augmented strongly CFTR-mediated iodide efflux from BHK cells expressing G551D-CFTR. To learn how revertant mutations influence G551D-CFTR function, we studied protein processing and single-channel behaviour. Neither G550E nor 4RK altered the expression and maturation of G551D-CFTR protein. By contrast, both revertants had marked effects on G551D-CFTR channel gating, increasing strongly opening frequency, while 4RK also diminished noticeably the duration of channel openings. Because G551D-CFTR channel gating is ATP independent, we investigated whether revertant mutations restore ATP dependence to G551D-CFTR. Like wild-type CFTR, the activity of 4RK-G551D-CFTR varied with ATP concentration, suggesting that 4RK confers some ATP dependence on the G551D-CFTR channel. Thus, the revertant mutations G550E and 4RK alter the gating pattern and ATP dependence of G551D-CFTR without restoring single-channel activity to wild-type levels. Based on their impact on the CF mutants F508del and G551D, we conclude that G550E and 4RK have direct effects on CFTR structure, but that their action on CFTR processing and channel function is CF mutation specific.
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Affiliation(s)
- Zhe Xu
- University of Bristol, School of Physiology and Pharmacology, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK.
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30
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CFTR structure and cystic fibrosis. Int J Biochem Cell Biol 2014; 52:15-25. [PMID: 24534272 DOI: 10.1016/j.biocel.2014.02.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 02/04/2014] [Accepted: 02/06/2014] [Indexed: 12/31/2022]
Abstract
CFTR (cystic fibrosis transmembrane conductance regulator) is a member of the ATP-binding cassette family of membrane proteins. Although almost all members of this family are transporters, CFTR functions as a channel with specificity for anions, in particular chloride and bicarbonate. In this review we look at what is known about CFTR structure and function within the context of the ATP-binding cassette family. We also review current strategies aimed at obtaining the high resolution structure of the protein.
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31
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The cystic fibrosis V232D mutation inhibits CFTR maturation by disrupting a hydrophobic pocket rather than formation of aberrant interhelical hydrogen bonds. Biochem Pharmacol 2014; 88:46-57. [PMID: 24412276 DOI: 10.1016/j.bcp.2013.12.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Revised: 12/30/2013] [Accepted: 12/31/2013] [Indexed: 11/21/2022]
Abstract
Processing mutations that inhibit folding and trafficking of CFTR are the main cause of cystic fibrosis. Repair of CFTR mutants requires an understanding of the mechanisms of misfolding caused by processing mutations. Previous studies on helix-loop-helix fragments of the V232D processing mutation suggested that its mechanism was to lock transmembrane (TM) segments 3 and 4 together by a non-native hydrogen bond (Asp232(TM4)/Gln207(TM3)). Here, we performed mutational analysis to test for Asp232/Gln207 interactions in full-length CFTR. The rationale was that a V232N mutation should mimic V232D and a V232D/Q207A mutant should mature if the processing defect was caused by hydrogen bonds. We report that only Val232 mutations to charged amino acids severely blocked CFTR maturation. The V232N mutation did not mimic V232D as V232N showed 40% maturation compared to 2% for V232D. Mutation of Val232 to large nonpolar residues (Leu, Phe) had little effect. The Q207L mutation did not rescue V232D because Q207L showed about 50% maturation in the presence of corrector VX-809 while V232D/Q207A could no longer be rescued. These results suggest that V232D inhibits maturation by disrupting a hydrophobic pocket between TM segments rather than forming a non-native hydrogen bond. Disulfide cross-linking analysis of cysteines W356C(TM6) and W1145C(TM12) suggest that the V232D mutation inhibits maturation by trapping CFTR as a partially folded intermediate. Since correctors can efficiently rescue V232D CFTR, the results suggest that hydrophilic processing mutations facing a hydrophobic pocket are good candidates for rescue with pharmacological chaperones.
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32
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Li J, Jaimes KF, Aller SG. Refined structures of mouse P-glycoprotein. Protein Sci 2013; 23:34-46. [PMID: 24155053 PMCID: PMC3892297 DOI: 10.1002/pro.2387] [Citation(s) in RCA: 280] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 10/14/2013] [Accepted: 10/14/2013] [Indexed: 01/17/2023]
Abstract
The recently determined C. elegans P-glycoprotein (Pgp) structure revealed significant deviations compared to the original mouse Pgp structure, which suggested possible misinterpretations in the latter model. To address this concern, we generated an experimental electron density map from single-wavelength anomalous dispersion phasing of an original mouse Pgp dataset to 3.8 Å resolution. The map exhibited significantly more detail compared to the original MAD map and revealed several regions of the structure that required de novo model building. The improved drug-free structure was refined to 3.8 Å resolution with a 9.4 and 8.1% decrease in Rwork and Rfree, respectively, (Rwork = 21.2%, Rfree = 26.6%) and a significant improvement in protein geometry. The improved mouse Pgp model contains ∼95% of residues in the favorable Ramachandran region compared to only 57% for the original model. The registry of six transmembrane helices was corrected, revealing amino acid residues involved in drug binding that were previously unrecognized. Registry shifts (rotations and translations) for three transmembrane (TM)4 and TM5 and the addition of three N-terminal residues were necessary, and were validated with new mercury labeling and anomalous Fourier density. The corrected position of TM4, which forms the frame of a portal for drug entry, had backbone atoms shifted >6 Å from their original positions. The drug translocation pathway of mouse Pgp is 96% identical to human Pgp and is enriched in aromatic residues that likely play a collective role in allowing a high degree of polyspecific substrate recognition.
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Affiliation(s)
- Jingzhi Li
- Department of Pharmacology and Toxicology, Center for Structural Biology, University of Alabama at Birmingham, Birmingham, Alabama, 35205
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33
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Loo TW, Bartlett MC, Clarke DM. Corrector VX-809 stabilizes the first transmembrane domain of CFTR. Biochem Pharmacol 2013; 86:612-9. [DOI: 10.1016/j.bcp.2013.06.028] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 06/27/2013] [Accepted: 06/28/2013] [Indexed: 11/25/2022]
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34
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Mechanism-based corrector combination restores ΔF508-CFTR folding and function. Nat Chem Biol 2013; 9:444-54. [PMID: 23666117 DOI: 10.1038/nchembio.1253] [Citation(s) in RCA: 319] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Accepted: 04/08/2013] [Indexed: 01/12/2023]
Abstract
The most common cystic fibrosis mutation, ΔF508 in nucleotide binding domain 1 (NBD1), impairs cystic fibrosis transmembrane conductance regulator (CFTR)-coupled domain folding, plasma membrane expression, function and stability. VX-809, a promising investigational corrector of ΔF508-CFTR misprocessing, has limited clinical benefit and an incompletely understood mechanism, hampering drug development. Given the effect of second-site suppressor mutations, robust ΔF508-CFTR correction most likely requires stabilization of NBD1 energetics and the interface between membrane-spanning domains (MSDs) and NBD1, which are both established primary conformational defects. Here we elucidate the molecular targets of available correctors: class I stabilizes the NBD1-MSD1 and NBD1-MSD2 interfaces, and class II targets NBD2. Only chemical chaperones, surrogates of class III correctors, stabilize human ΔF508-NBD1. Although VX-809 can correct missense mutations primarily destabilizing the NBD1-MSD1/2 interface, functional plasma membrane expression of ΔF508-CFTR also requires compounds that counteract the NBD1 and NBD2 stability defects in cystic fibrosis bronchial epithelial cells and intestinal organoids. Thus, the combination of structure-guided correctors represents an effective approach for cystic fibrosis therapy.
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Chong PA, Kota P, Dokholyan NV, Forman-Kay JD. Dynamics intrinsic to cystic fibrosis transmembrane conductance regulator function and stability. Cold Spring Harb Perspect Med 2013; 3:a009522. [PMID: 23457292 DOI: 10.1101/cshperspect.a009522] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) requires dynamic fluctuations between states in its gating cycle for proper channel function, including changes in the interactions between the nucleotide-binding domains (NBDs) and between the intracellular domain (ICD) coupling helices and NBDs. Such motions are also linked with fluctuating phosphorylation-dependent binding of CFTR's disordered regulatory (R) region to the NBDs and partners. Folding of CFTR is highly inefficient, with the marginally stable NBD1 sampling excited states or folding intermediates that are aggregation-prone. The severe CF-causing F508del mutation exacerbates the folding inefficiency of CFTR and leads to impaired channel regulation and function, partly as a result of perturbed NBD1-ICD interactions and enhanced sampling of these NBD1 excited states. Increased knowledge of the dynamics within CFTR will expand our understanding of the regulated channel gating of the protein as well as of the F508del defects in folding and function.
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Affiliation(s)
- P Andrew Chong
- Program in Molecular Structure and Function, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
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36
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Hunt JF, Wang C, Ford RC. Cystic fibrosis transmembrane conductance regulator (ABCC7) structure. Cold Spring Harb Perspect Med 2013; 3:a009514. [PMID: 23378596 DOI: 10.1101/cshperspect.a009514] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Structural studies of the cystic fibrosis transmembrane conductance regulator (CFTR) are reviewed. Like many membrane proteins, full-length CFTR has proven to be difficult to express and purify, hence much of the structural data available is for the more tractable, independently expressed soluble domains. Therefore, this chapter covers structural data for individual CFTR domains in addition to the sparser data available for the full-length protein. To set the context for these studies, we will start by reviewing structural information on model proteins from the ATP-binding cassette (ABC) transporter superfamily, to which CFTR belongs.
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Affiliation(s)
- John F Hunt
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
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Abstract
For cystic fibrosis (CF) patients most therapies focus on alleviating the disease symptoms. Yet the cellular basis of the disease has been well studied; mutations in the CF gene can impair folding, secretion, cell surface stability, and/or function of the CFTR chloride channel. Correction of these basic defects has been a challenge, but indicates that a deeper understanding of the molecular and cellular mechanism of mutations is a prerequisite for developing more efficient therapies.
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Affiliation(s)
- Tsukasa Okiyoneda
- Department of Physiology, McGill University, Montréal, Quebec, Canada
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Kim SJ, Skach WR. Mechanisms of CFTR Folding at the Endoplasmic Reticulum. Front Pharmacol 2012; 3:201. [PMID: 23248597 PMCID: PMC3521238 DOI: 10.3389/fphar.2012.00201] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Accepted: 11/23/2012] [Indexed: 12/20/2022] Open
Abstract
In the past decade much has been learned about how Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) folds and misfolds as the etiologic cause of cystic fibrosis (CF). CFTR folding is complex and hierarchical, takes place in multiple cellular compartments and physical environments, and involves several large networks of folding machineries. Insertion of transmembrane (TM) segments into the endoplasmic reticulum (ER) membrane and tertiary folding of cytosolic domains begin cotranslationally as the nascent polypeptide emerges from the ribosome, whereas posttranslational folding establishes critical domain-domain contacts needed to form a physiologically stable structure. Within the membrane, N- and C-terminal TM helices are sorted into bundles that project from the cytosol to form docking sites for nucleotide binding domains, NBD1 and NBD2, which in turn form a sandwich dimer for ATP binding. While tertiary folding is required for domain assembly, proper domain assembly also reciprocally affects folding of individual domains analogous to a jig-saw puzzle wherein the structure of each interlocking piece influences its neighbors. Superimposed on this process is an elaborate proteostatic network of cellular chaperones and folding machineries that facilitate the timing and coordination of specific folding steps in and across the ER membrane. While the details of this process require further refinement, we finally have a useful framework to understand key folding defect(s) caused by ΔF508 that provides a molecular target(s) for the next generation of CFTR small molecule correctors aimed at the specific defect present in the majority of CF patients.
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Affiliation(s)
- Soo Jung Kim
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University Portland, OR, USA
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He L, Kota P, Aleksandrov AA, Cui L, Jensen T, Dokholyan NV, Riordan JR. Correctors of ΔF508 CFTR restore global conformational maturation without thermally stabilizing the mutant protein. FASEB J 2012; 27:536-45. [PMID: 23104983 DOI: 10.1096/fj.12-216119] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Most cystic fibrosis is caused by the deletion of a single amino acid (F508) from CFTR and the resulting misfolding and destabilization of the protein. Compounds identified by high-throughput screening to improve ΔF508 CFTR maturation have already entered clinical trials, and it is important to understand their mechanisms of action to further improve their efficacy. Here, we showed that several of these compounds, including the investigational drug VX-809, caused a much greater increase (5- to 10-fold) in maturation at 27 than at 37°C (<2-fold), and the mature product remained short-lived (T(1/2)∼4.5 h) and thermally unstable, even though its overall conformational state was similar to wild type, as judged by resistance to proteolysis and interdomain cross-linking. Consistent with its inability to restore thermodynamic stability, VX-809 stimulated maturation 2-5-fold beyond that caused by several different stabilizing modifications of NBD1 and the NBD1/CL4 interface. The compound also promoted maturation of several disease-associated processing mutants on the CL4 side of this interface. Although these effects may reflect an interaction of VX-809 with this interface, an interpretation supported by computational docking, it also rescued maturation of mutants in other cytoplasmic loops, either by allosteric effects or via additional sites of action. In addition to revealing the capabilities and some of the limitations of this important investigational drug, these findings clearly demonstrate that ΔF508 CFTR can be completely assembled and evade cellular quality control systems, while remaining thermodynamically unstable. He, L., Kota, P., Aleksandrov, A. A., Cui, L., Jensen, T., Dokholyan, N. V., Riordan, J. R. Correctors of ΔF508 CFTR restore global conformational maturation without thermally stabilizing the mutant protein.
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Affiliation(s)
- Lihua He
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7248, USA
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40
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Liu X, O'Donnell N, Landstrom A, Skach WR, Dawson DC. Thermal instability of ΔF508 cystic fibrosis transmembrane conductance regulator (CFTR) channel function: protection by single suppressor mutations and inhibiting channel activity. Biochemistry 2012; 51:5113-24. [PMID: 22680785 DOI: 10.1021/bi300018e] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Deletion of Phe508 from cystic fibrosis transmembrane conductance regulator (CFTR) results in a temperature-sensitive folding defect that impairs protein maturation and chloride channel function. Both of these adverse effects, however, can be mitigated to varying extents by second-site suppressor mutations. To better understand the impact of second-site mutations on channel function, we compared the thermal sensitivity of CFTR channels in Xenopus oocytes. CFTR-mediated conductance of oocytes expressing wt or ΔF508 CFTR was stable at 22 °C and increased at 28 °C, a temperature permissive for ΔF508 CFTR expression in mammalian cells. At 37 °C, however, CFTR-mediated conductance was further enhanced, whereas that due to ΔF508 CFTR channels decreased rapidly toward background, a phenomenon referred to here as "thermal inactivation." Thermal inactivation of ΔF508 was mitigated by each of five suppressor mutations, I539T, R553M, G550E, R555K, and R1070W, but each exerted unique effects on the severity of, and recovery from, thermal inactivation. Another mutation, K1250A, known to increase open probability (P(o)) of ΔF508 CFTR channels, exacerbated thermal inactivation. Application of potentiators known to increase P(o) of ΔF508 CFTR channels at room temperature failed to protect channels from inactivation at 37 °C and one, PG-01, actually exacerbated thermal inactivation. Unstimulated ΔF508CFTR channels or those inhibited by CFTR(inh)-172 were partially protected from thermal inactivation, suggesting a possible inverse relationship between thermal stability and gating transitions. Thermal stability of channel function and temperature-sensitive maturation of the mutant protein appear to reflect related, but distinct facets of the ΔF508 CFTR conformational defect, both of which must be addressed by effective therapeutic modalities.
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Affiliation(s)
- Xuehong Liu
- Departments of Physiology & Pharmacology, Oregon Health & Science University, Portland, Oregon 97239, USA.
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Aleksandrov AA, Kota P, Cui L, Jensen T, Alekseev AE, Reyes S, He L, Gentzsch M, Aleksandrov LA, Dokholyan NV, Riordan JR. Allosteric modulation balances thermodynamic stability and restores function of ΔF508 CFTR. J Mol Biol 2012; 419:41-60. [PMID: 22406676 PMCID: PMC3891843 DOI: 10.1016/j.jmb.2012.03.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 02/29/2012] [Accepted: 03/05/2012] [Indexed: 10/28/2022]
Abstract
Most cystic fibrosis is caused by a deletion of a single residue (F508) in CFTR (cystic fibrosis transmembrane conductance regulator) that disrupts the folding and biosynthetic maturation of the ion channel protein. Progress towards understanding the underlying mechanisms and overcoming the defect remains incomplete. Here, we show that the thermal instability of human ΔF508 CFTR channel activity evident in both cell-attached membrane patches and planar phospholipid bilayers is not observed in corresponding mutant CFTRs of several non-mammalian species. These more stable orthologs are distinguished from their mammalian counterparts by the substitution of proline residues at several key dynamic locations in first N-terminal nucleotide-binding domain (NBD1), including the structurally diverse region, the γ-phosphate switch loop, and the regulatory insertion. Molecular dynamics analyses revealed that addition of the prolines could reduce flexibility at these locations and increase the temperatures of unfolding transitions of ΔF508 NBD1 to that of the wild type. Introduction of these prolines experimentally into full-length human ΔF508 CFTR together with the already recognized I539T suppressor mutation, also in the structurally diverse region, restored channel function and thermodynamic stability as well as its trafficking to and lifetime at the cell surface. Thus, while cellular manipulations that circumvent its culling by quality control systems leave ΔF508 CFTR dysfunctional at physiological temperature, restoration of the delicate balance between the dynamic protein's inherent stability and channel activity returns a near-normal state.
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Affiliation(s)
- Andrei A. Aleksandrov
- Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
- Cystic Fibrosis Treatment and Research Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
| | - Pradeep Kota
- Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Molecular and Cellular Biophysics Program, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
| | - Liying Cui
- Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
- Cystic Fibrosis Treatment and Research Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
| | - Tim Jensen
- Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
- Cystic Fibrosis Treatment and Research Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
| | - Alexey E. Alekseev
- Department of Medicine, Division of Cardiovascular Diseases, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA
| | - Santiago Reyes
- Department of Medicine, Division of Cardiovascular Diseases, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA
| | - Lihua He
- Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
- Cystic Fibrosis Treatment and Research Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
| | - Martina Gentzsch
- Department of Cell and Development Biology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
- Cystic Fibrosis Treatment and Research Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
| | - Luba A. Aleksandrov
- Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
- Cystic Fibrosis Treatment and Research Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
| | - Nikolay V. Dokholyan
- Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Molecular and Cellular Biophysics Program, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
| | - John R. Riordan
- Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
- Cystic Fibrosis Treatment and Research Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
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42
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Gulyás-Kovács A. Integrated analysis of residue coevolution and protein structure in ABC transporters. PLoS One 2012; 7:e36546. [PMID: 22590562 PMCID: PMC3348156 DOI: 10.1371/journal.pone.0036546] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 04/06/2012] [Indexed: 12/22/2022] Open
Abstract
Intraprotein side chain contacts can couple the evolutionary process of amino acid substitution at one position to that at another. This coupling, known as residue coevolution, may vary in strength. Conserved contacts thus not only define 3-dimensional protein structure, but also indicate which residue-residue interactions are crucial to a protein's function. Therefore, prediction of strongly coevolving residue-pairs helps clarify molecular mechanisms underlying function. Previously, various coevolution detectors have been employed separately to predict these pairs purely from multiple sequence alignments, while disregarding available structural information. This study introduces an integrative framework that improves the accuracy of such predictions, relative to previous approaches, by combining multiple coevolution detectors and incorporating structural contact information. This framework is applied to the ABC-B and ABC-C transporter families, which include the drug exporter P-glycoprotein involved in multidrug resistance of cancer cells, as well as the CFTR chloride channel linked to cystic fibrosis disease. The predicted coevolving pairs are further analyzed based on conformational changes inferred from outward- and inward-facing transporter structures. The analysis suggests that some pairs coevolved to directly regulate conformational changes of the alternating-access transport mechanism, while others to stabilize rigid-body-like components of the protein structure. Moreover, some identified pairs correspond to residues previously implicated in cystic fibrosis.
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Affiliation(s)
- Attila Gulyás-Kovács
- Laboratory of Cardiac/Membrane Physiology, Rockefeller University, New York, New York, United States of America.
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43
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Rabeh WM, Bossard F, Xu H, Okiyoneda T, Bagdany M, Mulvihill CM, Du K, di Bernardo S, Liu Y, Konermann L, Roldan A, Lukacs GL. Correction of both NBD1 energetics and domain interface is required to restore ΔF508 CFTR folding and function. Cell 2012; 148:150-63. [PMID: 22265408 DOI: 10.1016/j.cell.2011.11.024] [Citation(s) in RCA: 231] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 10/25/2011] [Accepted: 11/03/2011] [Indexed: 11/16/2022]
Abstract
The folding and misfolding mechanism of multidomain proteins remains poorly understood. Although thermodynamic instability of the first nucleotide-binding domain (NBD1) of ΔF508 CFTR (cystic fibrosis transmembrane conductance regulator) partly accounts for the mutant channel degradation in the endoplasmic reticulum and is considered as a drug target in cystic fibrosis, the link between NBD1 and CFTR misfolding remains unclear. Here, we show that ΔF508 destabilizes NBD1 both thermodynamically and kinetically, but correction of either defect alone is insufficient to restore ΔF508 CFTR biogenesis. Instead, both ΔF508-NBD1 energetic and the NBD1-MSD2 (membrane-spanning domain 2) interface stabilization are required for wild-type-like folding, processing, and transport function, suggesting a synergistic role of NBD1 energetics and topology in CFTR-coupled domain assembly. Identification of distinct structural deficiencies may explain the limited success of ΔF508 CFTR corrector molecules and suggests structure-based combination corrector therapies. These results may serve as a framework for understanding the mechanism of interface mutation in multidomain membrane proteins.
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Affiliation(s)
- Wael M Rabeh
- Department of Physiology, McGill University, Montréal, Quebec H3E 1Y6, Canada
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Corrector-mediated rescue of misprocessed CFTR mutants can be reduced by the P-glycoprotein drug pump. Biochem Pharmacol 2012; 83:345-54. [DOI: 10.1016/j.bcp.2011.11.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Revised: 11/17/2011] [Accepted: 11/18/2011] [Indexed: 11/18/2022]
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45
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Lukacs GL, Verkman AS. CFTR: folding, misfolding and correcting the ΔF508 conformational defect. Trends Mol Med 2011; 18:81-91. [PMID: 22138491 DOI: 10.1016/j.molmed.2011.10.003] [Citation(s) in RCA: 288] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 10/19/2011] [Accepted: 10/19/2011] [Indexed: 12/30/2022]
Abstract
Cystic fibrosis (CF), the most common lethal genetic disease in the Caucasian population, is caused by loss-of-function mutations of the CF transmembrane conductance regulator (CFTR), a cyclic AMP-regulated plasma membrane chloride channel. The most common mutation, deletion of phenylalanine 508 (ΔF508), impairs CFTR folding and, consequently, its biosynthetic and endocytic processing as well as chloride channel function. Pharmacological treatments may target the ΔF508 CFTR structural defect directly by binding to the mutant protein and/or indirectly by altering cellular protein homeostasis (proteostasis) to promote ΔF508 CFTR plasma membrane targeting and stability. This review discusses recent basic research aimed at elucidating the structural and trafficking defects of ΔF508 CFTR, a prerequisite for the rational design of CF therapy to correct the loss-of-function phenotype.
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Affiliation(s)
- Gergely L Lukacs
- Department of Physiology and GRASP, McGill University, Montréal, Quebec H3E 1Y6, Canada.
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46
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Abstract
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Deletion of Phe508 from the first nucleotide-binding domain of the CFTR chloride channel causes cystic fibrosis because it inhibits protein folding. Indirect approaches such as incubation at low temperatures can partially rescue ΔF508 CFTR, but the protein is unstable at the cell surface. Here, we show that direct binding of benzbromarone to the transmembrane domains promoted maturation and stabilized ΔF508 CFTR because its half-life at the cell surface was ∼10-fold longer than that for low-temperature rescue. Therefore, a search for small molecules that can rescue and stabilize ΔF508 CFTR could lead to the development of an effective therapy for cystic fibrosis.
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Affiliation(s)
- Tip W Loo
- Departments of Medicine and Biochemistry, University of Toronto, Toronto, Ontario, Canada
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47
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Wang C, Protasevich I, Yang Z, Seehausen D, Skalak T, Zhao X, Atwell S, Spencer Emtage J, Wetmore DR, Brouillette CG, Hunt JF. Integrated biophysical studies implicate partial unfolding of NBD1 of CFTR in the molecular pathogenesis of F508del cystic fibrosis. Protein Sci 2011; 19:1932-47. [PMID: 20687163 DOI: 10.1002/pro.480] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The lethal genetic disease cystic fibrosis is caused predominantly by in-frame deletion of phenylalanine 508 in the cystic fibrosis transmembrane conductance regulator (CFTR). F508 is located in the first nucleotide-binding domain (NBD1) of CFTR, which functions as an ATP-gated chloride channel on the cell surface. The F508del mutation blocks CFTR export to the surface due to aberrant retention in the endoplasmic reticulum. While it was assumed that F508del interferes with NBD1 folding, biophysical studies of purified NBD1 have given conflicting results concerning the mutation's influence on domain folding and stability. We have conducted isothermal (this paper) and thermal (accompanying paper) denaturation studies of human NBD1 using a variety of biophysical techniques, including simultaneous circular dichroism, intrinsic fluorescence, and static light-scattering measurements. These studies show that, in the absence of ATP, NBD1 unfolds via two sequential conformational transitions. The first, which is strongly influenced by F508del, involves partial unfolding and leads to aggregation accompanied by an increase in tryptophan fluorescence. The second, which is not significantly influenced by F508del, involves full unfolding of NBD1. Mg-ATP binding delays the first transition, thereby offsetting the effect of F508del on domain stability. Evidence suggests that the initial partial unfolding transition is partially responsible for the poor in vitro solubility of human NBD1. Second-site mutations that increase the solubility of isolated F508del-NBD1 in vitro and suppress the trafficking defect of intact F508del-CFTR in vivo also stabilize the protein against this transition, supporting the hypothesize that it is responsible for the pathological trafficking of F508del-CFTR.
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Affiliation(s)
- Chi Wang
- Department of Biological Sciences, 702A Fairchild Center, Columbia University, New York, New York 10027, USA
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48
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Loo TW, Bartlett MC, Clarke DM. The W232R suppressor mutation promotes maturation of a truncation mutant lacking both nucleotide-binding domains and restores interdomain assembly and activity of P-glycoprotein processing mutants. Biochemistry 2011; 50:672-85. [PMID: 21182301 DOI: 10.1021/bi1016809] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
ATP-binding cassette (ABC) proteins contain two nucleotide-binding domains (NBDs) and two transmembrane (TM) domains (TMDs). Interdomain interactions and packing of the TM segments are critical for function, and disruption by genetic mutations contributes to disease. P-glycoprotein (P-gp) is a useful model to identify mechanisms that repair processing defects because numerous arginine suppressor mutations have been identified in the TM segments. Here, we tested the prediction that a mechanism of arginine rescue was to promote intradomain interactions between TM segments and restore interdomain assembly. We found that suppressor W232R(TM4/TMD1) rescued mutants with processing mutations in any domain and restored defective NBD1-NBD2, NBD1-TMD2, and TMD1-TMD2 interactions. W232R also promoted packing of the TM segments because it rescued a truncation mutant lacking both NBDs. The mechanism of W232R rescue likely involved intradomain hydrogen bond interactions with Asn296(TM5) since only N296A abolished rescue by W232R and rescue was only observed when Trp232 was replaced with hydrogen-bonding residues. In TMD2, suppressor T945R(TM11) also promoted packing of the TM segments because it rescued the truncation mutant lacking the NBDs and suppressed formation of alternative topologies. We propose that T945R rescue was mediated by interactions with Glu875(TM10) since T945E/E875R promoted maturation while T945R/E875A did not.
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Affiliation(s)
- Tip W Loo
- Department of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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49
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Grove DE, Fan CY, Ren HY, Cyr DM. The endoplasmic reticulum-associated Hsp40 DNAJB12 and Hsc70 cooperate to facilitate RMA1 E3-dependent degradation of nascent CFTRDeltaF508. Mol Biol Cell 2010; 22:301-14. [PMID: 21148293 PMCID: PMC3031462 DOI: 10.1091/mbc.e10-09-0760] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
A specialized Hsp40 protein, DNAJB12, was found to function on the cytoplasmic face of the ER with the RMA1 E3 ligase to regulate the folding efficiency of CFTR. Relative contributions of folding kinetics versus protein quality control (QC) activity in the partitioning of non-native proteins between life and death are not clear. Cystic fibrosis transmembrane conductance regulator (CFTR) biogenesis serves as an excellent model to study this question because folding of nascent CFTR is inefficient and deletion of F508 causes accumulation of CFTRΔF508 in a kinetically trapped, but foldable state. Herein, a novel endoplasmic reticulum (ER)-associated Hsp40, DNAJB12 (JB12) is demonstrated to play a role in control of CFTR folding efficiency. JB12 cooperates with cytosolic Hsc70 and the ubiquitin ligase RMA1 to target CFTR and CFTRΔF508 for degradation. Modest elevation of JB12 decreased nascent CFTR and CFTRΔF508 accumulation while increasing association of Hsc70 with ER forms of CFTR and the RMA1 E3 complex. Depletion of JB12 increased CFTR folding efficiency up to threefold and permitted a pool of CFTRΔF508 to fold and escape the ER. Introduction of the V510D misfolding suppressor mutation into CFTRΔF508 modestly increased folding efficiency, whereas combined inactivation of JB12 and suppression of intrinsic folding defects permitted CFTRΔF508 to fold at 50% of wild-type efficiency. Therapeutic correction of CFTRΔF508 misfolding in cystic fibrosis patients may require repair of defective folding kinetics and suppression of ER QC factors, such as JB12.
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Affiliation(s)
- Diane E Grove
- Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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