1
|
Coatti GC, Vaghela N, Gillurkar P, Leir SH, Harris A. A promoter-dependent upstream activator augments CFTR expression in diverse epithelial cell types. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2024; 1867:195031. [PMID: 38679287 DOI: 10.1016/j.bbagrm.2024.195031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 04/22/2024] [Accepted: 04/23/2024] [Indexed: 05/01/2024]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) gene encodes an anion-selective channel found in epithelial cell membranes. Mutations in CFTR cause cystic fibrosis (CF), an inherited disorder that impairs epithelial function in multiple organs. Most men with CF are infertile due to loss of intact genital ducts. Here we investigated a novel epididymis-selective cis-regulatory element (CRE), located within a peak of open chromatin at -9.5 kb 5' to the CFTR gene promoter. Activation of the -9.5 kb CRE alone by CRISPRa had no impact on CFTR gene expression. However, CRISPRa co-activation of the -9.5 kb CRE and the CFTR gene promoter in epididymis cells significantly augmented CFTR mRNA and protein expression when compared to promoter activation alone. This increase was accompanied by enhanced chromatin accessibility at both sites. Furthermore, the combined CRISPRa strategy activated CFTR expression in other epithelial cells that lack open chromatin at the -9.5 kb site and in which the locus is normally inactive. However, the -9.5 kb CRE does not function as a classical enhancer of the CFTR promoter in transient reporter gene assays. These data provide a novel mechanism for activating/augmenting CFTR expression, which may have therapeutic utility for mutations that perturb CFTR transcription.
Collapse
Affiliation(s)
- Giuliana C Coatti
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Nirbhayaditya Vaghela
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Pulak Gillurkar
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Shih-Hsing Leir
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Ann Harris
- Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
| |
Collapse
|
2
|
Li H, Rodrat M, Al-Salmani MK, Veselu DF, Han ST, Raraigh KS, Cutting GR, Sheppard DN. Two rare variants that affect the same amino acid in CFTR have distinct responses to ivacaftor. J Physiol 2024; 602:333-354. [PMID: 38186087 PMCID: PMC10872379 DOI: 10.1113/jp285727] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 12/11/2023] [Indexed: 01/09/2024] Open
Abstract
Some residues in the cystic fibrosis transmembrane conductance regulator (CFTR) channel are the site of more than one CFTR variant that cause cystic fibrosis. Here, we investigated the function of S1159F and S1159P, two variants associated with different clinical phenotypes, which affect the same pore-lining residue in transmembrane segment 12 that are both strongly potentiated by ivacaftor when expressed in CFBE41o- bronchial epithelial cells. To study the single-channel behaviour of CFTR, we applied the patch-clamp technique to Chinese hamster ovary cells heterologously expressing CFTR variants incubated at 27°C to enhance channel residence at the plasma membrane. S1159F- and S1159P-CFTR formed Cl- channels activated by cAMP-dependent phosphorylation and gated by ATP that exhibited thermostability at 37°C. Both variants modestly reduced the single-channel conductance of CFTR. By severely attenuating channel gating, S1159F- and S1159P-CFTR reduced the open probability (Po ) of wild-type CFTR by ≥75% at ATP (1 mM); S1159F-CFTR caused the greater decrease in Po consistent with its more severe clinical phenotype. Ivacaftor (10-100 nM) doubled the Po of both CFTR variants without restoring Po values to wild-type levels, but concomitantly, ivacaftor decreased current flow through open channels. For S1159F-CFTR, the reduction of current flow was marked at high (supersaturated) ivacaftor concentrations (0.5-1 μM) and voltage-independent, identifying an additional detrimental action of elevated ivacaftor concentrations. In conclusion, S1159F and S1159P are gating variants, which also affect CFTR processing and conduction, but not stability, necessitating the use of combinations of CFTR modulators to optimally restore their channel activity. KEY POINTS: Dysfunction of the ion channel cystic fibrosis transmembrane conductance regulator (CFTR) causes the genetic disease cystic fibrosis (CF). This study investigated two rare pathogenic CFTR variants, S1159F and S1159P, which affect the same amino acid in CFTR, to understand the molecular basis of disease and response to the CFTR-targeted therapy ivacaftor. Both rare variants diminished CFTR function by modestly reducing current flow through the channel and severely inhibiting ATP-dependent channel gating with S1159F exerting the stronger adverse effect, which correlates with its association with more severe disease. Ivacaftor potentiated channel gating by both rare variants without restoring their activity to wild-type levels, but concurrently reduced current flow through open channels, particularly those of S1159F-CFTR. Our data demonstrate that S1159F and S1159P cause CFTR dysfunction by multiple mechanisms that require combinations of CFTR-targeted therapies to fully restore channel function.
Collapse
Affiliation(s)
- Hongyu Li
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Mayuree Rodrat
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
- Center of Research and Development for Biomedical Instrumentation, Institute of Molecular Biosciences, Mahidol University, Nakhon Pathom, Thailand
| | - Majid K Al-Salmani
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
- Department of Physiology, College of Medicine and Health Sciences, Sultan Qaboos University, Al Khoudh, Muscat, Sultanate of Oman
| | | | - Sangwoo T Han
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Karen S Raraigh
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Garry R Cutting
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - David N Sheppard
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| |
Collapse
|
3
|
Kerschner JL, Paranjapye A, Vaghela N, Wilson MD, Harris A. An ectopic enhancer restores CFTR expression through de novo chromatin looping. Gene Ther 2023; 30:478-486. [PMID: 36510002 PMCID: PMC11227122 DOI: 10.1038/s41434-022-00378-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 10/30/2022] [Accepted: 11/29/2022] [Indexed: 12/14/2022]
Abstract
Transcription of the cystic fibrosis transmembrane conductance regulator (CFTR) gene is regulated by both ubiquitous and cell-type selective cis-regulatory elements (CREs). These CREs include extragenic and intronic enhancers that bind lineage-specific transcription factors, and architectural protein-marked structural elements. Deletion of the airway-selective -35 kb enhancer in 16HBE14o- lung epithelial cells was shown earlier to disrupt normal enhancer-promoter looping at the CFTR locus and nearly abolish its expression. Using a 16HBE14o- clone that lacks the endogenous -35 kb CRE, we explore the impact of relocating the functional core of this element to an ectopic site in intron 1. The -35 kb sequence establishes a de novo enhancer signature in chromatin at the insertion site, and augments CFTR expression, albeit not fully restoring WT levels. The relocated -35 kb enhancer also initiates de novo chromatin contacts with the CFTR promoter and other known CFTR CREs. These results are broadly relevant to therapeutic gene editing.
Collapse
Affiliation(s)
- Jenny L Kerschner
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44116, USA
| | - Alekh Paranjapye
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44116, USA
- Department of Genetics, University of Pennsylvania, Philadelphia, PA, USA
| | - Nirbhayaditya Vaghela
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44116, USA
| | - Michael D Wilson
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44116, USA
| | - Ann Harris
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44116, USA.
| |
Collapse
|
4
|
Kerschner JL, Paranjapye A, Harris A. Cellular heterogeneity in the 16HBE14o - airway epithelial line impacts biological readouts. Physiol Rep 2023; 11:e15700. [PMID: 37269165 PMCID: PMC10238858 DOI: 10.14814/phy2.15700] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 04/15/2023] [Accepted: 04/16/2023] [Indexed: 06/04/2023] Open
Abstract
The airway epithelial cell line, 16HBE14o- , is an important cell model for studying airway disease. 16HBE14o- cells were originally generated from primary human bronchial epithelial cells by SV40-mediated immortalization, a process that is associated with genomic instability through long-term culture. Here, we explore the heterogeneity of these cells, with respect to expression of the cystic fibrosis transmembrane conductance regulator (CFTR) transcript and protein. We isolate clones of 16HBE14o- with stably higher and lower levels of CFTR in comparison to bulk 16HBE14o- , designated CFTRhigh and CFTRlow . Detailed characterization of the CFTR locus in these clones by ATAC-seq and 4C-seq showed open chromatin profiles and higher order chromatin structure that correlate with CFTR expression levels. Transcriptomic profiling of CFTRhigh and CFTRlow cells showed that the CFTRhigh cells had an elevated inflammatory/innate immune response phenotype. These results encourage caution in interpreting functional data from clonal lines of 16HBE14o- cells, generated after genomic or other manipulations.
Collapse
Affiliation(s)
- Jenny L. Kerschner
- Department of Genetics and Genome SciencesCase Western Reserve UniversityClevelandOhioUSA
| | - Alekh Paranjapye
- Department of Genetics and Genome SciencesCase Western Reserve UniversityClevelandOhioUSA
- Present address:
Department of GeneticsUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Ann Harris
- Department of Genetics and Genome SciencesCase Western Reserve UniversityClevelandOhioUSA
| |
Collapse
|
5
|
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.
Collapse
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.
| |
Collapse
|
6
|
Viotti Perisse I, Fan Z, Van Wettere A, Liu Y, Leir S, Keim J, Regouski M, Wilson MD, Cholewa KM, Mansbach SN, Kelley TJ, Wang Z, Harris A, White KL, Polejaeva IA. Sheep models of F508del and G542X cystic fibrosis mutations show cellular responses to human therapeutics. FASEB Bioadv 2021; 3:841-854. [PMID: 34632318 PMCID: PMC8493969 DOI: 10.1096/fba.2021-00043] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 06/24/2021] [Accepted: 06/28/2021] [Indexed: 02/05/2023] Open
Abstract
Cystic Fibrosis (CF) is a genetic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. The F508del and G542X are the most common mutations found in US patients, accounting for 86.4% and 4.6% of all mutations, respectively. The F508del causes deletion of the phenylalanine residue at position 508 and is associated with impaired CFTR protein folding. The G542X is a nonsense mutation that introduces a stop codon into the mRNA, thus preventing normal CFTR protein synthesis. Here, we describe the generation of CFTRF508del / F508del and CFTRG542X / G542X lambs using CRISPR/Cas9 and somatic cell nuclear transfer (SCNT). First, we introduced either F508del or G542X mutations into sheep fetal fibroblasts that were subsequently used as nuclear donors for SCNT. The newborn CF lambs develop pathology similar to CFTR -/- sheep and CF patients. Moreover, tracheal epithelial cells from the CFTRF508del / F508del lambs responded to a human CFTR (hCFTR) potentiator and correctors, and those from CFTRG542X / G542X lambs showed modest restoration of CFTR function following inhibition of nonsense-mediated decay (NMD) and aminoglycoside antibiotic treatments. Thus, the phenotype and electrophysiology of these novel models represent an important advance for testing new CF therapeutics and gene therapy to improve the health of patients with this life-limiting disorder.
Collapse
Affiliation(s)
- Iuri Viotti Perisse
- Department of Animal, Dairy and Veterinary SciencesUtah State UniversityLoganUtahUSA
| | - Zhiqiang Fan
- Department of Animal, Dairy and Veterinary SciencesUtah State UniversityLoganUtahUSA
| | - Arnaud Van Wettere
- Department of Animal, Dairy and Veterinary SciencesUtah State UniversityLoganUtahUSA
| | - Ying Liu
- Department of Animal, Dairy and Veterinary SciencesUtah State UniversityLoganUtahUSA
| | - Shih‐Hsing Leir
- Department of Genetics and Genome SciencesCase Western Reserve University School of MedicineClevelandOhioUSA
| | - Jacob Keim
- Department of Animal, Dairy and Veterinary SciencesUtah State UniversityLoganUtahUSA
| | - Misha Regouski
- Department of Animal, Dairy and Veterinary SciencesUtah State UniversityLoganUtahUSA
| | - Michael D. Wilson
- Department of Genetics and Genome SciencesCase Western Reserve University School of MedicineClevelandOhioUSA
| | - Kelly M. Cholewa
- Department of Genetics and Genome SciencesCase Western Reserve University School of MedicineClevelandOhioUSA
| | - Sara N. Mansbach
- Department of Genetics and Genome SciencesCase Western Reserve University School of MedicineClevelandOhioUSA
| | - Thomas J. Kelley
- Department of Genetics and Genome SciencesCase Western Reserve University School of MedicineClevelandOhioUSA
| | - Zhongde Wang
- Department of Animal, Dairy and Veterinary SciencesUtah State UniversityLoganUtahUSA
| | - Ann Harris
- Department of Genetics and Genome SciencesCase Western Reserve University School of MedicineClevelandOhioUSA
| | - Kenneth L. White
- Department of Animal, Dairy and Veterinary SciencesUtah State UniversityLoganUtahUSA
| | - Irina A. Polejaeva
- Department of Animal, Dairy and Veterinary SciencesUtah State UniversityLoganUtahUSA
| |
Collapse
|
7
|
Towards next generation therapies for cystic fibrosis: Folding, function and pharmacology of CFTR. J Cyst Fibros 2020; 19 Suppl 1:S25-S32. [PMID: 31902693 PMCID: PMC7052731 DOI: 10.1016/j.jcf.2019.12.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 12/16/2019] [Accepted: 12/18/2019] [Indexed: 12/19/2022]
Abstract
The treatment of cystic fibrosis (CF) has been transformed by orally-bioavailable small molecule modulators of the cystic fibrosis transmembrane conductance regulator (CFTR), which restore function to CF mutants. However, CFTR modulators are not available to all people with CF and better modulators are required to prevent disease progression. Here, we review selectively recent advances in CFTR folding, function and pharmacology. We highlight ensemble and single-molecule studies of CFTR folding, which provide new insight into CFTR assembly, its perturbation by CF mutations and rescue by CFTR modulators. We discuss species-dependent differences in the action of the F508del-CFTR mutation on CFTR expression, stability and function, which might influence pharmacological studies of CFTR modulators in CF animal models. Finally, we illuminate the identification of combinations of two CFTR potentiators (termed co-potentiators), which restore therapeutically-relevant levels of CFTR activity to rare CF mutations. Thus, mechanistic studies of CFTR folding, function and pharmacology inform the development of highly effective CFTR modulators.
Collapse
|
8
|
Laselva O, Erwood S, Du K, Ivakine Z, Bear CE. Activity of lumacaftor is not conserved in zebrafish Cftr bearing the major cystic fibrosis-causing mutation. FASEB Bioadv 2019; 1:661-670. [PMID: 32123813 PMCID: PMC6996396 DOI: 10.1096/fba.2019-00039] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 05/02/2019] [Accepted: 08/30/2019] [Indexed: 12/11/2022] Open
Abstract
F508del-cystic fibrosis transmembrane conductance regulator (CFTR) is the major mutant responsible for cystic fibrosis (CF). ORKAMBI®, approved for patients bearing this mutant, contains lumacaftor (VX-809) that partially corrects F508del-CFTR's processing defect and ivacaftor (VX-770) that potentiates its defective channel activity. Unfortunately, the clinical efficacy of ORKAMBI® is modest, highlighting the need to understand how the small molecules work so that superior compounds can be developed. Because, human CFTR (hCFTR) and zebrafish Cftr (zCftr) are structurally conserved as determined in recent cryo-EM structural models, we hypothesized that the consequences of the major mutation and small molecule modulators would be similar for the two species of protein. As expected, like the F508del mutation in hCFTR, the homologous mutation in zCftr (F507del) is misprocessed, yet not as severely as the human mutant and this defect was restored by low-temperature (27°C) culture conditions. After rescue to the cell surface, F507del-zCftr exhibited regulated channel activity that was potentiated by ivacaftor. Surprisingly, lumacaftor failed to rescue misprocessing of the F507del-zCftr at either 37 or 27°C suggesting that future comparative studies with F508del-hCFTR would provide insight into its structure: function relationships. Interestingly, the robust rescue of F508del-zCftr at 27°C and availability of methods for in vivo screening in zebrafish present the opportunity to define the cellular pathways underlying rescue.
Collapse
Affiliation(s)
- Onofrio Laselva
- Programme in Molecular MedicineHospital for Sick ChildrenTorontoCanada
- Department of PhysiologyUniversity of TorontoTorontoCanada
| | - Steven Erwood
- Programme in Genetics and Genome BiologyHospital for Sick ChildrenTorontoCanada
| | - Kai Du
- Programme in Molecular MedicineHospital for Sick ChildrenTorontoCanada
| | - Zhenya Ivakine
- Programme in Genetics and Genome BiologyHospital for Sick ChildrenTorontoCanada
| | - Christine E. Bear
- Programme in Molecular MedicineHospital for Sick ChildrenTorontoCanada
- Department of PhysiologyUniversity of TorontoTorontoCanada
- Department of BiochemistryUniversity of TorontoTorontoCanada
| |
Collapse
|
9
|
Bose SJ, Bijvelds MJC, Wang Y, Liu J, Cai Z, Bot AGM, de Jonge HR, Sheppard DN. Differential thermostability and response to cystic fibrosis transmembrane conductance regulator potentiators of human and mouse F508del-CFTR. Am J Physiol Lung Cell Mol Physiol 2019; 317:L71-L86. [PMID: 30969810 PMCID: PMC6689747 DOI: 10.1152/ajplung.00034.2019] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Cross-species comparative studies have highlighted differences between human and mouse cystic fibrosis transmembrane conductance regulator (CFTR), the epithelial Cl- channel defective in cystic fibrosis (CF). Here, we compare the impact of the most common CF mutation F508del on the function of human and mouse CFTR heterologously expressed in mammalian cells and their response to CFTR modulators using the iodide efflux and patch-clamp techniques. Once delivered to the plasma membrane, human F508del-CFTR exhibited a severe gating defect characterized by infrequent channel openings and was thermally unstable, deactivating within minutes at 37°C. By contrast, the F508del mutation was without effect on the gating pattern of mouse CFTR, and channel activity demonstrated thermostability at 37°C. Strikingly, at all concentrations tested, the clinically approved CFTR potentiator ivacaftor was without effect on the mouse F508del-CFTR Cl- channel. Moreover, eight CFTR potentiators, including ivacaftor, failed to generate CFTR-mediated iodide efflux from CHO cells expressing mouse F508del-CFTR. However, they all produced CFTR-mediated iodide efflux with human F508del-CFTR-expressing CHO cells, while fifteen CFTR correctors rescued the plasma membrane expression of both human and mouse F508del-CFTR. Interestingly, the CFTR potentiator genistein enhanced CFTR-mediated iodide efflux from CHO cells expressing either human or mouse F508del-CFTR, whereas it only potentiated human F508del-CFTR Cl- channels in cell-free membrane patches, suggesting that its action on mouse F508del-CFTR is indirect. Thus, the F508del mutation has distinct effects on human and mouse CFTR Cl- channels.
Collapse
Affiliation(s)
- Samuel J Bose
- School of Physiology, Pharmacology and Neuroscience, University of Bristol , Bristol , United Kingdom
| | - Marcel J C Bijvelds
- Department of Gastroenterology and Hepatology, Erasmus University Medical Center , Rotterdam , The Netherlands
| | - Yiting Wang
- School of Physiology, Pharmacology and Neuroscience, University of Bristol , Bristol , United Kingdom
| | - Jia Liu
- School of Physiology, Pharmacology and Neuroscience, University of Bristol , Bristol , United Kingdom
| | - Zhiwei Cai
- School of Physiology, Pharmacology and Neuroscience, University of Bristol , Bristol , United Kingdom
| | - Alice G M Bot
- Department of Gastroenterology and Hepatology, Erasmus University Medical Center , Rotterdam , The Netherlands
| | - Hugo R de Jonge
- Department of Gastroenterology and Hepatology, Erasmus University Medical Center , Rotterdam , The Netherlands
| | - David N Sheppard
- School of Physiology, Pharmacology and Neuroscience, University of Bristol , Bristol , United Kingdom
| |
Collapse
|
10
|
Semaniakou A, Croll RP, Chappe V. Animal Models in the Pathophysiology of Cystic Fibrosis. Front Pharmacol 2019; 9:1475. [PMID: 30662403 PMCID: PMC6328443 DOI: 10.3389/fphar.2018.01475] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 12/03/2018] [Indexed: 01/28/2023] Open
Abstract
Our understanding of the multiorgan pathology of cystic fibrosis (CF) has improved impressively during the last decades, but we still lack a full comprehension of the disease progression. Animal models have greatly contributed to the elucidation of specific mechanisms involved in CF pathophysiology and the development of new therapies. Soon after the cloning of the CF transmembrane conductance regulator (CFTR) gene in 1989, the first mouse model was generated and this model has dominated in vivo CF research ever since. Nonetheless, the failure of murine models to mirror human disease severity in the pancreas and lung has led to the generation of larger animal models such as pigs and ferrets. The following review presents and discusses data from the current animal models used in CF research.
Collapse
Affiliation(s)
- Anna Semaniakou
- Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
| | - Roger P Croll
- Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
| | - Valerie Chappe
- Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
| |
Collapse
|
11
|
Langron E, Prins S, Vergani P. Potentiation of the cystic fibrosis transmembrane conductance regulator by VX-770 involves stabilization of the pre-hydrolytic, O 1 state. Br J Pharmacol 2018; 175:3990-4002. [PMID: 30107029 DOI: 10.1111/bph.14475] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 07/30/2018] [Accepted: 08/05/2018] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND AND PURPOSE Cystic fibrosis (CF) is a debilitating hereditary disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes an anion channel. Wild type-CFTR gating is a non-equilibrium process. After ATP binding, CFTR enters a stable open state (O1 ). ATP hydrolysis leads it to a short-lived post-hydrolytic open state (O2 ), from which channels close. Here, we use mutations to probe the mechanism of VX-770, the first compound directly targeting the CFTR protein approved for treatment of CF. D1370N and K1250R mutations reduce or abolish catalytic activity, simplifying the gating scheme to an equilibrium (C↔O1 ); K464A-CFTR has a destabilized O1 state and rarely closes via hydrolysis. EXPERIMENTAL APPROACH Potentiation by VX-770 was measured using microscopic imaging of HEK293 cells expressing an anion-sensitive YFP-CFTR. A simple mathematical model was used to predict fluorescence quenching following extracellular iodide addition and estimate CFTR conductance. Membrane density of CFTR channels was measured in a parallel assay, using CFTR-pHTomato. KEY RESULTS VX-770 strongly potentiated WT-CFTR, D1370N-CFTR and K1250R-CFTR. K464A-CFTR was also strongly potentiated, regardless of whether it retained catalytic activity or not. CONCLUSIONS AND IMPLICATIONS Similar potentiation of hydrolytic and non-hydrolytic mutants suggests that VX-770 increases CFTR open probability mainly by stabilizing pre-hydrolytic O1 states with respect to closed states. Potentiation of K464A-CFTR channels suggests action of VX-770 did not strongly alter conformational dynamics at site 1. Understanding potentiator mechanism could help develop improved treatment for CF patients. The fluorescence assay presented here is a robust tool for such investigations.
Collapse
Affiliation(s)
- Emily Langron
- Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Stella Prins
- Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Paola Vergani
- Neuroscience, Physiology and Pharmacology, University College London, London, UK
| |
Collapse
|
12
|
Hwang TC, Yeh JT, Zhang J, Yu YC, Yeh HI, Destefano S. Structural mechanisms of CFTR function and dysfunction. J Gen Physiol 2018; 150:539-570. [PMID: 29581173 PMCID: PMC5881446 DOI: 10.1085/jgp.201711946] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 03/05/2018] [Indexed: 12/18/2022] Open
Abstract
Hwang et al. integrate new structural insights with prior functional studies to reveal the functional anatomy of CFTR chloride channels. Cystic fibrosis (CF) transmembrane conductance regulator (CFTR) chloride channel plays a critical role in regulating transepithelial movement of water and electrolyte in exocrine tissues. Malfunction of the channel because of mutations of the cftr gene results in CF, the most prevalent lethal genetic disease among Caucasians. Recently, the publication of atomic structures of CFTR in two distinct conformations provides, for the first time, a clear overview of the protein. However, given the highly dynamic nature of the interactions among CFTR’s various domains, better understanding of the functional significance of these structures requires an integration of these new structural insights with previously established biochemical/biophysical studies, which is the goal of this review.
Collapse
Affiliation(s)
- Tzyh-Chang Hwang
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO .,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO.,Department of Biological Engineering, University of Missouri, Columbia, MO
| | - Jiunn-Tyng Yeh
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO
| | - Jingyao Zhang
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO.,Department of Biological Engineering, University of Missouri, Columbia, MO
| | - Ying-Chun Yu
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO.,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
| | - Han-I Yeh
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO.,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
| | - Samantha Destefano
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO.,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO
| |
Collapse
|
13
|
Molecular Structure of the Human CFTR Ion Channel. Cell 2017; 169:85-95.e8. [PMID: 28340353 DOI: 10.1016/j.cell.2017.02.024] [Citation(s) in RCA: 351] [Impact Index Per Article: 50.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 02/09/2017] [Accepted: 02/14/2017] [Indexed: 01/13/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is an ATP-binding cassette (ABC) transporter that uniquely functions as an ion channel. Here, we present a 3.9 Å structure of dephosphorylated human CFTR without nucleotides, determined by electron cryomicroscopy (cryo-EM). Close resemblance of this human CFTR structure to zebrafish CFTR under identical conditions reinforces its relevance for understanding CFTR function. The human CFTR structure reveals a previously unresolved helix belonging to the R domain docked inside the intracellular vestibule, precluding channel opening. By analyzing the sigmoid time course of CFTR current activation, we propose that PKA phosphorylation of the R domain is enabled by its infrequent spontaneous disengagement, which also explains residual ATPase and gating activity of dephosphorylated CFTR. From comparison with MRP1, a feature distinguishing CFTR from all other ABC transporters is the helix-loop transition in transmembrane helix 8, which likely forms the structural basis for CFTR's channel function.
Collapse
|
14
|
Kirchner S, Cai Z, Rauscher R, Kastelic N, Anding M, Czech A, Kleizen B, Ostedgaard LS, Braakman I, Sheppard DN, Ignatova Z. Alteration of protein function by a silent polymorphism linked to tRNA abundance. PLoS Biol 2017; 15:e2000779. [PMID: 28510592 PMCID: PMC5433685 DOI: 10.1371/journal.pbio.2000779] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 04/13/2017] [Indexed: 01/22/2023] Open
Abstract
Synonymous single nucleotide polymorphisms (sSNPs) are considered neutral for protein function, as by definition they exchange only codons, not amino acids. We identified an sSNP that modifies the local translation speed of the cystic fibrosis transmembrane conductance regulator (CFTR), leading to detrimental changes to protein stability and function. This sSNP introduces a codon pairing to a low-abundance tRNA that is particularly rare in human bronchial epithelia, but not in other human tissues, suggesting tissue-specific effects of this sSNP. Up-regulation of the tRNA cognate to the mutated codon counteracts the effects of the sSNP and rescues protein conformation and function. Our results highlight the wide-ranging impact of sSNPs, which invert the programmed local speed of mRNA translation and provide direct evidence for the central role of cellular tRNA levels in mediating the actions of sSNPs in a tissue-specific manner. Synonymous single nucleotide polymorphisms (sSNPs) occur at high frequency in the human genome and are associated with ~50 diseases in humans; the responsible molecular mechanisms remain enigmatic. Here, we investigate the impact of the common sSNP, T2562G, on cystic fibrosis transmembrane conductance regulator (CFTR). Although this sSNP, by itself, does not cause cystic fibrosis (CF), it is prevalent in patients with CFTR-related disorders. T2562G sSNP modifies the local translation speed at the Thr854 codon, leading to changes in CFTR stability and channel function. This sSNP introduces a codon pairing to a low-abundance tRNA, which is particularly rare in human bronchial epithelia, but not in other human tissues, suggesting a tissue-specific effect of this sSNP. Enhancement of the cellular concentration of the tRNA cognate to the mutant ACG codon rescues the stability and conduction defects of T2562G-CFTR. These findings reveal an unanticipated mechanism—inverting the programmed local speed of mRNA translation in a tRNA-dependent manner—for sSNP-associated diseases.
Collapse
Affiliation(s)
- Sebastian Kirchner
- Biochemistry, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Zhiwei Cai
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Robert Rauscher
- Institute for Biochemistry and Molecular Biology, Department of Chemistry, University of Hamburg, Hamburg, Germany
| | - Nicolai Kastelic
- Biochemistry, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Melanie Anding
- Biochemistry, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Andreas Czech
- Institute for Biochemistry and Molecular Biology, Department of Chemistry, University of Hamburg, Hamburg, Germany
| | - Bertrand Kleizen
- Cellular Protein Chemistry, Department of Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands
| | - Lynda S. Ostedgaard
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Ineke Braakman
- Cellular Protein Chemistry, Department of Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands
| | - David N. Sheppard
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
- * E-mail: (ZI); (DNS)
| | - Zoya Ignatova
- Biochemistry, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
- Institute for Biochemistry and Molecular Biology, Department of Chemistry, University of Hamburg, Hamburg, Germany
- * E-mail: (ZI); (DNS)
| |
Collapse
|
15
|
Chen JH, Xu W, Sheppard DN. Altering intracellular pH reveals the kinetic basis of intraburst gating in the CFTR Cl - channel. J Physiol 2017; 595:1059-1076. [PMID: 27779763 DOI: 10.1113/jp273205] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 10/21/2016] [Indexed: 01/14/2023] Open
Abstract
KEY POINTS The cystic fibrosis transmembrane conductance regulator (CFTR), which is defective in the genetic disease cystic fibrosis (CF), forms a gated pathway for chloride movement regulated by intracellular ATP. To understand better CFTR function, we investigated the regulation of channel openings by intracellular pH. We found that short-lived channel closures during channel openings represent subtle changes in the structure of CFTR that are regulated by intracellular pH, in part, at ATP-binding site 1 formed by the nucleotide-binding domains. Our results provide a framework for future studies to understand better the regulation of channel openings, the dysfunction of CFTR in CF and the action of drugs that repair CFTR gating defects. ABSTRACT Cystic fibrosis transmembrane conductance regulator (CFTR) is an ATP-gated Cl- channel defective in the genetic disease cystic fibrosis (CF). The gating behaviour of CFTR is characterized by bursts of channel openings interrupted by brief, flickery closures, separated by long closures between bursts. Entry to and exit from an open burst is controlled by the interaction of ATP with two ATP-binding sites, sites 1 and 2, in CFTR. To understand better the kinetic basis of CFTR intraburst gating, we investigated the single-channel activity of human CFTR at different intracellular pH (pHi ) values. When compared with the control (pHi 7.3), acidifying pHi to 6.3 or alkalinizing pHi to 8.3 and 8.8 caused small reductions in the open-time constant (τo ) of wild-type CFTR. By contrast, the fast closed-time constant (τcf ), which describes the short-lived closures that interrupt open bursts, was greatly increased at pHi 5.8 and 6.3. To analyse intraburst kinetics, we used linear three-state gating schemes. All data were satisfactorily modelled by the C1 ↔ O ↔ C2 kinetic scheme. Changing the intracellular ATP concentration was without effect on τo , τcf and their responses to pHi changes. However, mutations that disrupt the interaction of ATP with ATP-binding site 1, including K464A, D572N and the CF-associated mutation G1349D all abolished the prolongation of τcf at pHi 6.3. Taken together, our data suggest that the regulation of CFTR intraburst gating is distinct from the ATP-dependent mechanism that controls channel opening and closing. However, our data also suggest that ATP-binding site 1 modulates intraburst gating.
Collapse
Affiliation(s)
- 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.,School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - 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
| | - David N Sheppard
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| |
Collapse
|
16
|
Abstract
Cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel expressed in the apical membrane of epithelia. Mutations in the CFTR gene are the cause of cystsic fibrosis. CFTR is the only ABC-protein that constitutes an ion channel pore forming subunit. CFTR gating is regulated in complex manner as phosphorylation is mandatory for channel activity and gating is directly regulated by binding of ATP to specific intracellular sites on the CFTR protein. This review covers our current understanding on the gating mechanism in CFTR and illustrates the relevance of alteration of these mechanisms in the onset of cystic fibrosis.
Collapse
Affiliation(s)
- Oscar Moran
- Istituto di Biofisica, CNR. Via De Marini, 6, 16149, Genoa, Italy.
| |
Collapse
|
17
|
Abstract
The anion channel cystic fibrosis transmembrane conductance regulator (CFTR) is a unique ATP-binding cassette (ABC) transporter. CFTR plays a pivotal role in transepithelial ion transport as its dysfunction in the genetic disease cystic fibrosis (CF) dramatically demonstrates. Phylogenetic analysis suggests that CFTR first appeared in aquatic vertebrates fulfilling important roles in osmosensing and organ development. Here, we review selectively, knowledge of CFTR structure, function and pharmacology, gleaned from cross-species comparative studies of recombinant CFTR proteins, including CFTR chimeras. The data argue that subtle changes in CFTR structure can affect strongly channel function and the action of CF mutations.
Collapse
|
18
|
Meyerholz DK. Lessons learned from the cystic fibrosis pig. Theriogenology 2016; 86:427-32. [PMID: 27142487 DOI: 10.1016/j.theriogenology.2016.04.057] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 12/14/2015] [Accepted: 03/14/2016] [Indexed: 12/01/2022]
Abstract
Deficient function in the anion channel cystic fibrosis (CF) transmembrane conductance regulator is the fundamental cause for CF. This is a monogenic condition that causes lesions in several organs including the respiratory tract, pancreas, liver, intestines, and reproductive tract. Lung disease is most notable, given it is the leading cause of morbidity and mortality in people with CF. Shortly after the identification of CF transmembrane conductance regulator, CF mouse models were developed that did not show spontaneous lung disease as seen in humans, and this spurred development of additional CF animal models. Pig models were considered a leading choice for several reasons including their similarity to humans in respiratory anatomy, physiology, and in size for translational imaging. The first CF pig models were reported in 2008 and have been extremely valuable to help clarify persistent questions in the field and advance understanding of disease pathogenesis. Because CF pigs are susceptible to lung disease like humans, they have direct utility in translational research. In addition, CF pig models are useful to compare and contrast with current CF mouse models, human clinical studies, and even newer CF animal models being characterized. This "triangulation" strategy could help identify genetic differences that underlie phenotypic variations, so as to focus and accelerate translational research.
Collapse
Affiliation(s)
- David K Meyerholz
- Department of Pathology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
| |
Collapse
|
19
|
Whitelaw CBA, Sheets TP, Lillico SG, Telugu BP. Engineering large animal models of human disease. J Pathol 2015; 238:247-56. [PMID: 26414877 PMCID: PMC4737318 DOI: 10.1002/path.4648] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 09/15/2015] [Accepted: 09/22/2015] [Indexed: 12/17/2022]
Abstract
The recent development of gene editing tools and methodology for use in livestock enables the production of new animal disease models. These tools facilitate site‐specific mutation of the genome, allowing animals carrying known human disease mutations to be produced. In this review, we describe the various gene editing tools and how they can be used for a range of large animal models of diseases. This genomic technology is in its infancy but the expectation is that through the use of gene editing tools we will see a dramatic increase in animal model resources available for both the study of human disease and the translation of this knowledge into the clinic. Comparative pathology will be central to the productive use of these animal models and the successful translation of new therapeutic strategies. © 2015 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.
Collapse
Affiliation(s)
- C Bruce A Whitelaw
- The Roslin Institute and Royal (Dick) School of Veterinary Science, Easter Bush Campus, University of Edinburgh, Edinburgh, EH25 9RG, UK
| | - Timothy P Sheets
- Animal Bioscience and Biotechnology Laboratory, ARS, Beltsville, MD, 20705, USA.,Department of Animal and Avian Sciences, Beltsville, MD, 20742, USA
| | - Simon G Lillico
- The Roslin Institute and Royal (Dick) School of Veterinary Science, Easter Bush Campus, University of Edinburgh, Edinburgh, EH25 9RG, UK
| | - Bhanu P Telugu
- Animal Bioscience and Biotechnology Laboratory, ARS, Beltsville, MD, 20705, USA.,Department of Animal and Avian Sciences, Beltsville, MD, 20742, USA
| |
Collapse
|