1
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Nemudraia A, Nemudryi A, Wiedenheft B. Repair of CRISPR-guided RNA breaks enables site-specific RNA excision in human cells. Science 2024; 384:808-814. [PMID: 38662916 PMCID: PMC11175973 DOI: 10.1126/science.adk5518] [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: 08/28/2023] [Accepted: 04/14/2024] [Indexed: 05/07/2024]
Abstract
Genome editing with CRISPR RNA-guided endonucleases generates DNA breaks that are resolved by cellular DNA repair machinery. However, analogous methods to manipulate RNA remain unavailable. We show that site-specific RNA breaks generated with type-III CRISPR complexes are repaired in human cells and that this repair can be used for programmable deletions in human transcripts to restore gene function. Collectively, this work establishes a technology for precise RNA manipulation with potential therapeutic applications.
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Affiliation(s)
- Anna Nemudraia
- Department of Microbiology and Cell Biology, Montana State University; Bozeman, MT, 59717, USA
| | - Artem Nemudryi
- Department of Microbiology and Cell Biology, Montana State University; Bozeman, MT, 59717, USA
| | - Blake Wiedenheft
- Department of Microbiology and Cell Biology, Montana State University; Bozeman, MT, 59717, USA
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2
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Chen J, Thrasher K, Fu L, Wang W, Aghamohammadzadeh S, Wen H, Tang L, Keeling KM, Falk Libby E, Bedwell DM, Rowe SM. The synthetic aminoglycoside ELX-02 induces readthrough of G550X-CFTR producing superfunctional protein that can be further enhanced by CFTR modulators. Am J Physiol Lung Cell Mol Physiol 2023; 324:L756-L770. [PMID: 37014818 PMCID: PMC10202470 DOI: 10.1152/ajplung.00038.2023] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 03/29/2023] [Accepted: 04/02/2023] [Indexed: 04/05/2023] Open
Abstract
Ten percent of cystic fibrosis (CF) patients carry a premature termination codon (PTC); no mutation-specific therapies exist for these individuals. ELX-02, a synthetic aminoglycoside, suppresses translation termination at PTCs (i.e., readthrough) by promoting the insertion of an amino acid at the PTC and restoring expression of full-length CFTR protein. The identity of amino acids inserted at PTCs affects the processing and function of the resulting full-length CFTR protein. We examined readthrough of the rare G550X-CFTR nonsense mutation due to its unique properties. We found that forskolin-induced swelling in G550X patient-derived intestinal organoids (PDOs) was significantly higher than in G542X PDOs (both UGA PTCs) with ELX-02 treatment, indicating greater CFTR function from the G550X allele. Using mass spectrometry, we identified tryptophan as the sole amino acid inserted in the G550X position during ELX-02- or G418-mediated readthrough, which differs from the three amino acids (cysteine, arginine, and tryptophan) inserted in the G542X position after treatment with G418. Compared with wild-type CFTR, Fischer rat thyroid (FRT) cells expressing the G550W-CFTR variant protein exhibited significantly increased forskolin-activated Cl- conductance, and G550W-CFTR channels showed increased PKA sensitivity and open probability. After treatment with ELX-02 and CFTR correctors, CFTR function rescued from the G550X allele in FRTs reached 20-40% of the wild-type level. These results suggest that readthrough of G550X produces greater CFTR function because of gain-of-function properties of the CFTR readthrough product that stem from its location in the signature LSGGQ motif found in ATP-binding cassette (ABC) transporters. G550X may be a particularly sensitive target for translational readthrough therapy.NEW & NOTEWORTHY We found that forskolin-induced swelling in G550X-CFTR patient-derived intestinal organoids (PDOs) was significantly higher than in G542X-CFTR PDOs after treatment with ELX-02. Tryptophan (W) was the sole amino acid inserted in the G550X position after readthrough. Resulting G550W-CFTR protein exhibited supernormal CFTR activity, PKA sensitivity, and open probability. These results show that aminoglycoside-induced readthrough of G550X produces greater CFTR function because of the gain-of-function properties of the CFTR readthrough product.
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Affiliation(s)
- Jianguo Chen
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Kari Thrasher
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Lianwu Fu
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Wei Wang
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | | | - Hui Wen
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Liping Tang
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Kim M Keeling
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Emily Falk Libby
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - David M Bedwell
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Steven M Rowe
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States
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3
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Allan KM, Astore MA, Kardia E, Wong SL, Fawcett LK, Bell JL, Visser S, Chen PC, Griffith R, Jaffe A, Sivam S, Vittorio O, Kuyucak S, Waters SA. Q1291H-CFTR molecular dynamics simulations and ex vivo theratyping in nasal epithelial models and clinical response to elexacaftor/tezacaftor/ivacaftor in a Q1291H/F508del patient. Front Mol Biosci 2023; 10:1148501. [PMID: 37325471 PMCID: PMC10267335 DOI: 10.3389/fmolb.2023.1148501] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 05/15/2023] [Indexed: 06/17/2023] Open
Abstract
Background: Cystic fibrosis (CF) is caused by a wide spectrum of mutations in the CF transmembrane conductance regulator (CFTR) gene, with some leading to non-classical clinical presentations. We present an integrated in vivo, in silico and in vitro investigation of an individual with CF carrying the rare Q1291H-CFTR allele and the common F508del allele. At age 56 years, the participant had obstructive lung disease and bronchiectasis, qualifying for Elexacaftor/Tezacaftor/Ivacaftor (ETI) CFTR modulator treatment due to their F508del allele. Q1291H CFTR incurs a splicing defect, producing both a normally spliced but mutant mRNA isoform and a misspliced isoform with a premature termination codon, causing nonsense mediated decay. The effectiveness of ETI in restoring Q1291H-CFTR is largely unknown. Methods: We collected clinical endpoint measurements, including forced expiratory volume in 1 s percent predicted (FEV1pp) and body mass index (BMI), and examined medical history. In silico simulations of the Q1291H-CFTR were compared to Q1291R, G551D, and wild-type (WT)-CFTR. We quantified relative Q1291H CFTR mRNA isoform abundance in patient-derived nasal epithelial cells. Differentiated pseudostratified airway epithelial cell models at air liquid interface were created and ETI treatment impact on CFTR was assessed by electrophysiology assays and Western blot. Results: The participant ceased ETI treatment after 3 months due to adverse events and no improvement in FEV1pp or BMI. In silico simulations of Q1291H-CFTR identified impairment of ATP binding similar to known gating mutants Q1291R and G551D-CFTR. Q1291H and F508del mRNA transcripts composed 32.91% and 67.09% of total mRNA respectively, indicating 50.94% of Q1291H mRNA was misspliced and degraded. Mature Q1291H-CFTR protein expression was reduced (3.18% ± 0.60% of WT/WT) and remained unchanged with ETI. Baseline CFTR activity was minimal (3.45 ± 0.25 μA/cm2) and not enhanced with ETI (5.73 ± 0.48 μA/cm2), aligning with the individual's clinical evaluation as a non-responder to ETI. Conclusion: The combination of in silico simulations and in vitro theratyping in patient-derived cell models can effectively assess CFTR modulator efficacy for individuals with non-classical CF manifestations or rare CFTR mutations, guiding personalized treatment strategies and optimizing clinical outcomes.
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Affiliation(s)
- Katelin M Allan
- School of Clinical Medicine, Discipline of Paediatrics and Child Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre, UNSW Sydney, Sydney, NSW, Australia
- School of Biomedical Sciences, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
| | - Miro A Astore
- School of Physics, The University of Sydney, Sydney, NSW, Australia
| | - Egi Kardia
- School of Clinical Medicine, Discipline of Paediatrics and Child Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre, UNSW Sydney, Sydney, NSW, Australia
- School of Biomedical Sciences, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
| | - Sharon L Wong
- School of Clinical Medicine, Discipline of Paediatrics and Child Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre, UNSW Sydney, Sydney, NSW, Australia
- School of Biomedical Sciences, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
| | - Laura K Fawcett
- School of Clinical Medicine, Discipline of Paediatrics and Child Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre, UNSW Sydney, Sydney, NSW, Australia
- School of Biomedical Sciences, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Department of Respiratory Medicine, Sydney Children's Hospital, Sydney, NSW, Australia
| | - Jessica L Bell
- School of Clinical Medicine, Discipline of Paediatrics and Child Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Children's Cancer Institute, UNSW Sydney, Sydney, NSW, Australia
| | - Simone Visser
- Department of Respiratory Medicine, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - Po-Chia Chen
- School of Physics, The University of Sydney, Sydney, NSW, Australia
| | - Renate Griffith
- School of Natural Sciences (Chemistry), University of Tasmania, Hobart, TAS, Australia
| | - Adam Jaffe
- School of Clinical Medicine, Discipline of Paediatrics and Child Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre, UNSW Sydney, Sydney, NSW, Australia
- Department of Respiratory Medicine, Sydney Children's Hospital, Sydney, NSW, Australia
| | - Sheila Sivam
- Department of Respiratory Medicine, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - Orazio Vittorio
- School of Biomedical Sciences, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Children's Cancer Institute, UNSW Sydney, Sydney, NSW, Australia
| | - Serdar Kuyucak
- School of Physics, The University of Sydney, Sydney, NSW, Australia
| | - Shafagh A Waters
- School of Clinical Medicine, Discipline of Paediatrics and Child Health, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Molecular and Integrative Cystic Fibrosis Research Centre, UNSW Sydney, Sydney, NSW, Australia
- School of Biomedical Sciences, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Department of Respiratory Medicine, Sydney Children's Hospital, Sydney, NSW, Australia
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4
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Allaire NE, Griesenbach U, Kerem B, Lueck JD, Stanleigh N, Oren YS. Gene, RNA, and ASO-based therapeutic approaches in Cystic Fibrosis. J Cyst Fibros 2023; 22 Suppl 1:S39-S44. [PMID: 36658041 PMCID: PMC10012168 DOI: 10.1016/j.jcf.2022.12.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 12/27/2022] [Accepted: 12/30/2022] [Indexed: 01/18/2023]
Abstract
Most people with Cystic Fibrosis (PwCF) harbor Cystic Fibrosis Transmembrane Conductance (CFTR) mutations that respond to highly effective CFTR modulators (HEM); however, a small fraction of non-responsive variants will require alternative approaches for treatment. Furthermore, the long-term goal to develop a cure for CF will require novel therapeutic strategies. Nucleic acid-based approaches offer the potential to address all CF-causing mutations and possibly a cure for all PwCF. In this minireview, we discuss current knowledge, recent progress, and critical questions surrounding the topic of Gene-, RNA-, and ASO-based therapies for the treatment of Cystic Fibrosis (CF).
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Affiliation(s)
| | - Uta Griesenbach
- National Heart and Lung Institute, Imperial College London and the UK Respiratory Gene Therapy Consortium, UK
| | - Batsheva Kerem
- Department of Genetics, The Life Sciences Institute, Hebrew University, Jerusalem, Israel
| | - John D Lueck
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY, USA
| | - Noemie Stanleigh
- Department of Genetics, The Life Sciences Institute, Hebrew University, Jerusalem, Israel
| | - Yifat S Oren
- SpliSenseTherapeutics, Biohouse Labs, Haddasah Ein Karem, Jerusalem, IL
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5
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Kim YJ, Nomakuchi T, Papaleonidopoulou F, Yang L, Zhang Q, Krainer AR. Gene-specific nonsense-mediated mRNA decay targeting for cystic fibrosis therapy. Nat Commun 2022; 13:2978. [PMID: 35624092 PMCID: PMC9142507 DOI: 10.1038/s41467-022-30668-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 05/06/2022] [Indexed: 12/20/2022] Open
Abstract
Low CFTR mRNA expression due to nonsense-mediated mRNA decay (NMD) is a major hurdle in developing a therapy for cystic fibrosis (CF) caused by the W1282X mutation in the CFTR gene. CFTR-W1282X truncated protein retains partial function, so increasing its levels by inhibiting NMD of its mRNA will likely be beneficial. Because NMD regulates the normal expression of many genes, gene-specific stabilization of CFTR-W1282X mRNA expression is more desirable than general NMD inhibition. Synthetic antisense oligonucleotides (ASOs) designed to prevent binding of exon junction complexes (EJC) downstream of premature termination codons (PTCs) attenuate NMD in a gene-specific manner. We describe cocktails of three ASOs that specifically increase the expression of CFTR-W1282X mRNA and CFTR protein upon delivery into human bronchial epithelial cells. This treatment increases the CFTR-mediated chloride current. These results set the stage for clinical development of an allele-specific therapy for CF caused by the W1282X mutation. The W1282X nonsense mutation in the CFTR gene causes cystic fibrosis by reducing its mRNA and functional protein levels. Here the authors developed antisense-oligonucleotide cocktails that restore CFTR protein function by gene-specific stabilization of CFTR mRNA.
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Affiliation(s)
- Young Jin Kim
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA.,Graduate Program in Genetics, Stony Brook University, Stony Brook, NY, 11794, USA.,Medical Scientist Training Program, Stony Brook University School of Medicine, Stony Brook, NY, 11794, USA
| | - Tomoki Nomakuchi
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA.,Medical Scientist Training Program, Stony Brook University School of Medicine, Stony Brook, NY, 11794, USA.,Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Foteini Papaleonidopoulou
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA.,Francis Crick Institute, London, 1140062, UK
| | - Lucia Yang
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA.,Graduate Program in Genetics, Stony Brook University, Stony Brook, NY, 11794, USA.,Medical Scientist Training Program, Stony Brook University School of Medicine, Stony Brook, NY, 11794, USA
| | - Qian Zhang
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA.,Graduate Program in Molecular and Cell Biology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Adrian R Krainer
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA.
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6
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Sanderlin EJ, Keenan MM, Mense M, Revenko AS, Monia BP, Guo S, Huang L. CFTR mRNAs with nonsense codons are degraded by the SMG6-mediated endonucleolytic decay pathway. Nat Commun 2022; 13:2344. [PMID: 35487895 PMCID: PMC9054838 DOI: 10.1038/s41467-022-29935-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 03/24/2022] [Indexed: 12/22/2022] Open
Abstract
Approximately 10% of cystic fibrosis patients harbor nonsense mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene which can generate nonsense codons in the CFTR mRNA and subsequently activate the nonsense-mediated decay (NMD) pathway resulting in rapid mRNA degradation. However, it is not known which NMD branches govern the decay of CFTR mRNAs containing nonsense codons. Here we utilize antisense oligonucleotides targeting NMD factors to evaluate the regulation of nonsense codon-containing CFTR mRNAs by the NMD pathway. We observe that CFTR mRNAs with nonsense codons G542X, R1162X, and W1282X, but not Y122X, require UPF2 and UPF3 for NMD. Furthermore, we demonstrate that all evaluated CFTR mRNAs harboring nonsense codons are degraded by the SMG6-mediated endonucleolytic pathway rather than the SMG5-SMG7-mediated exonucleolytic pathway. Finally, we show that upregulation of all evaluated CFTR mRNAs with nonsense codons by NMD pathway inhibition improves outcomes of translational readthrough therapy.
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Affiliation(s)
| | | | - Martin Mense
- Cystic Fibrosis Foundation Therapeutics Lab, Cystic Fibrosis Foundation, Lexington, MA, USA
| | | | | | - Shuling Guo
- Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA
| | - Lulu Huang
- Ionis Pharmaceuticals, Inc., Carlsbad, CA, USA.
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7
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Shaughnessy CA, Yadav S, Bratcher PE, Zeitlin PL. Receptor-mediated activation of CFTR via prostaglandin signaling pathways in the airway. Am J Physiol Lung Cell Mol Physiol 2022; 322:L305-L314. [PMID: 35020527 PMCID: PMC8858663 DOI: 10.1152/ajplung.00388.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Cystic fibrosis (CF) is a genetic disease caused by mutations of the gene encoding a cAMP-activated Cl- channel, the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR modulator therapies consist of small-molecule drugs that rescue mutant CFTR. Regimens of single or combinations of CFTR modulators still rely on endogenous levels of cAMP to regulate CFTR activity. We investigated CFTR activation by the natural mediator prostaglandin E2 (PGE2) and lubiprostone (a Food and Drug Administration-approved drug known to target prostaglandin receptors) and tested the hypothesis that receptor-mediated CFTR activators can be used in combination with currently available CFTR modulators to increase function of mutant CFTR. Primary-cultured airway epithelia were assayed in Ussing chambers. Experimental CFTR activators and established CFTR modulators were applied for 24 h and/or acutely and analyzed for their effect on CFTR activity as measured by changes in short-circuit current (ISC). In non-CF airway epithelia, acute application of lubiprostone and PGE2 activated CFTR to the levels comparable to forskolin (Fsk). Pretreatment (24 h) with antagonists to prostaglandin receptors EP2 and EP4 abolished the ability of lubiprostone to acutely activate CFTR. In F508del homozygous airway epithelia pretreated with the triple combination of elexacaftor, tezacaftor, and ivacaftor (ELEXA/TEZ/IVA; i.e., Trikafta), acute application of lubiprostone was able to maximally activate CFTR. Prolonged (24 h) cotreatment of F508del homozygous epithelia with ELEXA/TEZ/IVA and lubiprostone increased acute CFTR activation by ∼60% compared with the treatment with ELEXA/TEZ/IVA alone. This work establishes the feasibility of targeting prostaglandin receptors to activate CFTR on the airway epithelia and demonstrates that cotreatment with lubiprostone can further restore modulator-rescued CFTR.
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Affiliation(s)
| | - Sangya Yadav
- 1Department of Pediatrics, National Jewish Health, Denver, Colorado
| | - Preston E. Bratcher
- 1Department of Pediatrics, National Jewish Health, Denver, Colorado,2Department of Pediatrics, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado
| | - Pamela L. Zeitlin
- 1Department of Pediatrics, National Jewish Health, Denver, Colorado,2Department of Pediatrics, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado
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8
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Michaels WE, Pena-Rasgado C, Kotaria R, Bridges RJ, Hastings ML. Open reading frame correction using splice-switching antisense oligonucleotides for the treatment of cystic fibrosis. Proc Natl Acad Sci U S A 2022; 119:e2114886119. [PMID: 35017302 PMCID: PMC8784102 DOI: 10.1073/pnas.2114886119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 12/03/2021] [Indexed: 12/11/2022] Open
Abstract
CFTR gene mutations that result in the introduction of premature termination codons (PTCs) are common in cystic fibrosis (CF). This mutation type causes a severe form of the disease, likely because of low CFTR messenger RNA (mRNA) expression as a result of nonsense-mediated mRNA decay, as well as the production of a nonfunctional, truncated CFTR protein. Current therapeutics for CF, which target residual protein function, are less effective in patients with these types of mutations due in part to low CFTR protein levels. Splice-switching antisense oligonucleotides (ASOs), designed to induce skipping of exons in order to restore the mRNA open reading frame, have shown therapeutic promise preclinically and clinically for a number of diseases. We hypothesized that ASO-mediated skipping of CFTR exon 23 would recover CFTR activity associated with terminating mutations in the exon, including CFTR p.W1282X, the fifth most common mutation in CF. Here, we show that CFTR lacking the amino acids encoding exon 23 is partially functional and responsive to corrector and modulator drugs currently in clinical use. ASO-induced exon 23 skipping rescued CFTR expression and chloride current in primary human bronchial epithelial cells isolated from a homozygote CFTR-W1282X patient. These results support the use of ASOs in treating CF patients with CFTR class I mutations in exon 23 that result in unstable CFTR mRNA and truncations of the CFTR protein.
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Affiliation(s)
- Wren E Michaels
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064
- School of Graduate and Postdoctoral Studies, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064
| | - Cecilia Pena-Rasgado
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064
| | - Rusudan Kotaria
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064
| | - Robert J Bridges
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064;
| | - Michelle L Hastings
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Science and Medicine, North Chicago, IL 60064;
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9
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Kim YJ, Sivetz N, Layne J, Voss DM, Yang L, Zhang Q, Krainer AR. Exon-skipping antisense oligonucleotides for cystic fibrosis therapy. Proc Natl Acad Sci U S A 2022; 119:e2114858118. [PMID: 35017301 PMCID: PMC8784140 DOI: 10.1073/pnas.2114858118] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 11/16/2021] [Indexed: 11/25/2022] Open
Abstract
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF), and the CFTR-W1282X nonsense mutation causes a severe form of CF. Although Trikafta and other CFTR-modulation therapies benefit most CF patients, targeted therapy for patients with the W1282X mutation is lacking. The CFTR-W1282X protein has residual activity but is expressed at a very low level due to nonsense-mediated messenger RNA (mRNA) decay (NMD). NMD-suppression therapy and read-through therapy are actively being researched for CFTR nonsense mutants. NMD suppression could increase the mutant CFTR mRNA, and read-through therapies may increase the levels of full-length CFTR protein. However, these approaches have limitations and potential side effects: because the NMD machinery also regulates the expression of many normal mRNAs, broad inhibition of the pathway is not desirable, and read-through drugs are inefficient partly because the mutant mRNA template is subject to NMD. To bypass these issues, we pursued an exon-skipping antisense oligonucleotide (ASO) strategy to achieve gene-specific NMD evasion. A cocktail of two splice-site-targeting ASOs induced the expression of CFTR mRNA without the premature-termination-codon-containing exon 23 (CFTR-Δex23), which is an in-frame exon. Treatment of human bronchial epithelial cells with this cocktail of ASOs that target the splice sites flanking exon 23 results in efficient skipping of exon 23 and an increase in CFTR-Δex23 protein. The splice-switching ASO cocktail increases the CFTR-mediated chloride current in human bronchial epithelial cells. Our results set the stage for developing an allele-specific therapy for CF caused by the W1282X mutation.
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Affiliation(s)
- Young Jin Kim
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724
- Graduate Program in Genetics, Stony Brook University, Stony Brook, NY 11794
- Medical Scientist Training Program, Stony Brook University School of Medicine, Stony Brook, NY 11794
| | - Nicole Sivetz
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724
| | - Jessica Layne
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724
| | - Dillon M Voss
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724
- Graduate Program in Genetics, Stony Brook University, Stony Brook, NY 11794
- Medical Scientist Training Program, Stony Brook University School of Medicine, Stony Brook, NY 11794
| | - Lucia Yang
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724
- Graduate Program in Genetics, Stony Brook University, Stony Brook, NY 11794
- Medical Scientist Training Program, Stony Brook University School of Medicine, Stony Brook, NY 11794
| | - Qian Zhang
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724
- Graduate Program in Molecular and Cell Biology, Stony Brook University, Stony Brook, NY 11794
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10
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Nichols DP, Paynter AC, Heltshe SL, Donaldson SH, Frederick CA, Freedman SD, Gelfond D, Hoffman LR, Kelly A, Narkewicz MR, Pittman JE, Ratjen F, Rosenfeld M, Sagel SD, Schwarzenberg SJ, Singh PK, Solomon GM, Stalvey MS, Clancy JP, Kirby S, Van Dalfsen JM, Kloster MH, Rowe SM. Clinical Effectiveness of Elexacaftor/Tezacftor/Ivacaftor in People with Cystic Fibrosis. Am J Respir Crit Care Med 2021; 205:529-539. [PMID: 34784492 PMCID: PMC8906485 DOI: 10.1164/rccm.202108-1986oc] [Citation(s) in RCA: 154] [Impact Index Per Article: 51.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Rationale The cystic fibrosis (CF) modulator drug, elexacaftor/tezacaftor/ivacaftor (ETI), proved highly effective in controlled clinical trials for individuals with at least one F508del allele, which occurs in at least 85% of people with CF. Objectives PROMISE is a postapproval study to understand the broad effects of ETI through 30 months’ clinical use in a more diverse U.S. patient population with planned analyses after 6 months. Methods Prospective, observational study in 487 people with CF age 12 years or older with at least one F508del allele starting ETI for the first time. Assessments occurred before and 1, 3, and 6 months into ETI therapy. Outcomes included change in percent predicted FEV1 (ppFEV1), sweat chloride concentration, body mass index (BMI), and self-reported respiratory symptoms. Measurements and Main Results Average age was 25.1 years, and 44.1% entered the study using tezacaftor/ivacaftor or lumacaftor/ivacaftor, whereas 6.7% were using ivacaftor, consistent with F508del homozygosity and G551D allele, respectively. At 6 months into ETI therapy, ppFEV1 improved 9.76 percentage points (95% confidence interval [CI], 8.76 to 10.76) from baseline, cystic fibrosis questionnaire–revised respiratory domain score improved 20.4 points (95% CI, 18.3 to 22.5), and sweat chloride decreased −41.7 mmol/L (95% CI, −43.8 to −39.6). BMI also significantly increased. Changes were larger in those naive to modulators but substantial in all groups, including those treated with ivacaftor at baseline. Conclusions ETI by clinical prescription provided large improvements in lung function, respiratory symptoms, and BMI in a diverse population naive to modulator drug therapy, using existing two-drug combinations, or using ivacaftor alone. Each group also experienced significant reductions in sweat chloride concentration, which correlated with improved ppFEV1 in the overall study population. Clinical trial registered with www.clinicaltrials.gov (NCT NCT04038047).
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Affiliation(s)
- David P Nichols
- University of Washington School of Medicine, 12353, Pediatrics, Seattle, Washington, United States.,Seattle Children's Hospital, 7274, Pediatric Pulmonology, Seattle, Washington, United States;
| | - Alex C Paynter
- Seattle Children's Research Institute, 145793, Seattle, Washington, United States
| | - Sonya L Heltshe
- Seattle Children's Research Institute, Cystic Fibrosis Therapeutics Development Network Coordinating Center, Seattle, Washington, United States.,University of Washington School of Medicine, Pediatrics, Seattle, Washington, United States
| | | | - Carla A Frederick
- University at Buffalo Jacobs School of Medicine and Biomedical Sciences, 12291, Buffalo, New York, United States
| | - Steven D Freedman
- Beth Israel Deaconess Medical Center, Gastroenterology, Boston, Massachusetts, United States
| | - Daniel Gelfond
- Western New York Pediatric Gastroenterology, Batavia, New York, United States
| | - Lucas R Hoffman
- University of Washington School of Medicine, 12353, Seattle, Washington, United States.,Seattle Children's Hospital, 7274, Seattle, Washington, United States
| | - Andrea Kelly
- The Children's Hospital of Philadelphia, 6567, Pediatrics, Division of Endocrinology & Diabetes, Philadelphia, Pennsylvania, United States
| | - Michael R Narkewicz
- Children's Hospital Colorado and University of Colorado School of Medicine, Digestive Health Institute and Pediatrics, Aurora, Colorado, United States
| | - Jessica E Pittman
- Washington University in Saint Louis School of Medicine, 12275, Department of Pediatrics, Saint Louis, Missouri, United States
| | - Felix Ratjen
- University of Toronto HSC, Division of Respiratory Medicine, Toronto, Ontario, Canada
| | - Margaret Rosenfeld
- Seattle Children's, Pediatrics / Pulmonary, Seattle, Washington, United States
| | - Scott D Sagel
- University of Colorado School of Medicine, Pediatrics, Aurora, Colorado, United States
| | - Sarah Jane Schwarzenberg
- University of Minnesota Masonic Children's Hospital, 501779, Pediatrics, Minneapolis, Minnesota, United States
| | - Pradeep K Singh
- University of Washington, 7284, Department of Microbiology and Medicine, Seattle, Washington, United States
| | - George M Solomon
- University of Alabama at Birmingham, 9968, Medicine, Gregory Fleming James Cystic Fibrosis Research Center, Birmingham, Alabama, United States
| | - Michael S Stalvey
- The University of Alabama at Birmingham School of Medicine, 9967, Birmingham, Alabama, United States
| | - John P Clancy
- Cincinnati Children's Hospital Medical Center, 2518, Department of Pediatrics, Cincinnati, Ohio, United States.,Cincinnati Children's Hospital Medical Center, 2518, Division of Pulmonary Medicine, Cincinnati, Ohio, United States
| | - Shannon Kirby
- Seattle Children's Research Institute, 145793, Seattle, Washington, United States
| | - Jill M Van Dalfsen
- Cystic Fibrosis Foundation Therapeutics Development Network Coordinating Center, Seattle Children's Research Institute, Seattle, Washington, United States
| | - Margaret H Kloster
- Seattle Children's Research Institute, Cystic Fibrosis Therapeutics Development Network Coordinating Center, Seattle, Washington, United States
| | - Steven M Rowe
- University of Alabama at Birmingham, Medicine, Cystic Fibrosis Center, Birmingham, Alabama, United States
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11
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Mutyam V, Sharma J, Li Y, Peng N, Chen J, Tang LP, Falk Libby E, Singh AK, Conrath K, Rowe SM. Novel Correctors and Potentiators Enhance Translational Readthrough in CFTR Nonsense Mutations. Am J Respir Cell Mol Biol 2021; 64:604-616. [PMID: 33616476 DOI: 10.1165/rcmb.2019-0291oc] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Premature-termination codons (PTCs) in CFTR (cystic fibrosis [CF] transmembrane conductance regulator) result in nonfunctional CFTR protein and are the proximate cause of ∼11% of CF-causing alleles, for which no treatments exist. The CFTR corrector lumacaftor and the potentiator ivacaftor improve CFTR function with terminal PTC mutations and enhance the effect of readthrough agents. Novel correctors GLPG2222 (corrector 1 [C1]), GLPG3221 (corrector 2 [C2]), and potentiator GLPG1837 compare favorably with lumacaftor and ivacaftor in vitro. Here, we evaluated the effect of correctors C1a and C2a (derivatives of C1 and C2) and GLPG1837 alone or in combination with the readthrough compound G418 on CFTR function using heterologous Fischer rat thyroid (FRT) cells, the genetically engineered human bronchial epithelial (HBE) 16HBE14o- cell lines, and primary human cells with PTC mutations. In FRT lines pretreated with G418, GLPG1837 elicited dose-dependent increases in CFTR activity that exceeded those from ivacaftor in FRT-W1282X and FRT-R1162X cells. A three-mechanism strategy consisting of G418, GLPG1837, and two correctors (C1a + C2a) yielded the greatest functional improvements in FRT and 16HBE14o- PTC variants, noting that correction and potentiation without readthrough was sufficient to stimulate CFTR activity for W1282X cells. GLPG1837 + C1a + C2a restored substantial function in G542X/F508del HBE cells and restored even more function for W1282X/F508del cells, largely because of the corrector/potentiator effect, with no additional benefit from G418. In G542X/R553X or R1162X/R1162X organoids, enhanced forskolin-induced swelling was observed with G418 + GLPG1837 + C1a + C2a, although GLPG1837 + C1a + C2a alone was sufficient to improve forskolin-induced swelling in W1282X/W1282X organoids. Combination of CFTR correctors, potentiators, and readthrough compounds augments the functional repair of CFTR nonsense mutations, indicating the potential for novel correctors and potentiators to restore function to truncated W1282X CFTR.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Steven M Rowe
- Department of Medicine.,Department of Pediatrics.,Department of Cell Developmental and Integrative Biology, and.,Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
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12
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Sharma J, Du M, Wong E, Mutyam V, Li Y, Chen J, Wangen J, Thrasher K, Fu L, Peng N, Tang L, Liu K, Mathew B, Bostwick RJ, Augelli-Szafran CE, Bihler H, Liang F, Mahiou J, Saltz J, Rab A, Hong J, Sorscher EJ, Mendenhall EM, Coppola CJ, Keeling KM, Green R, Mense M, Suto MJ, Rowe SM, Bedwell DM. A small molecule that induces translational readthrough of CFTR nonsense mutations by eRF1 depletion. Nat Commun 2021; 12:4358. [PMID: 34272367 PMCID: PMC8285393 DOI: 10.1038/s41467-021-24575-x] [Citation(s) in RCA: 65] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 06/22/2021] [Indexed: 11/09/2022] Open
Abstract
Premature termination codons (PTCs) prevent translation of a full-length protein and trigger nonsense-mediated mRNA decay (NMD). Nonsense suppression (also termed readthrough) therapy restores protein function by selectively suppressing translation termination at PTCs. Poor efficacy of current readthrough agents prompted us to search for better compounds. An NMD-sensitive NanoLuc readthrough reporter was used to screen 771,345 compounds. Among the 180 compounds identified with readthrough activity, SRI-37240 and its more potent derivative SRI-41315, induce a prolonged pause at stop codons and suppress PTCs associated with cystic fibrosis in immortalized and primary human bronchial epithelial cells, restoring CFTR expression and function. SRI-41315 suppresses PTCs by reducing the abundance of the termination factor eRF1. SRI-41315 also potentiates aminoglycoside-mediated readthrough, leading to synergistic increases in CFTR activity. Combining readthrough agents that target distinct components of the translation machinery is a promising treatment strategy for diseases caused by PTCs. Premature termination codons can cause early translation termination and lead to disease. Here the authors perform a screen to identify compounds with readthrough activity and show that these reduce eRF1 levels to suppress premature termination associated with cystic fibrosis.
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Affiliation(s)
- Jyoti Sharma
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Medicine, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Microbiology, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Ming Du
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Eric Wong
- CFFT Lab, Cystic Fibrosis Foundation, Lexington, MA, USA
| | - Venkateshwar Mutyam
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Medicine, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Yao Li
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Medicine, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Jianguo Chen
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Medicine, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Jamie Wangen
- Department of Molecular Biology and Genetics and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Kari Thrasher
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Lianwu Fu
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Ning Peng
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Medicine, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Liping Tang
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Medicine, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Kaimao Liu
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | | | | | | | - Hermann Bihler
- CFFT Lab, Cystic Fibrosis Foundation, Lexington, MA, USA
| | - Feng Liang
- CFFT Lab, Cystic Fibrosis Foundation, Lexington, MA, USA
| | - Jerome Mahiou
- CFFT Lab, Cystic Fibrosis Foundation, Lexington, MA, USA
| | - Josef Saltz
- CFFT Lab, Cystic Fibrosis Foundation, Lexington, MA, USA
| | - Andras Rab
- Department of Pediatrics, Emory University, Atlanta, Georgia
| | - Jeong Hong
- Department of Pediatrics, Emory University, Atlanta, Georgia
| | - Eric J Sorscher
- Department of Pediatrics, Emory University, Atlanta, Georgia
| | - Eric M Mendenhall
- Department of Biological Sciences, The University of Alabama in Huntsville, Huntsville, AL, USA
| | - Candice J Coppola
- Department of Biological Sciences, The University of Alabama in Huntsville, Huntsville, AL, USA
| | - Kim M Keeling
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - Rachel Green
- Department of Molecular Biology and Genetics and Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Martin Mense
- CFFT Lab, Cystic Fibrosis Foundation, Lexington, MA, USA
| | | | - Steven M Rowe
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Medicine, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.,Department of Pediatrics, University of Alabama at Birmingham (UAB), Birmingham, AL, USA
| | - David M Bedwell
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA. .,Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.
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13
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Molecular Insights into Determinants of Translational Readthrough and Implications for Nonsense Suppression Approaches. Int J Mol Sci 2020; 21:ijms21249449. [PMID: 33322589 PMCID: PMC7764779 DOI: 10.3390/ijms21249449] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 11/27/2020] [Accepted: 12/05/2020] [Indexed: 02/07/2023] Open
Abstract
The fidelity of protein synthesis, a process shaped by several mechanisms involving specialized ribosome regions and external factors, ensures the precise reading of sense and stop codons. However, premature termination codons (PTCs) arising from mutations may, at low frequency, be misrecognized and result in PTC suppression, named ribosome readthrough, with production of full-length proteins through the insertion of a subset of amino acids. Since some drugs have been identified as readthrough inducers, this fidelity drawback has been explored as a therapeutic approach in several models of human diseases caused by nonsense mutations. Here, we focus on the mechanisms driving translation in normal and aberrant conditions, the potential fates of mRNA in the presence of a PTC, as well as on the results obtained in the research of efficient readthrough-inducing compounds. In particular, we describe the molecular determinants shaping the outcome of readthrough, namely the nucleotide and protein context, with the latter being pivotal to produce functional full-length proteins. Through the interpretation of experimental and mechanistic findings, mainly obtained in lysosomal and coagulation disorders, we also propose a scenario of potential readthrough-favorable features to achieve relevant rescue profiles, representing the main issue for the potential translatability of readthrough as a therapeutic strategy.
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14
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Peabody Lever JE, Mutyam V, Hathorne HY, Peng N, Sharma J, Edwards LJ, Rowe SM. Ataluren/ivacaftor combination therapy: Two N-of-1 trials in cystic fibrosis patients with nonsense mutations. Pediatr Pulmonol 2020; 55:1838-1842. [PMID: 32281737 PMCID: PMC9125681 DOI: 10.1002/ppul.24764] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 03/05/2020] [Accepted: 03/15/2020] [Indexed: 01/05/2023]
Abstract
Premature termination codons (PTCs) in cystic fibrosis transmembrane conductance regulator (CFTR) produce nonfunctional protein. No approved therapies exist for PTC mutations, including W1282X. We hypothesized that ivacaftor, combined with readthrough therapy, may benefit W1282X patients. Two N-of-1 clinical trials were conducted with ataluren and ivacaftor in various combinations. No meaningful clinical benefit was observed in either patient with ivacaftor alone or ataluren/ivacaftor combination. However, isolated improvements of uncertain significance were noted by a nasal potential difference (NPD) and FEV1 % with ivacaftor in Patient-1 and with ataluren/ivacaftor combination by NPD and body mass index in Patient-2. Drug regimen composed of readthrough agents and potentiators warrant further development for W1282X and other CFTR nonsense mutations.
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Affiliation(s)
- Jacelyn E Peabody Lever
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.,Department of Medicine, Medical Scientist Training Program, University of Alabama at Birmingham, Birmingham, Alabama
| | - Venkateshwar Mutyam
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.,Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Heather Y Hathorne
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.,Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Ning Peng
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jyoti Sharma
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Lloyd J Edwards
- Department of Biostatistics, University of Alabama at Birmingham, Birmingham, Alabama
| | - Steven M Rowe
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.,Department of Medicine, Medical Scientist Training Program, University of Alabama at Birmingham, Birmingham, Alabama.,Department of Medicine, Pediatrics and Cell Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
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15
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Erwood S, Laselva O, Bily TM, Brewer RA, Rutherford AH, Bear CE, Ivakine EA. Allele-Specific Prevention of Nonsense-Mediated Decay in Cystic Fibrosis Using Homology-Independent Genome Editing. Mol Ther Methods Clin Dev 2020; 17:1118-1128. [PMID: 32490033 PMCID: PMC7256445 DOI: 10.1016/j.omtm.2020.05.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 05/07/2020] [Indexed: 02/07/2023]
Abstract
Nonsense-mediated decay (NMD) is a major pathogenic mechanism underlying a diversity of genetic disorders. Nonsense variants tend to lead to more severe disease phenotypes and are often difficult targets for small molecule therapeutic development as a result of insufficient protein production. The treatment of cystic fibrosis (CF), an autosomal recessive disease caused by mutations in the CFTR gene, exemplifies the challenge of therapeutically addressing nonsense mutations in human disease. Therapeutic development in CF has led to multiple, highly successful protein modulatory interventions, yet no targeted therapies have been approved for nonsense mutations. Here, we have designed a CRISPR-Cas9-based strategy for the targeted prevention of NMD of CFTR transcripts containing the second most common nonsense variant listed in CFTR2, W1282X. By introducing a deletion of the downstream genic region following the premature stop codon, we demonstrate significantly increased protein expression of this mutant variant. Notably, in combination with protein modulators, genome editing significantly increases the potentiated channel activity of W1282X-CFTR in human bronchial epithelial cells. Furthermore, we show how the outlined approach can be modified to permit allele-specific editing. The described approach can be extended to other late-occurring nonsense mutations in the CFTR gene or applied as a generalized approach for gene-specific prevention of NMD in disorders where a truncated protein product retains full or partial functionality.
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Affiliation(s)
- Steven Erwood
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Onofrio Laselva
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Teija M.I. Bily
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Reid A. Brewer
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Alexandra H. Rutherford
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Christine E. Bear
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Evgueni A. Ivakine
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
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16
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Sharma J, Keeling KM, Rowe SM. Pharmacological approaches for targeting cystic fibrosis nonsense mutations. Eur J Med Chem 2020; 200:112436. [PMID: 32512483 DOI: 10.1016/j.ejmech.2020.112436] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 05/04/2020] [Accepted: 05/06/2020] [Indexed: 12/11/2022]
Abstract
Cystic fibrosis (CF) is a monogenic autosomal recessive disorder. The clinical manifestations of the disease are caused by ∼2,000 mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) protein. It is unlikely that any one approach will be efficient in correcting all defects. The recent approvals of ivacaftor, lumacaftor/ivacaftor and elexacaftor/tezacaftor/ivacaftor represent the genesis of a new era of precision combination medicine for the CF patient population. In this review, we discuss targeted translational readthrough approaches as mono and combination therapies for CFTR nonsense mutations. We examine the current status of efficacy of translational readthrough/nonsense suppression therapies and their limitations, including non-native amino acid incorporation at PTCs and nonsense-mediated mRNA decay (NMD), along with approaches to tackle these limitations. We further elaborate on combining various therapies such as readthrough agents, NMD inhibitors, and corrector/potentiators to improve the efficacy and safety of suppression therapy. These mutation specific strategies that are directed towards the basic CF defects should positively impact CF patients bearing nonsense mutations.
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Affiliation(s)
- Jyoti Sharma
- Department of Medicine, University of Alabama at Birmingham (UAB), USA; Department of Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), USA
| | - Kim M Keeling
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham (UAB), USA; Department of Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), USA
| | - Steven M Rowe
- Department of Medicine, University of Alabama at Birmingham (UAB), USA; Department of Pediatrics, University of Alabama at Birmingham (UAB), USA; Department of Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), USA.
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17
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Keenan MM, Huang L, Jordan NJ, Wong E, Cheng Y, Valley HC, Mahiou J, Liang F, Bihler H, Mense M, Guo S, Monia BP. Nonsense-mediated RNA Decay Pathway Inhibition Restores Expression and Function of W1282X CFTR. Am J Respir Cell Mol Biol 2020; 61:290-300. [PMID: 30836009 DOI: 10.1165/rcmb.2018-0316oc] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The recessive genetic disease cystic fibrosis (CF) is caused by loss-of-function mutations in the CFTR (CF transmembrane conductance regulator) gene. Approximately 10% of patients with CF have at least one allele with a nonsense mutation in CFTR. Nonsense mutations generate premature termination codons that can subject mRNA transcripts to rapid degradation through the nonsense-mediated mRNA decay (NMD) pathway. Currently, there are no approved therapies that specifically target nonsense mutations in CFTR. Here, we identified antisense oligonucleotides (ASOs) that target the NMD factor SMG1 to inhibit the NMD pathway, and determined their effects on the W1282X CFTR mutation. First, we developed and validated two in vitro models of the W1282X CFTR mutation. Next, we treated these cells with antisense oligonucleotides to inhibit NMD and measured the effects of these treatments on W1282X expression and function. SMG1-ASO-mediated NMD inhibition upregulated the RNA, protein, and surface-localized protein expression of the truncated W1282X gene product. Additionally, these ASOs increased the CFTR chloride channel function in cells homozygous for the W1282X mutation. Our approach suggests a new therapeutic strategy for patients harboring nonsense mutations and may be beneficial as a single agent in patients with CF and the W1282X mutation.
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Affiliation(s)
| | - Lulu Huang
- Ionis Pharmaceuticals, Carlsbad, California; and
| | - Nikole J Jordan
- Cystic Fibrosis Foundation Therapeutics Lab, Cystic Fibrosis Foundation, Lexington, Massachusetts
| | - Eric Wong
- Cystic Fibrosis Foundation Therapeutics Lab, Cystic Fibrosis Foundation, Lexington, Massachusetts
| | - Yi Cheng
- Cystic Fibrosis Foundation Therapeutics Lab, Cystic Fibrosis Foundation, Lexington, Massachusetts
| | - Hillary C Valley
- Cystic Fibrosis Foundation Therapeutics Lab, Cystic Fibrosis Foundation, Lexington, Massachusetts
| | - Jerome Mahiou
- Cystic Fibrosis Foundation Therapeutics Lab, Cystic Fibrosis Foundation, Lexington, Massachusetts
| | - Feng Liang
- Cystic Fibrosis Foundation Therapeutics Lab, Cystic Fibrosis Foundation, Lexington, Massachusetts
| | - Hermann Bihler
- Cystic Fibrosis Foundation Therapeutics Lab, Cystic Fibrosis Foundation, Lexington, Massachusetts
| | - Martin Mense
- Cystic Fibrosis Foundation Therapeutics Lab, Cystic Fibrosis Foundation, Lexington, Massachusetts
| | - Shuling Guo
- Ionis Pharmaceuticals, Carlsbad, California; and
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18
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Laselva O, Eckford PD, Bartlett C, Ouyang H, Gunawardena TN, Gonska T, Moraes TJ, Bear CE. Functional rescue of c.3846G>A (W1282X) in patient-derived nasal cultures achieved by inhibition of nonsense mediated decay and protein modulators with complementary mechanisms of action. J Cyst Fibros 2019; 19:717-727. [PMID: 31831337 DOI: 10.1016/j.jcf.2019.12.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 11/26/2019] [Accepted: 12/02/2019] [Indexed: 10/25/2022]
Abstract
BACKGROUND The nonsense mutation, c.3846G>A (aka: W1282X-CFTR) leads to a truncated transcript that is susceptible to nonsense-mediated decay (NMD) and produces a shorter protein that is unstable and lacks normal channel activity in patient-derived tissues. However, if overexpressed in a heterologous expression system, the truncated mutant protein has been shown to mediate CFTR channel function following the addition of potentiators. In this study, we asked if a quadruple combination of small molecules that together inhibit nonsense mediated decay, stabilize both halves of the mutant protein and potentiate CFTR channel activity could rescue the functional expression of W1282X-CFTR in patient derived nasal cultures. METHODS We identified the CFTR domains stabilized by corrector compounds supplied from AbbVie using a fragment based, biochemical approach. Rescue of the channel function of W1282X.-CFTR protein by NMD inhibition and small molecule protein modulators was studied using a bronchial cell line engineered to express W1282X and in primary nasal epithelial cultures derived from four patients homozygous for this mutation. RESULTS We confirmed previous studies showing that inhibition of NMD using the inhibitor: SMG1i, led to an increased abundance of the shorter transcript in a bronchial cell line. Interestingly, on top of SMG1i, treatment with a combination of two new correctors developed by Galapagos/AbbVie (AC1 and AC2-2, separately targeting either the first or second half of CFTR and promoting assembly, significantly increased the potentiated channel activity by the mutant in the bronchial epithelial cell line and in patient-derived nasal epithelial cultures. The average rescue effect in primary cultures was approximately 50% of the regulated chloride conductance measured in non-CF cultures. CONCLUSIONS These studies provide the first in-vitro evidence in patient derived airway cultures that the functional defects incurred by W1282X, has the potential to be effectively repaired pharmacologically.
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Affiliation(s)
- Onofrio Laselva
- Programme in Molecular Medicine, Hospital for Sick Children Research Institute, Toronto, Canada; Department of Physiology, University of Toronto, Toronto, Canada
| | - Paul Dw Eckford
- Programme in Molecular Medicine, Hospital for Sick Children Research Institute, Toronto, Canada
| | - Claire Bartlett
- Programme in Translational Medicine, Hospital for Sick Children Research Institute, Toronto, Canada
| | - Hong Ouyang
- Programme in Translational Medicine, Hospital for Sick Children Research Institute, Toronto, Canada
| | - Tarini Na Gunawardena
- Programme in Translational Medicine, Hospital for Sick Children Research Institute, Toronto, Canada
| | - Tanja Gonska
- Programme in Translational Medicine, Hospital for Sick Children Research Institute, Toronto, Canada; Department of Paediatrics, University of Toronto, Toronto, Canada
| | - Theo J Moraes
- Programme in Translational Medicine, Hospital for Sick Children Research Institute, Toronto, Canada; Department of Paediatrics, University of Toronto, Toronto, Canada.
| | - Christine E Bear
- Programme in Molecular Medicine, Hospital for Sick Children Research Institute, Toronto, Canada; Department of Physiology, University of Toronto, Toronto, Canada; Department of Biochemistry, University of Toronto, Toronto, Canada.
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19
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Aksit MA, Bowling AD, Evans TA, Joynt AT, Osorio D, Patel S, West N, Merlo C, Sosnay PR, Cutting GR, Sharma N. Decreased mRNA and protein stability of W1282X limits response to modulator therapy. J Cyst Fibros 2019; 18:606-613. [PMID: 30803905 DOI: 10.1016/j.jcf.2019.02.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 02/14/2019] [Accepted: 02/14/2019] [Indexed: 12/13/2022]
Abstract
BACKGROUND Cell-based studies have shown that W1282X generates a truncated protein that can be functionally augmented by modulators. However, modulator treatment of primary cells from individuals who carry two copies of W1282X generates no functional CFTR. To understand the lack of response to modulators, we investigated the effect of W1282X on CFTR RNA transcript levels. METHODS qRT-PCR and RNA-seq were performed on primary nasal epithelial (NE) cells of a previously studied individual who is homozygous for W1282X, her carrier parents and control individuals without nonsense variants in CFTR. RESULTS CFTR RNA bearing W1282X in NE cells shows a steady-state level of 4.2 ± 0.9% of wild-type (WT) CFTR RNA in the mother and 12.4 ± 1.3% in the father. NMDI14, an inhibitor of nonsense-mediated mRNA decay (NMD), restored W1282X mRNA to almost 50% of WT levels in the parental NE cells. RNA-seq of the NE cells homozygous for W1282X showed that CFTR transcript level was reduced to 1.7% of WT (p-value: 4.6e-3). Negligible truncated CFTR protein was generated by Flp-In 293 cells stably expressing the W1282X EMG even though CFTR transcript was well above levels observed in the parents and proband. Finally, we demonstrated that NMD inhibition improved the stability and response to correctors of W1282X-CFTR protein expressed in the Flp-In-293 cells. CONCLUSION These results show that W1282X can cause substantial degradation of CFTR mRNA that has to be addressed before efforts aimed at augmenting CFTR protein function can be effective.
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Affiliation(s)
- M A Aksit
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - A D Bowling
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - T A Evans
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - A T Joynt
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - D Osorio
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - S Patel
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD, United States
| | - N West
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD, United States
| | - C Merlo
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD, United States
| | - P R Sosnay
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD, United States
| | - G R Cutting
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - N Sharma
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States.
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Abstract
Cystic fibrosis (CF) is an autosomal recessive genetic disease caused by variants in the gene encoding the cystic fibrosis transmembrane conduction regulator (CFTR) protein. Loss of CFTR function disrupts chloride, bicarbonate and regulation of sodium transport, producing a cascade of mucus obstruction, inflammation, pulmonary infection, and ultimately damage in numerous organs. Established CF therapies treat the downstream consequences of CFTR dysfunction and have led to steady improvements in patient survival. A class of drugs termed CFTR modulators has recently entered the CF therapeutic landscape. These drugs differ fundamentally from prior therapies in that they aim to improve the function of disease-causing CFTR variants. This review summarizes the science behind CFTR modulators, including their targets, mechanism of action, clinical benefit, and future directions in the field. CFTR modulators have dramatically changed how CF is treated, validated CFTR as a therapeutic target, and opened the door to truly personalized therapies and treatment regimens.
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Affiliation(s)
- John P. Clancy
- Department of PediatricsCincinnati Childrens Hospital Medical CenterCincinnatiOhio
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21
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Phuan PW, Son JH, Tan JA, Li C, Musante I, Zlock L, Nielson DW, Finkbeiner WE, Kurth MJ, Galietta LJ, Haggie PM, Verkman AS. Combination potentiator ('co-potentiator') therapy for CF caused by CFTR mutants, including N1303K, that are poorly responsive to single potentiators. J Cyst Fibros 2018; 17:595-606. [PMID: 29903467 DOI: 10.1016/j.jcf.2018.05.010] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 05/11/2018] [Accepted: 05/15/2018] [Indexed: 10/14/2022]
Abstract
BACKGROUND Current modulator therapies for some cystic fibrosis-causing CFTR mutants, including N1303K, have limited efficacy. We provide evidence here to support combination potentiator (co-potentiator) therapy for mutant CFTRs that are poorly responsive to single potentiators. METHODS Functional synergy screens done on N1303K and W1282X CFTR, in which small molecules were tested with VX-770, identified arylsulfonamide-pyrrolopyridine, phenoxy-benzimidazole and flavone co-potentiators. RESULTS A previously identified arylsulfonamide-pyrrolopyridine co-potentiator (ASP-11) added with VX-770 increased N1303K-CFTR current 7-fold more than VX-770 alone. ASP-11 increased by ~65% of the current of G551D-CFTR compared to VX-770, was additive with VX-770 on F508del-CFTR, and activated wild-type CFTR in the absence of a cAMP agonist. ASP-11 efficacy with VX-770 was demonstrated in primary CF human airway cell cultures having N1303K, W1282X and G551D CFTR mutations. Structure-activity studies on 11 synthesized ASP-11 analogs produced compounds with EC50 down to 0.5 μM. CONCLUSIONS These studies support combination potentiator therapy for CF caused by some CFTR mutations that are not effectively treated by single potentiators.
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Affiliation(s)
- Puay-Wah Phuan
- Department of Medicine, University of California, San Francisco, CA 94143-0521, USA; Department of Physiology, University of California, San Francisco, CA 94143-0521, USA.
| | - Jung-Ho Son
- Department of Chemistry, University of California, Davis, CA 95616-5270, USA
| | - Joseph-Anthony Tan
- Department of Medicine, University of California, San Francisco, CA 94143-0521, USA; Department of Physiology, University of California, San Francisco, CA 94143-0521, USA
| | - Clarabella Li
- Department of Chemistry, University of California, Davis, CA 95616-5270, USA
| | - Ilaria Musante
- Telethon Institute for Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Lorna Zlock
- Department of Pathology University of California, San Francisco, CA 94143-0521, USA
| | - Dennis W Nielson
- Department of Pediatrics, University of California, San Francisco, CA 94143-0521, USA
| | - Walter E Finkbeiner
- Department of Pathology University of California, San Francisco, CA 94143-0521, USA
| | - Mark J Kurth
- Department of Chemistry, University of California, Davis, CA 95616-5270, USA
| | - Luis J Galietta
- Telethon Institute for Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Peter M Haggie
- Department of Medicine, University of California, San Francisco, CA 94143-0521, USA; Department of Physiology, University of California, San Francisco, CA 94143-0521, USA
| | - Alan S Verkman
- Department of Medicine, University of California, San Francisco, CA 94143-0521, USA; Department of Physiology, University of California, San Francisco, CA 94143-0521, USA
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22
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Harutyunyan M, Huang Y, Mun KS, Yang F, Arora K, Naren AP. Personalized medicine in CF: from modulator development to therapy for cystic fibrosis patients with rare CFTR mutations. Am J Physiol Lung Cell Mol Physiol 2017; 314:L529-L543. [PMID: 29351449 DOI: 10.1152/ajplung.00465.2017] [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] [Indexed: 02/08/2023] Open
Abstract
Cystic fibrosis (CF) is the most common life-shortening genetic disease affecting ~1 in 3,500 of the Caucasian population. CF is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. To date, more than 2,000 CFTR mutations have been identified, which produce a wide range of phenotypes. The CFTR protein, a chloride channel, is normally expressed on epithelial cells lining the lung, gut, and exocrine glands. Mutations in CFTR have led to pleiotropic effects in CF patients and have resulted in early morbidity and mortality. Research has focused on identifying small molecules, or modulators, that can restore CFTR function. In recent years, two modulators, ivacaftor (Kalydeco) and lumacaftor/ivacaftor (Orkambi), have been approved by the U.S. Food and Drug Administration to treat CF patients with certain CFTR mutations. The development of these modulators has served as proof-of-concept that targeting CFTR by modulators is a viable therapeutic option. Efforts to discover new modulators that could deliver a wider and greater clinical benefit are still ongoing. However, traditional randomized controlled trials (RCTs) require large numbers of patients and become impracticable to test the modulators' efficacy in CF patients with CFTR mutations at frequencies much lower than 1%, suggesting the need for personalized medicine in these CF patients.
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Affiliation(s)
- Misak Harutyunyan
- Department of Physiology, University of Cincinnati , Cincinnati, Ohio
| | - Yunjie Huang
- Division of Pulmonary Medicine, Department of Pediatrics, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio
| | - Kyu-Shik Mun
- Division of Pulmonary Medicine, Department of Pediatrics, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio
| | - Fanmuyi Yang
- Division of Pulmonary Medicine, Department of Pediatrics, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio
| | - Kavisha Arora
- Division of Pulmonary Medicine, Department of Pediatrics, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio
| | - Anjaparavanda P Naren
- Division of Pulmonary Medicine, Department of Pediatrics, Cincinnati Children's Hospital Medical Center , Cincinnati, Ohio
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23
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Luddi A, Crifasi L, Capaldo A, Piomboni P, Costantino-Ceccarini E. Suppression of galactocerebrosidase premature termination codon and rescue of galactocerebrosidase activity in twitcher cells. J Neurosci Res 2017; 94:1273-83. [PMID: 27638609 DOI: 10.1002/jnr.23790] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 05/06/2016] [Accepted: 05/23/2016] [Indexed: 11/10/2022]
Abstract
Krabbe's disease (KD) is a degenerative lysosomal storage disease resulting from deficiency of β-galactocerebrosidase activity. Over 100 mutations are known to cause the disease, and these usually occur in compound heterozygote patterns. In affected patients, nonsense mutations leading to a nonfunctional enzyme are often found associated with other mutations. The twitcher mouse is a naturally occurring model of KD, containing in β-galactocerebrosidase a premature stop codon, W339X. Recent studies have shown that selected compounds may induce the ribosomal bypass of premature stop codons without affecting the normal termination codons. The rescue of β-galactocerebrosidase activity induced by treatment with premature termination codon (PTC) 124, a well-characterized compound known to induce ribosomal read-through, was investigated on oligodendrocytes prepared from twitcher mice and on human fibroblasts from patients bearing nonsense mutations. The effectiveness of the nonsense-mediated mRNA decay (NMD) inhibitor 1 (NMDI1), a newly identified inhibitor of NMD, was also tested. Incubation of these cell lines with PTC124 and NMDI1 increased the levels of mRNA and rescued galactocerebrosidase enzymatic activity in a dose-dependent manner. The low but sustained expression of β-galactocerebrosidase in oligodendrocytes was sufficient to improve the morphology of the differentiated cells. Our in vitro approach provides the basis for further investigation of ribosomal read-through as an alternative therapeutic strategy to ameliorate the quality of life in selected KD patients. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Alice Luddi
- Department of Molecular and Developmental Medicine, Siena University, Siena, Italy.
| | - Laura Crifasi
- Department of Molecular and Developmental Medicine, Siena University, Siena, Italy
| | - Angela Capaldo
- Department of Molecular and Developmental Medicine, Siena University, Siena, Italy
| | - Paola Piomboni
- Department of Molecular and Developmental Medicine, Siena University, Siena, Italy
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Xue X, Mutyam V, Thakerar A, Mobley J, Bridges RJ, Rowe SM, Keeling KM, Bedwell DM. Identification of the amino acids inserted during suppression of CFTR nonsense mutations and determination of their functional consequences. Hum Mol Genet 2017; 26:3116-3129. [PMID: 28575328 PMCID: PMC5886253 DOI: 10.1093/hmg/ddx196] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 04/14/2017] [Accepted: 05/17/2017] [Indexed: 11/13/2022] Open
Abstract
In-frame premature termination codons (PTCs) account for ∼11% of all disease-associated mutations. PTC suppression therapy utilizes small molecules that suppress translation termination at a PTC to restore synthesis of a full-length protein. PTC suppression is mediated by the base pairing of a near-cognate aminoacyl-tRNA with a PTC and subsequently, the amino acid becomes incorporated into the nascent polypeptide at the site of the PTC. However, little is known about the identity of the amino acid(s) inserted at a PTC during this process in mammalian cells, or how the surrounding sequence context influences amino acid incorporation. Here, we determined the amino acids inserted at the cystic fibrosis transmembrane conductance regulator (CFTR) W1282X PTC (a UGA codon) in the context of its three upstream and downstream CFTR codons during G418-mediated suppression. We found that leucine, cysteine and tryptophan are inserted during W1282X suppression. Interestingly, these amino acids (and their proportions) are significantly different from those recently identified following G418-mediated suppression of the CFTR G542X UGA mutation. These results demonstrate for the first time that local mRNA sequence context plays a key role in near-cognate aminoacyl-tRNA selection during PTC suppression. We also found that some variant CFTR proteins generated by PTC suppression exhibit reduced maturation and activity, indicating the complexity of nonsense suppression therapy. However, both a CFTR corrector and potentiator enhanced activity of protein variants generated by G418-mediated suppression. These results suggest that PTC suppression in combination with CFTR modulators may be beneficial for the treatment of CF patients with PTCs.
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Affiliation(s)
- Xiaojiao Xue
- Department of Biochemistry and Molecular Genetics
- Gregory Fleming James Cystic Fibrosis Research Center
| | - Venkateshwar Mutyam
- Gregory Fleming James Cystic Fibrosis Research Center
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Amita Thakerar
- Department of Physiology and Biophysics, Chicago Medical School, North Chicago, IL 60064, USA
| | - James Mobley
- Department of Surgery, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Robert J. Bridges
- Department of Physiology and Biophysics, Chicago Medical School, North Chicago, IL 60064, USA
| | - Steven M. Rowe
- Gregory Fleming James Cystic Fibrosis Research Center
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Kim M. Keeling
- Department of Biochemistry and Molecular Genetics
- Gregory Fleming James Cystic Fibrosis Research Center
| | - David M. Bedwell
- Department of Biochemistry and Molecular Genetics
- Gregory Fleming James Cystic Fibrosis Research Center
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25
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Mutyam V, Libby EF, Peng N, Hadjiliadis D, Bonk M, Solomon GM, Rowe SM. Therapeutic benefit observed with the CFTR potentiator, ivacaftor, in a CF patient homozygous for the W1282X CFTR nonsense mutation. J Cyst Fibros 2017; 16:24-29. [PMID: 27707539 PMCID: PMC5241185 DOI: 10.1016/j.jcf.2016.09.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 08/29/2016] [Accepted: 09/15/2016] [Indexed: 12/23/2022]
Abstract
Premature termination codons (PTCs) in cystic fibrosis transmembrane conductance regulator (CFTR) gene result in nonfunctional CFTR protein and are the proximate cause of ~11% of CF causing alleles. Aminoglycosides and other novel agents are known to induce translational readthrough of PTCs, a potential therapeutic approach. Among PTCs, W1282X CFTR is unique, as it is a C-terminal CFTR mutation that can exhibit partial activity, even in the truncated state. The potentiator ivacaftor (VX-770) is approved for treating CF patients with G551D and other gating mutations. Based on previous studies demonstrating the beneficial effect of ivacaftor for PTC mutations following readthrough in vitro, we hypothesized that ivacaftor may enhance CFTR activity in CF patients expressing W1282X CFTR, and could be further enhanced by readthrough. Ivacaftor significantly increased CFTR activity in W1282X-expressing cells compared to R1162X CFTR cells, and was further enhanced by readthrough with the aminoglycoside G418. Primary nasal epithelial cells from a W1282X homozygous patient showed improved CFTR function in the presence of ivacaftor. Upon ivacaftor administration to the same patient, there was significant improvement in pulmonary exacerbation frequency, BMI, and insulin requirement, whereas FEV1 remained stable over 3years. These studies suggest that ivacaftor may have moderate clinical benefit in patients with preserved expression of the W1282X CFTR mutation by stimulating residual activity of the truncated protein, suggesting the need for further studies including the addition of efficacious readthrough agents.
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Affiliation(s)
- Venkateshwar Mutyam
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Emily Falk Libby
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Ning Peng
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Denis Hadjiliadis
- Department of Medicine, University of Pennsylvania Medical Center, PA, USA
| | - Michael Bonk
- Department of Medicine, University of Pennsylvania Medical Center, PA, USA
| | - George M Solomon
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA; Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Steven M Rowe
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA; Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA; Department of Cell Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA; Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL, USA.
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27
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Haggie PM, Phuan PW, Tan JA, Xu H, Avramescu RG, Perdomo D, Zlock L, Nielson DW, Finkbeiner WE, Lukacs GL, Verkman AS. Correctors and Potentiators Rescue Function of the Truncated W1282X-Cystic Fibrosis Transmembrane Regulator (CFTR) Translation Product. J Biol Chem 2016; 292:771-785. [PMID: 27895116 DOI: 10.1074/jbc.m116.764720] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 11/22/2016] [Indexed: 11/06/2022] Open
Abstract
W1282X is the fifth most common cystic fibrosis transmembrane regulator (CFTR) mutation that causes cystic fibrosis. Here, we investigated the utility of a small molecule corrector/potentiator strategy, as used for ΔF508-CFTR, to produce functional rescue of the truncated translation product of the W1282X mutation, CFTR1281, without the need for read-through. In transfected cell systems, certain potentiators and correctors, including VX-809 and VX-770, increased CFTR1281 activity. To identify novel correctors and potentiators with potentially greater efficacy on CFTR1281, functional screens were done of ∼30,000 synthetic small molecules and drugs/nutraceuticals in CFTR1281-transfected cells. Corrector scaffolds of 1-arylpyrazole-4-arylsulfonyl-piperazine and spiro-piperidine-quinazolinone classes were identified with up to ∼5-fold greater efficacy than VX-809, some of which were selective for CFTR1281, whereas others also corrected ΔF508-CFTR. Several novel potentiator scaffolds were identified with efficacy comparable with VX-770; remarkably, a phenylsulfonamide-pyrrolopyridine acted synergistically with VX-770 to increase CFTR1281 function ∼8-fold over that of VX-770 alone, normalizing CFTR1281 channel activity to that of wild type CFTR. Corrector and potentiator combinations were tested in primary cultures and conditionally reprogrammed cells generated from nasal brushings from one W1282X homozygous subject. Although robust chloride conductance was seen with correctors and potentiators in homozygous ΔF508 cells, increased chloride conductance was not found in W1282X cells despite the presence of adequate transcript levels. Notwithstanding the negative data in W1282X cells from one human subject, we speculate that corrector and potentiator combinations may have therapeutic efficacy in cystic fibrosis caused by the W1282X mutation, although additional studies are needed on human cells from W1282X subjects.
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Affiliation(s)
| | | | | | - Haijin Xu
- the Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Radu G Avramescu
- the Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Doranda Perdomo
- the Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | | | - Dennis W Nielson
- Pediatrics, University of California, San Francisco, California 94143-0521 and
| | | | - Gergely L Lukacs
- the Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
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28
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Ruwald MH, Xu Parks X, Moss AJ, Zareba W, Baman J, McNitt S, Kanters JK, Shimizu W, Wilde AA, Jons C, Lopes CM. Stop-codon and C-terminal nonsense mutations are associated with a lower risk of cardiac events in patients with long QT syndrome type 1. Heart Rhythm 2015; 13:122-31. [PMID: 26318259 DOI: 10.1016/j.hrthm.2015.08.033] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND In long QT syndrome type 1 (LQT1), the location and type of mutations have been shown to affect the clinical outcome. Although haploinsufficiency, including stop-codon and frameshift mutations, has been associated with a lower risk of cardiac events in patients with LQT1, nonsense mutations have been presumed functionally equivalent. OBJECTIVE The purpose of this study was to evaluate clinical differences between patients with nonsense mutations. METHODS The study sample comprised 1090 patients with genetically confirmed mutations. Patients were categorized into 5 groups, depending on mutation type and location: missense not located in the high-risk cytoplasmic loop (c-loop) (n = 698), which is used as reference; missense c-loop (n = 192); stop-codon (n = 67); frameshift (n = 39); and others (n = 94). The primary outcome was a composite end point of syncope, aborted cardiac arrest, and long QT syndrome-related death (cardiac events). Outcomes were evaluated using the multivariate Cox proportional hazards regression analysis. Standard patch clamp techniques were used. RESULTS Compared to patients with missense non-c-loop mutations, the risk of cardiac events was reduced significantly in patients with stop-codon mutations (hazard ratio [HR] 0.57; 95% confidence interval [CI] 0.34-0.96; P = .035), but not in patients with frameshift mutations (HR 1.01; 95% CI 0.58-1.77; P = .97). Our data suggest that currents of the most common stop-codon mutant channel (Q530X) were larger than those of haploinsufficient channels (wild type: 42 ± 6 pA/pF, n = 20; Q530X+wild type: 79 ± 14 pA/pF, n = 20; P < .05) and voltage dependence of activation was altered. CONCLUSION Stop-codon mutations are associated with a lower risk of cardiac events in patients with LQT1, while frameshift mutations are associated with the same risk as the majority of the missense mutations. Our data indicate functional differences between these previously considered equivalent mutation subtypes.
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Affiliation(s)
- Martin H Ruwald
- Heart Research Follow-up Program, Division of Cardiology, University of Rochester Medical Center, Rochester, New York; Department of Cardiology, Gentofte Hospital, Hellerup, Denmark
| | - Xiaorong Xu Parks
- Cardiovascular Research Institute, Department of Medicine, University of Rochester, Rochester, New York
| | - Arthur J Moss
- Heart Research Follow-up Program, Division of Cardiology, University of Rochester Medical Center, Rochester, New York
| | - Wojciech Zareba
- Heart Research Follow-up Program, Division of Cardiology, University of Rochester Medical Center, Rochester, New York
| | - Jayson Baman
- Heart Research Follow-up Program, Division of Cardiology, University of Rochester Medical Center, Rochester, New York
| | - Scott McNitt
- Heart Research Follow-up Program, Division of Cardiology, University of Rochester Medical Center, Rochester, New York
| | - Jorgen K Kanters
- Department of Cardiology, Gentofte Hospital, Hellerup, Denmark; Laboratory of Experimental Cardiology, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Wataru Shimizu
- Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan
| | - Arthur A Wilde
- AMC Heart Centre, Department of Clinical and Experimental Cardiology, Academic Medical Centre, Amsterdam, The Netherlands
| | - Christian Jons
- Department of Cardiology, Gentofte Hospital, Hellerup, Denmark
| | - Coeli M Lopes
- Cardiovascular Research Institute, Department of Medicine, University of Rochester, Rochester, New York.
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Oren YS, McClure ML, Rowe SM, Sorscher EJ, Bester AC, Manor M, Kerem E, Rivlin J, Zahdeh F, Mann M, Geiger T, Kerem B. The unfolded protein response affects readthrough of premature termination codons. EMBO Mol Med 2014; 6:685-701. [PMID: 24705877 PMCID: PMC4023889 DOI: 10.1002/emmm.201303347] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
One-third of monogenic inherited diseases result from premature termination codons (PTCs). Readthrough of in-frame PTCs enables synthesis of full-length functional proteins. However, extended variability in the response to readthrough treatment is found among patients, which correlates with the level of nonsense transcripts. Here, we aimed to reveal cellular pathways affecting this inter-patient variability. We show that activation of the unfolded protein response (UPR) governs the response to readthrough treatment by regulating the levels of transcripts carrying PTCs. Quantitative proteomic analyses showed substantial differences in UPR activation between patients carrying PTCs, correlating with their response. We further found a significant inverse correlation between the UPR and nonsense-mediated mRNA decay (NMD), suggesting a feedback loop between these homeostatic pathways. We uncovered and characterized the mechanism underlying this NMD-UPR feedback loop, which augments both UPR activation and NMD attenuation. Importantly, this feedback loop enhances the response to readthrough treatment, highlighting its clinical importance. Altogether, our study demonstrates the importance of the UPR and its regulatory network for genetic diseases caused by PTCs and for cell homeostasis under normal conditions.
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Affiliation(s)
- Yifat S Oren
- Department of Genetics, The Hebrew University, Jerusalem, Israel
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Fosso MY, Li Y, Garneau-Tsodikova S. New trends in aminoglycosides use. MEDCHEMCOMM 2014; 5:1075-1091. [PMID: 25071928 PMCID: PMC4111210 DOI: 10.1039/c4md00163j] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Despite their inherent toxicity and the acquired bacterial resistance that continuously threaten their long-term clinical use, aminoglycosides (AGs) still remain valuable components of the antibiotic armamentarium. Recent literature shows that the AGs' role has been further expanded as multi-tasking players in different areas of study. This review aims at presenting some of the new trends observed in the use of AGs in the past decade, along with the current understanding of their mechanisms of action in various bacterial and eukaryotic cellular processes.
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Affiliation(s)
- Marina Y. Fosso
- University of Kentucky, Department of Pharmaceutical Sciences, College of Pharmacy, BioPharm Complex, Room 423, 789 South Limestone Street, Lexington, KY, 40536-0596, U.S.A
| | - Yijia Li
- University of Kentucky, Department of Pharmaceutical Sciences, College of Pharmacy, BioPharm Complex, Room 423, 789 South Limestone Street, Lexington, KY, 40536-0596, U.S.A
| | - Sylvie Garneau-Tsodikova
- University of Kentucky, Department of Pharmaceutical Sciences, College of Pharmacy, BioPharm Complex, Room 423, 789 South Limestone Street, Lexington, KY, 40536-0596, U.S.A
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Xue X, Mutyam V, Tang L, Biswas S, Du M, Jackson LA, Dai Y, Belakhov V, Shalev M, Chen F, Schacht J, J Bridges R, Baasov T, Hong J, Bedwell DM, Rowe SM. Synthetic aminoglycosides efficiently suppress cystic fibrosis transmembrane conductance regulator nonsense mutations and are enhanced by ivacaftor. Am J Respir Cell Mol Biol 2014; 50:805-16. [PMID: 24251786 DOI: 10.1165/rcmb.2013-0282oc] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
New drugs are needed to enhance premature termination codon (PTC) suppression to treat the underlying cause of cystic fibrosis (CF) and other diseases caused by nonsense mutations. We tested new synthetic aminoglycoside derivatives expressly developed for PTC suppression in a series of complementary CF models. Using a dual-luciferase reporter system containing the four most prevalent CF transmembrane conductance regulator (CFTR) nonsense mutations (G542X, R553X, R1162X, and W1282X) within their local sequence contexts (the three codons on either side of the PTC), we found that NB124 promoted the most readthrough of G542X, R1162X, and W1282X PTCs. NB124 also restored full-length CFTR expression and chloride transport in Fischer rat thyroid cells stably transduced with a CFTR-G542XcDNA transgene, and was superior to gentamicin and other aminoglycosides tested. NB124 restored CFTR function to roughly 7% of wild-type activity in primary human bronchial epithelial (HBE) CF cells (G542X/delF508), a highly relevant preclinical model with endogenous CFTR expression. Efficacy was further enhanced by addition of the CFTR potentiator, ivacaftor (VX-770), to airway cells expressing CFTR PTCs. NB124 treatment rescued CFTR function in a CF mouse model expressing a human CFTR-G542X transgene; efficacy was superior to gentamicin and exhibited favorable pharmacokinetic properties, suggesting that in vitro results translated to clinical benefit in vivo. NB124 was also less cytotoxic than gentamicin in a tissue-based model for ototoxicity. These results provide evidence that NB124 and other synthetic aminoglycosides provide a 10-fold improvement in therapeutic index over gentamicin and other first-generation aminoglycosides, providing a promising treatment for a wide array of CFTR nonsense mutations.
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Nonsense-mediated decay in genetic disease: friend or foe? MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2014; 762:52-64. [PMID: 25485595 DOI: 10.1016/j.mrrev.2014.05.001] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 05/02/2014] [Accepted: 05/03/2014] [Indexed: 12/11/2022]
Abstract
Eukaryotic cells utilize various RNA quality control mechanisms to ensure high fidelity of gene expression, thus protecting against the accumulation of nonfunctional RNA and the subsequent production of abnormal peptides. Messenger RNAs (mRNAs) are largely responsible for protein production, and mRNA quality control is particularly important for protecting the cell against the downstream effects of genetic mutations. Nonsense-mediated decay (NMD) is an evolutionarily conserved mRNA quality control system in all eukaryotes that degrades transcripts containing premature termination codons (PTCs). By degrading these aberrant transcripts, NMD acts to prevent the production of truncated proteins that could otherwise harm the cell through various insults, such as dominant negative effects or the ER stress response. Although NMD functions to protect the cell against the deleterious effects of aberrant mRNA, there is a growing body of evidence that mutation-, codon-, gene-, cell-, and tissue-specific differences in NMD efficiency can alter the underlying pathology of genetic disease. In addition, the protective role that NMD plays in genetic disease can undermine current therapeutic strategies aimed at increasing the production of full-length functional protein from genes harboring nonsense mutations. Here, we review the normal function of this RNA surveillance pathway and how it is regulated, provide current evidence for the role that it plays in modulating genetic disease phenotypes, and how NMD can be used as a therapeutic target.
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Dransfield MT, Wilhelm AM, Flanagan B, Courville C, Tidwell SL, Raju SV, Gaggar A, Steele C, Tang LP, Liu B, Rowe SM. Acquired cystic fibrosis transmembrane conductance regulator dysfunction in the lower airways in COPD. Chest 2014; 144:498-506. [PMID: 23538783 DOI: 10.1378/chest.13-0274] [Citation(s) in RCA: 145] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Cigarette smoke and smoking-induced inflammation decrease cystic fibrosis transmembrane conductance regulator (CFTR) activity and mucociliary transport in the nasal airway and cultured bronchial epithelial cells. This raises the possibility that lower airway CFTR dysfunction may contribute to the pathophysiology of COPD. We compared lower airway CFTR activity in current and former smokers with COPD, current smokers without COPD, and lifelong nonsmokers to examine the relationships between clinical characteristics and CFTR expression and function. METHODS Demographic, spirometry, and symptom questionnaire data were collected. CFTR activity was determined by nasal potential difference (NPD) and lower airway potential difference (LAPD) assays. The primary measure of CFTR function was the total change in chloride transport (Δchloride-free isoproterenol). CFTR protein expression in endobronchial biopsy specimens was measured by Western blot. RESULTS Compared with healthy nonsmokers (n = 11), current smokers (n = 17) showed a significant reduction in LAPD CFTR activity (Δchloride-free isoproterenol, -8.70 mV vs -15.9 mV; P = .003). Similar reductions were observed in smokers with and without COPD. Former smokers with COPD (n = 7) showed a nonsignificant reduction in chloride conductance (-12.7 mV). A similar pattern was observed for CFTR protein expression. Univariate analysis demonstrated correlations between LAPD CFTR activity and current smoking, the presence of chronic bronchitis, and dyspnea scores. CONCLUSIONS Smokers with and without COPD have reduced lower airway CFTR activity compared with healthy nonsmokers, and this finding correlates with disease phenotype. Acquired CFTR dysfunction may contribute to COPD pathogenesis.
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Affiliation(s)
- Mark T Dransfield
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL; Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL.
| | - Andrew M Wilhelm
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL
| | - Brian Flanagan
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
| | - Clifford Courville
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
| | - Sherry L Tidwell
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL; Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - S Vamsee Raju
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL; Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - Amit Gaggar
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL; Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - Chad Steele
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL; Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - Li Ping Tang
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - Bo Liu
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
| | - Steven M Rowe
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL; UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, AL; Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL
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Chaaban MR, Kejner A, Rowe SM, Woodworth BA. Cystic fibrosis chronic rhinosinusitis: a comprehensive review. Am J Rhinol Allergy 2013; 27:387-95. [PMID: 24119602 PMCID: PMC3899543 DOI: 10.2500/ajra.2013.27.3919] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Advances in the care of patients with cystic fibrosis (CF) have improved pulmonary outcomes and survival. In addition, rapid developments regarding the underlying genetic and molecular basis of the disease have led to numerous novel targets for treatment. However, clinical and basic scientific research focusing on therapeutic strategies for CF-associated chronic rhinosinusitis (CRS) lags behind the evidence-based approaches currently used for pulmonary disease. METHODS This review evaluates the available literature and provides an update concerning the pathophysiology, current treatment approaches, and future pharmaceutical tactics in the management of CRS in patients with CF. RESULTS Optimal medical and surgical strategies for CF CRS are lacking because of a dearth of well-performed clinical trials. Medical and surgical interventions are supported primarily by level 2 or 3 evidence and are aimed at improving clearance of mucus, infection, and inflammation. A number of novel therapeutics that target the basic defect in the cystic fibrosis transmembrane conductance regulator channel are currently under investigation. Ivacaftor, a corrector of the G551D mutation, was recently approved by the Food and Drug Administration. However, sinonasal outcomes using this and other novel drugs are pending. CONCLUSION CRS is a lifelong disease in CF patients that can lead to substantial morbidity and decreased quality of life. A multidisciplinary approach will be necessary to develop consistent and evidence-based treatment paradigms.
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Affiliation(s)
| | | | - Steven M. Rowe
- Medicine, and
- the Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Bradford A. Woodworth
- From the Departments of Surgery/Division of Otolaryngology and
- the Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
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Cho HY, Lee BH, Cheong HI. Translational read-through of a nonsense mutation causing Bartter syndrome. J Korean Med Sci 2013; 28:821-6. [PMID: 23772144 PMCID: PMC3677996 DOI: 10.3346/jkms.2013.28.6.821] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 04/11/2013] [Indexed: 11/20/2022] Open
Abstract
Bartter syndrome (BS) is classified into 5 genotypes according to underlying mutant genes and BS III is caused by loss-of-function mutations in the CLCNKB gene encoding for basolateral ClC-Kb. BS III is the most common genotype in Korean patients with BS and W610X is the most common CLCNKB mutation in Korean BS III. In this study, we tested the hypothesis that the CLCNKB W610X mutation can be rescued in vitro using aminoglycoside antibiotics, which are known to induce translational read-through of a nonsense mutation. The CLCNKB cDNA was cloned into a eukaryotic expression vector and the W610X nonsense mutation was generated by site-directed mutagenesis. Cultured polarized MDCK cells were transfected with the vectors, and the read-through was induced using an aminoglycoside derivative, G418. Cellular expression of the target protein was monitored via immunohistochemistry. While cells transfected with the mutant CLCNKB failed to express ClC-Kb, G418 treatment of the cells induced the full-length protein expression, which was localized to the basolateral plasma membranes. It is demonstrated that the W610X mutation in CLCNKB can be a good candidate for trial of translational read-through induction as a therapeutic modality.
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Affiliation(s)
- Hee Yeon Cho
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Beom Hee Lee
- Department of Pediatrics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
| | - Hae Il Cheong
- Department of Pediatrics, Seoul National University Children's Hospital, Seoul, Korea
- Research Coordination Center for Rare Diseases, Seoul National University Hospital, Seoul, Korea
- Kidney Research Institute, Medical Research Center, Seoul National University College of Medicine, Seoul, Korea
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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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Leonard A, Leal T, Lebecque P. [Mucoviscidosis: CFTR mutation-specific therapy: a ray of sunshine in a cloudy sky]. Arch Pediatr 2012. [PMID: 23199563 DOI: 10.1016/j.arcped.2012.10.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
There is a need to find a cure for pulmonary disease in cystic fibrosis (CF), though full benefit of this approach will be restricted to those patients with well-preserved lungs. The most promising route is currently that of a pharmacological mutation-specific approach aiming at correcting the mechanism by which mutations lead to impairment of chloride conductance across respiratory epithelial cells. In the past 14years, 7 candidate drugs (CPX, 4PBA, gentamicin, PTC124, VX-770 or Ivacaftor, VX-809 or Lumacaftor, and Miglustat) have been investigated in CF patients. A postulate of 14 out of the 15 published studies has been that an effective agent had to improve total chloride secretion as assessed in vivo by nasal potential difference measurements. The present review casts a critical look at these studies. Apparent inconsistencies are discussed as well as possible limitations of nasal potential difference measurements as outcome parameters in these trials. Primarily targeting a mutation carried by less than 2% of French CF patients, the 2 Ivacaftor studies could well be a milestone on the long road toward a cure for CF. However, further data on safety and long-term efficacy are obviously needed and the current price of this medication in the US would make it unaffordable for European patients.
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Affiliation(s)
- A Leonard
- Unité de pneumologie pédiatrique et mucoviscidose, cliniques Saint-Luc, université de Louvain, Bruxelles, Belgique.
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Lee HLR, Dougherty JP. Pharmaceutical therapies to recode nonsense mutations in inherited diseases. Pharmacol Ther 2012; 136:227-66. [PMID: 22820013 DOI: 10.1016/j.pharmthera.2012.07.007] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/12/2012] [Indexed: 12/21/2022]
Abstract
Nonsense codons, generated from nonsense mutations or frameshifts, contribute significantly to the spectrum of inherited human diseases such as cystic fibrosis, Duchenne muscular dystrophy, hemophilia, spinal muscular atrophy, and many forms of cancer. The presence of a mutant nonsense codon results in premature termination to preclude the synthesis of a full-length protein and leads to aberrations in gene expression. Suppression therapy to recode a premature termination codon with an amino acid allowing readthrough to rescue the production of a full-length protein presents a promising strategy for treatment of patients suffering from debilitating nonsense-mediated disorders. Suppression therapy using aminoglycosides to promote readthrough in vitro have been known since the sixties. Recent progress in the field of recoding via pharmaceuticals has led to the continuous discovery and development of several pharmacological agents with nonsense suppression activities. Here, we review the mechanisms that are involved in discriminating normal versus premature termination codons, the factors involved in readthrough efficiency, the epidemiology of several well-known nonsense-mediated diseases, and the various pharmacological agents (aminoglycoside and non-aminoglycoside compounds) that are currently being employed in nonsense suppression therapy studies. We also discuss how these therapeutic agents can be used to regulate gene expression for gene therapy applications.
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Affiliation(s)
- Hui-Ling Rose Lee
- Department of Molecular Genetics, Microbiology, and Immunology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, NJ, USA
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Sloane PA, Shastry S, Wilhelm A, Courville C, Tang LP, Backer K, Levin E, Raju SV, Li Y, Mazur M, Byan-Parker S, Grizzle W, Sorscher EJ, Dransfield MT, Rowe SM. A pharmacologic approach to acquired cystic fibrosis transmembrane conductance regulator dysfunction in smoking related lung disease. PLoS One 2012; 7:e39809. [PMID: 22768130 PMCID: PMC3387224 DOI: 10.1371/journal.pone.0039809] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 05/27/2012] [Indexed: 01/08/2023] Open
Abstract
Background Mucus stasis in chronic obstructive pulmonary disease (COPD) is a significant contributor to morbidity and mortality. Potentiators of cystic fibrosis transmembrane conductance regulator (CFTR) activity pharmacologically enhance CFTR function; ivacaftor is one such agent approved to treat CF patients with the G551D-CFTR gating mutation. CFTR potentiators may also be useful for other diseases of mucus stasis, including COPD. Methods and Findings In primary human bronchial epithelial cells, exposure to cigarette smoke extract diminished CFTR-mediated anion transport (65.8±0.2% of control, P<0.005) and mucociliary transport (0.17±0.05 µm/sec vs. 2.4±0.47 µm/sec control, P<0.05) by reducing airway surface liquid depth (7.3±0.6 µm vs. 13.0±0.6 µm control, P<0.005) and augmenting mucus expression (by 64%, P<0.05) without altering transepithelial resistance. Smokers with or without COPD had reduced CFTR activity measured by nasal potential difference compared to age-matched non-smokers (−6.3±1.4 and −8.0±2.0 mV, respectively vs. −15.2±2.7 mV control, each P<0.005, n = 12–14/group); this CFTR decrement was associated with symptoms of chronic bronchitis as measured by the Breathlessness Cough and Sputum Score (r = 0.30, P<0.05) despite controlling for smoking (r = 0.31, P<0.05). Ivacaftor activated CFTR-dependent chloride transport in non-CF epithelia and ameliorated the functional CFTR defect induced by smoke to 185±36% of non-CF control (P<0.05), thereby increasing airway surface liquid (from 7.3±0.6 µm to 10.1±0.4 µm, P<0.005) and mucociliary transport (from 0.27±0.11 µm/s to 2.7±0.28 µm/s, P<0.005). Conclusions Cigarette smoking reduces CFTR activity and is causally related to reduced mucus transport in smokers due to inhibition of CFTR dependent fluid transport. These effects are reversible by the CFTR potentiator ivacaftor, representing a potential therapeutic strategy to augment mucociliary clearance in patients with smoking related lung disease.
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Affiliation(s)
- Peter A. Sloane
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Suresh Shastry
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Andrew Wilhelm
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Clifford Courville
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Li Ping Tang
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Kyle Backer
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Elina Levin
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - S. Vamsee Raju
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Yao Li
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Marina Mazur
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Suzanne Byan-Parker
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - William Grizzle
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Eric J. Sorscher
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Mark T. Dransfield
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Steven M. Rowe
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- UAB Lung Health Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- * E-mail:
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Cystic fibrosis: insight into CFTR pathophysiology and pharmacotherapy. Clin Biochem 2012; 45:1132-44. [PMID: 22698459 DOI: 10.1016/j.clinbiochem.2012.05.034] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Revised: 05/15/2012] [Accepted: 05/28/2012] [Indexed: 12/14/2022]
Abstract
Cystic fibrosis is the most common life-threatening recessively inherited disease in Caucasians. Due to early provision of care in specialized reference centers and more comprehensive care, survival has improved over time. Despite great advances in supportive care and in our understanding of its pathophysiology, there is still no cure for the disease. Therapeutic strategies aimed at rescuing the abnormal protein are either being sought after or under investigation. This review highlights salient insights into pathophysiology and candidate molecules suitable for CFTR pharmacotherapy. Clinical trials using Ataluren, VX-809 and ivacaftor have provided encouraging data. Preclinical data with inhibitors of phosphodiesterase type 5, such as sildenafil and analogs, have highlighted their potential for CFTR pharmacotherapy. Because sildenafil and analogs are in clinical use for other clinical applications, research on this class of drugs might speed up the development of new therapies for CF.
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McClure M, DeLucas LJ, Wilson L, Ray M, Rowe SM, Wu X, Dai Q, Hong JS, Sorscher EJ, Kappes JC, Barnes S. Purification of CFTR for mass spectrometry analysis: identification of palmitoylation and other post-translational modifications. Protein Eng Des Sel 2011; 25:7-14. [PMID: 22119790 DOI: 10.1093/protein/gzr054] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Post-translational modifications (PTMs) play a crucial role during biogenesis of many transmembrane proteins. Previously, it had not been possible to evaluate PTMs in cystic fibrosis transmembrane conductance regulator (CFTR), the epithelial ion channel responsible for cystic fibrosis, because of difficulty obtaining sufficient amounts of purified protein. We recently used an inducible overexpression strategy to generate recombinant CFTR protein at levels suitable for purification and detailed analysis. Using liquid chromatography (LC) tandem and multiple reaction ion monitoring (MRM) mass spectrometry, we identified specific sites of PTMs, including palmitoylation, phosphorylation, methylation and possible ubiquitination. Many of these covalent CFTR modifications have not been described previously, but are likely to influence key and clinically important molecular processes including protein maturation, gating and the mechanisms underlying certain mutations associated with disease.
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Affiliation(s)
- Michelle McClure
- Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Rowe SM, Sloane P, Tang LP, Backer K, Mazur M, Buckley-Lanier J, Nudelman I, Belakhov V, Bebok Z, Schwiebert E, Baasov T, Bedwell DM. Suppression of CFTR premature termination codons and rescue of CFTR protein and function by the synthetic aminoglycoside NB54. J Mol Med (Berl) 2011; 89:1149-61. [PMID: 21779978 DOI: 10.1007/s00109-011-0787-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 05/18/2011] [Accepted: 06/23/2011] [Indexed: 01/28/2023]
Abstract
Certain aminoglycosides are capable of inducing "translational readthrough" of premature termination codons (PTCs). However, toxicity and relative lack of efficacy deter treatment with clinically available aminoglycosides for genetic diseases caused by PTCs, including cystic fibrosis (CF). Using a structure-based approach, the novel aminoglycoside NB54 was developed that exhibits reduced toxicity and enhanced suppression of PTCs in cell-based reporter assays relative to gentamicin. We examined whether NB54 administration rescued CFTR protein and function in clinically relevant CF models. In a fluorescence-based halide efflux assay, NB54 partially restored halide efflux in a CF bronchial epithelial cell line (CFTR genotype W1282X/F508del), but not in a CF epithelial cell line lacking a PTC (F508del/F508del). In polarized airway epithelial cells expressing either a CFTR-W1282X or -G542X cDNA, treatment with NB54 increased stimulated short-circuit current (I (SC)) with greater efficiency than gentamicin. NB54 and gentamicin induced comparable increases in forskolin-stimulated I (SC) in primary airway epithelial cells derived from a G542X/F508del CF donor. Systemic administration of NB54 to Cftr-/- mice expressing a human CFTR-G542X transgene restored 15-17% of the average stimulated transepithelial chloride currents observed in wild-type (Cftr+/+) mice, comparable to gentamicin. NB54 exhibited reduced cellular toxicity in vitro and was tolerated at higher concentrations than gentamicin in vivo. These results provide evidence that synthetic aminoglycosides are capable of PTC suppression in relevant human CF cells and a CF animal model and support further development of these compounds as a treatment modality for genetic diseases caused by PTCs.
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Affiliation(s)
- Steven M Rowe
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA.
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Keeling KM, Bedwell DM. Suppression of nonsense mutations as a therapeutic approach to treat genetic diseases. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 2:837-52. [PMID: 21976286 DOI: 10.1002/wrna.95] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Suppression therapy is a treatment strategy for genetic diseases caused by nonsense mutations. This therapeutic approach utilizes pharmacological agents that suppress translation termination at in-frame premature termination codons (PTCs) to restore translation of a full-length, functional polypeptide. The efficiency of various classes of compounds to suppress PTCs in mammalian cells is discussed along with the current limitations of this therapy. We also elaborate on approaches to improve the efficiency of suppression that include methods to enhance the effectiveness of current suppression drugs and the design or discovery of new, more effective suppression agents. Finally, we discuss the role of nonsense-mediated mRNA decay (NMD) in limiting the effectiveness of suppression therapy, and describe tactics that may allow the efficiency of NMD to be modulated in order to enhance suppression therapy.
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Affiliation(s)
- Kim M Keeling
- Department of Microbiology, Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, AL, USA
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Pyle LC, Ehrhardt A, Mitchell LH, Fan L, Ren A, Naren AP, Li Y, Clancy JP, Bolger GB, Sorscher EJ, Rowe SM. Regulatory domain phosphorylation to distinguish the mechanistic basis underlying acute CFTR modulators. Am J Physiol Lung Cell Mol Physiol 2011; 301:L587-97. [PMID: 21724857 DOI: 10.1152/ajplung.00465.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Modulator compounds intended to overcome disease-causing mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) show significant promise in clinical testing for cystic fibrosis. However, the mechanism(s) of action underlying these compounds are not fully understood. Activation of CFTR ion transport requires PKA-regulated phosphorylation of the regulatory domain (R-D) and dimerization of the nucleotide binding domains. Using a newly developed assay, we evaluated nine compounds including both CFTR potentatiators and activators discovered via various high-throughput screening strategies to acutely augment CFTR activity. We found considerable differences in the effects on R-D phosphorylation. Some (including UC(CF)-152) stimulated robust phosphorylation, and others had little effect (e.g., VRT-532 and VX-770). We then compared CFTR activation by UC(CF)-152 and VRT-532 in Ussing chamber studies using two epithelial models, CFBE41o(-) and Fischer rat thyroid cells, expressing various CFTR forms. UC(CF)-152 activated wild-type-, G551D-, and rescued F508del-CFTR currents but did not potentiate cAMP-mediated CFTR activation. In contrast, VRT-532 moderately activated CFTR short-circuit current and strongly potentiated forskolin-mediated current. Combined with the result that UC(CF)-152, but not VRT-532 or VX-770, acts by increasing CFTR R-D phosphorylation, these findings indicate that potentiation of endogenous cAMP-mediated activation of mutant CFTR is not due to a pathway involving augmented R-D phosphorylation. This study presents an assay useful to distinguish preclinical compounds by a crucial mechanism underlying CFTR activation, delineates two types of compound able to acutely augment CFTR activity (e.g., activators and potentiators), and demonstrates that a number of different mechanisms can be successfully employed to activate mutant CFTR.
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Affiliation(s)
- Louise C Pyle
- Departments of Genetics, University of Alabama at Birmingham, 35294-0006, USA
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Canani RB, Costanzo MD, Leone L, Pedata M, Meli R, Calignano A. Potential beneficial effects of butyrate in intestinal and extraintestinal diseases. World J Gastroenterol 2011; 17:1519-28. [PMID: 21472114 PMCID: PMC3070119 DOI: 10.3748/wjg.v17.i12.1519] [Citation(s) in RCA: 813] [Impact Index Per Article: 62.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Revised: 01/12/2011] [Accepted: 01/17/2011] [Indexed: 02/06/2023] Open
Abstract
The multiple beneficial effects on human health of the short-chain fatty acid butyrate, synthesized from non-absorbed carbohydrate by colonic microbiota, are well documented. At the intestinal level, butyrate plays a regulatory role on the transepithelial fluid transport, ameliorates mucosal inflammation and oxidative status, reinforces the epithelial defense barrier, and modulates visceral sensitivity and intestinal motility. In addition, a growing number of studies have stressed the role of butyrate in the prevention and inhibition of colorectal cancer. At the extraintestinal level, butyrate exerts potentially useful effects on many conditions, including hemoglobinopathies, genetic metabolic diseases, hypercholesterolemia, insulin resistance, and ischemic stroke. The mechanisms of action of butyrate are different; many of these are related to its potent regulatory effects on gene expression. These data suggest a wide spectrum of positive effects exerted by butyrate, with a high potential for a therapeutic use in human medicine.
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Cystic fibrosis transmembrane conductance regulator protein repair as a therapeutic strategy in cystic fibrosis. Curr Opin Pulm Med 2011; 16:591-7. [PMID: 20829696 DOI: 10.1097/mcp.0b013e32833f1d00] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
PURPOSE OF REVIEW Recent progress in understanding the production, processing, and function of the cystic fibrosis gene product, the cystic fibrosis transmembrane conductance regulator (CFTR), has revealed new therapeutic targets to repair the mutant protein. Classification of CFTR mutations and new treatment strategies to address each will be described here. RECENT FINDINGS High-throughput screening and other drug discovery efforts have identified small molecules that restore activity to mutant CFTR. Compounds such as VX-770 that potentiate CFTR have demonstrated exciting results in recent clinical trials and demonstrate robust effects across several CFTR mutation classes in the laboratory. A number of novel F508del CFTR processing correctors restore protein to the cell surface and improve ion channel function in vitro and are augmented by coadministration of CFTR potentiators. Ongoing discovery efforts that target protein folding, CFTR trafficking, and cell stress have also indicated promising results. Aminoglycosides and the novel small molecule ataluren induce translational readthrough of nonsense mutations in CFTR and other genetic diseases in vitro and in vivo and have shown activity in proof of concept trials, and ataluren is now being studied in confirmatory trials. SUMMARY An improved understanding of the molecular mechanisms underlying the basic genetic defect in cystic fibrosis have led to new treatment strategies to repair the mutant protein.
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Simon AJ, Lev A, Wolach B, Gavrieli R, Amariglio N, Rosenthal E, Gazit E, Eyal E, Rechavi G, Somech R. The effect of gentamicin-induced readthrough on a novel premature termination codon of CD18 leukocyte adhesion deficiency patients. PLoS One 2010; 5:e13659. [PMID: 21103413 PMCID: PMC2982813 DOI: 10.1371/journal.pone.0013659] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 09/23/2010] [Indexed: 12/22/2022] Open
Abstract
Background Leukocyte adhesion deficiency 1 (LAD1) is an inherited disorder of neutrophil function. Nonsense mutations in the affected CD18 (ITB2) gene have rarely been described. In other genes containing such mutations, treatments with aminoglycoside types of antibiotics (e.g., gentamicin) were reported to partially correct the premature protein termination, by induction of readthrough mechanism. Methodology/Principal Findings Genetic analysis was performed on 2 LAD1 patients. Expression, functional and immunofluorescence assays of CD18 in the patients were used to determine the in-vivo and in-vitro effects of gentamicin-induced readthrough. A theoretical modeling of the corrected CD18 protein was developed to predict the protein function. Results We found a novel premature termination codon, C562T (R188X), in exon 6 of the CD18 gene that caused a severe LAD1 phenotype in two unrelated Palestinian children. In-vivo studies on these patients' cells after gentamicin treatment showed abnormal adhesion and chemotactic functions, while in-vitro studies showed mislocalization of the corrected protein to the cytoplasm and not to the cell surface. A theoretical modeling of the corrected CD18 protein suggested that the replacement of the wild type arginine by gentamicin induced tryptophan at the position of the nonsense mutation, although enabled the expression of the entire CD18 protein, this was not sufficient to stabilize the CD18/11 heterodimer at the cell surface. Conclusion A novel nonsense mutation in the CD18 gene causing a complete absence of CD18 protein and severe LAD1 clinical phenotype is reported. Both in vivo and in vitro treatments with gentamicin resulted in the expression of a corrected full-length dysfunctional or mislocalized CD18 protein. However, while the use of gentamicin increased the expression of CD18, it did not improve leukocyte adhesion and chemotaxis. Moreover, the integrity of the CD18/CD11 complex at the cell surface was impaired, due to abnormal CD18 protein and possibly lack of CD11a expression.
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Affiliation(s)
- Amos J. Simon
- Cancer Research Center, Chaim Sheba Medical Center, Tel Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Hematology Laboratory, Chaim Sheba Medical Center, Tel Hashomer, Israel
| | - Atar Lev
- Cancer Research Center, Chaim Sheba Medical Center, Tel Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Baruch Wolach
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Laboratory for Leukocyte Function and Department of Pediatrics, Meir Medical Center, Kfar Saba, Israel
| | - Ronit Gavrieli
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Laboratory for Leukocyte Function and Department of Pediatrics, Meir Medical Center, Kfar Saba, Israel
| | - Ninette Amariglio
- Cancer Research Center, Chaim Sheba Medical Center, Tel Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Hematology Laboratory, Chaim Sheba Medical Center, Tel Hashomer, Israel
| | - Ester Rosenthal
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Hematology Laboratory, Chaim Sheba Medical Center, Tel Hashomer, Israel
| | - Ephraim Gazit
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Tissue Typing Laboratory, Chaim Sheba Medical Center, Tel Hashomer, Israel
| | - Eran Eyal
- Cancer Research Center, Chaim Sheba Medical Center, Tel Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Gideon Rechavi
- Cancer Research Center, Chaim Sheba Medical Center, Tel Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Raz Somech
- Cancer Research Center, Chaim Sheba Medical Center, Tel Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Pediatric Immunology Service, Chaim Sheba Medical Center, Edmond and Lily Safra Children's Hospital, Tel Hashomer, Israel
- * E-mail:
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Pyle LC, Fulton JC, Sloane PA, Backer K, Mazur M, Prasain J, Barnes S, Clancy JP, Rowe SM. Activation of the cystic fibrosis transmembrane conductance regulator by the flavonoid quercetin: potential use as a biomarker of ΔF508 cystic fibrosis transmembrane conductance regulator rescue. Am J Respir Cell Mol Biol 2010; 43:607-616. [PMID: 20042712 PMCID: PMC2970857 DOI: 10.1165/rcmb.2009-0281oc] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 10/24/2009] [Indexed: 12/10/2023] Open
Abstract
Therapies to correct the ΔF508 cystic fibrosis transmembrane conductance regulator (CFTR) folding defect require sensitive methods to detect channel activity in vivo. The β₂ adrenergic receptor agonists, which provide the CFTR stimuli commonly used in nasal potential difference assays, may not overcome the channel gating defects seen in ΔF508 CFTR after plasma membrane localization. In this study, we identify an agent, quercetin, that enhances the detection of surface ΔF508 CFTR, and is suitable for nasal perfusion. A screen of flavonoids in CFBE41o⁻ cells stably transduced with ΔF508 CFTR, corrected to the cell surface with low temperature growth, revealed that quercetin stimulated an increase in the short-circuit current. This increase was dose-dependent in both Fisher rat thyroid and CFBE41o⁻ cells. High concentrations inhibited Cl⁻ conductance. In CFBE41o⁻ airway cells, quercetin (20 μg/ml) activated ΔF508 CFTR, whereas the β₂ adrenergic receptor agonist isoproterenol did not. Quercetin had limited effects on cAMP levels, but did not produce detectable phosphorylation of the isolated CFTR R-domain, suggesting an activation independent of channel phosphorylation. When perfused in the nares of Cftr(+) mice, quercetin (20 μg/ml) produced a hyperpolarization of the potential difference that was absent in Cftr(-/-) mice. Finally, quercetin-induced, dose-dependent hyperpolarization of the nasal potential difference was also seen in normal human subjects. Quercetin activates CFTR-mediated anion transport in respiratory epithelia in vitro and in vivo, and may be useful in studies intended to detect the rescue of ΔF508 CFTR by nasal potential difference.
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Affiliation(s)
- Louise C. Pyle
- Departments of Medicine, Pediatrics, Pharmacology, Genetics, and Physiology, and Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jennifer C. Fulton
- Departments of Medicine, Pediatrics, Pharmacology, Genetics, and Physiology, and Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Peter A. Sloane
- Departments of Medicine, Pediatrics, Pharmacology, Genetics, and Physiology, and Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Kyle Backer
- Departments of Medicine, Pediatrics, Pharmacology, Genetics, and Physiology, and Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Marina Mazur
- Departments of Medicine, Pediatrics, Pharmacology, Genetics, and Physiology, and Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jeevan Prasain
- Departments of Medicine, Pediatrics, Pharmacology, Genetics, and Physiology, and Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Stephen Barnes
- Departments of Medicine, Pediatrics, Pharmacology, Genetics, and Physiology, and Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - J. P. Clancy
- Departments of Medicine, Pediatrics, Pharmacology, Genetics, and Physiology, and Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
| | - Steven M. Rowe
- Departments of Medicine, Pediatrics, Pharmacology, Genetics, and Physiology, and Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
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Congenital diarrheal disorders: improved understanding of gene defects is leading to advances in intestinal physiology and clinical management. J Pediatr Gastroenterol Nutr 2010; 50:360-6. [PMID: 20216094 DOI: 10.1097/mpg.0b013e3181d135ef] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Congenital diarrheal disorders (CDD, Online Mendelian Inheritance in Man [OMIM] 251850) represent one of the most challenging clinical conditions for pediatric gastroenterologists because of the severity of the clinical picture and the broad range of disorders in its differential diagnosis. The number of conditions included within CDD has gradually increased. Recent advances made in the pathophysiology of these conditions have led to a better understanding of the more common diarrheal diseases. Based on the body of data accumulated in recent years, we suggest that CDD be classified in 4 categories depending on the alteration in absorption and transport of nutrients and electrolytes, enterocyte differentiation and polarization, enteroendocrine cell differentiation, and modulation of the intestinal immune response. Our knowledge of the genes responsible for CDD is also rapidly increasing, thanks to linkage studies based on genome-wide analysis of polymorphisms. In this context, the identification of disease genes is a step forward in the diagnostic approach to a patient in whom CDD is strongly suspected. However, it is conceivable that faster, less expensive molecular procedures will, in the near future, become available. This approach could spare the patient invasive procedures and limit complications associated with a delay in diagnosis. Furthermore, carrier and prenatal molecular diagnosis may help pediatricians better manage the condition in the early stages of life.
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Rowe SM, Pyle LC, Jurkevante A, Varga K, Collawn J, Sloane PA, Woodworth B, Mazur M, Fulton J, Fan L, Li Y, Fortenberry J, Sorscher EJ, Clancy JP. DeltaF508 CFTR processing correction and activity in polarized airway and non-airway cell monolayers. Pulm Pharmacol Ther 2010; 23:268-78. [PMID: 20226262 DOI: 10.1016/j.pupt.2010.02.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 02/13/2010] [Accepted: 02/17/2010] [Indexed: 12/21/2022]
Abstract
We examined the activity of DeltaF508 cystic fibrosis transmembrane conductance regulator (CFTR) stably expressed in polarized cystic fibrosis bronchial epithelial cells (CFBE41o(-)) human airway cells and Fisher Rat Thyroid (FRT) cells following treatment with low temperature and a panel of small molecule correctors of DeltaF508 CFTR misprocessing. Corr-4a increased DeltaF508 CFTR-dependent Cl(-) conductance in both cell types, whereas treatment with VRT-325 or VRT-640 increased activity only in FRT cells. Total currents stimulated by forskolin and genistein demonstrated similar dose/response effects to Corr-4a treatment in each cell type. When examining the relative contribution of forskolin and genistein to total stimulated current, CFBE41o(-) cells had smaller forskolin-stimulated I(sc) following either low temperature or corr-4a treatment (10-30% of the total I(sc) produced by the combination of both CFTR agonists). In contrast, forskolin consistently contributed greater than 40% of total I(sc) in DeltaF508 CFTR-expressing FRT cells corrected with low temperature, and corr-4a treatment preferentially enhanced forskolin dependent currents only in FRT cells (60% of total I(sc)). DeltaF508 CFTR cDNA transcript levels, DeltaF508 CFTR C band levels, or cAMP signaling did not account for the reduced forskolin response in CFBE41o(-) cells. Treatment with non-specific inhibitors of phosphodiesterases (papaverine) or phosphatases (endothall) did not restore DeltaF508 CFTR activation by forskolin in CFBE41o(-) cells, indicating that the Cl(-) transport defect in airway cells is distal to cAMP or its metabolism. The results identify important differences in DeltaF508 CFTR activation in polarizing epithelial models of CF, and have important implications regarding detection of rescued of DeltaF508 CFTR in vivo.
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Affiliation(s)
- S M Rowe
- Department of Medicine, University of Alabama at Birmingham, 1530 3rd Ave. South, Birmingham, AL 35294-0005, United States.
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