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Dreano E, Burgel PR, Hatton A, Bouazza N, Chevalier B, Macey J, Leroy S, Durieu I, Weiss L, Grenet D, Stremler N, Ohlmann C, Reix P, Porzio M, Roux Claude P, Rémus N, Douvry B, Montcouquiol S, Cosson L, Mankikian J, Languepin J, Houdouin V, Le Clainche L, Guillaumot A, Pouradier D, Tissot A, Priou P, Mély L, Chedevergne F, Lebourgeois M, Lebihan J, Martin C, Zavala F, Da Silva J, Lemonnier L, Kelly-Aubert M, Golec A, Foucaud P, Marguet C, Edelman A, Hinzpeter A, de Carli P, Girodon E, Sermet-Gaudelus I, Pranke I. Theratyping cystic fibrosis patients to guide elexacaftor/tezacaftor/ivacaftor out-of-label prescription. Eur Respir J 2023; 62:2300110. [PMID: 37696564 DOI: 10.1183/13993003.00110-2023] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 08/16/2023] [Indexed: 09/13/2023]
Abstract
BACKGROUND Around 20% of people with cystic fibrosis (pwCF) do not have access to the triple combination elexacaftor/tezacaftor/ivacaftor (ETI) in Europe because they do not carry the F508del allele on the CF transmembrane conductance regulator (CFTR) gene. Considering that pwCF carrying rare variants may benefit from ETI, including variants already validated by the US Food and Drug Administration (FDA), a compassionate use programme was launched in France. PwCF were invited to undergo a nasal brushing to investigate whether the pharmacological rescue of CFTR activity by ETI in human nasal epithelial cell (HNEC) cultures was predictive of the clinical response. METHODS CFTR activity correction was studied by short-circuit current in HNEC cultures at basal state (dimethyl sulfoxide (DMSO)) and after ETI incubation and expressed as percentage of normal (wild-type (WT)) CFTR activity after sequential addition of forskolin and Inh-172 (ΔI ETI/DMSO%WT). RESULTS 11 pwCF carried variants eligible for ETI according to the FDA label and 28 carried variants not listed by the FDA. ETI significantly increased CFTR activity of FDA-approved CFTR variants (I601F, G85E, S492F, M1101K, R347P, R74W;V201M;D1270N and H1085R). We point out ETI correction of non-FDA-approved variants, including N1303K, R334W, R1066C, Q552P and terminal splicing variants (4374+1G>A and 4096-3C>G). ΔI ETI/DMSO%WT was significantly correlated to change in percentage predicted forced expiratory volume in 1 s and sweat chloride concentration (p<0.0001 for both). G85E, R74W;V201M;D1270N, Q552P and M1101K were rescued more efficiently by other CFTR modulator combinations than ETI. CONCLUSIONS Primary nasal epithelial cells hold promise for expanding the prescription of CFTR modulators in pwCF carrying rare mutants. Additional variants should be discussed for ETI indication.
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Affiliation(s)
- Elise Dreano
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
| | - Pierre Régis Burgel
- Université Paris-Cité, Paris, France
- Respiratory Medicine and Cystic Fibrosis National Reference Center, Cochin Hospital, AP-HP, Paris, France
- INSERM U1016, Institut Cochin, Paris, France
- ERN-LUNG CF Network, Frankfurt, Germany
| | - Aurelie Hatton
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
| | - Naim Bouazza
- Université Paris-Cité, Paris, France
- Unité de Recherche Clinique, Hôpital Necker Enfants Malades, AP-HP, Paris, France
| | - Benoit Chevalier
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
| | - Julie Macey
- Centre de Ressources et de Compétence de la Mucoviscidose, CHU Pellegrin, Bordeaux, France
| | - Sylvie Leroy
- Centre de Ressources et de Compétence de la Mucoviscidose, CHU, Nice, France
| | - Isabelle Durieu
- Centre de Référence Adulte de la Mucoviscidose, Hospices Civils de Lyon, Université de Lyon, Équipe d'Accueil Health Services and Performance Research (HESPER) 7425, Lyon, France
| | - Laurence Weiss
- Centre de Ressources et de Compétence de la Mucoviscidose Pédiatrique, CHU, Strasbourg, France
| | - Dominique Grenet
- Centre de Ressources et de Compétence de la Mucoviscidose, Hôpital Foch, Suresnes, France
| | - Nathalie Stremler
- Centre de Ressources et de Compétence de la Mucoviscidose, Hôpital de la Timone, Marseille, France
| | - Camille Ohlmann
- Centre de Ressources et de Compétence de la Mucoviscidose Pédiatrique, Hospices Civils de Lyon, Bron, France
| | - Philippe Reix
- Centre de Ressources et de Compétence de la Mucoviscidose Pédiatrique, Hospices Civils de Lyon, Bron, France
| | - Michele Porzio
- Centre de Ressources et de Compétence de la Mucoviscidose Adulte, CHU, Strasbourg, France
| | - Pauline Roux Claude
- Centre de Ressources et de Compétence de la Mucoviscidose Adulte, CHU, Besancon, France
| | - Natacha Rémus
- Centre de Ressources et de Compétence de la Mucoviscidose Mixte, CHIC, Créteil, France
| | - Benoit Douvry
- Centre de Ressources et de Compétence de la Mucoviscidose Mixte, CHIC, Créteil, France
| | - Sylvie Montcouquiol
- Centre de Ressources et de Compétence de la Mucoviscidose Adulte, CHU, Clermont Ferrand, France
| | - Laure Cosson
- Centre de Ressources et de Compétence de la Mucoviscidose Pédiatrique, CHU, Tours, France
| | - Julie Mankikian
- Centre de Ressources et de Compétence de la Mucoviscidose Adulte, CHU, Tours, France
| | - Jeanne Languepin
- Centre de Ressources et de Compétence de la Mucoviscidose Mixte, CHU, Limoges, France
| | - Veronique Houdouin
- Centre de Ressources et de Compétence de la Mucoviscidose Pédiatrique, Hôpital Robert Debré, Paris, France
| | - Laurence Le Clainche
- Centre de Ressources et de Compétence de la Mucoviscidose Pédiatrique, Hôpital Robert Debré, Paris, France
| | - Anne Guillaumot
- Centre de Ressources et de Compétence de la Mucoviscidose Adulte, CHU, Nancy, France
| | - Delphine Pouradier
- Centre de Ressources et de Compétence de la Mucoviscidose Pédiatrique, Hôpital Mignot, Le Chesnay, France
| | - Adrien Tissot
- Centre de Ressources et de Compétence de la Mucoviscidose Adulte, CHU, Nantes, France
| | - Pascaline Priou
- Centre de Ressources et de Compétence de la Mucoviscidose Adulte, CHU, Angers, France
| | - Laurent Mély
- Centre de Ressources et de Compétence de la Mucoviscidose, Hôpital René Sabran, Hospices Civils de Lyon, Giens, France
| | - Frederique Chedevergne
- Cystic Fibrosis National Pediatric Reference Center, Pneumo-Allergologie Pédiatrique, Hôpital Necker Enfants Malades, AP-HP, Paris, France
| | - Muriel Lebourgeois
- Cystic Fibrosis National Pediatric Reference Center, Pneumo-Allergologie Pédiatrique, Hôpital Necker Enfants Malades, AP-HP, Paris, France
| | - Jean Lebihan
- Centre de Ressources et de Compétence de la Mucoviscidose Adulte, Centre de Perharidy, Roscoff, France
| | - Clémence Martin
- Université Paris-Cité, Paris, France
- Respiratory Medicine and Cystic Fibrosis National Reference Center, Cochin Hospital, AP-HP, Paris, France
| | - Flora Zavala
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
| | - Jennifer Da Silva
- Respiratory Medicine and Cystic Fibrosis National Reference Center, Cochin Hospital, AP-HP, Paris, France
| | | | - Mairead Kelly-Aubert
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
| | - Anita Golec
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
| | | | - Christophe Marguet
- Centre de Ressources et de Compétence de la Mucoviscidose Pédiatrique, CHU, Rouen, France
| | - Aleksander Edelman
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
| | - Alexandre Hinzpeter
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
| | | | - Emmanuelle Girodon
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
- Service de Médecine Génomique des Maladies de Système et d'Organe, Hôpital Cochin, Paris, France
- These three authors contributed equally to this work as co-last authors
| | - Isabelle Sermet-Gaudelus
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
- ERN-LUNG CF Network, Frankfurt, Germany
- Centre de Ressources et de Compétence de la Mucoviscidose Pédiatrique, Hôpital Mignot, Le Chesnay, France
- These three authors contributed equally to this work as co-last authors
| | - Iwona Pranke
- INSERM, CNRS, Institut Necker Enfants Malades, Paris, France
- Université Paris-Cité, Paris, France
- These three authors contributed equally to this work as co-last authors
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Lemmens-Gruber R, Tzotzos S. The Epithelial Sodium Channel-An Underestimated Drug Target. Int J Mol Sci 2023; 24:ijms24097775. [PMID: 37175488 PMCID: PMC10178586 DOI: 10.3390/ijms24097775] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 04/14/2023] [Accepted: 04/15/2023] [Indexed: 05/15/2023] Open
Abstract
Epithelial sodium channels (ENaC) are part of a complex network of interacting biochemical pathways and as such are involved in several disease states. Dependent on site and type of mutation, gain- or loss-of-function generated symptoms occur which span from asymptomatic to life-threatening disorders such as Liddle syndrome, cystic fibrosis or generalized pseudohypoaldosteronism type 1. Variants of ENaC which are implicated in disease assist further understanding of their molecular mechanisms in order to create models for specific pharmacological targeting. Identification and characterization of ENaC modifiers not only furthers our basic understanding of how these regulatory processes interact, but also enables discovery of new therapeutic targets for the disease conditions caused by ENaC dysfunction. Numerous test compounds have revealed encouraging results in vitro and in animal models but less in clinical settings. The EMA- and FDA-designated orphan drug solnatide is currently being tested in phase 2 clinical trials in the setting of acute respiratory distress syndrome, and the NOX1/ NOX4 inhibitor setanaxib is undergoing clinical phase 2 and 3 trials for therapy of primary biliary cholangitis, liver stiffness, and carcinoma. The established ENaC blocker amiloride is mainly used as an add-on drug in the therapy of resistant hypertension and is being studied in ongoing clinical phase 3 and 4 trials for special applications. This review focuses on discussing some recent developments in the search for novel therapeutic agents.
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Affiliation(s)
- Rosa Lemmens-Gruber
- Department of Pharmaceutical Sciences, Division of Pharmacology and Toxicology, University of Vienna, A-1090 Vienna, Austria
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3
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Zhang L, Wang X, Chen J, Sheng S, Kleyman TR. Extracellular intersubunit interactions modulate epithelial Na + channel gating. J Biol Chem 2023; 299:102914. [PMID: 36649907 PMCID: PMC9975279 DOI: 10.1016/j.jbc.2023.102914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 12/13/2022] [Accepted: 01/12/2023] [Indexed: 01/15/2023] Open
Abstract
Epithelial Na+ channels (ENaCs) and related channels have large extracellular domains where specific factors interact and induce conformational changes, leading to altered channel activity. However, extracellular structural transitions associated with changes in ENaC activity are not well defined. Using crosslinking and two-electrode voltage clamp in Xenopus oocytes, we identified several pairs of functional intersubunit contacts where mouse ENaC activity was modulated by inducing or breaking a disulfide bond between introduced Cys residues. Specifically, crosslinking E499C in the β-subunit palm domain and N510C in the α-subunit palm domain activated ENaC, whereas crosslinking βE499C with αQ441C in the α-subunit thumb domain inhibited ENaC. We determined that bridging βE499C to αN510C or αQ441C altered the Na+ self-inhibition response via distinct mechanisms. Similar to bridging βE499C and αQ441C, we found that crosslinking palm domain αE557C with thumb domain γQ398C strongly inhibited ENaC activity. In conclusion, we propose that certain residues at specific subunit interfaces form microswitches that convey a conformational wave during ENaC gating and its regulation.
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Affiliation(s)
- Lei Zhang
- Departments of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Department of Nephrology, Hunan Key Laboratory of Kidney Disease and Blood Purification, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China; The Third Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Xueqi Wang
- Departments of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Department of Nephrology, Hunan Key Laboratory of Kidney Disease and Blood Purification, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China; The Third Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Jingxin Chen
- Departments of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Shaohu Sheng
- Departments of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
| | - Thomas R Kleyman
- Departments of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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4
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Brown EF, Mitaera T, Fronius M. COVID-19 and Liquid Homeostasis in the Lung—A Perspective through the Epithelial Sodium Channel (ENaC) Lens. Cells 2022; 11:cells11111801. [PMID: 35681496 PMCID: PMC9180030 DOI: 10.3390/cells11111801] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 05/23/2022] [Accepted: 05/25/2022] [Indexed: 01/26/2023] Open
Abstract
Infections with a new corona virus in 2019 lead to the definition of a new disease known as Corona Virus Disease 2019 (COVID-19). The sever cases of COVID-19 and the main cause of death due to virus infection are attributed to respiratory distress. This is associated with the formation of pulmonary oedema that impairs blood oxygenation and hypoxemia as main symptoms of respiratory distress. An important player for the maintenance of a defined liquid environment in lungs needed for normal lung function is the epithelial sodium channel (ENaC). The present article reviews the implications of SARS-CoV-2 infections from the perspective of impaired function of ENaC. The rationale for this perspective is derived from the recognition that viral spike protein and ENaC share a common proteolytic cleavage site. This cleavage site is utilized by the protease furin, that is essential for ENaC activity. Furin cleavage of spike ‘activates’ the virus protein to enable binding to host cell membrane receptors and initiate cell infection. Based on the importance of proteolytic cleavage for ENaC function and activation of spike, it seems feasible to assume that virus infections are associated with impaired ENaC activity. This is further supported by symptoms of COVID-19 that are reminiscent of impaired ENaC function in the respiratory tract.
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Affiliation(s)
- Emily F. Brown
- Department of Physiology, University of Otago, Dunedin 9054, New Zealand; (E.F.B.); (T.M.)
- HeartOtago, University of Otago, Dunedin, New Zealand
| | - Tamapuretu Mitaera
- Department of Physiology, University of Otago, Dunedin 9054, New Zealand; (E.F.B.); (T.M.)
- HeartOtago, University of Otago, Dunedin, New Zealand
| | - Martin Fronius
- Department of Physiology, University of Otago, Dunedin 9054, New Zealand; (E.F.B.); (T.M.)
- HeartOtago, University of Otago, Dunedin, New Zealand
- Healthy Hearts for Aotearoa New Zealand, Centre of Research Excellence, New Zealand
- Maurice Wilkins Centre for Molecular Discovery, Centre of Research Excellence, New Zealand
- Correspondence: ; Tel.: +64-3-471-6081
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5
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Zhang L, Wang X, Chen J, Kleyman TR, Sheng S. Accessibility of ENaC extracellular domain central core residues. J Biol Chem 2022; 298:101860. [PMID: 35339489 PMCID: PMC9052164 DOI: 10.1016/j.jbc.2022.101860] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 03/16/2022] [Accepted: 03/21/2022] [Indexed: 11/20/2022] Open
Abstract
The epithelial Na+ channel (ENaC)/degenerin family has a similar extracellular architecture, where specific regulatory factors interact and alter channel gating behavior. The extracellular palm domain serves as a key link to the channel pore. In this study, we used cysteine-scanning mutagenesis to assess the functional effects of Cys-modifying reagents on palm domain β10 strand residues in mouse ENaC. Of the 13 ENaC α subunit mutants with Cys substitutions examined, only mutants at sites in the proximal region of β10 exhibited changes in channel activity in response to methanethiosulfonate reagents. Additionally, Cys substitutions at three proximal sites of β and γ subunit β10 strands also rendered mutant channels methanethiosulfonate-responsive. Moreover, multiple Cys mutants were activated by low concentrations of thiophilic Cd2+. Using the Na+ self-inhibition response to assess ENaC gating behavior, we identified four α, two β, and two γ subunit β10 strand mutations that changed the Na+ self-inhibition response. Our results suggest that the proximal regions of β10 strands in all three subunits are accessible to small aqueous compounds and Cd2+ and have a role in modulating ENaC gating. These results are consistent with a structural model of mouse ENaC that predicts the presence of aqueous tunnels adjacent to the proximal part of β10 and with previously resolved structures of a related family member where palm domain structural transitions were observed with channels in an open or closed state.
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Affiliation(s)
- Lei Zhang
- Departments of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Department of Nephrology, Hunan Key Laboratory of Kidney Disease and Blood Purification, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China; The Third Xiangya Hospital of Central South University, Changsha, Hunan, China
| | - Xueqi Wang
- Departments of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Department of Nephrology, Hunan Key Laboratory of Kidney Disease and Blood Purification, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China; The Third Xiangya Hospital of Central South University, Changsha, Hunan, China
| | - Jingxin Chen
- Departments of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Thomas R Kleyman
- Departments of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
| | - Shaohu Sheng
- Departments of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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6
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Blaconà G, Raso R, Castellani S, Pierandrei S, Del Porto P, Ferraguti G, Ascenzioni F, Conese M, Lucarelli M. Downregulation of epithelial sodium channel (ENaC) activity in cystic fibrosis cells by epigenetic targeting. Cell Mol Life Sci 2022; 79:257. [PMID: 35462606 PMCID: PMC9035428 DOI: 10.1007/s00018-022-04190-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 01/28/2022] [Accepted: 02/02/2022] [Indexed: 12/31/2022]
Abstract
The pathogenic mechanism of cystic fibrosis (CF) includes the functional interaction of the cystic fibrosis transmembrane conductance regulator (CFTR) protein with the epithelial sodium channel (ENaC). The reduction of ENaC activity may constitute a therapeutic option for CF. This hypothesis was evaluated using drugs that target the protease-dependent activation of the ENaC channel and the transcriptional activity of its coding genes. To this aim we used: camostat, a protease inhibitor; S-adenosyl methionine (SAM), showed to induce DNA hypermethylation; curcumin, known to produce chromatin condensation. SAM and camostat are drugs already clinically used in other pathologies, while curcumin is a common dietary compound. The experimental systems used were CF and non-CF immortalized human bronchial epithelial cell lines as well as human bronchial primary epithelial cells. ENaC activity and SCNN1A, SCNN1B and SCNN1G gene expression were analyzed, in addition to SCNN1B promoter methylation. In both immortalized and primary cells, the inhibition of extracellular peptidases and the epigenetic manipulations reduced ENaC activity. Notably, the reduction in primary cells was much more effective. The SCNN1B appeared to be the best target to reduce ENaC activity, in respect to SCNN1A and SCNN1G. Indeed, SAM treatment resulted to be effective in inducing hypermethylation of SCNN1B gene promoter and in lowering its expression. Importantly, CFTR expression was unaffected, or even upregulated, after treatments. These results open the possibility of CF patients’ treatment by epigenetic targeting.
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Affiliation(s)
- Giovanna Blaconà
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Roberto Raso
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Stefano Castellani
- Department of Biomedical Sciences and Human Oncology, University of Bari, Bari, Italy
| | - Silvia Pierandrei
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Paola Del Porto
- Department of Biology and Biotechnology "Charles Darwin", Sapienza University of Rome, Rome, Italy
| | - Giampiero Ferraguti
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Fiorentina Ascenzioni
- Department of Biology and Biotechnology "Charles Darwin", Sapienza University of Rome, Rome, Italy
| | - Massimo Conese
- Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy.
| | - Marco Lucarelli
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy. .,Pasteur Institute, Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy.
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7
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Govindan R, Banerjee P, Dhania NK, Senapati S. FTIR based approach to study EnaC mechanosensory functions. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 167:79-86. [PMID: 34293339 DOI: 10.1016/j.pbiomolbio.2021.07.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 07/07/2021] [Accepted: 07/14/2021] [Indexed: 10/20/2022]
Abstract
The pulmonary epithelial sodium ion channel (ENaC) is gaining importance for its sodium gating and mechanosensitive roles. The mechano functional studies on ENaC suggest direct molecular interactions between the ENaC protein with cytoskeleton microtubules and other extracellular matrix components. Also, in few mechanotransduction studies, ENaC was shown to respond both to membrane stretch as well as cell volume changes. However, the conformational characteristic of ENaC during sodium and mechano gating are yet to be fully elucidated. Thus obtaining ENaC protein conformational spectrum based on Fourier Transform Infrared Radiation (FTIR) spectroscopy in solution will be useful in predicting the nature of conformational changes occurring during any cell volume changes in an epithelial cell. The conformational spectrum looks promising in studying the disease biology of cystic fibrosis (CF) and CF like conditions that arise due to abnormal ion conductance membrane proteins and subsequent frequent fluid retentions. This review article presents the basics of epithelial ENaC protein as a gated mechanosensor and FTIR for developing fluid dynamics of ENaC protein. This can be applied to develop an ENaC based quantum mechanosensor for the prognosis as well as diagnosis of cystic fibrosis (CF) and allied lung diseases.
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Affiliation(s)
- Rekha Govindan
- Department of Biochemistry, PM Sayeed Calicut University Centre, Andrott, Lakshadweep, 682551, India
| | - Pratibha Banerjee
- Department of Human Genetics & Molecular Medicine, Central University of Punjab, Bathinda, 151401, India
| | - Narender K Dhania
- Department of Human Genetics & Molecular Medicine, Central University of Punjab, Bathinda, 151401, India.
| | - Sabyasachi Senapati
- Department of Human Genetics & Molecular Medicine, Central University of Punjab, Bathinda, 151401, India
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Abstract
Bronchiectasis is a complex, heterogeneous disorder defined by both a radiological abnormality of permanent bronchial dilatation and a clinical syndrome. There are multiple underlying causes including severe infections, mycobacterial disease, autoimmune conditions, hypersensitivity disorders, and genetic conditions. The pathophysiology of disease is understood in terms of interdependent concepts of chronic infection, inflammation, impaired mucociliary clearance, and structural lung damage. Neutrophilic inflammation is characteristic of the disease, with elevated levels of harmful proteases such as neutrophil elastase associated with worse outcomes. Recent data show that neutrophil extracellular trap formation may be the key mechanism leading to protease release and severe bronchiectasis. Despite the dominant of neutrophilic disease, eosinophilic subtypes are recognized and may require specific treatments. Neutrophilic inflammation is associated with elevated bacterial loads and chronic infection with organisms such as Pseudomonas aeruginosa. Loss of diversity of the normal lung microbiota and dominance of proteobacteria such as Pseudomonas and Haemophilus are features of severe bronchiectasis and link to poor outcomes. Ciliary dysfunction is also a key feature, exemplified by the rare genetic syndrome of primary ciliary dyskinesia. Mucus symptoms arise through goblet cell hyperplasia and metaplasia and reduced ciliary function through dyskinesia and loss of ciliated cells. The contribution of chronic inflammation, infection, and mucus obstruction leads to progressive structural lung damage. The heterogeneity of the disease is the most challenging aspect of management. An understanding of the pathophysiology of disease and their biomarkers can help to guide personalized medicine approaches utilizing the concept of "treatable traits."
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Affiliation(s)
- Holly R Keir
- Scottish Centre for Respiratory Research, University of Dundee, Dundee, United Kingdom
| | - James D Chalmers
- Scottish Centre for Respiratory Research, University of Dundee, Dundee, United Kingdom
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9
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Abstract
The Epithelial Na+ Channel, ENaC, comprised of 3 subunits (αβγ, or sometimes δβγENaC), plays a critical role in regulating salt and fluid homeostasis in the body. It regulates fluid reabsorption into the blood stream from the kidney to control blood volume and pressure, fluid absorption in the lung to control alveolar fluid clearance at birth and maintenance of normal airway surface liquid throughout life, and fluid absorption in the distal colon and other epithelial tissues. Moreover, recent studies have also revealed a role for sodium movement via ENaC in nonepithelial cells/tissues, such as endothelial cells in blood vessels and neurons. Over the past 25 years, major advances have been made in our understanding of ENaC structure, function, regulation, and role in human disease. These include the recently solved three-dimensional structure of ENaC, ENaC function in various tissues, and mutations in ENaC that cause a hereditary form of hypertension (Liddle syndrome), salt-wasting hypotension (PHA1), or polymorphism in ENaC that contributes to other diseases (such as cystic fibrosis). Moreover, great strides have been made in deciphering the regulation of ENaC by hormones (e.g., the mineralocorticoid aldosterone, glucocorticoids, vasopressin), ions (e.g., Na+ ), proteins (e.g., the ubiquitin-protein ligase NEDD4-2, the kinases SGK1, AKT, AMPK, WNKs & mTORC2, and proteases), and posttranslational modifications [e.g., (de)ubiquitylation, glycosylation, phosphorylation, acetylation, palmitoylation]. Characterization of ENaC structure, function, regulation, and role in human disease, including using animal models, are described in this article, with a special emphasis on recent advances in the field. © 2021 American Physiological Society. Compr Physiol 11:1-29, 2021.
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Affiliation(s)
- Daniela Rotin
- The Hospital for Sick Children, and The University of Toronto, Toronto, Canada
| | - Olivier Staub
- Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland
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10
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Rooj AK, Cormet-Boyaka E, Clark EB, Qadri YJ, Lee W, Boddu R, Agarwal A, Tambi R, Uddin M, Parpura V, Sorscher EJ, Fuller CM, Berdiev BK. Association of cystic fibrosis transmembrane conductance regulator with epithelial sodium channel subunits carrying Liddle's syndrome mutations. Am J Physiol Lung Cell Mol Physiol 2021; 321:L308-L320. [PMID: 34037494 DOI: 10.1152/ajplung.00298.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The association of the cystic fibrosis transmembrane conductance regulator (CFTR) and epithelial sodium channel (ENaC) in the pathophysiology of cystic fibrosis (CF) is controversial. Previously, we demonstrated a close physical association between wild-type (WT) CFTR and WT ENaC. We have also shown that the F508del CFTR fails to associate with ENaC unless the mutant protein is rescued pharmacologically or by low temperature. In this study, we present the evidence for a direct physical association between WT CFTR and ENaC subunits carrying Liddle's syndrome mutations. We show that all three ENaC subunits bearing Liddle's syndrome mutations (both point mutations and the complete truncation of the carboxy terminus), could be coimmunoprecipitated with WT CFTR. The biochemical studies were complemented by fluorescence lifetime imaging microscopy (FLIM), a distance-dependent approach that monitors protein-protein interactions between fluorescently labeled molecules. Our measurements revealed significantly increased fluorescence resonance energy transfer between CFTR and all tested ENaC combinations as compared with controls (ECFP and EYFP cotransfected cells). Our findings are consistent with the notion that CFTR and ENaC are within reach of each other even in the setting of Liddle's syndrome mutations, suggestive of a direct intermolecular interaction between these two proteins.
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Affiliation(s)
- Arun K Rooj
- Department of Cell, Developmental & Integrative Biology, The University of Alabama at Birmingham School of Medicine, Birmingham, Alabama
| | | | - Edlira B Clark
- Department of Cell, Developmental & Integrative Biology, The University of Alabama at Birmingham School of Medicine, Birmingham, Alabama
| | - Yawar J Qadri
- Department of Anesthesiology, The Emory University School of Medicine, Atlanta, Georgia
| | - William Lee
- Department of Neurobiology, The University of Alabama at Birmingham School of Medicine, Birmingham, Alabama
| | - Ravindra Boddu
- Department of Medicine, The University of Alabama at Birmingham School of Medicine, Birmingham, Alabama
| | - Anupam Agarwal
- Department of Medicine, The University of Alabama at Birmingham School of Medicine, Birmingham, Alabama
| | - Richa Tambi
- College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates
| | - Mohammed Uddin
- College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham School of Medicine, Birmingham, Alabama
| | - Eric J Sorscher
- Department of Pediatrics, The Emory University School of Medicine, Atlanta, Georgia
| | - Cathy M Fuller
- Department of Cell, Developmental & Integrative Biology, The University of Alabama at Birmingham School of Medicine, Birmingham, Alabama
| | - Bakhrom K Berdiev
- Department of Cell, Developmental & Integrative Biology, The University of Alabama at Birmingham School of Medicine, Birmingham, Alabama.,College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates
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11
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Pierandrei S, Truglio G, Ceci F, Del Porto P, Bruno SM, Castellani S, Conese M, Ascenzioni F, Lucarelli M. DNA Methylation Patterns Correlate with the Expression of SCNN1A, SCNN1B, and SCNN1G (Epithelial Sodium Channel, ENaC) Genes. Int J Mol Sci 2021; 22:ijms22073754. [PMID: 33916525 PMCID: PMC8038451 DOI: 10.3390/ijms22073754] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 03/12/2021] [Accepted: 03/23/2021] [Indexed: 12/17/2022] Open
Abstract
The interplay between the cystic fibrosis transmembrane conductance regulator (CFTR) and the epithelial sodium channel (ENaC) in respiratory epithelia has a crucial role in the pathogenesis of cystic fibrosis (CF). The comprehension of the mechanisms of transcriptional regulation of ENaC genes is pivotal to better detail the pathogenic mechanism and the genotype-phenotype relationship in CF, as well as to realize therapeutic approaches based on the transcriptional downregulation of ENaC genes. Since we aimed to study the epigenetic transcriptional control of ENaC genes, an assessment of their expression and DNA methylation patterns in different human cell lines, nasal brushing samples, and leucocytes was performed. The mRNA expression of CFTR and ENaC subunits α, β and γ (respectively SCNN1A, SCNN1B, and SCNN1G genes) was studied by real time PCR. DNA methylation of 5'-flanking region of SCNN1A, SCNN1B, and SCNN1G genes was studied by HpaII/PCR. The levels of expression and DNA methylation of ENaC genes in the different cell lines, brushing samples, and leukocytes were very variable. The DNA regions studied of each ENaC gene showed different methylation patterns. A general inverse correlation between expression and DNA methylation was evidenced. Leukocytes showed very low expression of all the 3 ENaC genes corresponding to a DNA methylated pattern. The SCNN1A gene resulted to be the most expressed in some cell lines that, accordingly, showed a completely demethylated pattern. Coherently, a heavy and moderate methylated pattern of, respectively, SCNN1B and SCNN1G genes corresponded to low levels of expression. As exceptions, we found that dexamethasone treatment appeared to stimulate the expression of all the 3 ENaC genes, without an evident modulation of the DNA methylation pattern, and that in nasal brushing a considerable expression of all the 3 ENaC genes were found despite an apparent methylated pattern. At least part of the expression modulation of ENaC genes seems to depend on the DNA methylation patterns of specific DNA regions. This points to epigenetics as a controlling mechanism of ENaC function and as a possible therapeutic approach for CF.
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Affiliation(s)
- Silvia Pierandrei
- Department of Experimental Medicine, Sapienza University of Rome, Viale Regina Elena 324, 00161 Roma, Italy; (S.P.); (G.T.); (F.C.); (S.M.B.)
| | - Gessica Truglio
- Department of Experimental Medicine, Sapienza University of Rome, Viale Regina Elena 324, 00161 Roma, Italy; (S.P.); (G.T.); (F.C.); (S.M.B.)
| | - Fabrizio Ceci
- Department of Experimental Medicine, Sapienza University of Rome, Viale Regina Elena 324, 00161 Roma, Italy; (S.P.); (G.T.); (F.C.); (S.M.B.)
| | - Paola Del Porto
- Department of Biology and Biotechnology “Charles Darwin”, Sapienza University of Rome, Via dei Sardi 70, 00185 Roma, Italy;
| | - Sabina Maria Bruno
- Department of Experimental Medicine, Sapienza University of Rome, Viale Regina Elena 324, 00161 Roma, Italy; (S.P.); (G.T.); (F.C.); (S.M.B.)
| | - Stefano Castellani
- Department of Biomedical Sciences and Human Oncology, University of Bari, Piazza Giulio Cesare 11, 70124 Bari, Italy;
| | - Massimo Conese
- Department of Medical and Surgical Sciences, University of Foggia, Via Napoli 121, 71122 Foggia, Italy;
| | - Fiorentina Ascenzioni
- Department of Biology and Biotechnology “Charles Darwin”, Sapienza University of Rome, Via dei Sardi 70, 00185 Roma, Italy;
- Correspondence: (F.A.); (M.L.)
| | - Marco Lucarelli
- Department of Experimental Medicine, Sapienza University of Rome, Viale Regina Elena 324, 00161 Roma, Italy; (S.P.); (G.T.); (F.C.); (S.M.B.)
- Pasteur Institute, Cenci Bolognetti Foundation, Sapienza University of Rome, Viale Regina Elena 291, 00161 Roma, Italy
- Correspondence: (F.A.); (M.L.)
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12
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Haq IJ, Althaus M, Gardner AI, Yeoh HY, Joshi U, Saint-Criq V, Verdon B, Townshend J, O'Brien C, Ben-Hamida M, Thomas M, Bourke S, van der Sluijs P, Braakman I, Ward C, Gray MA, Brodlie M. Clinical and molecular characterization of the R751L-CFTR mutation. Am J Physiol Lung Cell Mol Physiol 2020; 320:L288-L300. [PMID: 33296276 PMCID: PMC8476205 DOI: 10.1152/ajplung.00137.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Cystic fibrosis (CF) arises from mutations in the CF transmembrane conductance regulator (CFTR) gene, resulting in progressive and life-limiting respiratory disease. R751L is a rare CFTR mutation that is poorly characterized. Our aims were to describe the clinical and molecular phenotypes associated with R751L. Relevant clinical data were collected from three heterozygote individuals harboring R751L (2 patients with G551D/R751L and 1 with F508del/R751L). Assessment of R751L-CFTR function was made in primary human bronchial epithelial cultures (HBEs) and Xenopus oocytes. Molecular properties of R751L-CFTR were investigated in the presence of known CFTR modulators. Although sweat chloride was elevated in all three patients, the clinical phenotype associated with R751L was mild. Chloride secretion in F508del/R751L HBEs was reduced compared with non-CF HBEs and associated with a reduction in sodium absorption by the epithelial sodium channel (ENaC). However, R751L-CFTR function in Xenopus oocytes, together with folding and cell surface transport of R751L-CFTR, was not different from wild-type CFTR. Overall, R751L-CFTR was associated with reduced sodium chloride absorption but had functional properties similar to wild-type CFTR. This is the first report of R751L-CFTR that combines clinical phenotype with characterization of functional and biological properties of the mutant channel. Our work will build upon existing knowledge of mutations within this region of CFTR and, importantly, inform approaches for clinical management. Elevated sweat chloride and reduced chloride secretion in HBEs may be due to alternative non-CFTR factors, which require further investigation.
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Affiliation(s)
- Iram J Haq
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom.,Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Mike Althaus
- Institute for Functional Gene Analytics, Department of Natural Sciences, Bonn-Rhein-Sieg University of Applied Sciences, Rheinbach, Germany
| | - Aaron Ions Gardner
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Hui Ying Yeoh
- Cellular Protein Chemistry, Science4Life, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Urjita Joshi
- Cellular Protein Chemistry, Science4Life, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Vinciane Saint-Criq
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Bernard Verdon
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Jennifer Townshend
- Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Christopher O'Brien
- Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Mahfud Ben-Hamida
- Department of Paediatrics, West Cumberland Hospital, Whitehaven, United Kingdom
| | - Matthew Thomas
- Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Stephen Bourke
- Respiratory Medicine, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Peter van der Sluijs
- Cellular Protein Chemistry, Science4Life, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Ineke Braakman
- Cellular Protein Chemistry, Science4Life, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Chris Ward
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Michael A Gray
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Malcolm Brodlie
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom.,Paediatric Respiratory Medicine, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
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13
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Hawley MH, Moschovis PP, Lu M, Kinane TB, Yonker LM. The future is here: Integrating genetics into the pediatric pulmonary clinic. Pediatr Pulmonol 2020; 55:1810-1818. [PMID: 32533912 PMCID: PMC7384239 DOI: 10.1002/ppul.24723] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 02/28/2020] [Indexed: 02/02/2023]
Abstract
Recognition of underlying genetic etiologies of disease is increasing at an exponential rate, likely due to greater access to and lower cost of genetic testing. Monogenic causes of disease, or conditions resulting from a mutation or mutations in a single gene, are now well recognized in every subspecialty, including pediatric pulmonary medicine; thus, it is important to consider genetic conditions when evaluating children with respiratory disease. In the pediatric pulmonary clinic, genetic testing should be considered when multiple family members present with similar or related clinical features and when individuals have unusual clinical presentations, such as early-onset disease or complex, syndromic features. This review provides a practical guide for genetic diagnosis in the pediatric pulmonary setting, including a review of genetic concepts, considerations for test selection and results in interpretation, as well as an overview of genetic differential diagnoses for common pediatric pulmonary phenotypes. Genetic conditions that commonly present to the pediatric pulmonary clinic are reviewed in a companion article by Yonker et al.
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Affiliation(s)
- Megan H Hawley
- Pulmonary Division, Massachusetts General Hospital for Children, Boston, Massachusetts.,Laboratory for Molecular Medicine, Partners HealthCare Personalized Medicine, Cambridge, Massachusetts
| | - Peter P Moschovis
- Pulmonary Division, Massachusetts General Hospital for Children, Boston, Massachusetts.,Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
| | - Mengdi Lu
- Pulmonary Division, Massachusetts General Hospital for Children, Boston, Massachusetts.,Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
| | - T Bernard Kinane
- Pulmonary Division, Massachusetts General Hospital for Children, Boston, Massachusetts.,Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
| | - Lael M Yonker
- Pulmonary Division, Massachusetts General Hospital for Children, Boston, Massachusetts.,Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
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14
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Han ST, Cutting GR. Molecular Genetics of Cystic Fibrosis. Respir Med 2020. [DOI: 10.1007/978-3-030-42382-7_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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15
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Wang X, Chen J, Shi S, Sheng S, Kleyman TR. Analyses of epithelial Na + channel variants reveal that an extracellular β-ball domain critically regulates ENaC gating. J Biol Chem 2019; 294:16765-16775. [PMID: 31551351 DOI: 10.1074/jbc.ra119.010001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 09/19/2019] [Indexed: 11/06/2022] Open
Abstract
Epithelial Na+ channel (ENaC)-mediated Na+ transport has a key role in the regulation of extracellular fluid volume, blood pressure, and extracellular [K+]. Among the thousands of human ENaC variants, only a few exist whose functional consequences have been experimentally tested. Here, we used the Xenopus oocyte expression system to investigate the functional roles of four nonsynonymous human ENaC variants located within the β7-strand and its adjacent loop of the α-subunit extracellular β-ball domain. αR350Wβγ and αG355Rβγ channels exhibited 2.5- and 1.8-fold greater amiloride-sensitive currents than WT αβγ human ENaCs, respectively, whereas αV351Aβγ channels conducted significantly less current than WT. Currents in αH354Rβγ-expressing oocytes were similar to those expressing WT. Surface expression levels of three mutants (αR350Wβγ, αV351Aβγ, and αG355Rβγ) were similar to that of WT. However, three mutant channels (αR350Wβγ, αH354Rβγ, and αG355Rβγ) exhibited a reduced Na+ self-inhibition response. Open probability of αR350Wβγ was significantly greater than that of WT. Moreover, other Arg-350 variants, including αR350G, αR350L, and αR350Q, also had significantly increased channel activity. A direct comparison of αR350W and two previously reported gain-of-function variants revealed that αR350W increases ENaC activity similarly to αW493R, but to a much greater degree than does αC479R. Our results indicate that αR350W along with αR350G, αR350L, and αR350Q, and αG355R are novel gain-of-function variants that function as gating modifiers. The location of these multiple functional variants suggests that the αENaC β-ball domain portion that interfaces with the palm domain of βENaC critically regulates ENaC gating.
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Affiliation(s)
- Xueqi Wang
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Nephrology, The Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, China.,The Third Xiangya Hospital of Central South University, Changsha, Hunan 410013, China
| | - Jingxin Chen
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Shujie Shi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Shaohu Sheng
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Thomas R Kleyman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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16
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Shaik FA, Jaggupilli A, Chelikani P. Highly conserved intracellular H208 residue influences agonist selectivity in bitter taste receptor T2R14. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:183057. [PMID: 31493373 DOI: 10.1016/j.bbamem.2019.183057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 08/23/2019] [Accepted: 08/26/2019] [Indexed: 11/19/2022]
Abstract
Bitter taste receptors (T2Rs) are a specialized class of cell membrane receptors of the G protein-coupled receptor family and perform a crucial role in chemosensation. The 25 T2Rs in humans are activated by structurally diverse ligands of plant, animal and microbial origin. The mechanisms of activation of these receptors are poorly understood. Therefore, identification of structural determinants of T2Rs that regulate its efficacy could be beneficial in understanding the molecular mechanisms of T2R activation. In this work, we characterized a highly conserved histidine (H208), present at TM5-ICL3 region of T2R14 and its role in agonist-induced T2R14 signaling. Surprisingly, mutation of the conserved H208 (H208A) did not result in increased basal activity of T2R14, in contrast to similar H206A mutation in T2R4 that showed constitutive or basal activity. However, H208A mutation in T2R14 resulted in an increase in agonist-induced efficacy for Flufenamic acid (FFA). Interestingly, H208A did not affect the potency of another T2R14 agonist Diphenhydramine (DPH). The H208R compensatory mutation showed FFA response similar to wild-type T2R14. Molecular modeling suggests a FFA-induced shift in TM3 and TM5 helices of H208A, which changes the network of interactions connecting TM5-ICL3-TM6. This report identifies a crucial residue on the intracellular surface of T2Rs that is involved in bitter ligand selectivity. It also highlights the varied roles carried out by some conserved residues in different T2Rs.
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Affiliation(s)
- Feroz Ahmed Shaik
- Manitoba Chemosensory Biology Research Group, Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada
| | - Appalaraju Jaggupilli
- Manitoba Chemosensory Biology Research Group, Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada
| | - Prashen Chelikani
- Manitoba Chemosensory Biology Research Group, Department of Oral Biology, University of Manitoba, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada.
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17
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Musante I, Scudieri P, Venturini A, Guidone D, Caci E, Castellani S, Conese M, Galietta LJV. Peripheral localization of the epithelial sodium channel in the apical membrane of bronchial epithelial cells. Exp Physiol 2019; 104:866-875. [PMID: 30924990 DOI: 10.1113/ep087590] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/15/2019] [Indexed: 12/14/2022]
Abstract
NEW FINDINGS What is the central question of this study? What is the precise subcellular localization of the epithelial sodium channel (ENaC) in human airway epithelium? What is the main finding and its importance? ENaC protein has an unexpected localization in the peripheral region of the apical membrane of bronchial epithelial cells, very close to tight junctions. This may be important for the mechanism of Na+ absorption ABSTRACT: The epithelial sodium channel (ENaC) has a key role in absorbing fluid across the human airway epithelium. Altered activity of ENaC may perturb the process of mucociliary clearance, thus impairing the innate defence mechanisms against microbial agents. The proteins forming ENaC are present on the apical membrane of the epithelium. However, their precise localization is unknown. In the present study, we used two antibodies recognizing the α and β ENaC subunits. Both antibodies revealed a restricted localization of ENaC in the peripheral region of the apical membrane of cultured bronchial epithelial cells, close to but not overlapping with tight junctions. In contrast, the cystic fibrosis transmembrane conductance regulator chloride channel was more diffusely expressed on the whole apical membrane. Modulation of ENaC activity by aprotinin or elastase resulted in a decrease or increase in the peripheral localization, respectively. Our results suggest that sodium absorption is mainly occurring close to tight junctions where this cation may be rapidly expelled by the Na+ /K+ pump present in lateral membranes. This arrangement of channels and pumps may limit Na+ build-up in other regions of the cells.
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Affiliation(s)
- Ilaria Musante
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Paolo Scudieri
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Arianna Venturini
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Daniela Guidone
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Emanuela Caci
- UOC Genetica Medica, IRCCS Istituto Giannina Gaslini, Genova, Italy
| | - Stefano Castellani
- Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy
| | - Massimo Conese
- Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy
| | - Luis J V Galietta
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy.,Department of Translational Medical Sciences (DISMET), Federico II University of Naples, Naples, Italy
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18
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Mutchler SM, Kleyman TR. New insights regarding epithelial Na+ channel regulation and its role in the kidney, immune system and vasculature. Curr Opin Nephrol Hypertens 2019; 28:113-119. [PMID: 30585851 PMCID: PMC6349474 DOI: 10.1097/mnh.0000000000000479] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
PURPOSE OF REVIEW This review describes recent findings regarding the epithelial Na channel (ENaC) and its roles in physiologic and pathophysiologic states. We discuss new insights regarding ENaC's structure, its regulation by various factors, its potential role in hypertension and nephrotic syndrome, and its roles in the immune system and vasculature. RECENT FINDINGS A recently resolved structure of ENaC provides clues regarding mechanisms of ENaC activation by proteases. The use of amiloride in nephrotic syndrome, and associated complications are discussed. ENaC is expressed in dendritic cells and contributes to immune system activation and increases in blood pressure in response to NaCl. ENaC is expressed in endothelial ENaC and has a role in regulating vascular tone. SUMMARY New findings have emerged regarding ENaC and its role in the kidney, immune system, and vasculature.
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Affiliation(s)
- Stephanie M. Mutchler
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA
| | - Thomas R. Kleyman
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA
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19
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Zhao C, Crosby J, Lv T, Bai D, Monia BP, Guo S. Antisense oligonucleotide targeting of mRNAs encoding ENaC subunits α, β, and γ improves cystic fibrosis-like disease in mice. J Cyst Fibros 2018; 18:334-341. [PMID: 30100257 DOI: 10.1016/j.jcf.2018.07.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/11/2018] [Accepted: 07/20/2018] [Indexed: 12/19/2022]
Abstract
BACKGROUND The epithelial sodium channel ENaC consists of three subunits encoded by Scnn1a, Scnn1b, and Scnn1g and increased sodium absorption through this channel is hypothesized to lead to mucus dehydration and accumulation in cystic fibrosis (CF) patients. METHODS We identified potent and specific antisense oligonucleotides (ASOs) targeting mRNAs encoding the ENaC subunits and evaluated these ASOs in mouse models of CF-like lung disease. RESULTS ASOs designed to target mRNAs encoding each ENaC subunit or a control ASO were administered directly into the lungs of mice. The reductions in ENaC subunits correlated well with a reduction in amiloride sensitive channel conductance. In addition, levels of mucus markers Gob5, AGR2, Muc5ac, and Muc5b, periodic acid-Schiff's reagent (PAS) goblet cell staining, and neutrophil recruitment were reduced and lung function was improved when levels of any of the ENaC subunits were decreased. CONCLUSIONS Delivery of ASOs targeting mRNAs encoding each of the three ENaC subunits directly into the lung improved disease phenotypes in a mouse model of CF-like lung disease. These findings suggest that targeting ENaC subunits could be an effective approach for the treatment of CF.
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Affiliation(s)
- Chenguang Zhao
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA.
| | - Jeff Crosby
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Tinghong Lv
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Dong Bai
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Brett P Monia
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Shuling Guo
- Ionis Pharmaceuticals, 2855 Gazelle Court, Carlsbad, CA 92010, USA
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20
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Moore PJ, Tarran R. The epithelial sodium channel (ENaC) as a therapeutic target for cystic fibrosis lung disease. Expert Opin Ther Targets 2018; 22:687-701. [PMID: 30028216 DOI: 10.1080/14728222.2018.1501361] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
INTRODUCTION Cystic fibrosis is an autosomal recessive disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that codes for the CFTR anion channel. In the absence of functional CFTR, the epithelial Na+ channel is also dysregulated. Airway surface liquid (ASL) hydration is maintained by a balance between epithelial sodium channel (ENaC)-led Na+ absorption and CFTR-dependent anion secretion. This finely tuned homeostatic mechanism is required to maintain sufficient airway hydration to permit the efficient mucus clearance necessary for a sterile lung environment. In CF airways, the lack of CFTR and increased ENaC activity lead to ASL/mucus dehydration that causes mucus obstruction, neutrophilic infiltration, and chronic bacterial infection. Rehydration of ASL/mucus in CF airways can be achieved by inhibiting Na+ absorption with pharmacological inhibitors of ENaC. Areas covered: In this review, we discuss ENaC structure and function and its role in CF lung disease and focus on ENaC inhibition as a potential therapeutic target to rehydrate CF mucus. We also discuss the failure of the first generation of pharmacological inhibitors of ENaC and recent alternate strategies to attenuate ENaC activity in the CF lung. Expert opinion: ENaC is an attractive therapeutic target to rehydrate CF ASL that may serve as a monotherapy or function in parallel with other treatments. Given the increased number of strategies being employed to inhibit ENaC, this is an exciting and optimistic time to be in this field.
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Affiliation(s)
- Patrick J Moore
- a Marsico Lung Institute , University of North Carolina , Chapel Hill , NC , USA
| | - Robert Tarran
- a Marsico Lung Institute , University of North Carolina , Chapel Hill , NC , USA.,b Department of Cell Biology & Physiology , University of North Carolina , Chapel Hill , NC , USA
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21
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Nikolic A. Pathophysiology and Genetics of Bronchiectasis Unrelated to Cystic Fibrosis. Lung 2018; 196:383-392. [PMID: 29754320 DOI: 10.1007/s00408-018-0121-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 05/04/2018] [Indexed: 10/16/2022]
Abstract
Bronchiectasis is characterized by deregulated inflammatory response and recurrent bacterial infection resulting in progressive lung damage and an irreversible dilatation of bronchi and bronchioles. Generally accepted model of the development of bronchiectasis is the "vicious cycle hypothesis" that proposes compromising of the mucociliary clearance by an initial event, which leads to the infection of the respiratory tract followed by further impairment of mucociliary function, bacterial proliferation, and more inflammation. Bronchiectasis is a very common symptom in patients with cystic fibrosis (CF), while bronchiectasis unrelated to CF is heterogeneous pathology of unknown cause with a large number of potential contributory factors and poorly understood pathogenesis. It is presumed that bronchiectasis unrelated to CF is a multifactorial condition predisposed by genetic factors. Different molecules have been implicated in the onset and development of idiopathic bronchiectasis, as well as modulation of the disease severity and response to therapy. Most of these molecules are involved in the processes that contribute to the homeostasis of the lung tissue, especially mucociliary clearance, protease-antiprotease balance, and immunomodulation. Evaluation of the studies performed towards investigation of the role these molecules play in bronchiectasis identifies genetic variants that may be of potential importance for clinical management of the disease, and also of interest for future research efforts. This review focuses on the molecules with major roles in lung homeostasis and their involvement in bronchiectasis unrelated to CF.
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Affiliation(s)
- Aleksandra Nikolic
- Laboratory for Molecular Biology, Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444A, PO Box 23, 11010, Belgrade, Serbia.
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22
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Shobair M, Popov KI, Dang YL, He H, Stutts MJ, Dokholyan NV. Mapping allosteric linkage to channel gating by extracellular domains in the human epithelial sodium channel. J Biol Chem 2018; 293:3675-3684. [PMID: 29358325 DOI: 10.1074/jbc.ra117.000604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 01/08/2018] [Indexed: 11/06/2022] Open
Abstract
The epithelial sodium channel (ENaC) mediates sodium absorption in lung, kidney, and colon epithelia. Channels in the ENaC/degenerin family possess an extracellular region that senses physicochemical changes in the extracellular milieu and allosterically regulates the channel opening. Proteolytic cleavage activates the ENaC opening, by the removal of specific segments in the finger domains of the α- and γ ENaC-subunits. Cleavage causes perturbations in the extracellular region that propagate to the channel gate. However, it is not known how the channel structure mediates the propagation of activation signals through the extracellular sensing domains. Here, to identify the structure-function determinants that mediate allosteric ENaC activation, we performed MD simulations, thiol modification of residues substituted by cysteine, and voltage-clamp electrophysiology recordings. Our simulations of an ENaC heterotetramer, α1βα2γ, in the proteolytically cleaved and uncleaved states revealed structural pathways in the α-subunit that are responsible for ENaC proteolytic activation. To validate these findings, we performed site-directed mutagenesis to introduce cysteine substitutions in the extracellular domains of the α-, β-, and γ ENaC-subunits. Insertion of a cysteine at the α-subunit Glu557 site, predicted to stabilize a closed state of ENaC, inhibited ENaC basal activity and retarded the kinetics of proteolytic activation by 2-fold. Our results suggest that the lower palm domain of αENaC is essential for ENaC activation. In conclusion, our integrated computational and experimental approach suggests key structure-function determinants for ENaC proteolytic activation and points toward a mechanistic model for the allosteric communication in the extracellular domains of the ENaC/degenerin family channels.
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Affiliation(s)
- Mahmoud Shobair
- From the Program in Molecular and Cellular Biophysics.,Curriculum in Bioinformatics and Computational Biology.,Department of Biochemistry and Biophysics, and.,Cystic Fibrosis and Pulmonary Diseases Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | | | - Yan L Dang
- Cystic Fibrosis and Pulmonary Diseases Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Hong He
- Cystic Fibrosis and Pulmonary Diseases Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - M Jackson Stutts
- Cystic Fibrosis and Pulmonary Diseases Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Nikolay V Dokholyan
- From the Program in Molecular and Cellular Biophysics, .,Curriculum in Bioinformatics and Computational Biology.,Department of Biochemistry and Biophysics, and.,Cystic Fibrosis and Pulmonary Diseases Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
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23
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Polfus LM, Boerwinkle E, Gibbs RA, Metcalf G, Muzny D, Veeraraghavan N, Grove M, Shete S, Wallace S, Milewicz D, Hanchard N, Lupski JR, Hashmi SS, Gupta-Malhotra M. Whole-exome sequencing reveals an inherited R566X mutation of the epithelial sodium channel β-subunit in a case of early-onset phenotype of Liddle syndrome. Cold Spring Harb Mol Case Stud 2017; 2:a001255. [PMID: 27900368 PMCID: PMC5111009 DOI: 10.1101/mcs.a001255] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
To comprehensively evaluate a European–American child with severe hypertension, whole-exome sequencing (WES) was performed on the child and parents, which identified causal variation of the proband's early-onset disease. The proband's hypertension was resistant to treatment, requiring a multiple drug regimen including amiloride, spironolactone, and hydrochlorothiazide. We suspected a monogenic form of hypertension because of the persistent hypokalemia with low plasma levels of renin and aldosterone. To address this, we focused on rare functional variants and indels, and performed gene-based tests incorporating linkage scores and allele frequency and filtered on deleterious functional mutations. Drawing upon clinical presentation, 27 genes were selected evidenced to cause monogenic hypertension and matched to the gene-based results. This resulted in the identification of a stop-gain mutation in an epithelial sodium channel (ENaC), SCNN1B, an established Liddle syndrome gene, shared by the child and her father. Interestingly, the father also harbored a missense mutation (p.Trp552Arg) in the α-subunit of the ENaC trimer, SCNN1A, possibly pointing to pseudohypoaldosteronism type I. This case is unique in that we present the early-onset disease and treatment response caused by a canonical stop-gain mutation (p.Arg566*) as well as ENaC digenic hits in the father, emphasizing the utility of WES informing precision medicine.
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Affiliation(s)
- Linda M Polfus
- Human Genetics Center, The University of Texas Health Science Center at Houston, Houston, Texas 70130, USA
| | - Eric Boerwinkle
- Human Genetics Center, The University of Texas Health Science Center at Houston, Houston, Texas 70130, USA;; Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 70130, USA
| | - Richard A Gibbs
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 70130, USA
| | - Ginger Metcalf
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 70130, USA
| | - Donna Muzny
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 70130, USA
| | | | - Megan Grove
- Human Genetics Center, The University of Texas Health Science Center at Houston, Houston, Texas 70130, USA
| | - Sanjay Shete
- Department of Biostatistics, MD Anderson Cancer Center, The University of Texas Health Science Center, Houston, Texas 77030, USA
| | - Stephanie Wallace
- Division of Medical Genetics, Department of Internal Medicine, The University of Texas Health Science Center, Houston, Texas 77030, USA
| | - Dianna Milewicz
- Division of Medical Genetics, Department of Internal Medicine, The University of Texas Health Science Center, Houston, Texas 77030, USA
| | - Neil Hanchard
- Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 70130, USA
| | - James R Lupski
- Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 70130, USA
| | - Syed Shahrukh Hashmi
- Department of Pediatrics, Children's Memorial Hermann Hospital, The University of Texas Health Science Center, Houston, Texas, Medical School, Texas 77030, USA
| | - Monesha Gupta-Malhotra
- Department of Pediatric Cardiology, Johns Hopkins All Children's Hospital, St. Petersburg, Florida 33701, USA
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24
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Salih M, Gautschi I, van Bemmelen MX, Di Benedetto M, Brooks AS, Lugtenberg D, Schild L, Hoorn EJ. A Missense Mutation in the Extracellular Domain of αENaC Causes Liddle Syndrome. J Am Soc Nephrol 2017; 28:3291-3299. [PMID: 28710092 DOI: 10.1681/asn.2016111163] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 06/04/2017] [Indexed: 11/03/2022] Open
Abstract
Liddle syndrome is an autosomal dominant form of hypokalemic hypertension due to mutations in the β- or γ-subunit of the epithelial sodium channel (ENaC). Here, we describe a family with Liddle syndrome due to a mutation in αENaC. The proband was referred because of resistant hypokalemic hypertension, suppressed renin and aldosterone, and no mutations in the genes encoding β- or γENaC. Exome sequencing revealed a heterozygous, nonconservative T>C single-nucleotide mutation in αENaC that substituted Cys479 with Arg (C479R). C479 is a highly conserved residue in the extracellular domain of ENaC and likely involved in a disulfide bridge with the partner cysteine C394. In oocytes, the C479R and C394S mutations resulted in similar twofold increases in amiloride-sensitive ENaC current. Quantification of mature cleaved αENaC in membrane fractions showed that the number of channels did not increase with these mutations. Trypsin, which increases open probability of the channel by proteolytic cleavage, resulted in significantly higher currents in the wild type than in C479R or C394S mutants. In summary, a mutation in the extracellular domain of αENaC causes Liddle syndrome by increasing intrinsic channel activity. This mechanism differs from that of the β- and γ-mutations, which result in an increase in channel density at the cell surface. This mutation may explain other cases of patients with resistant hypertension and also provides novel insight into ENaC activation, which is relevant for kidney sodium reabsorption and salt-sensitive hypertension.
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Affiliation(s)
| | - Ivan Gautschi
- Département de Pharmacologie et de Toxicologie, Université de Lausanne, Lausanne, Switzerland; and
| | - Miguel X van Bemmelen
- Département de Pharmacologie et de Toxicologie, Université de Lausanne, Lausanne, Switzerland; and
| | - Michael Di Benedetto
- Département de Pharmacologie et de Toxicologie, Université de Lausanne, Lausanne, Switzerland; and
| | - Alice S Brooks
- Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Dorien Lugtenberg
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Laurent Schild
- Département de Pharmacologie et de Toxicologie, Université de Lausanne, Lausanne, Switzerland; and
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25
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Yuan T, Jiang L, Chen C, Peng X, Nie M, Li X, Xing X, Li X, Chen L. Glucose tolerance and insulin responsiveness in Gitelman syndrome patients. Endocr Connect 2017; 6:243-252. [PMID: 28432081 PMCID: PMC5632718 DOI: 10.1530/ec-17-0014] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 04/21/2017] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Impaired glucose metabolism and insulin sensitivity have been reported in patients with Gitelman syndrome (GS), but insulin secretion and the related mechanisms are not well understood. DESIGN AND METHODS The serum glucose levels, insulin secretion and insulin sensitivity were evaluated in patients with GS (n = 28), patients with type 2 diabetes mellitus (DM) and healthy individuals (n = 20 in both groups) using an oral glucose tolerance test. Serum and urine sodium, potassium and creatinine levels were measured at 0, 30, 60, 120 and 180 min after an oral glucose load was administered. RESULTS The areas under the serum glucose curves were higher in the GS patients than those in the healthy controls (17.4 ± 5.1 mmol·h/L vs 14.5 ± 2.8 mmol·h/L, P = 0.02) but lower than those in the DM patients (24.8 ± 5.3 mmol·h/L, P < 0.001). The areas under the serum insulin curves and the insulin secretion indexes in GS patients were higher than those in DM patients and lower than those in healthy subjects. The insulin secretion-sensitivity index of GS patients was between that of healthy subjects and DM patients, but the insulin sensitivity indices were not different among the three groups. After one hour of glucose administration, the serum potassium level significantly decreased from baseline, and the urinary potassium-to-creatinine ratio increased gradually and peaked at 2 h. CONCLUSIONS Glucose metabolism and insulin secretion were impaired in GS patients, but insulin sensitivity was comparable between GS patients and patients with type 2 DM. After administration of an oral glucose load, the plasma potassium level decreased in GS patients due to the increased excretion of potassium in the urine.
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Affiliation(s)
- Tao Yuan
- Department of Endocrinology & Key Laboratory of EndocrinologyThe National Health and Family Planning Commission, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Lanping Jiang
- Department of NephrologyPeking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Chen Chen
- Department of PediatricsState Key Laboratory of Medical Genetics, Xiangya Hospital, Central South University, Changsha, China
| | - Xiaoyan Peng
- Department of NephrologyPeking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Min Nie
- Department of Endocrinology & Key Laboratory of EndocrinologyThe National Health and Family Planning Commission, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Xuemei Li
- Department of NephrologyPeking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Xiaoping Xing
- Department of Endocrinology & Key Laboratory of EndocrinologyThe National Health and Family Planning Commission, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Xuewang Li
- Department of NephrologyPeking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Limeng Chen
- Department of NephrologyPeking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
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26
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Rauh R, Hoerner C, Korbmacher C. δβγ-ENaC is inhibited by CFTR but stimulated by cAMP in Xenopus laevis oocytes. Am J Physiol Lung Cell Mol Physiol 2016; 312:L277-L287. [PMID: 27941075 DOI: 10.1152/ajplung.00375.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 12/05/2016] [Accepted: 12/05/2016] [Indexed: 11/22/2022] Open
Abstract
The epithelial sodium channel (ENaC) and the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel critically regulate airway surface liquid by driving fluid absorption and secretion, respectively. Their functional interplay is complex and incompletely understood. ENaC is a heteromeric channel with three well-characterized subunits (α, β, and γ). In humans, an additional δ-ENaC subunit exists in lung and several other tissues, where it may replace the α-subunit to form δβγ-ENaC. Little is known about the physiological role of δβγ-ENaC and its possible interaction with CFTR. The aim of the present study was to investigate the effect of human CFTR on human δβγ-ENaC heterologously expressed in Xenopus laevis oocytes. In oocytes coexpressing δβγ-ENaC and CFTR the ENaC-mediated amiloride-sensitive whole cell current (ΔIami) was reduced by ~50% compared with that measured in oocytes expressing δβγ-ENaC alone. Moreover, basal level of proteolytic ENaC activation was reduced in the presence of CFTR. The inhibitory effect of CFTR on δβγ-ENaC was due to a combination of decreased average open probability (Po) and reduced channel expression at the cell surface. Interestingly, in oocytes expressing δβγ-ENaC, increasing intracellular [cAMP] by IBMX and forskolin increased ΔIami by ~50%. This stimulatory effect was not observed for human and rat αβγ-ENaC and was independent of CFTR coexpression and coactivation. Experiments with a mutant channel (δβS520Cγ-ENaC) which can be converted to a channel with a Po of nearly 1 suggested that cAMP activates δβγ-ENaC by increasing Po In conclusion, our results demonstrate that δβγ-ENaC is inhibited by CFTR but activated by cAMP.
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Affiliation(s)
- Robert Rauh
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Christian Hoerner
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Christoph Korbmacher
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
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27
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Ray EC, Chen J, Kelly TN, He J, Hamm LL, Gu D, Shimmin LC, Hixson JE, Rao DC, Sheng S, Kleyman TR. Human epithelial Na+ channel missense variants identified in the GenSalt study alter channel activity. Am J Physiol Renal Physiol 2016; 311:F908-F914. [PMID: 27582106 PMCID: PMC5130461 DOI: 10.1152/ajprenal.00426.2016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 08/22/2016] [Indexed: 12/31/2022] Open
Abstract
Mutations in genes encoding subunits of the epithelial Na+ channel (ENaC) can cause early onset familial hypertension, demonstrating the importance of this channel in modulating blood pressure. It remains unclear whether other genetic variants resulting in subtler alterations of channel function result in hypertension or altered sensitivity of blood pressure to dietary salt. This study sought to identify functional human ENaC variants to examine how these variants alter channel activity and to explore whether these variants are associated with altered sensitivity of blood pressure to dietary salt. Six-hundred participants of the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) study with salt-sensitive or salt-resistant blood pressure underwent sequencing of the genes encoding ENaC subunits. Functional effects of identified variants were examined in a Xenopus oocyte expression system. Variants that increased channel activity included three in the gene encoding the α-subunit (αS115N, αR476W, and αV481M), one in the β-subunit (βS635N), and one in the γ-subunit (γL438Q). One α-subunit variant (αA334T) and one γ-subunit variant (βD31N) decreased channel activity. Several α-subunit extracellular domain variants altered channel inhibition by extracellular Na+ (Na+ self-inhibition). One variant (αA334T) decreased and one (αV481M) increased cell surface expression. Association between these variants and salt sensitivity did not reach statistical significance. This study identifies novel functional human ENaC variants and demonstrates that some variants alter channel cell surface expression and/or Na+ self-inhibition.
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Affiliation(s)
- Evan C Ray
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Jingxin Chen
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Tanika N Kelly
- Department of Epidemiology, Tulane University, New Orleans, Louisiana
| | - Jiang He
- Department of Epidemiology, Tulane University, New Orleans, Louisiana.,Department of Medicine, Tulane University, New Orleans, Louisiana
| | - L Lee Hamm
- Department of Medicine, Tulane University, New Orleans, Louisiana
| | - Dongfeng Gu
- State Key Laboratory of Cardiovascular Disease, Division of Population Genetics, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Lawrence C Shimmin
- Human Genetics Center, University of Texas School of Public Health, Houston, Texas
| | - James E Hixson
- Human Genetics Center, University of Texas School of Public Health, Houston, Texas
| | - Dabeeru C Rao
- Division of Biostatistics, Washington University School of Medicine, St. Louis, Missouri
| | - Shaohu Sheng
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania;
| | - Thomas R Kleyman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.,Departments of Cell Biology and Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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28
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Straniero L, Soldà G, Costantino L, Seia M, Melotti P, Colombo C, Asselta R, Duga S. Whole-gene CFTR sequencing combined with digital RT-PCR improves genetic diagnosis of cystic fibrosis. J Hum Genet 2016; 61:977-984. [PMID: 27488443 DOI: 10.1038/jhg.2016.101] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 05/31/2016] [Accepted: 07/07/2016] [Indexed: 11/09/2022]
Abstract
Despite extensive screening, 1-5% of cystic fibrosis (CF) patients lack a definite molecular diagnosis. Next-generation sequencing (NGS) is making affordable genetic testing based on the identification of variants in extended genomic regions. In this frame, we analyzed 23 CF patients and one carrier by whole-gene CFTR resequencing: 4 were previously characterized and served as controls; 17 were cases lacking a complete diagnosis after a full conventional CFTR screening; 3 were consecutive subjects referring to our centers, not previously submitted to any screening. We also included in the custom NGS design the coding portions of the SCNN1A, SCNN1B and SCNN1G genes, encoding the subunits of the sodium channel ENaC, which were found to be mutated in CF-like patients. Besides 2 novel SCNN1B missense mutations, we identified 22 previously-known CFTR mutations, including 2 large deletions (whose breakpoints were precisely mapped), and novel deep-intronic variants, whose role on splicing was excluded by ex-vivo analyses. Finally, for 2 patients, compound heterozygotes for a CFTR mutation and the intron-9c.1210-34TG[11-12]T5 allele-known to be associated with decreased CFTR mRNA levels-the molecular diagnosis was implemented by measuring the residual level of wild-type transcript by digital reverse transcription polymerase chain reaction performed on RNA extracted from nasal brushing.
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Affiliation(s)
- Letizia Straniero
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - Giulia Soldà
- Department of Biomedical Sciences, Humanitas University, Milan, Italy.,Humanitas Clinical and Research Center, Milan, Italy
| | - Lucy Costantino
- Medical Genetics Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Manuela Seia
- Medical Genetics Laboratory, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Paola Melotti
- Cystic Fibrosis Center, Azienda Ospedaliera Universitaria Integrata di Verona, Verona, Italy
| | - Carla Colombo
- Cystic Fibrosis Center of Milan, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Rosanna Asselta
- Department of Biomedical Sciences, Humanitas University, Milan, Italy.,Humanitas Clinical and Research Center, Milan, Italy
| | - Stefano Duga
- Department of Biomedical Sciences, Humanitas University, Milan, Italy.,Humanitas Clinical and Research Center, Milan, Italy
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29
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Hanukoglu I, Hanukoglu A. Epithelial sodium channel (ENaC) family: Phylogeny, structure-function, tissue distribution, and associated inherited diseases. Gene 2016; 579:95-132. [PMID: 26772908 PMCID: PMC4756657 DOI: 10.1016/j.gene.2015.12.061] [Citation(s) in RCA: 238] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 12/20/2015] [Accepted: 12/22/2015] [Indexed: 01/24/2023]
Abstract
The epithelial sodium channel (ENaC) is composed of three homologous subunits and allows the flow of Na(+) ions across high resistance epithelia, maintaining body salt and water homeostasis. ENaC dependent reabsorption of Na(+) in the kidney tubules regulates extracellular fluid (ECF) volume and blood pressure by modulating osmolarity. In multi-ciliated cells, ENaC is located in cilia and plays an essential role in the regulation of epithelial surface liquid volume necessary for cilial transport of mucus and gametes in the respiratory and reproductive tracts respectively. The subunits that form ENaC (named as alpha, beta, gamma and delta, encoded by genes SCNN1A, SCNN1B, SCNN1G, and SCNN1D) are members of the ENaC/Degenerin superfamily. The earliest appearance of ENaC orthologs is in the genomes of the most ancient vertebrate taxon, Cyclostomata (jawless vertebrates) including lampreys, followed by earliest representatives of Gnathostomata (jawed vertebrates) including cartilaginous sharks. Among Euteleostomi (bony vertebrates), Actinopterygii (ray finned-fishes) branch has lost ENaC genes. Yet, most animals in the Sarcopterygii (lobe-finned fish) branch including Tetrapoda, amphibians and amniotes (lizards, crocodiles, birds, and mammals), have four ENaC paralogs. We compared the sequences of ENaC orthologs from 20 species and established criteria for the identification of ENaC orthologs and paralogs, and their distinction from other members of the ENaC/Degenerin superfamily, especially ASIC family. Differences between ENaCs and ASICs are summarized in view of their physiological functions and tissue distributions. Structural motifs that are conserved throughout vertebrate ENaCs are highlighted. We also present a comparative overview of the genotype-phenotype relationships in inherited diseases associated with ENaC mutations, including multisystem pseudohypoaldosteronism (PHA1B), Liddle syndrome, cystic fibrosis-like disease and essential hypertension.
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Affiliation(s)
- Israel Hanukoglu
- Laboratory of Cell Biology, Faculty of Natural Sciences, Ariel University, Ariel, Israel.
| | - Aaron Hanukoglu
- Division of Pediatric Endocrinology, E. Wolfson Medical Center, Holon, Israel; Sackler School of Medicine, Tel-Aviv University, Tel Aviv, Israel
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30
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Assessment of epithelial sodium channel variants in nonwhite cystic fibrosis patients with non-diagnostic CFTR genotypes. J Cyst Fibros 2016; 15:52-9. [DOI: 10.1016/j.jcf.2015.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 03/31/2015] [Accepted: 04/01/2015] [Indexed: 11/23/2022]
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31
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Shobair M, Dagliyan O, Kota P, Dang YL, He H, Stutts MJ, Dokholyan NV. Gain-of-Function Mutation W493R in the Epithelial Sodium Channel Allosterically Reconfigures Intersubunit Coupling. J Biol Chem 2015; 291:3682-92. [PMID: 26668308 DOI: 10.1074/jbc.m115.678052] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Indexed: 12/21/2022] Open
Abstract
Sodium absorption in epithelial cells is rate-limited by the epithelial sodium channel (ENaC) activity in lung, kidney, and the distal colon. Pathophysiological conditions, such as cystic fibrosis and Liddle syndrome, result from water-electrolyte imbalance partly due to malfunction of ENaC regulation. Because the quaternary structure of ENaC is yet undetermined, the bases of pathologically linked mutations in ENaC subunits α, β, and γ are largely unknown. Here, we present a structural model of heterotetrameric ENaC α1βα2γ that is consistent with previous cross-linking results and site-directed mutagenesis experiments. By using this model, we show that the disease-causing mutation αW493R rewires structural dynamics of the intersubunit interfaces α1β and α2γ. Changes in dynamics can allosterically propagate to the channel gate. We demonstrate that cleavage of the γ-subunit, which is critical for full channel activation, does not mediate activation of ENaC by αW493R. Our molecular dynamics simulations led us to identify a channel-activating electrostatic interaction between α2Arg-493 and γGlu-348 at the α2γ interface. By neutralizing a sodium-binding acidic patch at the α1β interface, we reduced ENaC activation of αW493R by more than 2-fold. By combining homology modeling, molecular dynamics, cysteine cross-linking, and voltage clamp experiments, we propose a dynamics-driven model for the gain-of-function in ENaC by αW493R. Our integrated computational and experimental approach advances our understanding of structure, dynamics, and function of ENaC in its disease-causing state.
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Affiliation(s)
- Mahmoud Shobair
- From the Program in Molecular and Cellular Biophysics, Curriculum in Bioinformatics and Computational Biology, Department of Biochemistry and Biophysics, and
| | - Onur Dagliyan
- From the Program in Molecular and Cellular Biophysics, Department of Biochemistry and Biophysics, and
| | - Pradeep Kota
- From the Program in Molecular and Cellular Biophysics, Department of Biochemistry and Biophysics, and
| | - Yan L Dang
- Cystic Fibrosis and Pulmonary Diseases Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Hong He
- Cystic Fibrosis and Pulmonary Diseases Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - M Jackson Stutts
- Cystic Fibrosis and Pulmonary Diseases Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Nikolay V Dokholyan
- From the Program in Molecular and Cellular Biophysics, Curriculum in Bioinformatics and Computational Biology, Department of Biochemistry and Biophysics, and Cystic Fibrosis and Pulmonary Diseases Research and Treatment Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
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Rademacher J, Schulz A, Hedtfeld S, Stanke F, Ringshausen F, Welte T, Tümmler B. Nasal potential difference of carriers of the W493R ENaC variant with non-cystic fibrosis bronchiectasis. Eur Respir J 2015; 47:322-4. [PMID: 26453628 DOI: 10.1183/13993003.01128-2015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 08/12/2015] [Indexed: 11/05/2022]
Affiliation(s)
- Jessica Rademacher
- Dept of Respiratory Medicine, Hannover Medical School, Hannover, Germany
| | - Angela Schulz
- Clinic for Paediatric Pneumology, Allergology and Neonatology, Hannover Medical School, Hannover, Germany Biomedical Research in Endstage and Obstructive Lung Disease (BREATH), German Center for Lung Research, Hannover, Germany
| | - Silke Hedtfeld
- Clinic for Paediatric Pneumology, Allergology and Neonatology, Hannover Medical School, Hannover, Germany
| | - Frauke Stanke
- Clinic for Paediatric Pneumology, Allergology and Neonatology, Hannover Medical School, Hannover, Germany Biomedical Research in Endstage and Obstructive Lung Disease (BREATH), German Center for Lung Research, Hannover, Germany
| | - Felix Ringshausen
- Dept of Respiratory Medicine, Hannover Medical School, Hannover, Germany Biomedical Research in Endstage and Obstructive Lung Disease (BREATH), German Center for Lung Research, Hannover, Germany
| | - Tobias Welte
- Dept of Respiratory Medicine, Hannover Medical School, Hannover, Germany Biomedical Research in Endstage and Obstructive Lung Disease (BREATH), German Center for Lung Research, Hannover, Germany
| | - Burkhard Tümmler
- Clinic for Paediatric Pneumology, Allergology and Neonatology, Hannover Medical School, Hannover, Germany Biomedical Research in Endstage and Obstructive Lung Disease (BREATH), German Center for Lung Research, Hannover, Germany
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Greer T, Hao L, Nechyporenko A, Lee S, Vezina CM, Ricke WA, Marker PC, Bjorling DE, Bushman W, Li L. Custom 4-Plex DiLeu Isobaric Labels Enable Relative Quantification of Urinary Proteins in Men with Lower Urinary Tract Symptoms (LUTS). PLoS One 2015; 10:e0135415. [PMID: 26267142 PMCID: PMC4534462 DOI: 10.1371/journal.pone.0135415] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2015] [Accepted: 07/21/2015] [Indexed: 12/19/2022] Open
Abstract
The relative quantification of proteins using liquid chromatography mass spectrometry (LC-MS) has allowed researchers to compile lists of potential disease markers. These complex quantitative workflows often include isobaric labeling of enzymatically-produced peptides to analyze their relative abundances across multiple samples in a single LC-MS run. Recent efforts by our lab have provided scientists with cost-effective alternatives to expensive commercial labels. Although the quantitative performance of these dimethyl leucine (DiLeu) labels has been reported using known ratios of complex protein and peptide standards, their potential in large-scale proteomics studies using a clinically relevant system has never been investigated. Our work rectifies this oversight by implementing 4-plex DiLeu to quantify proteins in the urine of aging human males who suffer from lower urinary tract symptoms (LUTS). Protein abundances in 25 LUTS and 15 control patients were compared, revealing that of the 836 proteins quantified, 50 were found to be differentially expressed (>20% change) and statistically significant (p-value <0.05). Gene ontology (GO) analysis of the differentiated proteins showed that many were involved in inflammatory responses and implicated in fibrosis. While confirmation of individual protein abundance changes would be required to verify protein expression, this study represents the first report using the custom isobaric label, 4-plex DiLeu, to quantify protein abundances in a clinically relevant system.
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Affiliation(s)
- Tyler Greer
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Ling Hao
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Anatoliy Nechyporenko
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Sanghee Lee
- Department of Urology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Chad M. Vezina
- School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Will A. Ricke
- Department of Urology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Paul C. Marker
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Dale E. Bjorling
- School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Wade Bushman
- Department of Urology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Lingjun Li
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail:
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The Contribution of the Airway Epithelial Cell to Host Defense. Mediators Inflamm 2015; 2015:463016. [PMID: 26185361 PMCID: PMC4491388 DOI: 10.1155/2015/463016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Accepted: 12/11/2014] [Indexed: 12/19/2022] Open
Abstract
In the context of cystic fibrosis, the epithelial cell has been characterized in terms of its ion transport capabilities. The ability of an epithelial cell to initiate CFTR-mediated chloride and bicarbonate transport has been recognized early as a means to regulate the thickness of the epithelial lining fluid and recently as a means to regulate the pH, thereby determining critically whether or not host defense proteins such as mucins are able to fold appropriately. This review describes how the epithelial cell senses the presence of pathogens and inflammatory conditions, which, in turn, facilitates the activation of CFTR and thus directly promotes pathogens clearance and innate immune defense on the surface of the epithelial cell. This paper summarizes functional data that describes the effect of cytokines, chemokines, infectious agents, and inflammatory conditions on the ion transport properties of the epithelial cell and relates these key properties to the molecular pathology of cystic fibrosis. Recent findings on the role of cystic fibrosis modifier genes that underscore the role of the epithelial ion transport in host defense and inflammation are discussed.
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Griesenbach U, Alton EW. Recent advances in understanding and managing cystic fibrosis transmembrane conductance regulator dysfunction. F1000PRIME REPORTS 2015; 7:64. [PMID: 26097737 PMCID: PMC4447040 DOI: 10.12703/p7-64] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cystic fibrosis is the most common autosomal recessive genetic disease in Caucasians and has been extensively studied for many decades. The cystic fibrosis transmembrane conductance regulator gene was identified in 1989. It encodes a complex protein which has numerous cellular functions. Our understanding of cystic fibrosis pathophysiology and genetics is constantly expanding and being refined, leading to improved management of the disease and increased life expectancy in affected individuals.
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Agné AM, Baldin JP, Benjamin AR, Orogo-Wenn MC, Wichmann L, Olson KR, Walters DV, Althaus M. Hydrogen sulfide decreases β-adrenergic agonist-stimulated lung liquid clearance by inhibiting ENaC-mediated transepithelial sodium absorption. Am J Physiol Regul Integr Comp Physiol 2015; 308:R636-49. [PMID: 25632025 DOI: 10.1152/ajpregu.00489.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 01/19/2015] [Indexed: 01/11/2023]
Abstract
In pulmonary epithelia, β-adrenergic agonists regulate the membrane abundance of the epithelial sodium channel (ENaC) and, thereby, control the rate of transepithelial electrolyte absorption. This is a crucial regulatory mechanism for lung liquid clearance at birth and thereafter. This study investigated the influence of the gaseous signaling molecule hydrogen sulfide (H2S) on β-adrenergic agonist-regulated pulmonary sodium and liquid absorption. Application of the H2S-liberating molecule Na2S (50 μM) to the alveolar compartment of rat lungs in situ decreased baseline liquid absorption and abrogated the stimulation of liquid absorption by the β-adrenergic agonist terbutaline. There was no additional effect of Na2S over that of the ENaC inhibitor amiloride. In electrophysiological Ussing chamber experiments with native lung epithelia (Xenopus laevis), Na2S inhibited the stimulation of amiloride-sensitive current by terbutaline. β-adrenergic agonists generally increase ENaC abundance by cAMP formation and activation of PKA. Activation of this pathway by forskolin and 3-isobutyl-1-methylxanthine increased amiloride-sensitive currents in H441 pulmonary epithelial cells. This effect was inhibited by Na2S in a dose-dependent manner (5-50 μM). Na2S had no effect on cellular ATP concentration, cAMP formation, and activation of PKA. By contrast, Na2S prevented the cAMP-induced increase in ENaC activity in the apical membrane of H441 cells. H441 cells expressed the H2S-generating enzymes cystathionine-β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase, and they produced H2S amounts within the employed concentration range. These data demonstrate that H2S prevents the stimulation of ENaC by cAMP/PKA and, thereby, inhibits the proabsorptive effect of β-adrenergic agonists on lung liquid clearance.
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Affiliation(s)
- Alisa M Agné
- Institute of Animal Physiology, Department of Molecular Cell Physiology, Justus-Liebig University, Giessen, Germany
| | - Jan-Peter Baldin
- Institute of Animal Physiology, Department of Molecular Cell Physiology, Justus-Liebig University, Giessen, Germany
| | - Audra R Benjamin
- Division of Clinical Sciences, St. George's University of London, London, United Kingdom
| | - Maria C Orogo-Wenn
- Division of Clinical Sciences, St. George's University of London, London, United Kingdom
| | - Lukas Wichmann
- Institute of Animal Physiology, Department of Molecular Cell Physiology, Justus-Liebig University, Giessen, Germany
| | - Kenneth R Olson
- Department of Physiology, Indiana University School of Medicine-South Bend, South Bend, Indiana; and
| | - Dafydd V Walters
- Division of Clinical Sciences, St. George's University of London, London, United Kingdom
| | - Mike Althaus
- Institute of Animal Physiology, Department of Molecular Cell Physiology, Justus-Liebig University, Giessen, Germany;
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Warnock DG, Kusche-Vihrog K, Tarjus A, Sheng S, Oberleithner H, Kleyman TR, Jaisser F. Blood pressure and amiloride-sensitive sodium channels in vascular and renal cells. Nat Rev Nephrol 2014; 10:146-57. [PMID: 24419567 DOI: 10.1038/nrneph.2013.275] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Sodium transport in the distal nephron is mediated by epithelial sodium channel activity. Proteolytic processing of external domains and inhibition with increased sodium concentrations are important regulatory features of epithelial sodium channel complexes expressed in the distal nephron. By contrast, sodium channels expressed in the vascular system are activated by increased external sodium concentrations, which results in changes in the mechanical properties and function of endothelial cells. Mechanosensitivity and shear stress affect both epithelial and vascular sodium channel activity. Guyton's hypothesis stated that blood pressure control is critically dependent on vascular tone and fluid handling by the kidney. The synergistic effects, and complementary regulation, of the epithelial and vascular systems are consistent with the Guytonian model of volume and blood pressure regulation, and probably reflect sequential evolution of the two systems. The integration of vascular tone, renal perfusion and regulation of renal sodium reabsorption is the central underpinning of the Guytonian model. In this Review, we focus on the expression and regulation of sodium channels, and we outline the emerging evidence that describes the central role of amiloride-sensitive sodium channels in the efferent (vascular) and afferent (epithelial) arms of this homeostatic system.
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Affiliation(s)
- David G Warnock
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, 1720 2nd Avenue South, Birmingham, AL 34294-0007, USA
| | - Kristina Kusche-Vihrog
- Institut für Physiologie II, Westfälische Wilhelms Universität, Robert-Koch-Straße 27, 48149 Münster, Germany
| | - Antoine Tarjus
- INSERM U872 Team 1, Centre de Recherche des Cordeliers, Université René Descartes, Université Pierre et Marie Curie, 15 rue de l'Ecole de Médecine, 75006 Paris, France
| | - Shaohu Sheng
- Renal and Electrolyte Division, Department of Medicine, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA 15261, USA
| | - Hans Oberleithner
- Institut für Physiologie II, Westfälische Wilhelms Universität, Robert-Koch-Straße 27, 48149 Münster, Germany
| | - Thomas R Kleyman
- Renal and Electrolyte Division, Department of Medicine, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA 15261, USA
| | - Frederic Jaisser
- INSERM U872 Team 1, Centre de Recherche des Cordeliers, Université René Descartes, Université Pierre et Marie Curie, 15 rue de l'Ecole de Médecine, 75006 Paris, France
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Schoenberger M, Althaus M. Novel small molecule epithelial sodium channel inhibitors as potential therapeutics in cystic fibrosis – a patent evaluation. Expert Opin Ther Pat 2013; 23:1383-9. [DOI: 10.1517/13543776.2013.829454] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Ramos MD, Trujillano D, Olivar R, Sotillo F, Ossowski S, Manzanares J, Costa J, Gartner S, Oliva C, Quintana E, Gonzalez MI, Vazquez C, Estivill X, Casals T. Extensive sequence analysis of CFTR, SCNN1A, SCNN1B, SCNN1G and SERPINA1 suggests an oligogenic basis for cystic fibrosis-like phenotypes. Clin Genet 2013; 86:91-5. [PMID: 23837941 DOI: 10.1111/cge.12234] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 07/05/2013] [Accepted: 07/05/2013] [Indexed: 02/03/2023]
Abstract
The term cystic fibrosis (CF)-like disease is used to describe patients with a borderline sweat test and suggestive CF clinical features but without two CFTR(cystic fibrosis transmembrane conductance regulator) mutations. We have performed the extensive molecular analysis of four candidate genes (SCNN1A, SCNN1B, SCNN1G and SERPINA1) in a cohort of 10 uncharacterized patients with CF and CF-like disease. We have used whole-exome sequencing to characterize mutations in the CFTR gene and these four candidate genes. CFTR molecular analysis allowed a complete characterization of three of four CF patients. Candidate variants in SCNN1A, SCNN1B, SCNN1G and SERPINA1 in six patients with CF-like phenotypes were confirmed by Sanger sequencing and were further supported by in silico predictive analysis, pedigree studies, sweat test in other family members, and analysis in CF patients and healthy subjects. Our results suggest that CF-like disease probably results from complex genotypes in several genes in an oligogenic form, with rare variants interacting with environmental factors.
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Affiliation(s)
- M D Ramos
- Center for Molecular Genetic Diagnosis, Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain
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Aarbiou J, Copreni E, Buijs-Offerman RM, van der Wegen P, Castellani S, Carbone A, Tilesi F, Fradiani P, Hiemstra PS, Yueksekdag G, Diana A, Rosenecker J, Ascenzioni F, Conese M, Scholte BJ. Lentiviral small hairpin RNA delivery reduces apical sodium channel activity in differentiated human airway epithelial cells. J Gene Med 2013; 14:733-45. [PMID: 23074129 DOI: 10.1002/jgm.2672] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 09/27/2012] [Accepted: 10/07/2012] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Epithelial sodium channel (ENaC) hyperactivity has been implicated in the pathogenesis of cystic fibrosis (CF) by dysregulation of fluid and electrolytes in the airways. In the present study, we show proof-of-principle for ENaC inhibition by lentiviral-mediated RNA interference. METHODS Immortalized normal (H441) and CF mutant (CFBE) airway cells, and differentiated human bronchial epithelial cells in air liquid interface culture (HBEC-ALI) were transduced with a vesicular stomatitis virus G glycoprotein pseudotyped lentiviral (LV) vector expressing a short hairpin RNA (shRNA) targeting the α subunit of ENaC (ENaCα), and a marker gene. Efficacy of ENaCα down-regulation was assayed by the real-time polymerase chain reaction (PCR), membrane potential assay, western blotting, short-circuit currents and fluid absorption. Off-target effects were investigated by a lab-on-a-chip quantitative PCR array. RESULTS Transduction to near one hundred percentage efficiency of H441, CFBE and HBEC-ALI was achieved by the addition of the LV vector before differentiation and polarization. Transduction resulted in the inhibition of ENaCα mRNA and antigen expression, and a proportional decrease in ENaC-dependent short circuit current and fluid transport. No effect on transepithelial resistance or cAMP-induced secretion responses was observed in HBEC-ALI. The production of interferon α and pro-inflammatory cytokine mRNA, indicating Toll-like receptor 3 or RNA-induced silencing complex mediated off-target effects, was not observed in HBEC-ALI transduced with this vector. CONCLUSIONS We have established a generic method for studying the effect of RNA interference in HBEC-ALI using standard lentiviral vectors. Down-regulation of ENaCα by lentiviral shRNA expression vectors as shown in the absence off-target effects has potential therapeutic value in the treatment of cystic fibrosis.
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Affiliation(s)
- Jamil Aarbiou
- Department of Cell Biology, Erasmus MC, Rotterdam, The Netherlands
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Chloride transport-driven alveolar fluid secretion is a major contributor to cardiogenic lung edema. Proc Natl Acad Sci U S A 2013; 110:E2308-16. [PMID: 23645634 DOI: 10.1073/pnas.1216382110] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Alveolar fluid clearance driven by active epithelial Na(+) and secondary Cl(-) absorption counteracts edema formation in the intact lung. Recently, we showed that impairment of alveolar fluid clearance because of inhibition of epithelial Na(+) channels (ENaCs) promotes cardiogenic lung edema. Concomitantly, we observed a reversal of alveolar fluid clearance, suggesting that reversed transepithelial ion transport may promote lung edema by driving active alveolar fluid secretion. We, therefore, hypothesized that alveolar ion and fluid secretion may constitute a pathomechanism in lung edema and aimed to identify underlying molecular pathways. In isolated perfused lungs, alveolar fluid clearance and secretion were determined by a double-indicator dilution technique. Transepithelial Cl(-) secretion and alveolar Cl(-) influx were quantified by radionuclide tracing and alveolar Cl(-) imaging, respectively. Elevated hydrostatic pressure induced ouabain-sensitive alveolar fluid secretion that coincided with transepithelial Cl(-) secretion and alveolar Cl(-) influx. Inhibition of either cystic fibrosis transmembrane conductance regulator (CFTR) or Na(+)-K(+)-Cl(-) cotransporters (NKCC) blocked alveolar fluid secretion, and lungs of CFTR(-/-) mice were protected from hydrostatic edema. Inhibition of ENaC by amiloride reproduced alveolar fluid and Cl(-) secretion that were again CFTR-, NKCC-, and Na(+)-K(+)-ATPase-dependent. Our findings show a reversal of transepithelial Cl(-) and fluid flux from absorptive to secretory mode at hydrostatic stress. Alveolar Cl(-) and fluid secretion are triggered by ENaC inhibition and mediated by NKCC and CFTR. Our results characterize an innovative mechanism of cardiogenic edema formation and identify NKCC1 as a unique therapeutic target in cardiogenic lung edema.
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Tsui LC, Dorfman R. The cystic fibrosis gene: a molecular genetic perspective. Cold Spring Harb Perspect Med 2013; 3:a009472. [PMID: 23378595 DOI: 10.1101/cshperspect.a009472] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The positional cloning of the gene responsible for cystic fibrosis (CF) was the important first step in understanding the basic defect and pathophysiology of the disease. This study aims to provide a historical account of key developments as well as factors that contributed to the cystic fibrosis transmembrane conductance regulator (CFTR) gene identification work. A redefined gene structure based on the full sequence of the gene derived from the Human Genome Project is presented, along with brief reviews of the transcription regulatory sequences for the CFTR gene, the role of mRNA splicing in gene regulation and CF disease, and, various related sequences in the human genome and other species. Because CF mutations and genotype-phenotype correlations are covered by our colleagues (Ferec C, Cutting GR. 2012. Assessing the disease-liability of mutations in CFTR. Cold Spring Harb Perspect Med doi: 10.1101/cshperspect.a009480), we only attempt to provide an introduction of the CF mutation database here for reference purposes.
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Affiliation(s)
- Lap-Chee Tsui
- The University of Hong Kong, Hong Kong, Special Administrative Region, China.
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43
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Chen J, Kleyman TR, Sheng S. Gain-of-function variant of the human epithelial sodium channel. Am J Physiol Renal Physiol 2012; 304:F207-13. [PMID: 23136006 DOI: 10.1152/ajprenal.00563.2012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Epithelial Na(+) channel (ENaC) mutations are associated with several human disorders, underscoring the importance of these channels in human health. Recent human genome sequencing projects have revealed a large number of ENaC gene variations, several of which have been found in individuals with salt-sensitive hypertension, cystic fibrosis, and other disorders. However, the functional consequences of most variants are unknown. In this study, we used the Xenopus oocyte expression system to examine the functional properties of a human ENaC variant. Oocytes expressing αβγL511Q human ENaCs showed 4.6-fold greater amiloride-sensitive currents than cells expressing wild-type channels. The γL511Q variant did not significantly alter channel surface expression. Single channel recordings revealed that the variant had fourfold higher open probability than wild type. In addition, γL511Q largely eliminated the Na(+) self-inhibition response, which reflects a downregulation of ENaC open probability by extracellular Na(+). Moreover, γL511Q diminished chymotrypsin-induced activation of the mutant channel. We conclude that γL511Q is a gain-of-function human ENaC variant. Our results suggest that γL511Q enhances ENaC activity by increasing channel open probability and dampens channel regulation by extracellular Na(+) and proteases.
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Affiliation(s)
- Jingxin Chen
- Dept. of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
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44
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Rauh R, Soell D, Haerteis S, Diakov A, Nesterov V, Krueger B, Sticht H, Korbmacher C. A mutation in the β-subunit of ENaC identified in a patient with cystic fibrosis-like symptoms has a gain-of-function effect. Am J Physiol Lung Cell Mol Physiol 2012; 304:L43-55. [PMID: 23087020 DOI: 10.1152/ajplung.00093.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
In some patients with atypical cystic fibrosis (CF), only one allele of the CF transmembrane conductance regulator (CFTR) gene is affected. Mutations of the epithelial sodium channel (ENaC) may contribute to the pathophysiology of the disease in these patients. To functionally characterize a mutation in the β-subunit of ENaC (βV348M) recently identified in a patient with severe CF-like symptoms (Mutesa et al. 2009), we expressed wild-type (wt) αβγENaC or mutant αβV348MγENaC in Xenopus laevis oocytes. The βV348M mutation stimulated amiloride-sensitive whole-cell current (ΔI(ami)) by ∼40% but had no effect on surface expression or single-channel conductance of ENaC. Instead the mutation increased channel open probability (P(o)). Proteolytic activation of mutant ENaC by chymotrypsin was reduced compared with that of wt ENaC (∼3.0-fold vs. ∼4.2-fold), which is consistent with the increased baseline P(o) of mutant ENaC. Similarly, the ENaC activator S3969 stimulated mutant ENaC currents to a lesser degree (by ∼2.6-fold) than wt ENaC currents (by ∼3.5-fold). The gain-of-function effect of the βV348M mutation was confirmed by whole-cell current measurements in HEK293 cells transiently transfected with wt or mutant ENaC. Computational channel modeling in combination with functional expression of different βV348 mutants in oocytes suggests that the βV348M mutation increases channel P(o) by destabilizing the closed channel state. Our findings indicate that the gain-of-function effect of the βV348M mutation may contribute to CF pathophysiology by inappropriately increasing sodium and fluid absorption in the respiratory tract.
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Affiliation(s)
- Robert Rauh
- Institut für Zelluläre und Molekulare Physiologie, Erlangen, Germany.
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45
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Butterworth MB, Zhang L, Heidrich EM, Myerburg MM, Thibodeau PH. Activation of the epithelial sodium channel (ENaC) by the alkaline protease from Pseudomonas aeruginosa. J Biol Chem 2012; 287:32556-65. [PMID: 22859302 DOI: 10.1074/jbc.m112.369520] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that significantly contributes to the mortality of patients with cystic fibrosis. Chronic infection by Pseudomonas induces sustained immune and inflammatory responses and damage to the airway. The ability of Pseudomonas to resist host defenses is aided, in part, by secreted proteases, which act as virulence factors in multiple modes of infection. Recent studies suggest that misregulation of protease activity in the cystic fibrosis lung may alter fluid secretion and pathogen clearance by proteolytic activation of the epithelial sodium channel (ENaC). To evaluate the possibility that proteolytic activation of ENaC may contribute to the virulence of Pseudomonas, primary human bronchial epithelial cells were exposed to P. aeruginosa and ENaC function was assessed by short circuit current measurements. Apical treatment with a strain known to express high levels of alkaline protease (AP) resulted in an increase in basal ENaC current and a loss of trypsin-inducible ENaC current, consistent with sustained activation of ENaC. To further characterize this AP-induced ENaC activation, AP was purified, and its folding, activity, and ability to activate ENaC were assessed. AP folding was efficient under pH and calcium conditions thought to exist in the airway surface liquid of normal and cystic fibrosis (CF) lungs. Short circuit measurements of ENaC in polarized monolayers indicated that AP activated ENaC in immortalized cell lines as well as post-transplant, primary human bronchial epithelial cells from both CF and non-CF patients. This activation was mapped to the γ-subunit of ENaC. Based on these data, patho-mechanisms associated with AP in the CF lung are proposed wherein secretion of AP leads to decreased airway surface liquid volume and a corresponding decrease in mucocilliary clearance of pulmonary pathogens.
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Affiliation(s)
- Michael B Butterworth
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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Novel mutation in the epithelial sodium channel causing type I pseudohypoaldosteronism in a patient misdiagnosed with cystic fibrosis. Eur J Pediatr 2012; 171:997-1000. [PMID: 22371258 DOI: 10.1007/s00431-012-1697-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 02/08/2012] [Indexed: 10/28/2022]
Abstract
UNLABELLED Cystic fibrosis (CF) is an inherited disorder with a devastating prognosis. Determination of chloride concentration in sweat has been the gold standard test for diagnosing CF for over 50 years and still remains the primary screening test. However, now that the genetic cause is known and can be studied, genetic confirmation is mandatory in every suspected patient. We present a patient who had been clinically diagnosed and whose genetic testing could not confirm CF, leading us to search for other options that may also give a positive sweat test. The patient turned out to suffer type 1 pseudohypoaldosteronism, a condition that may cause severe dehydration, hyponatremia and hyperkalemia episodes if not diagnosed and treated early with sodium supplementation. We found a genetic variation in the epithelial sodium channel gene which has not been reported previously, and we discuss the possibility of it being the cause of our patient's phenotype. CONCLUSION this patient clearly illustrates the usefulness of genetic confirmation for CF for the diagnosis and genetic counselling, even when it is clinically oriented, and describes a novel mutation of the amiloride-sensitive epithelial sodium channel possibly causing type 1 pseudohypoaldosteronism.
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Thibodeau PH, Butterworth MB. Proteases, cystic fibrosis and the epithelial sodium channel (ENaC). Cell Tissue Res 2012; 351:309-23. [PMID: 22729487 DOI: 10.1007/s00441-012-1439-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 04/20/2012] [Indexed: 02/06/2023]
Abstract
Proteases perform a diverse array of biological functions. From simple peptide digestion for nutrient absorption to complex signaling cascades, proteases are found in organisms from prokaryotes to humans. In the human airway, proteases are associated with the regulation of the airway surface liquid layer, tissue remodeling, host defense and pathogenic infection and inflammation. A number of proteases are released in the airways under both physiological and pathophysiological states by both the host and invading pathogens. In airway diseases such as cystic fibrosis, proteases have been shown to be associated with increased morbidity and airway disease progression. In this review, we focus on the regulation of proteases and discuss specifically those proteases found in human airways. Attention then shifts to the epithelial sodium channel (ENaC), which is regulated by proteolytic cleavage and that is considered to be an important component of cystic fibrosis disease. Finally, we discuss bacterial proteases, in particular, those of the most prevalent bacterial pathogen found in cystic fibrosis, Pseudomonas aeruginosa.
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Affiliation(s)
- P H Thibodeau
- Department of Cell Biology, University of Pittsburgh School of Medicine, 3500 Terrace Street, S327 Biomedical Science Tower, Pittsburgh, PA 15261, USA
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Thiol-reactive compounds from garlic inhibit the epithelial sodium channel (ENaC). Bioorg Med Chem 2012; 20:3979-84. [PMID: 22668601 DOI: 10.1016/j.bmc.2012.05.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 05/09/2012] [Accepted: 05/10/2012] [Indexed: 12/15/2022]
Abstract
The epithelial sodium channel (ENaC) is a key factor in the transepithelial movement of sodium, and consequently salt and water homeostasis in various organs. Dysregulated activity of ENaC is associated with human diseases such as hypertension, the salt-wasting syndrome pseudohypoaldosteronism type 1, cystic fibrosis, pulmonary oedema or intestinal disorders. Therefore it is important to identify novel compounds that affect ENaC activity. This study investigated if garlic (Allium sativum) and its characteristic organosulfur compounds have impact on ENaCs. Human ENaCs were heterologously expressed in Xenopus oocytes and their activity was measured as transmembrane currents by the two-electrode voltage-clamp technique. The application of freshly prepared extract from 5g of fresh garlic (1% final concentration) decreased transmembrane currents of ENaC-expressing oocytes within 10 min. This effect was dose-dependent and irreversible. It was fully sensitive to the ENaC-inhibitor amiloride and was not apparent on native control oocytes. The effect of garlic was blocked by dithiothreitol and l-cysteine indicating involvement of thiol-reactive compounds. The garlic organosulsur compounds S-allylcysteine, alliin and diallyl sulfides had no effect on ENaC. By contrast, the thiol-reactive garlic compound allicin significantly inhibited ENaC to a similar extent as garlic extract. These data indicate that thiol-reactive compounds which are present in garlic inhibit ENaC.
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Althaus M. Gasotransmitters: novel regulators of epithelial na(+) transport? Front Physiol 2012; 3:83. [PMID: 22509167 PMCID: PMC3321473 DOI: 10.3389/fphys.2012.00083] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 03/20/2012] [Indexed: 11/13/2022] Open
Abstract
The vectorial transport of Na(+) across epithelia is crucial for the maintenance of Na(+) and water homeostasis in organs such as the kidneys, lung, or intestine. Dysregulated Na(+) transport processes are associated with various human diseases such as hypertension, the salt-wasting syndrome pseudohypoaldosteronism type 1, pulmonary edema, cystic fibrosis, or intestinal disorders, which indicate that a precise regulation of epithelial Na(+) transport is essential. Novel regulatory signaling molecules are gasotransmitters. There are currently three known gasotransmitters: nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H(2)S). These molecules are endogenously produced in mammalian cells by specific enzymes and have been shown to regulate various physiological processes. There is a growing body of evidence which indicates that gasotransmitters may also regulate Na(+) transport across epithelia. This review will summarize the available data concerning NO, CO, and H(2)S dependent regulation of epithelial Na(+) transport processes and will discuss whether or not these mediators can be considered as true physiological regulators of epithelial Na(+) transport biology.
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Affiliation(s)
- Mike Althaus
- Institute of Animal Physiology, Justus Liebig University of Giessen Giessen, Germany
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Abstract
The central goal of this overview article is to summarize recent findings in renal epithelial transport,focusing chiefly on the connecting tubule (CNT) and the cortical collecting duct (CCD).Mammalian CCD and CNT are involved in fine-tuning of electrolyte and fluid balance through reabsorption and secretion. Specific transporters and channels mediate vectorial movements of water and solutes in these segments. Although only a small percent of the glomerular filtrate reaches the CNT and CCD, these segments are critical for water and electrolyte homeostasis since several hormones, for example, aldosterone and arginine vasopressin, exert their main effects in these nephron sites. Importantly, hormones regulate the function of the entire nephron and kidney by affecting channels and transporters in the CNT and CCD. Knowledge about the physiological and pathophysiological regulation of transport in the CNT and CCD and particular roles of specific channels/transporters has increased tremendously over the last two decades.Recent studies shed new light on several key questions concerning the regulation of renal transport.Precise distribution patterns of transport proteins in the CCD and CNT will be reviewed, and their physiological roles and mechanisms mediating ion transport in these segments will also be covered. Special emphasis will be given to pathophysiological conditions appearing as a result of abnormalities in renal transport in the CNT and CCD.
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Affiliation(s)
- Alexander Staruschenko
- Department of Physiology and Kidney Disease Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
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