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Omori S, Hanazono Y, Nishi H, Kinoshita K. The role of the STAS domain in SLC26A9 for chloride ion transporter function. Biophys J 2024; 123:1751-1762. [PMID: 38773769 PMCID: PMC11214054 DOI: 10.1016/j.bpj.2024.05.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 12/25/2023] [Accepted: 05/16/2024] [Indexed: 05/24/2024] Open
Abstract
The anion exchanger solute carrier family 26 (SLC26)A9, consisting of the transmembrane (TM) domain and the cytoplasmic STAS domain, plays an essential role in regulating chloride transport across cell membranes. Recent studies have indicated that C-terminal helices block the entrance of the putative ion transport pathway. However, the precise functions of the STAS domain and C-terminal helix, as well as the underlying molecular mechanisms governing the transport process, remain poorly understood. In this study, we performed molecular dynamics simulations of three distinct models of human SLC26A9, full-length, STAS domain removal (ΔSTAS), and C-terminus removal (ΔC), to investigate their conformational dynamics and ion-binding properties. Stable binding of ions to the binding sites was exclusively observed in the ΔC model in these simulations. Comparing the full-length and ΔC simulations, the ΔC model displayed enhanced motion of the STAS domain. Furthermore, comparing the ΔSTAS and ΔC simulations, the ΔSTAS simulation failed to exhibit stable ion bindings to the sites despite the absence of the C-terminus blocking the ion transmission pathway in both systems. These results suggest that the removal of the C-terminus not only unblocks the access of ions to the permeation pathway but also triggers STAS domain motion, gating the TM domain to promote ions' entry into their binding site. Further analysis revealed that the asymmetric motion of the STAS domain leads to the expansion of the ion permeation pathway within the TM domain, resulting in the stiffening of the flexible TM12 helix near the ion-binding site. This structural change in the TM12 helix stabilizes chloride ion binding, which is essential for SLC26A9's alternate-access mechanism. Overall, our study provides new insights into the molecular mechanisms of SLC26A9 transport and may pave the way for the development of novel treatments for diseases associated with dysregulated ion transport.
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Affiliation(s)
- Satoshi Omori
- Graduate School of Information Sciences, Tohoku University, Sendai, Miyagi, Japan; Department of Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga, Japan
| | - Yuya Hanazono
- Graduate School of Information Sciences, Tohoku University, Sendai, Miyagi, Japan; Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
| | - Hafumi Nishi
- Graduate School of Information Sciences, Tohoku University, Sendai, Miyagi, Japan; Faculty of Core Research, Ochanomizu University, Bunkyo-ku, Tokyo, Japan; Tohoku Medical Megabank Organization, Tohoku University, Sendai, Miyagi, Japan
| | - Kengo Kinoshita
- Graduate School of Information Sciences, Tohoku University, Sendai, Miyagi, Japan; Tohoku Medical Megabank Organization, Tohoku University, Sendai, Miyagi, Japan; Institute of Development, Aging, and Cancer, Tohoku University, Sendai, Miyagi, Japan.
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2
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Zajac M, Lepissier A, Dréano E, Chevalier B, Hatton A, Kelly-Aubert M, Guidone D, Planelles G, Edelman A, Girodon E, Hinzpeter A, Crambert G, Pranke I, Galietta LJV, Sermet-Gaudelus I. Putting bicarbonate on the spot: pharmacological insights for CFTR correction in the airway epithelium. Front Pharmacol 2023; 14:1293578. [PMID: 38149052 PMCID: PMC10750368 DOI: 10.3389/fphar.2023.1293578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 11/17/2023] [Indexed: 12/28/2023] Open
Abstract
Introduction: Cystic fibrosis (CF) is caused by defective Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) proteins. CFTR controls chloride (Cl-) and bicarbonate (HCO3 -) transport into the Airway Surface Liquid (ASL). We investigated the impact of F508del-CFTR correction on HCO3 - secretion by studying transepithelial HCO3 - fluxes. Methods: HCO3 - secretion was measured by pH-stat technique in primary human respiratory epithelial cells from healthy subjects (WT) and people with CF (pwCF) carrying at least one F508del variant. Its changes after CFTR modulation by the triple combination VX445/661/770 and in the context of TNF-α+IL-17 induced inflammation were correlated to ASL pH and transcriptional levels of CFTR and other HCO3 - transporters of airway epithelia such as SLC26A4 (Pendrin), SLC26A9 and NBCe1. Results: CFTR-mediated HCO3 - secretion was not detected in F508del primary human respiratory epithelial cells. It was rescued up to ∼ 80% of the WT level by VX-445/661/770. In contrast, TNF-α+IL-17 normalized transepithelial HCO3 - transport and increased ASL pH. This was related to an increase in SLC26A4 and CFTR transcript levels. VX-445/661/770 induced an increase in pH only in the context of inflammation. Effects on HCO3 - transport were not different between F508del homozygous and F508del compound heterozygous CF airway epithelia. Conclusion: Our studies show that correction of F508del-CFTR HCO3 - is not sufficient to buffer acidic ASL and inflammation is a key regulator of HCO3 - secretion in CF airways. Prediction of the response to CFTR modulators by theratyping should take into account airway inflammation.
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Affiliation(s)
- Miroslaw Zajac
- INSERM U1151, Institut Necker Enfants Malades, Paris, France
- Université de Paris-Cité, Paris, France
- Centre de Référence Maladie Rare Pour La Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
- Department of Physics and Biophysics, Institute of Biology, Warsaw University of Life Sciences, Warsaw, Poland
| | - Agathe Lepissier
- INSERM U1151, Institut Necker Enfants Malades, Paris, France
- Université de Paris-Cité, Paris, France
- Centre de Référence Maladie Rare Pour La Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Elise Dréano
- INSERM U1151, Institut Necker Enfants Malades, Paris, France
- Université de Paris-Cité, Paris, France
- Centre de Référence Maladie Rare Pour La Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Benoit Chevalier
- INSERM U1151, Institut Necker Enfants Malades, Paris, France
- Université de Paris-Cité, Paris, France
- Centre de Référence Maladie Rare Pour La Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Aurélie Hatton
- INSERM U1151, Institut Necker Enfants Malades, Paris, France
- Université de Paris-Cité, Paris, France
- Centre de Référence Maladie Rare Pour La Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Mairead Kelly-Aubert
- INSERM U1151, Institut Necker Enfants Malades, Paris, France
- Université de Paris-Cité, Paris, France
- Centre de Référence Maladie Rare Pour La Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Daniela Guidone
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy
| | | | - Aleksander Edelman
- INSERM U1151, Institut Necker Enfants Malades, Paris, France
- Université de Paris-Cité, Paris, France
- Centre de Référence Maladie Rare Pour La Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Emmanuelle Girodon
- Université de Paris-Cité, Paris, France
- Service de Médecine Génomique des Maladies de Système et d’Organe, Hôpital Cochin, Paris, France
| | - Alexandre Hinzpeter
- INSERM U1151, Institut Necker Enfants Malades, Paris, France
- Université de Paris-Cité, Paris, France
- Centre de Référence Maladie Rare Pour La Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Gilles Crambert
- U1138/CNRS ERL 8228, Centre de Recherche des Cordeliers, Paris, France
| | - Iwona Pranke
- INSERM U1151, Institut Necker Enfants Malades, Paris, France
- Université de Paris-Cité, Paris, France
- Centre de Référence Maladie Rare Pour La Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | | | - Isabelle Sermet-Gaudelus
- INSERM U1151, Institut Necker Enfants Malades, Paris, France
- Université de Paris-Cité, Paris, France
- Centre de Référence Maladie Rare Pour La Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
- European Reference Network for Rare Diseases, Frankfurt, Belgium
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3
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Graeber SY, Mall MA. The future of cystic fibrosis treatment: from disease mechanisms to novel therapeutic approaches. Lancet 2023; 402:1185-1198. [PMID: 37699417 DOI: 10.1016/s0140-6736(23)01608-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 07/23/2023] [Accepted: 07/31/2023] [Indexed: 09/14/2023]
Abstract
With the 2019 breakthrough in the development of highly effective modulator therapy providing unprecedented clinical benefits for over 90% of patients with cystic fibrosis who are genetically eligible for treatment, this rare disease has become a front runner of transformative molecular therapy. This success is based on fundamental research, which led to the identification of the disease-causing CFTR gene and our subsequent understanding of the disease mechanisms underlying the pathogenesis of cystic fibrosis, working together with a continuously evolving clinical research and drug development pipeline. In this Series paper, we focus on advances since 2018, and remaining knowledge gaps in our understanding of the molecular mechanisms of CFTR dysfunction in the airway epithelium and their links to mucus dysfunction, impaired host defences, airway infection, and chronic inflammation of the lungs of people with cystic fibrosis. We review progress in (and the remaining obstacles to) pharmacological approaches to rescue CFTR function, and novel strategies for improved symptomatic therapies for cystic fibrosis, including how these might be applicable to common lung diseases, such as bronchiectasis and chronic obstructive pulmonary disease. Finally, we discuss the promise of genetic therapies and gene editing approaches to restore CFTR function in the lungs of all patients with cystic fibrosis independent of their CFTR genotype, and the unprecedented opportunities to transform cystic fibrosis from a fatal disease to a treatable and potentially curable one.
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Affiliation(s)
- Simon Y Graeber
- Department of Pediatric Respiratory Medicine, Immunology and Critical Care Medicine, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany; Cystic Fibrosis Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany; German Center for Lung Research, associated partner site, Berlin, Germany; Berlin Institute of Health at Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Marcus A Mall
- Department of Pediatric Respiratory Medicine, Immunology and Critical Care Medicine, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany; Cystic Fibrosis Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany; German Center for Lung Research, associated partner site, Berlin, Germany; Berlin Institute of Health at Charité-Universitätsmedizin Berlin, Berlin, Germany.
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4
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Gavioli Santos L, Villa-Nova Pereira S, Henrique Pezzo Kmit A, Cardoso Bonadia L, Silvia Bertuzzo C, Dirceu Ribeiro J, Nitsch Mazzola T, Augusto Lima Marson F. Identification of Single Nucleotide Variants in SLC26A9 Gene in Patients with Cystic Fibrosis (p.Phe508del Homozygous) and its Association to Orkambi® (Lumacaftor and Ivacaftor) Response in vitro. Gene 2023; 871:147428. [PMID: 37068695 DOI: 10.1016/j.gene.2023.147428] [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: 02/04/2023] [Revised: 03/28/2023] [Accepted: 04/10/2023] [Indexed: 04/19/2023]
Abstract
BACKGROUND Since patients with cystic fibrosis with different Cystic Fibrosis Transmembrane Regulator (CFTR) genotypes present a wide response variability for modulator drugs such as Orkambi®, it is important to screen variants in candidate genes with an impact on precision and personalized medicine, such as Solute Carrier Family 26, member 9 (SLC26A9) gene. METHODS Sanger sequencing for the exons and intron-exon boundary junctions of the SLC26A9 gene was employed in nine individuals with p.Phe508del homozygous genotype for the CFTR gene who were not under CFTR modulators therapy. The sequencing variants were evaluated by in silico prediction tools. The CFTR function was measured by cAMP-stimulated current (ΔIsc-eq-FSK) in polarized CFTR of human nasal epithelial cells cultured in micro-Ussing chambers with Orkambi®. RESULTS We found 24 intronic variants, three in the coding region (missense variants - rs74146719 and rs16856462 and synonymous - rs33943971), and three in the three prime untranslated region (3' UTR) region in the SLC26A9 gene. Twenty variants were considered benign according to American College of Medical Genetics and Genomics guidelines, and ten were classified as uncertain significance. Although some variants had deleterious predictions or possible alterations in splicing, the majority of predictions were benign or neutral. When we analyzed the ΔIsc-eq-FSK response to Orkambi®, there were no significant differences within the genotypes and alleles for all 30 variants in the SLC26A9 gene. CONCLUSIONS Among the nine individuals with p.Phe508del homozygous genotype for the CFTR gene, no pathogenic SLC26A9 variants were found, and we did not detect associations from the 30 SLC26A9 variants and the response to the Orkambi® in vitro.
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Affiliation(s)
- Luana Gavioli Santos
- Laboratory of Medical Genetics and Genome Medicine, Department of Medical Genetics, Faculty of Medical Sciences, University of Campinas, Tessália Vieira de Camargo, 126, Cidade Universitária Zeferino Vaz, Campinas 13083-887, São Paulo, Brazil.
| | - Stéphanie Villa-Nova Pereira
- Laboratory of Medical Genetics and Genome Medicine, Department of Medical Genetics, Faculty of Medical Sciences, University of Campinas, Tessália Vieira de Camargo, 126, Cidade Universitária Zeferino Vaz, Campinas 13083-887, São Paulo, Brazil.
| | - Arthur Henrique Pezzo Kmit
- Center for Investigation in Pediatrics, Faculty of Medical Sciences, University of Campinas, Tessália Vieira de Camargo, 126, Cidade Universitária Zeferino Vaz, Campinas 13083-887, São Paulo, Brazil.
| | - Luciana Cardoso Bonadia
- Laboratory of Medical Genetics and Genome Medicine, Department of Medical Genetics, Faculty of Medical Sciences, University of Campinas, Tessália Vieira de Camargo, 126, Cidade Universitária Zeferino Vaz, Campinas 13083-887, São Paulo, Brazil.
| | - Carmem Silvia Bertuzzo
- Laboratory of Medical Genetics and Genome Medicine, Department of Medical Genetics, Faculty of Medical Sciences, University of Campinas, Tessália Vieira de Camargo, 126, Cidade Universitária Zeferino Vaz, Campinas 13083-887, São Paulo, Brazil.
| | - José Dirceu Ribeiro
- Center for Investigation in Pediatrics, Faculty of Medical Sciences, University of Campinas, Tessália Vieira de Camargo, 126, Cidade Universitária Zeferino Vaz, Campinas 13083-887, São Paulo, Brazil.
| | - Taís Nitsch Mazzola
- Center for Investigation in Pediatrics, Faculty of Medical Sciences, University of Campinas, Tessália Vieira de Camargo, 126, Cidade Universitária Zeferino Vaz, Campinas 13083-887, São Paulo, Brazil.
| | - Fernando Augusto Lima Marson
- Laboratory of Medical Genetics and Genome Medicine, Department of Medical Genetics, Faculty of Medical Sciences, University of Campinas, Tessália Vieira de Camargo, 126, Cidade Universitária Zeferino Vaz, Campinas 13083-887, São Paulo, Brazil; Center for Investigation in Pediatrics, Faculty of Medical Sciences, University of Campinas, Tessália Vieira de Camargo, 126, Cidade Universitária Zeferino Vaz, Campinas 13083-887, São Paulo, Brazil; Laboratory of Human and Medical Genetics, Laboratory of Cell and Molecular Tumor Biology and Bioactive Compounds, São Francisco University, Avenida São Francisco de Assis, 218, Jardim São José, Bragança Paulista 12916-900, São Paulo, Brazil.
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5
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Sinha M, Zabini D, Guntur D, Nagaraj C, Enyedi P, Olschewski H, Kuebler WM, Olschewski A. Chloride channels in the lung: Challenges and perspectives for viral infections, pulmonary arterial hypertension, and cystic fibrosis. Pharmacol Ther 2022; 237:108249. [PMID: 35878810 DOI: 10.1016/j.pharmthera.2022.108249] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 07/06/2022] [Accepted: 07/11/2022] [Indexed: 10/16/2022]
Abstract
Fine control over chloride homeostasis in the lung is required to maintain membrane excitability, transepithelial transport as well as intra- and extracellular ion and water homeostasis. Over the last decades, a growing number of chloride channels and transporters have been identified in the cells of the pulmonary vasculature and the respiratory tract. The importance of these proteins is underpinned by the fact that impairment of their physiological function is associated with functional dysregulation, structural remodeling, or hereditary diseases of the lung. This paper reviews the field of chloride channels and transporters in the lung and discusses chloride channels in disease processes such as viral infections including SARS-CoV- 2, pulmonary arterial hypertension, cystic fibrosis and asthma. Although chloride channels have become a hot research topic in recent years, remarkably few of them have been targeted by pharmacological agents. As such, we complement the putative pathophysiological role of chloride channels here with a summary of their therapeutic potential.
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Affiliation(s)
- Madhushri Sinha
- Experimental Anaesthesiology, Department of Anaesthesiology and Intensive Care Medicine, Medical University of Graz, Auenbruggerplatz 5, 8036 Graz, Austria.
| | - Diana Zabini
- Department of Physiology, Neue Stiftingtalstrasse 6/V, 8010 Graz, Austria.
| | - Divya Guntur
- Experimental Anaesthesiology, Department of Anaesthesiology and Intensive Care Medicine, Medical University of Graz, Auenbruggerplatz 5, 8036 Graz, Austria.
| | - Chandran Nagaraj
- Ludwig Boltzmann Institute for Lung Vascular Research, Neue Stiftingtalstraße 6, 8010 Graz, Austria.
| | - Peter Enyedi
- Department of Physiology, Semmelweis University, Tűzoltó utca 37-47, 1094 Budapest, Hungary.
| | - Horst Olschewski
- Department of Internal Medicine, Division of Pulmonology, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria.
| | - Wolfgang M Kuebler
- Institute of Physiology, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany.
| | - Andrea Olschewski
- Experimental Anaesthesiology, Department of Anaesthesiology and Intensive Care Medicine, Medical University of Graz, Auenbruggerplatz 5, 8036 Graz, Austria; Ludwig Boltzmann Institute for Lung Vascular Research, Neue Stiftingtalstraße 6, 8010 Graz, Austria.
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6
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Amatngalim GD, Rodenburg LW, Aalbers BL, Raeven HH, Aarts EM, Sarhane D, Spelier S, Lefferts JW, Silva IA, Nijenhuis W, Vrendenbarg S, Kruisselbrink E, Brunsveld JE, van Drunen CM, Michel S, de Winter-de Groot KM, Heijerman HG, Kapitein LC, Amaral MD, van der Ent CK, Beekman JM. Measuring cystic fibrosis drug responses in organoids derived from 2D differentiated nasal epithelia. Life Sci Alliance 2022; 5:e202101320. [PMID: 35922154 PMCID: PMC9351388 DOI: 10.26508/lsa.202101320] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 07/15/2022] [Accepted: 07/15/2022] [Indexed: 11/24/2022] Open
Abstract
Cystic fibrosis is caused by genetic defects that impair the CFTR channel in airway epithelial cells. These defects may be overcome by specific CFTR modulating drugs, for which the efficacy can be predicted in a personalized manner using 3D nasal-brushing-derived airway organoids in a forskolin-induced swelling assay. Despite of this, previously described CFTR function assays in 3D airway organoids were not fully optimal, because of inefficient organoid differentiation and limited scalability. In this report, we therefore describe an alternative method of culturing nasal-brushing-derived airway organoids, which are created from an equally differentiated airway epithelial monolayer of a 2D air-liquid interface culture. In addition, we have defined organoid culture conditions, with the growth factor/cytokine combination neuregulin-1<i>β</i> and interleukin-1<i>β</i>, which enabled consistent detection of CFTR modulator responses in nasal-airway organoid cultures from subjects with cystic fibrosis.
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Affiliation(s)
- Gimano D Amatngalim
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Lisa W Rodenburg
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Bente L Aalbers
- Department of Pulmonology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Henriette Hm Raeven
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Ellen M Aarts
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Dounia Sarhane
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Sacha Spelier
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Juliet W Lefferts
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Iris Al Silva
- BioISI-Biosystems and Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, Lisboa, Portugal
| | - Wilco Nijenhuis
- Department of Biology, Cell Biology, Neurobiology and Biophysics, Faculty of Science, Utrecht University, Utrecht, The Netherlands
- Centre for Living Technologies, Eindhoven-Wageningen-Utrecht Alliance, Utrecht, The Netherlands
| | - Sacha Vrendenbarg
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Evelien Kruisselbrink
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Jesse E Brunsveld
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Cornelis M van Drunen
- Department of Otorhinolaryngology, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Sabine Michel
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
| | - Karin M de Winter-de Groot
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
| | - Harry G Heijerman
- Department of Pulmonology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Lukas C Kapitein
- Department of Biology, Cell Biology, Neurobiology and Biophysics, Faculty of Science, Utrecht University, Utrecht, The Netherlands
- Centre for Living Technologies, Eindhoven-Wageningen-Utrecht Alliance, Utrecht, The Netherlands
| | - Magarida D Amaral
- BioISI-Biosystems and Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, Lisboa, Portugal
| | - Cornelis K van der Ent
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
| | - Jeffrey M Beekman
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht University, Member of ERN-LUNG, Utrecht, The Netherlands
- Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
- Centre for Living Technologies, Eindhoven-Wageningen-Utrecht Alliance, Utrecht, The Netherlands
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7
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Philp AR, Miranda F, Gianotti A, Mansilla A, Scudieri P, Musante I, Vega G, Figueroa CD, Galietta LJV, Sarmiento JM, Flores CA. KCa3.1 differentially regulates trachea and bronchi epithelial gene expression in a chronic-asthma mouse model. Physiol Genomics 2022; 54:273-282. [PMID: 35658672 DOI: 10.1152/physiolgenomics.00134.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ion channels are potentially exploitable as pharmacological targets to treat asthma. This study evaluated the role of KCa3.1 channels, encoded by Kcnn4, in regulating the gene expression of mouse airway epithelium and the development of asthma traits. We used the ovalbumin (OVA) challenge as an asthma model in wild type and Kcnn4-/- mice, performed histological analysis, and measured serum IgE to evaluate asthma traits. We analyzed gene expression of isolated epithelial cells of trachea or bronchi using mRNA sequencing and gene ontology and performed Ussing chamber experiments in mouse trachea to evaluate anion secretion. Gene expression of epithelial cells from mouse airways differed between trachea and bronchi, indicating regional differences in the inflammatory and transepithelial transport properties of proximal and distal airways. We found that Kcnn4 silencing reduced mast cell numbers, mucus, and collagen in the airways, and reduced the amount of epithelial anion secretion in the OVA-challenged animals. Additionally, gene expression was differentially modified in the trachea and bronchi, with Kcnn4 genetic silencing significantly altering the expression of genes involved in the TNF pathway, supporting the potential of KCa3.1 as a therapeutic target for asthma.
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Affiliation(s)
- Amber R Philp
- Centro de Estudios Científicos, Valdivia, Los Rios, Chile.,Austral University of Chile, Valdivia, Chile
| | - Fernando Miranda
- Departamento de Fisiología, Austral University of Chile, Valdivia, Chile
| | | | - Agustín Mansilla
- Centro de Estudios Científicos, Valdivia, Los Rios, Chile.,Austral University of Chile, Valdivia, Chile
| | | | | | - Génesis Vega
- Centro de Estudios Científicos, Valdivia, Los Rios, Chile
| | | | - Luis J V Galietta
- TIGEM, Pozzuoli, Italia.,Department of Translational Medical Sciences, University of Naples Federico II, Naples, Italy
| | - José M Sarmiento
- Departamento de Fisiología, Austral University of Chile, Valdivia, Chile
| | - Carlos A Flores
- Centro de Estudios Científicos, Valdivia, Los Rios, Chile.,Universidad San Sebastián, Valdivia, Chile
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8
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Genetic evidence supports the development of SLC26A9 targeting therapies for the treatment of lung disease. NPJ Genom Med 2022; 7:28. [PMID: 35396391 PMCID: PMC8993824 DOI: 10.1038/s41525-022-00299-9] [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: 12/30/2021] [Accepted: 03/04/2022] [Indexed: 12/19/2022] Open
Abstract
Over 400 variants in the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) are CF-causing. CFTR modulators target variants to improve lung function, but marked variability in response exists and current therapies do not address all CF-causing variants highlighting unmet needs. Alternative epithelial ion channel/transporters such as SLC26A9 could compensate for CFTR dysfunction, providing therapeutic targets that may benefit all individuals with CF. We investigate the relationship between rs7512462, a marker of SLC26A9 activity, and lung function pre- and post-treatment with CFTR modulators in Canadian and US CF cohorts, in the general population, and in those with chronic obstructive pulmonary disease (COPD). Rs7512462 CC genotype is associated with greater lung function in CF individuals with minimal function variants (for which there are currently no approved therapies; p = 0.008); and for gating (p = 0.033) and p.Phe508del/ p.Phe508del (p = 0.006) genotypes upon treatment with CFTR modulators. In parallel, human nasal epithelia with CC and p.Phe508del/p.Phe508del after Ussing chamber analysis of a combination of approved and experimental modulator treatments show greater CFTR function (p = 0.0022). Beyond CF, rs7512462 is associated with peak expiratory flow in a meta-analysis of the UK Biobank and Spirometa Consortium (p = 2.74 × 10-44) and provides p = 0.0891 in an analysis of COPD case-control status in the UK Biobank defined by spirometry. These findings support SLC26A9 as a therapeutic target to improve lung function for all people with CF and in individuals with other obstructive lung diseases.
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9
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SLC26A9 is selected for endoplasmic reticulum associated degradation (ERAD) via Hsp70-dependent targeting of the soluble STAS domain. Biochem J 2021; 478:4203-4220. [PMID: 34821356 PMCID: PMC8826537 DOI: 10.1042/bcj20210644] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 11/23/2021] [Accepted: 11/24/2021] [Indexed: 12/24/2022]
Abstract
SLC26A9, a member of the solute carrier protein family, transports chloride ions across various epithelia. SLC26A9 also associates with other ion channels and transporters linked to human health, and in some cases these heterotypic interactions are essential to support the biogenesis of both proteins. Therefore, understanding how this complex membrane protein is initially folded might provide new therapeutic strategies to overcome deficits in the function of SLC26A9 partners, one of which is associated with Cystic Fibrosis. To this end, we developed a novel yeast expression system for SLC26A9. This facile system has been used extensively with other ion channels and transporters to screen for factors that oversee protein folding checkpoints. As commonly observed for other channels and transporters, we first noted that a substantial fraction of SLC26A9 is targeted for endoplasmic reticulum associated degradation (ERAD), which destroys folding-compromised proteins in the early secretory pathway. We next discovered that ERAD selection requires the Hsp70 chaperone, which can play a vital role in ERAD substrate selection. We then created SLC26A9 mutants and found that the transmembrane-rich domain of SLC26A9 was quite stable, whereas the soluble cytosolic STAS domain was responsible for Hsp70-dependent ERAD. To support data obtained in the yeast model, we were able to recapitulate Hsp70-facilitated ERAD of the STAS domain in human tissue culture cells. These results indicate that a critical barrier to nascent membrane protein folding can reside within a specific soluble domain, one that is monitored by components associated with the ERAD machinery.
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10
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Heawchaiyaphum C, Pientong C, Yoshiyama H, Iizasa H, Panthong W, Ekalaksananan T. General Features and Novel Gene Signatures That Identify Epstein-Barr Virus-Associated Epithelial Cancers. Cancers (Basel) 2021; 14:cancers14010031. [PMID: 35008199 PMCID: PMC8750470 DOI: 10.3390/cancers14010031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/16/2021] [Accepted: 12/19/2021] [Indexed: 11/16/2022] Open
Abstract
Epstein-Barr virus (EBV) is associated with various types of human malignancies, including nasopharyngeal carcinoma (NPC), EBV-associated gastric carcinoma (EBVaGC), and oral squamous cell carcinoma (OSCC). The present study aimed to identify gene signatures and common signaling pathways that can be used to predict the prognosis of EBV-associated epithelial cancers (EBVaCAs) by performing an integrated bioinformatics analysis of cell lines and tumor tissues. We identified 12 differentially expressed genes (DEGs) in the EBVaCA cell lines. Among them, only four DEGs, including BAMBI, SLC26A9, SGPP2, and TMC8, were significantly upregulated. However, SLC26A9 and TMC8, but not BAMBI and SGPP2, were significantly upregulated in EBV-positive tumor tissues compared to EBV-negative tumor tissues. Next, we identified IL6/JAK/STAT3 and TNF-α/NF-κB signaling pathways as common hallmarks of EBVaCAs. The expression of key genes related to the two hallmarks was upregulated in both EBV-infected cell lines and EBV-positive tumor tissues. These results suggest that SLC26A9 and TMC8 might be gene signatures that can effectively predict the prognosis of EBVaCAs and provide new insights into the molecular mechanisms of EBV-driven epithelial cancers.
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Affiliation(s)
- Chukkris Heawchaiyaphum
- Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand; (C.H.); (C.P.); (W.P.)
- HPV&EBV and Carcinogenesis (HEC) Research Group, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Chamsai Pientong
- Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand; (C.H.); (C.P.); (W.P.)
- HPV&EBV and Carcinogenesis (HEC) Research Group, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Hironori Yoshiyama
- Department of Microbiology, Shimane University Faculty of Medicine, Izumo 693-8501, Japan; (H.Y.); (H.I.)
| | - Hisashi Iizasa
- Department of Microbiology, Shimane University Faculty of Medicine, Izumo 693-8501, Japan; (H.Y.); (H.I.)
| | - Watcharapong Panthong
- Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand; (C.H.); (C.P.); (W.P.)
- HPV&EBV and Carcinogenesis (HEC) Research Group, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Tipaya Ekalaksananan
- Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand; (C.H.); (C.P.); (W.P.)
- HPV&EBV and Carcinogenesis (HEC) Research Group, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
- Correspondence: ; Tel.: +66-4336-3808; Fax:+66-4334-8385
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11
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Recurring exposure to low humidity induces transcriptional and protein level changes in the vocal folds of rabbits. Sci Rep 2021; 11:24180. [PMID: 34921171 PMCID: PMC8683398 DOI: 10.1038/s41598-021-03489-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 11/24/2021] [Indexed: 11/08/2022] Open
Abstract
Voice disorders are an important human health condition. Hydration is a commonly recommended preventive measure for voice disorders though it is unclear how vocal fold dehydration is harmful at the cellular level. Airway surface dehydration can result from exposure to low humidity air. Here we have induced airway surface dehydration in New Zealand White rabbits exposed to a recurring 8-h low humidity environment over 15 days. This model mimics an occupational exposure to a low humidity environment. Exposure to moderate humidity was the control condition. Full thickness soft-tissue samples, including the vocal folds and surrounding laryngeal tissue, were collected for molecular analysis. RT-qPCR demonstrated a significant upregulation of MUC4 (mucin 4) and SCL26A9 (chloride channel) and a large fold-change though statistically non-significant upregulation of SCNNA1 (epithelial sodium channel). Proteomic analysis demonstrated differential regulation of proteins clustering into prospective functional groups of muscle structure and function, oxidative stress response, and protein chaperonin stress response. Together, the data demonstrate that recurring exposure to low humidity is sufficient to induce both transcriptional and translational level changes in laryngeal tissue and suggest that low humidity exposure induces cellular stress at the level of the vocal folds.
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12
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Synergy in Cystic Fibrosis Therapies: Targeting SLC26A9. Int J Mol Sci 2021; 22:ijms222313064. [PMID: 34884866 PMCID: PMC8658147 DOI: 10.3390/ijms222313064] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 11/24/2021] [Accepted: 12/01/2021] [Indexed: 11/16/2022] Open
Abstract
SLC26A9, a constitutively active Cl- transporter, has gained interest over the past years as a relevant disease modifier in several respiratory disorders including Cystic Fibrosis (CF), asthma, and non-CF bronchiectasis. SLC26A9 contributes to epithelial Cl- secretion, thus preventing mucus obstruction under inflammatory conditions. Additionally, SLC26A9 was identified as a CF gene modifier, and its polymorphisms were shown to correlate with the response to drugs modulating CFTR, the defective protein in CF. Here, we aimed to investigate the relationship between SLC26A9 and CFTR, and its role in CF pathogenesis. Our data show that SLC26A9 expression contributes to enhanced CFTR expression and function. While knocking-down SLC26A9 in human bronchial cells leads to lower wt- and F508del-CFTR expression, function, and response to CFTR correctors, the opposite occurs upon its overexpression, highlighting SLC26A9 relevance for CF. Accordingly, F508del-CFTR rescue by the most efficient correctors available is further enhanced by increasing SLC26A9 expression. Interestingly, SLC26A9 overexpression does not increase the PM expression of non-F508del CFTR traffic mutants, namely those unresponsive to corrector drugs. Altogether, our data indicate that SLC26A9 stabilizes CFTR at the ER level and that the efficacy of CFTR modulator drugs may be further enhanced by increasing its expression.
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13
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Laselva O, Guerra L, Castellani S, Favia M, Di Gioia S, Conese M. Small-molecule drugs for cystic fibrosis: Where are we now? Pulm Pharmacol Ther 2021; 72:102098. [PMID: 34793977 DOI: 10.1016/j.pupt.2021.102098] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Revised: 10/24/2021] [Accepted: 11/12/2021] [Indexed: 01/05/2023]
Abstract
The cystic fibrosis (CF) lung disease is due to the lack/dysfunction of the CF Transmembrane Conductance Regulator (CFTR), a chloride channel expressed by epithelial cells as the main regulator of ion and fluid homeostasis. More than 2000 genetic variation in the CFTR gene are known, among which those with identified pathomechanism have been divided into six VI mutation classes. A major advancement in the pharmacotherapy of CF has been the development of small-molecule drugs hitting the root of the disease, i.e. the altered ion and fluid transport through the airway epithelium. These drugs, called CFTR modulators, have been advanced to the clinics to treat nearly 90% of CF patients, including the CFTR potentiator ivacaftor, approved for residual function mutations (Classes III and IV), and combinations of correctors (lumacaftor, tezacaftor, elexacaftor) and ivacaftor for patients bearing at least one the F508del mutation, the most frequent mutation belonging to class II. To cover the 10% of CF patients without etiological therapies, other novel small-molecule CFTR modulators are in evaluation of their effectiveness in all the CFTR mutation classes: read-through agents for Class I, correctors, potentiators and amplifiers from different companies for Class II-V, stabilizers for Class VI. In alternative, other solute carriers, such as SLC26A9 and SLC6A14, are the focus of intensive investigation. Finally, other molecular targets are being evaluated for patients with no approved CFTR modulator therapy or as means of enhancing CFTR modulatory therapy, including small molecules forming ion channels, inhibitors of the ENaC sodium channel and potentiators of the calcium-activated chloride channel TMEM16A. This paper aims to give an up-to-date overview of old and novel CFTR modulators as well as of novel strategies based on small-molecule drugs. Further investigations in in-vivo and cell-based models as well as carrying out large prospective studies will be required to determine if novel CFTR modulators, stabilizers, amplifiers, and the ENaC inhibitors or TMEM16A potentiators will further improve the clinical outcomes in CF management.
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Affiliation(s)
- Onofrio Laselva
- Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy
| | - Lorenzo Guerra
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Stefano Castellani
- Department of Medical Sciences and Human Oncology, University of Bari, Bari, Italy
| | - Maria Favia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Bari, Italy
| | - Sante Di Gioia
- Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy
| | - Massimo Conese
- Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy.
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14
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Pinto MC, Silva IAL, Figueira MF, Amaral MD, Lopes-Pacheco M. Pharmacological Modulation of Ion Channels for the Treatment of Cystic Fibrosis. J Exp Pharmacol 2021; 13:693-723. [PMID: 34326672 PMCID: PMC8316759 DOI: 10.2147/jep.s255377] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 06/30/2021] [Indexed: 12/12/2022] Open
Abstract
Cystic fibrosis (CF) is a life-shortening monogenic disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR) protein, an anion channel that transports chloride and bicarbonate across epithelia. Despite clinical progress in delaying disease progression with symptomatic therapies, these individuals still develop various chronic complications in lungs and other organs, which significantly restricts their life expectancy and quality of life. The development of high-throughput assays to screen drug-like compound libraries have enabled the discovery of highly effective CFTR modulator therapies. These novel therapies target the primary defect underlying CF and are now approved for clinical use for individuals with specific CF genotypes. However, the clinically approved modulators only partially reverse CFTR dysfunction and there is still a considerable number of individuals with CF carrying rare CFTR mutations who remain without any effective CFTR modulator therapy. Accordingly, additional efforts have been pursued to identify novel and more potent CFTR modulators that may benefit a larger CF population. The use of ex vivo individual-derived specimens has also become a powerful tool to evaluate novel drugs and predict their effectiveness in a personalized medicine approach. In addition to CFTR modulators, pro-drugs aiming at modulating alternative ion channels/transporters are under development to compensate for the lack of CFTR function. These therapies may restore normal mucociliary clearance through a mutation-agnostic approach (ie, independent of CFTR mutation) and include inhibitors of the epithelial sodium channel (ENaC), modulators of the calcium-activated channel transmembrane 16A (TMEM16, or anoctamin 1) or of the solute carrier family 26A member 9 (SLC26A9), and anionophores. The present review focuses on recent progress and challenges for the development of ion channel/transporter-modulating drugs for the treatment of CF.
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Affiliation(s)
- Madalena C Pinto
- Biosystems & Integrative Sciences Institute (BioISI), Faculty of Sciences, University of Lisboa, Lisboa, Portugal
| | - Iris A L Silva
- Biosystems & Integrative Sciences Institute (BioISI), Faculty of Sciences, University of Lisboa, Lisboa, Portugal
| | - Miriam F Figueira
- Marsico Lung Institute/Cystic Fibrosis Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Margarida D Amaral
- Biosystems & Integrative Sciences Institute (BioISI), Faculty of Sciences, University of Lisboa, Lisboa, Portugal
| | - Miquéias Lopes-Pacheco
- Biosystems & Integrative Sciences Institute (BioISI), Faculty of Sciences, University of Lisboa, Lisboa, Portugal
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15
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Girón Moreno RM, García-Clemente M, Diab-Cáceres L, Martínez-Vergara A, Martínez-García MÁ, Gómez-Punter RM. Treatment of Pulmonary Disease of Cystic Fibrosis: A Comprehensive Review. Antibiotics (Basel) 2021; 10:486. [PMID: 33922413 PMCID: PMC8144952 DOI: 10.3390/antibiotics10050486] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 04/13/2021] [Accepted: 04/17/2021] [Indexed: 01/08/2023] Open
Abstract
Cystic fibrosis (CF) is a genetic disease that causes absence or dysfunction of a protein named transmembrane conductance regulatory protein (CFTR) that works as an anion channel. As a result, the secretions of the organs where CFTR is expressed are very viscous, so their functionality is altered. The main cause of morbidity is due to the involvement of the respiratory system as a result of recurrent respiratory infections by different pathogens. In recent decades, survival has been increasing, rising by around age 50. This is due to the monitoring of patients in multidisciplinary units, early diagnosis with neonatal screening, and advances in treatments. In this chapter, we will approach the different therapies used in CF for the treatment of symptoms, obstruction, inflammation, and infection. Moreover, we will discuss specific and personalized treatments to correct the defective gene and repair the altered protein CFTR. The obstacle for personalized CF treatment is to predict the drug response of patients due to genetic complexity and heterogeneity of uncommon mutations.
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Affiliation(s)
- Rosa María Girón Moreno
- Servicio de Neumología, Instituto de Investigación Sanitaria La Princesa, 28006 Madrid, Spain; (R.M.G.M.); (R.M.G.-P.)
| | - Marta García-Clemente
- Servicio de Neumología, Hospital Universitario Central de Asturias, C/Avenida de Roma S/n, 33011 Oviedo, Spain
| | - Layla Diab-Cáceres
- Servicio de Neumología, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain;
| | | | | | - Rosa Mar Gómez-Punter
- Servicio de Neumología, Instituto de Investigación Sanitaria La Princesa, 28006 Madrid, Spain; (R.M.G.M.); (R.M.G.-P.)
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16
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Iafusco F, Maione G, Rosanio FM, Mozzillo E, Franzese A, Tinto N. Cystic Fibrosis-Related Diabetes (CFRD): Overview of Associated Genetic Factors. Diagnostics (Basel) 2021; 11:diagnostics11030572. [PMID: 33810109 PMCID: PMC8005125 DOI: 10.3390/diagnostics11030572] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Accepted: 03/19/2021] [Indexed: 12/21/2022] Open
Abstract
Cystic fibrosis (CF) is the most common autosomal recessive disease in the Caucasian population and is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene that encodes for a chloride/bicarbonate channel expressed on the membrane of epithelial cells of the airways and of the intestine, as well as in cells with exocrine and endocrine functions. A common nonpulmonary complication of CF is cystic fibrosis-related diabetes (CFRD), a distinct form of diabetes due to insulin insufficiency or malfunction secondary to destruction/derangement of pancreatic betacells, as well as to other factors that affect their function. The prevalence of CFRD increases with age, and 40–50% of CF adults develop the disease. Several proposed hypotheses on how CFRD develops have emerged, including exocrine-driven fibrosis and destruction of the entire pancreas, as well as contrasting theories on the direct or indirect impact of CFTR mutation on islet function. Among contributors to the development of CFRD, in addition to CFTR genotype, there are other genetic factors related and not related to type 2 diabetes. This review presents an overview of the current understanding on genetic factors associated with glucose metabolism abnormalities in CF.
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Affiliation(s)
- Fernanda Iafusco
- Department of Molecular Medicine and Medical Biotechnology, University of Naples “Federico II”, 80131 Naples, Italy; (F.I.); (G.M.)
- CEINGE Advanced Biotechnology, 80131 Naples, Italy
| | - Giovanna Maione
- Department of Molecular Medicine and Medical Biotechnology, University of Naples “Federico II”, 80131 Naples, Italy; (F.I.); (G.M.)
- CEINGE Advanced Biotechnology, 80131 Naples, Italy
| | - Francesco Maria Rosanio
- Regional Center of Pediatric Diabetology, Department of Translational Medical Sciences, Section of Pediatrics, University of Naples “Federico II”, 80131 Naples, Italy; (F.M.R.); (E.M.); (A.F.)
| | - Enza Mozzillo
- Regional Center of Pediatric Diabetology, Department of Translational Medical Sciences, Section of Pediatrics, University of Naples “Federico II”, 80131 Naples, Italy; (F.M.R.); (E.M.); (A.F.)
| | - Adriana Franzese
- Regional Center of Pediatric Diabetology, Department of Translational Medical Sciences, Section of Pediatrics, University of Naples “Federico II”, 80131 Naples, Italy; (F.M.R.); (E.M.); (A.F.)
| | - Nadia Tinto
- Department of Molecular Medicine and Medical Biotechnology, University of Naples “Federico II”, 80131 Naples, Italy; (F.I.); (G.M.)
- CEINGE Advanced Biotechnology, 80131 Naples, Italy
- Correspondence:
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17
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Mall MA, Mayer-Hamblett N, Rowe SM. Cystic Fibrosis: Emergence of Highly Effective Targeted Therapeutics and Potential Clinical Implications. Am J Respir Crit Care Med 2020; 201:1193-1208. [PMID: 31860331 DOI: 10.1164/rccm.201910-1943so] [Citation(s) in RCA: 130] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cystic fibrosis (CF) remains the most common life-shortening hereditary disease in white populations, with high morbidity and mortality related to chronic airway mucus obstruction, inflammation, infection, and progressive lung damage. In 1989, the discovery that CF is caused by mutations in the CFTR (cystic fibrosis transmembrane conductance regulator) gene that encodes a cAMP-dependent anion channel vital for proper Cl- and HCO3- transport across epithelial surfaces provided a solid foundation for unraveling underlying disease mechanisms and the development of therapeutics targeting the basic defect in people with CF. In this review, we focus on recent advances in our understanding of the molecular defects caused by different classes of CFTR mutations, implications for pharmacological rescue of mutant CFTR, and insights into how CFTR dysfunction impairs key host defense mechanisms, such as mucociliary clearance and bacterial killing in CF airways. Furthermore, we review the path that led to the recent breakthrough in the development of highly effective CFTR-directed therapeutics, now applicable for up to 90% of people with CF who carry responsive CFTR mutations, including those with just a single copy of the most common F508del mutation. Finally, we discuss the remaining challenges and strategies to develop highly effective targeted therapies for all patients and the unprecedented potential of these novel therapies to transform CF from a fatal to a treatable chronic condition.
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Affiliation(s)
- Marcus A Mall
- Department of Pediatric Pulmonology, Immunology, and Intensive Care Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Berlin Institute of Health, Berlin, Germany.,German Center for Lung Research (DZL), Berlin, Germany
| | - Nicole Mayer-Hamblett
- Department of Pediatrics and.,Department of Biostatistics, University of Washington, Seattle, Washington.,Seattle Children's Hospital, Seattle, Washington
| | - Steven M Rowe
- Department of Medicine.,Department of Pediatrics, and.,Department of Cell, Developmental and Integrative Biology, Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama
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18
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Chi X, Jin X, Chen Y, Lu X, Tu X, Li X, Zhang Y, Lei J, Huang J, Huang Z, Zhou Q, Pan X. Structural insights into the gating mechanism of human SLC26A9 mediated by its C-terminal sequence. Cell Discov 2020; 6:55. [PMID: 32818062 PMCID: PMC7417587 DOI: 10.1038/s41421-020-00193-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 07/07/2020] [Indexed: 11/25/2022] Open
Abstract
The human SLC26 transporter family exhibits various transport characteristics, and family member SLC26A9 performs multiple roles, including acting as Cl-/HCO3- exchangers, Cl- channels, and Na+ transporters. Some mutations of SLC26A9 are correlated with abnormalities in respiration and digestion systems. As a potential target colocalizing with CFTR in cystic fibrosis patients, SLC26A9 is of great value in drug development. Here, we present a cryo-EM structure of the human SLC26A9 dimer at 2.6 Å resolution. A segment at the C-terminal end is bound to the entry of the intracellular vestibule of the putative transport pathway, which has been proven by electrophysiological experiments to be a gating modulator. Multiple chloride and sodium ions are resolved in the high-resolution structure, identifying novel ion-binding pockets for the first time. Together, our structure takes important steps in elucidating the structural features and regulatory mechanism of SLC26A9, with potential significance in the treatment of cystic fibrosis.
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Affiliation(s)
- Ximin Chi
- Key Laboratory of Structural Biology of Zhejiang Province, Institute of Biology, Westlake Institute for Advanced Study, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, Zhejiang 310024 China
| | - Xueqin Jin
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Yun Chen
- Key Laboratory of Structural Biology of Zhejiang Province, Institute of Biology, Westlake Institute for Advanced Study, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, Zhejiang 310024 China
| | - Xiaoli Lu
- Key Laboratory of Structural Biology of Zhejiang Province, Institute of Biology, Westlake Institute for Advanced Study, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, Zhejiang 310024 China
| | - Xinyu Tu
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191 China
| | - Xiaorong Li
- Key Laboratory of Structural Biology of Zhejiang Province, Institute of Biology, Westlake Institute for Advanced Study, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, Zhejiang 310024 China
| | - Yuanyuan Zhang
- Key Laboratory of Structural Biology of Zhejiang Province, Institute of Biology, Westlake Institute for Advanced Study, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, Zhejiang 310024 China
| | - Jianlin Lei
- Technology Center for Protein Sciences, Ministry of Education Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084 China
| | - Jing Huang
- Key Laboratory of Structural Biology of Zhejiang Province, Institute of Biology, Westlake Institute for Advanced Study, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, Zhejiang 310024 China
| | - Zhuo Huang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University, Beijing, 100191 China
- Key Laboratory for Neuroscience, Ministry of Education/National Health and Family Planning Commission, Peking University, Beijing, 100191 China
| | - Qiang Zhou
- Key Laboratory of Structural Biology of Zhejiang Province, Institute of Biology, Westlake Institute for Advanced Study, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, Zhejiang 310024 China
| | - Xiaojing Pan
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084 China
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19
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Laselva O, Bartlett C, Popa A, Ouyang H, Gunawardena TNA, Gonska T, Moraes TJ, Bear CE. Emerging preclinical modulators developed for F508del-CFTR have the potential to be effective for ORKAMBI resistant processing mutants. J Cyst Fibros 2020; 20:106-119. [PMID: 32741662 DOI: 10.1016/j.jcf.2020.07.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 07/07/2020] [Accepted: 07/22/2020] [Indexed: 10/23/2022]
Abstract
BACKGROUND F508del is prototypical of Class 2 CFTR mutations associated with protein misprocessing and reduced function. Corrector compounds like lumacaftor partially rescue the processing defect of F508del-CFTR whereas potentiators like ivacaftor, enhance its channel activity once trafficked to the cell surface. We asked if emerging modulators developed for F508del-CFTR can rescue Class 2 mutations previously shown to be poorly responsive to lumacaftor and ivacaftor. METHODS Rescue of mutant CFTRs by the correctors: AC1, AC2-1 or AC2-2 and the potentiator, AP2, was studied in HEK-293 cells and in primary human nasal epithelial (HNE) cultures, using a membrane potential assay and Ussing chamber, respectively. RESULTS In HEK-293 cells, we found that a particular combination of corrector molecules (AC1 plus AC2-1) and a potentiator (AP2) was effective in rescuing both the misprocessing and reduced function of M1101K and G85E respectively. These findings were recapitulated in patient-derived nasal cultures, although another corrector combination, AC1 plus AC2-2 also improved misprocessing in these primary tissues. Interestingly, while this corrector combination only led to a modest increase in the abundance of mature N1303K-CFTR it did enable its functional expression in the presence of the potentiator, AP2, in part, because the nominal corrector, AC2-2 also exhibits potentiator activity. CONCLUSIONS Strategic combinations of novel modulators can potentially rescue Class 2 mutants thought to be relatively unresponsive to lumacaftor and ivacaftor.
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Affiliation(s)
- Onofrio Laselva
- Programme in Molecular Medicine, Hospital for Sick Children, Toronto, Canada; Department of Physiology, University of Toronto, Toronto, Canada
| | - Claire Bartlett
- Programme in Translational Medicine, Hospital for Sick Children, Toronto, Canada
| | - Alec Popa
- Programme in Molecular Medicine, Hospital for Sick Children, Toronto, Canada
| | - Hong Ouyang
- Programme in Translational Medicine, Hospital for Sick Children, Toronto, Canada
| | | | - Tanja Gonska
- Programme in Translational Medicine, Hospital for Sick Children, Toronto, Canada; Department of Paediatrics, University of Toronto, Toronto, Canada
| | - Theo J Moraes
- Programme in Translational Medicine, Hospital for Sick Children, Toronto, Canada; Department of Paediatrics, University of Toronto, Toronto, Canada
| | - Christine E Bear
- Programme in Molecular Medicine, Hospital for Sick Children, Toronto, Canada; Department of Physiology, University of Toronto, Toronto, Canada; Department of Biochemistry, University of Toronto, Toronto, Canada.
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20
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Lam ATN, Aksit MA, Vecchio-Pagan B, Shelton CA, Osorio DL, Anzmann AF, Goff LA, Whitcomb DC, Blackman SM, Cutting GR. Increased expression of anion transporter SLC26A9 delays diabetes onset in cystic fibrosis. J Clin Invest 2020; 130:272-286. [PMID: 31581148 DOI: 10.1172/jci129833] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 09/25/2019] [Indexed: 12/16/2022] Open
Abstract
Diabetes is a common complication of cystic fibrosis (CF) that affects approximately 20% of adolescents and 40%-50% of adults with CF. The age at onset of CF-related diabetes (CFRD) (marked by clinical diagnosis and treatment initiation) is an important measure of the disease process. DNA variants associated with age at onset of CFRD reside in and near SLC26A9. Deep sequencing of the SLC26A9 gene in 762 individuals with CF revealed that 2 common DNA haplotypes formed by the risk variants account for the association with diabetes. Single-cell RNA sequencing (scRNA-Seq) indicated that SLC26A9 is predominantly expressed in pancreatic ductal cells and frequently coexpressed with CF transmembrane conductance regulator (CFTR) along with transcription factors that have binding sites 5' of SLC26A9. These findings were replicated upon reanalysis of scRNA-Seq data from 4 independent studies. DNA fragments derived from the 5' region of SLC26A9-bearing variants from the low-risk haplotype generated 12%-20% higher levels of expression in PANC-1 and CFPAC-1 cells compared with the high- risk haplotype. Taken together, our findings indicate that an increase in SLC26A9 expression in ductal cells of the pancreas delays the age at onset of diabetes, suggesting a CFTR-agnostic treatment for a major complication of CF.
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Affiliation(s)
- Anh-Thu N Lam
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Melis A Aksit
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Briana Vecchio-Pagan
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland, USA
| | - Celeste A Shelton
- University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Ariel Precision Medicine, Pittsburgh, Pennsylvania, USA
| | - Derek L Osorio
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Arianna F Anzmann
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Loyal A Goff
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | | | - Scott M Blackman
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Garry R Cutting
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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21
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Lopes-Pacheco M. CFTR Modulators: The Changing Face of Cystic Fibrosis in the Era of Precision Medicine. Front Pharmacol 2020; 10:1662. [PMID: 32153386 PMCID: PMC7046560 DOI: 10.3389/fphar.2019.01662] [Citation(s) in RCA: 269] [Impact Index Per Article: 67.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 12/19/2019] [Indexed: 12/22/2022] Open
Abstract
Cystic fibrosis (CF) is a lethal inherited disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, which result in impairment of CFTR mRNA and protein expression, function, stability or a combination of these. Although CF leads to multifaceted clinical manifestations, the respiratory disorder represents the major cause of morbidity and mortality of these patients. The life expectancy of CF patients has substantially lengthened due to early diagnosis and improvements in symptomatic therapeutic regimens. Quality of life remains nevertheless limited, as these individuals are subjected to considerable clinical, psychosocial and economic burdens. Since the discovery of the CFTR gene in 1989, tremendous efforts have been made to develop therapies acting more upstream on the pathogenesis cascade, thereby overcoming the underlying dysfunctions caused by CFTR mutations. In this line, the advances in cell-based high-throughput screenings have been facilitating the fast-tracking of CFTR modulators. These modulator drugs have the ability to enhance or even restore the functional expression of specific CF-causing mutations, and they have been classified into five main groups depending on their effects on CFTR mutations: potentiators, correctors, stabilizers, read-through agents, and amplifiers. To date, four CFTR modulators have reached the market, and these pharmaceutical therapies are transforming patients' lives with short- and long-term improvements in clinical outcomes. Such breakthroughs have paved the way for the development of novel CFTR modulators, which are currently under experimental and clinical investigations. Furthermore, recent insights into the CFTR structure will be useful for the rational design of next-generation modulator drugs. This review aims to provide a summary of recent developments in CFTR-directed therapeutics. Barriers and future directions are also discussed in order to optimize treatment adherence, identify feasible and sustainable solutions for equitable access to these therapies, and continue to expand the pipeline of novel modulators that may result in effective precision medicine for all individuals with CF.
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Affiliation(s)
- Miquéias Lopes-Pacheco
- Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisbon, Lisbon, Portugal
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22
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Morrison CB, Markovetz MR, Ehre C. Mucus, mucins, and cystic fibrosis. Pediatr Pulmonol 2019; 54 Suppl 3:S84-S96. [PMID: 31715083 PMCID: PMC6853602 DOI: 10.1002/ppul.24530] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 09/06/2019] [Indexed: 02/06/2023]
Abstract
Cystic fibrosis (CF) is both the most common and most lethal genetic disease in the Caucasian population. CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and is characterized by the accumulation of thick, adherent mucus plaques in multiple organs, of which the lungs, gastrointestinal tract and pancreatic ducts are the most commonly affected. A similar pathogenesis cascade is observed in all of these organs: loss of CFTR function leads to altered ion transport, consisting of decreased chloride and bicarbonate secretion via the CFTR channel and increased sodium absorption via epithelial sodium channel upregulation. Mucosa exposed to changes in ionic concentrations sustain severe pathophysiological consequences. Altered mucus biophysical properties and weakened innate defense mechanisms ensue, furthering the progression of the disease. Mucins, the high-molecular-weight glycoproteins responsible for the viscoelastic properties of the mucus, play a key role in the disease but the actual mechanism of mucus accumulation is still undetermined. Multiple hypotheses regarding the impact of CFTR malfunction on mucus have been proposed and are reviewed here. (a) Dehydration increases mucin monomer entanglement, (b) defective Ca2+ chelation compromises mucin expansion, (c) ionic changes alter mucin interactions, and (d) reactive oxygen species increase mucin crosslinking. Although one biochemical change may dominate, it is likely that all of these mechanisms play some role in the progression of CF disease. This article discusses recent findings on the initial cause(s) of aberrant mucus properties in CF and examines therapeutic approaches aimed at correcting mucus properties.
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Affiliation(s)
- Cameron Bradley Morrison
- Marsico Lung Institute/Cystic Fibrosis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Matthew Raymond Markovetz
- Marsico Lung Institute/Cystic Fibrosis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Camille Ehre
- Marsico Lung Institute/Cystic Fibrosis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.,Division of Pediatric Pulmonology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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23
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Alternative chloride transport pathways as pharmacological targets for the treatment of cystic fibrosis. J Cyst Fibros 2019; 19 Suppl 1:S37-S41. [PMID: 31662238 DOI: 10.1016/j.jcf.2019.10.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 09/27/2019] [Accepted: 10/18/2019] [Indexed: 01/06/2023]
Abstract
Cystic fibrosis is a hereditary disease that originates from mutations in the epithelial chloride channel CFTR. Whereas established therapies for the treatment of cystic fibrosis target CFTR to repair its function, alternative therapeutic strategies aim for the restoration of chloride transport by the activation of other chloride transport proteins such as TMEM16A or SLC26A9 or by the application of synthetic anionophores. TMEM16A is an anion-selective channel that is activated by the binding of Ca2+ from the cytoplasm. Pharmacological efforts aim for the increase of its open probability at resting Ca2+ concentrations. SLC26 is an uncoupled chloride transporter, which shuttles chloride across the membrane by an alternate-access mechanism. Its activation requires its mobilization from intracellular stores. Finally, anionophores are small synthetic molecules that bind chloride to form lipid-soluble complexes, which shuttle the anion across the membrane. All three approaches are currently pursued and have provided promising initial results.
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24
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Walter JD, Sawicka M, Dutzler R. Cryo-EM structures and functional characterization of murine Slc26a9 reveal mechanism of uncoupled chloride transport. eLife 2019; 8:46986. [PMID: 31339488 PMCID: PMC6656431 DOI: 10.7554/elife.46986] [Citation(s) in RCA: 75] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 06/21/2019] [Indexed: 12/14/2022] Open
Abstract
The epithelial anion transporter SLC26A9 contributes to airway surface hydration and gastric acid production. Colocalizing with CFTR, SLC26A9 has been proposed as a target for the treatment of cystic fibrosis. To provide molecular details of its transport mechanism, we present cryo-EM structures and a functional characterization of murine Slc26a9. These structures define the general architecture of eukaryotic SLC26 family members and reveal an unusual mode of oligomerization which relies predominantly on the cytosolic STAS domain. Our data illustrates conformational transitions of Slc26a9, supporting a rapid alternate-access mechanism which mediates uncoupled chloride transport with negligible bicarbonate or sulfate permeability. The characterization of structure-guided mutants illuminates the properties of the ion transport path, including a selective anion binding site located in the center of a mobile module within the transmembrane domain. This study thus provides a structural foundation for the understanding of the entire SLC26 family and potentially facilitates their therapeutic exploitation. Many processes in the human body are regulated by chloride and other charged particles (known as ions) moving in and out of cells. Each cell is surrounded by a membrane barrier, which prevents ions from entering or exiting. Therefore, to control the levels of ions inside the cell, specific proteins in the membrane act as channels or transporters to provide routes for the ions to pass through the membrane. Channel proteins form pores that, when open, allow a steady stream of ions to pass through the membrane. Transporter proteins, on the other hand, generally contain a pocket that is only accessible from one side of the membrane. When individual ions enter this pocket the transporter changes shape. This causes the entrance of the pocket to close and then re-open on the other side of the membrane. Inside the lung, an ion channel known as CFTR provides a route for chloride ions to move out of cells, which helps clear harmful material from the airways. Mutations affecting this protein cause the mucus lining the airways to become very sticky, leading to a severe disease known as cystic fibrosis. CFTR works together with another protein that is also found in the membrane, called SLC26A9. Previous studies have suggested that SLC26A9 also allows chloride ions to pass through the membrane. It was not clear, however, if SLC26A9 operates as an ion channel or a transporter protein, or how the protein is arranged in the membrane. Now, Walter, Sawicka and Dutzler combined two techniques known as cryo-electron microscopy and patch-clamp electrophysiology to reveal the detailed three-dimensional structure of the mouse version of SLC26A9, which is highly similar to the human form. The experiments found that mouse SLC26A9 proteins form pairs in the membrane referred to as homodimers, which arranged themselves in an unexpected way. Further investigation into the structure of these homodimers suggests that despite having many channel-like properties, SLC26A9 operates as a fast transporter, rather than a true channel. These findings help us understand the role of SLC26A9 and other similar proteins in the lung and other parts of the body. In the future it may be possible to develop drugs that target SLC26A9 to treat cystic fibrosis and other severe lung diseases.
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Affiliation(s)
- Justin D Walter
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Marta Sawicka
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Raimund Dutzler
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
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