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Luo S, Rollins S, Schmitz-Abe K, Tam A, Li Q, Shi J, Lin J, Wang R, Agrawal PB. The solute carrier family 26 member 9 modifies rapidly progressing cystic fibrosis associated with homozygous F508del CFTR mutation. Clin Chim Acta 2024; 561:119765. [PMID: 38852790 DOI: 10.1016/j.cca.2024.119765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 05/14/2024] [Accepted: 06/04/2024] [Indexed: 06/11/2024]
Abstract
BACKGROUND AND AIMS Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations to the CF transmembrane conductance regulator (CFTR). Symptoms and severity of the disease can be quite variable suggesting modifier genes play an important role. MATERIALS AND METHODS Exome sequencing was performed on six individuals carrying homozygous deltaF508 for CFTR genotype but present with rapidly progressing CF (RPCF). Data was analyzed using an unbiased genome-wide genetic burden test against 3076 controls. Single cell RNA sequencing data from LungMAP was utilized to evaluate unique and co-expression of candidate genes, and structural modeling to evaluate the deleterious effects of identified candidate variants. RESULTS We have identified solute carrier family 26 member 9 (SLC26A9) as a modifier gene to be associated with RPCF. Two rare missense SLC26A9 variants were discovered in three of six individuals deemed to have RPCF: c.229G > A; p.G77S (present in two patients), and c.1885C > T; p.P629S. Co-expression of SLC26A9 and CFTR mRNA is limited across different lung cell types, with the highest level of co-expression seen in human (6.3 %) and mouse (9.0 %) alveolar type 2 (AT2) cells. Structural modeling suggests deleterious effects of these mutations as they are in critical protein domains which might affect the anion transport capability of SLC26A9. CONCLUSION The enrichment of rare and potentially deleterious SLC26A9 mutations in patients with RPCF suggests SLC26A9 may act as an alternative anion transporter in CF and is a modifier gene associated with this lung phenotype.
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Affiliation(s)
- Shiyu Luo
- Division of Neonatology, Department of Pediatrics, University of Miami Miller School of Medicine and Holtz Children's Hospital, Jackson Health System, Miami, FL 33136, USA; Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Stuart Rollins
- Division of Pulmonary Medicine, Boston Children's Hospital, USA; Department of Medicine, Harvard Medical School, USA
| | - Klaus Schmitz-Abe
- Division of Neonatology, Department of Pediatrics, University of Miami Miller School of Medicine and Holtz Children's Hospital, Jackson Health System, Miami, FL 33136, USA; Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Amy Tam
- Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Qifei Li
- Division of Neonatology, Department of Pediatrics, University of Miami Miller School of Medicine and Holtz Children's Hospital, Jackson Health System, Miami, FL 33136, USA; Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Jiahai Shi
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Jasmine Lin
- Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Ruobing Wang
- Division of Pulmonary Medicine, Boston Children's Hospital, USA; Department of Medicine, Harvard Medical School, USA; Center for Regenerative Medicine of Boston University and Boston Medical Center, Boston, MA 02115, USA.
| | - Pankaj B Agrawal
- Division of Neonatology, Department of Pediatrics, University of Miami Miller School of Medicine and Holtz Children's Hospital, Jackson Health System, Miami, FL 33136, USA; Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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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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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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Sermet-Gaudelus I, Girodon E, Vermeulen F, Solomon G, Melotti P, Graeber S, Bronsveld I, Rowe S, Wilschanski M, Tümmler B, Cutting G, Gonska T. ECFS standards of care on CFTR-related disorders: Diagnostic criteria of CFTR dysfunction. J Cyst Fibros 2022; 21:922-936. [DOI: 10.1016/j.jcf.2022.09.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Revised: 09/06/2022] [Accepted: 09/14/2022] [Indexed: 11/06/2022]
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Differential CFTR-Interactome Proximity Labeling Procedures Identify Enrichment in Multiple SLC Transporters. Int J Mol Sci 2022; 23:ijms23168937. [PMID: 36012204 PMCID: PMC9408702 DOI: 10.3390/ijms23168937] [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: 07/12/2022] [Revised: 08/05/2022] [Accepted: 08/08/2022] [Indexed: 11/16/2022] Open
Abstract
Proteins interacting with CFTR and its mutants have been intensively studied using different experimental approaches. These studies provided information on the cellular processes leading to proper protein folding, routing to the plasma membrane, recycling, activation and degradation. Recently, new approaches have been developed based on the proximity labeling of protein partners or proteins in close vicinity and their subsequent identification by mass spectrometry. In this study, we evaluated TurboID- and APEX2-based proximity labeling of WT CFTR and compared the obtained data to those reported in databases. The CFTR-WT interactome was then compared to that of two CFTR (G551D and W1282X) mutants and the structurally unrelated potassium channel KCNK3. The two proximity labeling approaches identified both known and additional CFTR protein partners, including multiple SLC transporters. Proximity labeling approaches provided a more comprehensive picture of the CFTR interactome and improved our knowledge of the CFTR environment.
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Liu L, Yamamoto A, Yamaguchi M, Taniguchi I, Nomura N, Nakakuki M, Kozawa Y, Fukuyasu T, Higuchi M, Niwa E, Tamada T, Ishiguro H. Bicarbonate transport of airway surface epithelia in luminally perfused mice bronchioles. J Physiol Sci 2022; 72:4. [PMID: 35196991 PMCID: PMC10717372 DOI: 10.1186/s12576-022-00828-2] [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: 12/26/2021] [Accepted: 02/14/2022] [Indexed: 01/06/2023]
Abstract
HCO3- secretion in distal airways is critical for airway mucosal defense. HCO3-/H+ transport across the apical membrane of airway surface epithelial cells was studied by measuring intracellular pH in luminally microperfused freshly dissected mice bronchioles. Functional studies demonstrated that CFTR, ENaC, Cl--HCO3- exchange, Na+-H+ exchange, and Na+-HCO3- cotransport are involved in apical HCO3-/H+ transport. RT-PCR of isolated bronchioles detected fragments from Cftr, α, β, γ subunits of ENaC, Ae2, Ae3, NBCe1, NBCe2, NBCn1, NDCBE, NBCn2, Nhe1, Nhe2, Nhe4, Nhe5, Slc26a4, Slc26a6, and Slc26a9. We assume that continuous decline of intracellular pH following alkaline load demonstrates time course of HCO3- secretion into the lumen which is perfused with a HCO3--free solution. Forskolin-stimulated HCO3- secretion was substantially inhibited by luminal application of CFTRinh-172 (5 μM), H2DIDS (200 μM), and amiloride (1 μM). In bronchioles from a cystic fibrosis mouse model, basal and acetylcholine-stimulated HCO3- secretion was substantially impaired, but forskolin transiently accelerated HCO3- secretion of which the magnitude was comparable to wild-type bronchioles. In conclusion, we have characterized apical HCO3-/H+ transport in native bronchioles. We have demonstrated that cAMP-mediated and Ca2+-mediated pathways are involved in HCO3- secretion and that apical HCO3- secretion is largely mediated by CFTR and H2DIDS-sensitive Cl--HCO3- exchanger, most likely Slc26a9. The impairment of HCO3- secretion in bronchioles from a cystic fibrosis mouse model may be related to the pathogenesis of early lung disease in cystic fibrosis.
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Affiliation(s)
- Libin Liu
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Akiko Yamamoto
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Makoto Yamaguchi
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Itsuka Taniguchi
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Nao Nomura
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Miyuki Nakakuki
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yuka Kozawa
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Tomoya Fukuyasu
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Mayuko Higuchi
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Erina Niwa
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Tsutomu Tamada
- Department of Respiratory Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Hiroshi Ishiguro
- Department of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan.
- Research Center of Health, Physical Fitness, and Sports, Nagoya University, Furo-cho E5-2 (130), Chikusa-ku, Nagoya, 464-8601, Japan.
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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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Hanssens LS, Duchateau J, Casimir GJ. CFTR Protein: Not Just a Chloride Channel? Cells 2021; 10:2844. [PMID: 34831067 PMCID: PMC8616376 DOI: 10.3390/cells10112844] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 10/15/2021] [Accepted: 10/19/2021] [Indexed: 12/17/2022] Open
Abstract
Cystic fibrosis (CF) is a recessive genetic disease caused by mutations in a gene encoding a protein called Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). The CFTR protein is known to acts as a chloride (Cl-) channel expressed in the exocrine glands of several body systems where it also regulates other ion channels, including the epithelial sodium (Na+) channel (ENaC) that plays a key role in salt absorption. This function is crucial to the osmotic balance of the mucus and its viscosity. However, the pathophysiology of CF is more challenging than a mere dysregulation of epithelial ion transport, mainly resulting in impaired mucociliary clearance (MCC) with consecutive bronchiectasis and in exocrine pancreatic insufficiency. This review shows that the CFTR protein is not just a chloride channel. For a long time, research in CF has focused on abnormal Cl- and Na+ transport. Yet, the CFTR protein also regulates numerous other pathways, such as the transport of HCO3-, glutathione and thiocyanate, immune cells, and the metabolism of lipids. It influences the pH homeostasis of airway surface liquid and thus the MCC as well as innate immunity leading to chronic infection and inflammation, all of which are considered as key pathophysiological characteristics of CF.
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Affiliation(s)
- Laurence S. Hanssens
- Department of Pediatric Pulmonology and Cystic Fibrosis Clinic, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Avenue J.J. Crocq 15, 1020 Brussels, Belgium;
| | - Jean Duchateau
- Laboratoire Académique de Pédiatrie, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Avenue J.J. Crocq 15, 1020 Brussels, Belgium;
| | - Georges J. Casimir
- Department of Pediatric Pulmonology and Cystic Fibrosis Clinic, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Avenue J.J. Crocq 15, 1020 Brussels, Belgium;
- Laboratoire Académique de Pédiatrie, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles (ULB), Avenue J.J. Crocq 15, 1020 Brussels, Belgium;
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Zajac M, Dreano E, Edwards A, Planelles G, Sermet-Gaudelus I. Airway Surface Liquid pH Regulation in Airway Epithelium Current Understandings and Gaps in Knowledge. Int J Mol Sci 2021; 22:3384. [PMID: 33806154 PMCID: PMC8037888 DOI: 10.3390/ijms22073384] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 03/08/2021] [Accepted: 03/08/2021] [Indexed: 12/22/2022] Open
Abstract
Knowledge on the mechanisms of acid and base secretion in airways has progressed recently. The aim of this review is to summarize the known mechanisms of airway surface liquid (ASL) pH regulation and their implication in lung diseases. Normal ASL is slightly acidic relative to the interstitium, and defects in ASL pH regulation are associated with various respiratory diseases, such as cystic fibrosis. Basolateral bicarbonate (HCO3-) entry occurs via the electrogenic, coupled transport of sodium (Na+) and HCO3-, and, together with carbonic anhydrase enzymatic activity, provides HCO3- for apical secretion. The latter mainly involves CFTR, the apical chloride/bicarbonate exchanger pendrin and paracellular transport. Proton (H+) secretion into ASL is crucial to maintain its relative acidity compared to the blood. This is enabled by H+ apical secretion, mainly involving H+/K+ ATPase and vacuolar H+-ATPase that carry H+ against the electrochemical potential gradient. Paracellular HCO3- transport, the direction of which depends on the ASL pH value, acts as an ASL protective buffering mechanism. How the transepithelial transport of H+ and HCO3- is coordinated to tightly regulate ASL pH remains poorly understood, and should be the focus of new studies.
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Affiliation(s)
- Miroslaw Zajac
- Department of Physics and Biophysics, Institute of Biology, Warsaw University of Life Sciences, 02-776 Warsaw, Poland;
| | - Elise Dreano
- Institut Necker Enfants Malades, INSERM U1151, 75015 Paris, France;
- Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, 75006 Paris, France;
| | - Aurelie Edwards
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA;
| | - Gabrielle Planelles
- Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, 75006 Paris, France;
- Laboratoire de Physiologie rénale et Tubulopathies, CNRS ERL 8228, 75006 Paris, France
| | - Isabelle Sermet-Gaudelus
- Institut Necker Enfants Malades, INSERM U1151, 75015 Paris, France;
- Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, 75006 Paris, France;
- Centre de Référence Maladies Rares, Mucoviscidose et Maladies de CFTR, Hôpital Necker Enfants Malades, 75015 Paris, France
- Clinical Trial Network, European Cystic Fibrosis Society, BT2 Belfast, Ireland
- European Respiratory Network Lung, 75006 Paris, France
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Engelbrecht HR, Dalvie S, Agenbag G, Stein DJ, Ramesar RS. Whole-exome sequencing in an Afrikaner family with bipolar disorder. J Affect Disord 2020; 276:69-75. [PMID: 32697718 DOI: 10.1016/j.jad.2020.06.045] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 06/04/2020] [Accepted: 06/16/2020] [Indexed: 10/23/2022]
Abstract
BACKGROUND Bipolar disorder (BD) has considerable heritability, with genome-wide association studies indicating that multiple common genetic variants contribute to risk. Less work has been undertaken to assess the contribution of rare variation in the development of this complex disorder, particularly in isolated populations. Using whole-exome sequencing (WES), the aim of this study was to identify rare, potentially damaging variants contributing to risk for BD in the Afrikaner population. METHODS WES was performed on eight Afrikaner family members, five affected and three unaffected. The analyses focused on i) the identification of rare, damaging variation, and ii) the molecular pathways in which these rare variants play a role using in silico prediction tools such as wANNOVAR and KOBAS 3.0. RESULTS Two rare and potentially damaging missense variants in FAM71B and SLC26A9 were shared by affected family members but were absent in unaffected members. In addition, variants in genes that play a role in pathways involved in signal transduction and synaptic transmission were shared by the five affected individuals. LIMITATIONS Two main limitations affect this study: the limited number of cases and controls, and the fact that whole-exome sequencing can only capture a small fragment of the genome which may harbor mutations. CONCLUSION This is the first WES study of BD in an Afrikaner family, and findings suggest that novel candidate genes may contribute to risk for BD in this population. Future work in larger samples of this population as well as in other populations is needed to fully investigate the role of the candidate genes found here.
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Affiliation(s)
- Hannah-Ruth Engelbrecht
- SA MRC Research Unit for Genomic and Precision Medicine, Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Observatory, 7925.
| | - Shareefa Dalvie
- SA MRC Unit on Risk & Resilience in Mental Disorders, Department of Psychiatry and Neuroscience Institute, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town.
| | - Gloudi Agenbag
- SA MRC Research Unit for Genomic and Precision Medicine, Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Observatory, 7925.
| | - Dan J Stein
- SA MRC Unit on Risk & Resilience in Mental Disorders, Department of Psychiatry and Neuroscience Institute, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town.
| | - Raj S Ramesar
- SA MRC Research Unit for Genomic and Precision Medicine, Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Observatory, 7925.
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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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12
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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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13
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Touré A. Importance of SLC26 Transmembrane Anion Exchangers in Sperm Post-testicular Maturation and Fertilization Potential. Front Cell Dev Biol 2019; 7:230. [PMID: 31681763 PMCID: PMC6813192 DOI: 10.3389/fcell.2019.00230] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 09/26/2019] [Indexed: 12/17/2022] Open
Abstract
In mammals, sperm cells produced within the testis are structurally differentiated but remain immotile and are unable to fertilize the oocyte unless they undergo a series of maturation events during their transit in the male and female genital tracts. This post-testicular functional maturation is known to rely on the micro-environment of both male and female genital tracts, and is tightly controlled by the pH of their luminal milieus. In particular, within the epididymis, the establishment of a low bicarbonate (HCO3–) concentration contributes to luminal acidification, which is necessary for sperm maturation and subsequent storage in a quiescent state. Following ejaculation, sperm is exposed to the basic pH of the female genital tract and bicarbonate (HCO3–), calcium (Ca2+), and chloride (Cl–) influxes induce biochemical and electrophysiological changes to the sperm cells (cytoplasmic alkalinization, increased cAMP concentration, and protein phosphorylation cascades), which are indispensable for the acquisition of fertilization potential, a process called capacitation. Solute carrier 26 (SLC26) members are conserved membranous proteins that mediate the transport of various anions across the plasma membrane of epithelial cells and constitute important regulators of pH and HCO3– concentration. Most SLC26 members were shown to physically interact and cooperate with the cystic fibrosis transmembrane conductance regulator channel (CFTR) in various epithelia, mainly by stimulating its Cl– channel activity. Among SLC26 members, the function of SLC26A3, A6, and A8 were particularly investigated in the male genital tract and the sperm cells. In this review, we will focus on SLC26s contributions to ionic- and pH-dependent processes during sperm post-testicular maturation. We will specify the current knowledge regarding their functions, based on data from the literature generated by means of in vitro and in vivo studies in knock-out mouse models together with genetic studies of infertile patients. We will also discuss the limits of those studies, the current research gaps and identify some key points for potential developments in this field.
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Affiliation(s)
- Aminata Touré
- INSERM U1016, Centre National de la Recherche Scientifique, UMR 8104, Institut Cochin, Université de Paris, Paris, France
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14
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Airway surface liquid acidification initiates host defense abnormalities in Cystic Fibrosis. Sci Rep 2019; 9:6516. [PMID: 31019198 PMCID: PMC6482305 DOI: 10.1038/s41598-019-42751-4] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 04/03/2019] [Indexed: 12/14/2022] Open
Abstract
Cystic fibrosis (CF) is caused by defective Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein. Morbidity is mainly due to early airway infection. We hypothesized that S. aureus clearance during the first hours of infection was impaired in CF human Airway Surface Liquid (ASL) because of a lowered pH. The ASL pH of human bronchial epithelial cell lines and primary respiratory cells from healthy controls (WT) and patients with CF was measured with a pH microelectrode. The antimicrobial capacity of airway cells was studied after S. aureus apical infection by counting surviving bacteria. ASL was significantly more acidic in CF than in WT respiratory cells. This was consistent with a defect in bicarbonate secretion involving CFTR and SLC26A4 (pendrin) and a persistent proton secretion by ATP12A. ASL demonstrated a defect in S. aureus clearance which was improved by pH normalization. Pendrin inhibition in WT airways recapitulated the CF airway defect and increased S. aureus proliferation. ATP12A inhibition by ouabain decreased bacterial proliferation. Antimicrobial peptides LL-37 and hBD1 demonstrated a pH-dependent activity. Normalizing ASL pH might improve innate airway defense in newborns with CF during onset of S. aureus infection. Pendrin activation and ATP12A inhibition could represent novel therapeutic strategies to normalize pH in CF airways.
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15
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Balázs A, Mall MA. Role of the SLC26A9 Chloride Channel as Disease Modifier and Potential Therapeutic Target in Cystic Fibrosis. Front Pharmacol 2018; 9:1112. [PMID: 30327603 PMCID: PMC6174851 DOI: 10.3389/fphar.2018.01112] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 09/10/2018] [Indexed: 12/13/2022] Open
Abstract
The solute carrier family 26, member 9 (SLC26A9) is an epithelial chloride channel that is expressed in several organs affected in patients with cystic fibrosis (CF) including the lungs, the pancreas, and the intestine. Emerging evidence suggests SLC26A9 as a modulator of wild-type and mutant CFTR function, and as a potential alternative target to circumvent the basic ion transport defect caused by deficient CFTR-mediated chloride transport in CF. In this review, we summarize in vitro studies that revealed multifaceted molecular and functional interactions between SLC26A9 and CFTR that may be implicated in normal transepithelial chloride secretion in health, as well as impaired chloride/fluid transport in CF. Further, we focus on recent genetic association studies and investigations utilizing genetically modified mouse models that identified SLC26A9 as a disease modifier and supported an important role of this alternative chloride channel in the pathophysiology of several organ manifestations in CF, as well as other chronic lung diseases such as asthma and non-CF bronchiectasis. Collectively, these findings and the overlapping endogenous expression with CFTR suggest SLC26A9 an attractive novel therapeutic target that may be exploited to restore epithelial chloride secretion in patients with CF irrespective of their CFTR genotype. In addition, pharmacological activation of SLC26A9 may help to augment the effect of CFTR modulator therapies in patients with CF carrying responsive mutations such as the most common disease-causing mutation F508del-CFTR. However, future research and development including the identification of compounds that activate SLC26A9-mediated chloride transport are needed to explore this alternative chloride channel as a therapeutic target in CF and potentially other muco-obstructive lung diseases.
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Affiliation(s)
- Anita Balázs
- 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, Giessen, Germany
| | - 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, Giessen, Germany
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16
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Liu X, Li T, Tuo B. Physiological and Pathophysiological Relevance of the Anion Transporter Slc26a9 in Multiple Organs. Front Physiol 2018; 9:1197. [PMID: 30233393 PMCID: PMC6127633 DOI: 10.3389/fphys.2018.01197] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 08/08/2018] [Indexed: 02/05/2023] Open
Abstract
Transepithelial Cl- and HCO3- transport is crucial for the function of all epithelia, and HCO3- is a biological buffer that maintains acid-base homeostasis. In most epithelia, a series of Cl-/HCO3- exchangers and Cl- channels that mediate Cl- absorption and HCO3- secretion have been detected in the luminal and basolateral membranes. Slc26a9 belongs to the solute carrier 26 (Slc26) family of anion transporters expressed in the epithelia of multiple organs. This review summarizes the expression pattern and functional diversity of Slc26a9 in different systems based on all investigations performed thus far. Furthermore, the physical and functional interactions between Slc26a9 and cystic fibrosis transmembrane conductance regulator (CFTR) are discussed due to their overlapping expression pattern in multiple organs. Finally, we focus on the relationship between slc26a9 mutations and disease onset. An understanding of the physiological and pathophysiological relevance of Slc26a9 in multiple organs offers new possibilities for disease therapy.
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Affiliation(s)
- Xuemei Liu
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical University, Zunyi, China.,Digestive Disease Institute of Guizhou Province, Zunyi, China
| | - Taolang Li
- Department of Thyroid and Breast Surgery, Affiliated Hospital, Zunyi Medical University, Zunyi, China
| | - Biguang Tuo
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical University, Zunyi, China.,Digestive Disease Institute of Guizhou Province, Zunyi, China
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17
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Bergougnoux A, Taulan-Cadars M, Claustres M, Raynal C. Current and future molecular approaches in the diagnosis of cystic fibrosis. Expert Rev Respir Med 2018; 12:415-426. [PMID: 29580110 DOI: 10.1080/17476348.2018.1457438] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
INTRODUCTION Cystic Fibrosis is among the first diseases to have general population genetic screening tests and one of the most common indications of prenatal and preimplantation genetic diagnosis for single gene disorders. During the past twenty years, thanks to the evolution of diagnostic techniques, our knowledge of CFTR genetics and pathophysiological mechanisms involved in cystic fibrosis has significantly improved. Areas covered: Sanger sequencing and quantitative methods greatly contributed to the identification of more than 2,000 sequence variations reported worldwide in the CFTR gene. We are now entering a new technological age with the generalization of high throughput approaches such as Next Generation Sequencing and Droplet Digital PCR technologies in diagnostics laboratories. These powerful technologies open up new perspectives for scanning the entire CFTR locus, exploring modifier factors that possibly influence the clinical evolution of patients, and for preimplantation and prenatal diagnosis. Expert commentary: Such breakthroughs would, however, require powerful bioinformatics tools and relevant functional tests of variants for analysis and interpretation of the resulting data. Ultimately, an optimal use of all those resources may improve patient care and therapeutic decision-making.
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Affiliation(s)
- Anne Bergougnoux
- a Laboratoire de Génétique Moléculaire , Centre Hospitalier Universitaire de Montpellier , Montpellier , France.,b EA 7402 , Université de Montpellier , Montpellier , France
| | | | | | - Caroline Raynal
- a Laboratoire de Génétique Moléculaire , Centre Hospitalier Universitaire de Montpellier , Montpellier , France
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18
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Li H, Salomon JJ, Sheppard DN, Mall MA, Galietta LJ. Bypassing CFTR dysfunction in cystic fibrosis with alternative pathways for anion transport. Curr Opin Pharmacol 2017; 34:91-97. [PMID: 29065356 DOI: 10.1016/j.coph.2017.10.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 09/20/2017] [Accepted: 10/04/2017] [Indexed: 12/20/2022]
Abstract
One therapeutic strategy for cystic fibrosis (CF) seeks to restore anion transport to affected epithelia by targeting other apical membrane Cl- channels to bypass dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel. The properties and regulation of the Ca2+-activated Cl- channel TMEM16A argue that long-acting small molecules which target directly TMEM16A are required to overcome CFTR loss. Through genetic studies of lung diseases, SLC26A9, a member of the solute carrier 26 family of anion transporters, has emerged as a promising target to bypass CFTR dysfunction. An alternative strategy to circumvent CFTR dysfunction is to deliver to CF epithelia artificial anion transporters that shuttle Cl- across the apical membrane. Recently, powerful, non-toxic, biologically-active artificial anion transporters have emerged.
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Affiliation(s)
- Hongyu Li
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Johanna J Salomon
- Division of Pediatric Pulmonology and Allergy and Cystic Fibrosis Center, Department of Pediatrics, University Hospital Heidelberg, Heidelberg, Germany; Department of Translational Pulmonology, Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - David N Sheppard
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Marcus A Mall
- Division of Pediatric Pulmonology and Allergy and Cystic Fibrosis Center, Department of Pediatrics, University Hospital Heidelberg, Heidelberg, Germany; Department of Translational Pulmonology, Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - Luis Jv Galietta
- Telethon Institute for Genetics and Medicine (Tigem), Pozzuoli, Italy.
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19
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Airway mucus, inflammation and remodeling: emerging links in the pathogenesis of chronic lung diseases. Cell Tissue Res 2017; 367:537-550. [PMID: 28108847 DOI: 10.1007/s00441-016-2562-z] [Citation(s) in RCA: 111] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 12/19/2016] [Indexed: 12/12/2022]
Abstract
Airway mucus obstruction is a hallmark of many chronic lung diseases including rare genetic disorders such as cystic fibrosis (CF) and primary ciliary dyskinesia, as well as common lung diseases such as asthma and chronic obstructive pulmonary disease (COPD), which have emerged as a leading cause of morbidity and mortality worldwide. However, the role of excess airway mucus in the in vivo pathogenesis of these diseases remains poorly understood. The generation of mice with airway-specific overexpression of epithelial Na+ channels (ENaC), exhibiting airway surface dehydration (mucus hyperconcentration), impaired mucociliary clearance (MCC) and mucus plugging, led to a model of muco-obstructive lung disease that shares key features of CF and COPD. In this review, we summarize recent progress in the understanding of causes of impaired MCC and in vivo consequences of airway mucus obstruction that can be inferred from studies in βENaC-overexpressing mice. These studies confirm that mucus hyperconcentration on airway surfaces plays a critical role in the pathophysiology of impaired MCC, mucus adhesion and airway plugging that cause airflow obstruction and provide a nidus for bacterial infection. In addition, these studies support the emerging concept that excess airway mucus per se, probably via several mechanisms including hypoxic epithelial necrosis, retention of inhaled irritants or allergens, and potential immunomodulatory effects, is a potent trigger of chronic airway inflammation and associated lung damage, even in the absence of bacterial infection. Finally, these studies suggest that improvement of mucus clearance may be a promising therapeutic strategy for a spectrum of muco-obstructive lung diseases.
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20
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Langford R, Hurrion E, Dawson PA. Genetics and pathophysiology of mammalian sulfate biology. J Genet Genomics 2017; 44:7-20. [DOI: 10.1016/j.jgg.2016.08.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 08/08/2016] [Accepted: 08/11/2016] [Indexed: 12/23/2022]
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21
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Strug LJ, Gonska T, He G, Keenan K, Ip W, Boëlle PY, Lin F, Panjwani N, Gong J, Li W, Soave D, Xiao B, Tullis E, Rabin H, Parkins MD, Price A, Zuberbuhler PC, Corvol H, Ratjen F, Sun L, Bear CE, Rommens JM. Cystic fibrosis gene modifier SLC26A9 modulates airway response to CFTR-directed therapeutics. Hum Mol Genet 2016; 25:4590-4600. [PMID: 28171547 PMCID: PMC5886039 DOI: 10.1093/hmg/ddw290] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 07/12/2016] [Accepted: 08/25/2016] [Indexed: 12/18/2022] Open
Abstract
Cystic fibrosis is realizing the promise of personalized medicine. Recent advances in drug development that target the causal CFTR directly result in lung function improvement, but variability in response is demanding better prediction of outcomes to improve management decisions. The genetic modifier SLC26A9 contributes to disease severity in the CF pancreas and intestine at birth and here we assess its relationship with disease severity and therapeutic response in the airways. SLC26A9 association with lung disease was assessed in individuals from the Canadian and French CF Gene Modifier consortia with CFTR-gating mutations and in those homozygous for the common Phe508del mutation. Variability in response to a CFTR-directed therapy attributed to SLC26A9 genotype was assessed in Canadian patients with gating mutations. A primary airway model system determined if SLC26A9 shows modification of Phe508del CFTR function upon treatment with a CFTR corrector. In those with gating mutations that retain cell surface-localized CFTR we show that SLC26A9 modifies lung function while this is not the case in individuals homozygous for Phe508del where cell surface expression is lacking. Treatment response to ivacaftor, which aims to improve CFTR-channel opening probability in patients with gating mutations, shows substantial variability in response, 28% of which can be explained by rs7512462 in SLC26A9 (P = 0.0006). When homozygous Phe508del primary bronchial cells are treated to restore surface CFTR, SLC26A9 likewise modifies treatment response (P = 0.02). Our findings indicate that SLC26A9 airway modification requires CFTR at the cell surface, and that a common variant in SLC26A9 may predict response to CFTR-directed therapeutics.
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Affiliation(s)
- Lisa J. Strug
- Program in Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- Division of Biostatistics, Dalla Lana School of Public Health, University of Toronto, Ontario, Canada
- The Centre for Applied Genomics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Tanja Gonska
- Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada
- Division of Gastroenterology, Hepatology and Nutrition, The Hospital for Sick Children, Toronto, Ontario, Canada
- Program in Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Gengming He
- Program in Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Katherine Keenan
- Program in Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Wan Ip
- Program in Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Pierre-Yves Boëlle
- Sorbonne Universités, Université Pierre et Marie Curie (UPMC) Paris 06, Paris, France
- Assistance Publique-Hôpitaux de Paris (AP-HP), Hôpital St. Antoine, Biostatistics Department; Inserm U1136, Paris, France
| | - Fan Lin
- Program in Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Naim Panjwani
- Program in Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Jiafen Gong
- Program in Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Weili Li
- Program in Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- The Centre for Applied Genomics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - David Soave
- Program in Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- Division of Biostatistics, Dalla Lana School of Public Health, University of Toronto, Ontario, Canada
| | - Bowei Xiao
- Program in Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Elizabeth Tullis
- Department of Respiratory Medicine and Li Ka Shing Knowledge Institute, St. Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Harvey Rabin
- Department of Medicine, University of Calgary, Calgary, Alberta, Canada
- The Department of Microbiology, Immunology and Infectious Disease, University of Calgary, Calgary, Alberta, Canada
| | - Michael D. Parkins
- Department of Medicine, University of Calgary, Calgary, Alberta, Canada
- The Department of Microbiology, Immunology and Infectious Disease, University of Calgary, Calgary, Alberta, Canada
| | - April Price
- Division of Paediatric Respirology, Department of Paediatrics, Children's Hospital at London Health Sciences Centre, London, Ontario, Canada
| | | | - Harriet Corvol
- Sorbonne Universités, Université Pierre et Marie Curie (UPMC) Paris 06, Paris, France
- AP-HP, Hôpital Trousseau, Pediatric Pulmonary Department; Institut National de la Santé et al Recherche Medicale (INSERM) U938, Paris, France
| | - Felix Ratjen
- Program in Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
- Division of Respiratory Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Lei Sun
- Division of Biostatistics, Dalla Lana School of Public Health, University of Toronto, Ontario, Canada
- Department of Statistical Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Christine E. Bear
- Program in Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, CanadaDepartments of
- Biochemistry
- Physiology
| | - Johanna M. Rommens
- Program in Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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22
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Gaitch N, Hubert D, Gameiro C, Burgel PR, Houriez F, Martinez B, Honoré I, Chapron J, Kanaan R, Dusser D, Girodon E, Bienvenu T. CFTR and/or pancreatitis susceptibility genes mutations as risk factors of pancreatitis in cystic fibrosis patients? Pancreatology 2016; 16:515-22. [PMID: 27086061 DOI: 10.1016/j.pan.2016.03.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 03/27/2016] [Accepted: 03/29/2016] [Indexed: 12/11/2022]
Abstract
BACKGROUND/OBJECTIVES Currently, factors that promote the occurrence of pancreatitis episodes in patients affected with cystic fibrosis (CF) and pancreatic sufficiency (PS) are largely unknown. METHODS Six genes involved in pancreatitis or in ion transport into the pancreatic duct were investigated by next generation sequencing in 59 adult CF-PS patients with two identified CF mutations. Data on predisposing environmental factors were also recorded. RESULTS 19 experienced at least one episode of acute pancreatitis (AP) (AP+) and 40 patients did not (AP-). No influence of environmental factor was evidenced. No specific CFTR genotype was found predictive of pancreatitis. Patients sharing the same CFTR genotype may or may not experience AP episodes. Frequent and rare missense variants were found in 78.9% patients in group AP+ and 67.5% in group AP- but a few of them were pathogenic. CONCLUSIONS AP or recurrent AP (RAP) is a frequent complication in our series of adult CF-PS patients. The majority of mild CFTR mutations found in group AP+ were located in the first transmembrane region. No clear other genetic factor could be found predictive of AP/RAP. Further experiments in large homogenous cohorts of CF-PS patients, including whole genome sequencing, may identify genetic predisposing factors to pancreatitis.
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Affiliation(s)
- Natacha Gaitch
- AP-HP, Laboratoire de Génétique et Biologie Moléculaires, HU Paris Centre, Site Cochin, France
| | - Dominique Hubert
- Service de Pneumologie, HU Paris Centre, Site Cochin and Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Christine Gameiro
- AP-HP, Laboratoire de Génétique et Biologie Moléculaires, HU Paris Centre, Site Cochin, France
| | - Pierre-Régis Burgel
- Service de Pneumologie, HU Paris Centre, Site Cochin and Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Florence Houriez
- AP-HP, Laboratoire de Génétique et Biologie Moléculaires, HU Paris Centre, Site Cochin, France
| | - Brigitte Martinez
- AP-HP, Laboratoire de Génétique et Biologie Moléculaires, HU Paris Centre, Site Cochin, France
| | - Isabelle Honoré
- Service de Pneumologie, HU Paris Centre, Site Cochin and Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Jeanne Chapron
- Service de Pneumologie, HU Paris Centre, Site Cochin and Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Reem Kanaan
- Service de Pneumologie, HU Paris Centre, Site Cochin and Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Daniel Dusser
- Service de Pneumologie, HU Paris Centre, Site Cochin and Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Emmanuelle Girodon
- AP-HP, Laboratoire de Génétique et Biologie Moléculaires, HU Paris Centre, Site Cochin, France
| | - Thierry Bienvenu
- AP-HP, Laboratoire de Génétique et Biologie Moléculaires, HU Paris Centre, Site Cochin, France; Université Paris Descartes Paris, Institut Cochin, INSERM U1016, Paris, France.
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Salomon JJ, Spahn S, Wang X, Füllekrug J, Bertrand CA, Mall MA. Generation and functional characterization of epithelial cells with stable expression of SLC26A9 Cl- channels. Am J Physiol Lung Cell Mol Physiol 2016; 310:L593-602. [PMID: 26801567 DOI: 10.1152/ajplung.00321.2015] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 01/16/2016] [Indexed: 01/01/2023] Open
Abstract
Recent studies identified the SLC26A9 Cl(-) channel as a modifier and potential therapeutic target in cystic fibrosis (CF). However, understanding of the regulation of SLC26A9 in epithelia remains limited and cellular models with stable expression for biochemical and functional studies are missing. We, therefore, generated Fisher rat thyroid (FRT) epithelial cells with stable expression of HA-tagged SLC26A9 via retroviral transfection and characterized SLC26A9 expression and function using Western blotting, immunolocalization, whole cell patch-clamp, and transepithelial bioelectric studies in Ussing chambers. We demonstrate stable expression of SLC26A9 in transfected FRT (SLC26A9-FRT) cells on the mRNA and protein level. Immunolocalization and Western blotting detected SLC26A9 in different intracellular compartments and to a lesser extent at the cell surface. Whole cell patch-clamp recordings demonstrated significantly increased constitutive Cl(-) currents in SLC26A9-FRT compared with control-transduced FRT (Control-FRT) cells (P < 0.01). Similar, transepithelial measurements showed that the basal short circuit current was significantly increased in SLC26A9-FRT vs. Control-FRT cell monolayers (P < 0.01). SLC26A9-mediated Cl(-) currents were increased by cAMP-dependent stimulation (IBMX and forskolin) and inhibited by GlyH-101, niflumic acid, DIDS, and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), as well as RNAi knockdown of WNK1 implicated in epithelial osmoregulation. Our results support that these novel epithelial cells with stable expression of SLC26A9 will be a useful model for studies of pharmacological regulation including the identification of activators of SLC26A9 Cl(-) channels that may compensate deficient cystic fibrosis transmembrane regulator (CFTR)-mediated Cl(-) secretion and serve as an alternative therapeutic target in patients with CF and potentially other muco-obstructive lung diseases.
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Affiliation(s)
- Johanna J Salomon
- Department of Translational Pulmonology, Translational Lung Research Center Heidelberg (TLRC), Member of the German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - Stephan Spahn
- Department of Translational Pulmonology, Translational Lung Research Center Heidelberg (TLRC), Member of the German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - Xiaohui Wang
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; and
| | - Joachim Füllekrug
- Molecular Cell Biology Laboratory, Department of Internal Medicine IV, University of Heidelberg, Heidelberg, Germany
| | - Carol A Bertrand
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; and
| | - Marcus A Mall
- Department of Translational Pulmonology, Translational Lung Research Center Heidelberg (TLRC), Member of the German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany;
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Novel Roles for Chloride Channels, Exchangers, and Regulators in Chronic Inflammatory Airway Diseases. Mediators Inflamm 2015; 2015:497387. [PMID: 26612971 PMCID: PMC4647060 DOI: 10.1155/2015/497387] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 10/13/2015] [Indexed: 01/14/2023] Open
Abstract
Chloride transport proteins play critical roles in inflammatory airway diseases, contributing to the detrimental aspects of mucus overproduction, mucus secretion, and airway constriction. However, they also play crucial roles in contributing to the innate immune properties of mucus and mucociliary clearance. In this review, we focus on the emerging novel roles for a chloride channel regulator (CLCA1), a calcium-activated chloride channel (TMEM16A), and two chloride exchangers (SLC26A4/pendrin and SLC26A9) in chronic inflammatory airway diseases.
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25
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Should diffuse bronchiectasis still be considered a CFTR-related disorder? J Cyst Fibros 2015; 14:646-53. [DOI: 10.1016/j.jcf.2015.02.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 02/27/2015] [Accepted: 02/27/2015] [Indexed: 12/31/2022]
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Mall MA, Galietta LJV. Targeting ion channels in cystic fibrosis. J Cyst Fibros 2015; 14:561-70. [PMID: 26115565 DOI: 10.1016/j.jcf.2015.06.002] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 05/28/2015] [Accepted: 06/01/2015] [Indexed: 12/12/2022]
Abstract
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause a characteristic defect in epithelial ion transport that plays a central role in the pathogenesis of cystic fibrosis (CF). Hence, pharmacological correction of this ion transport defect by targeting of mutant CFTR, or alternative ion channels that may compensate for CFTR dysfunction, has long been considered as an attractive approach to a causal therapy of this life-limiting disease. The recent introduction of the CFTR potentiator ivacaftor into the therapy of a subgroup of patients with specific CFTR mutations was a major milestone and enormous stimulus for seeking effective ion transport modulators for all patients with CF. In this review, we discuss recent breakthroughs and setbacks with CFTR modulators designed to rescue mutant CFTR including the common mutation F508del. Further, we examine the alternative chloride channels TMEM16A and SLC26A9, as well as the epithelial sodium channel ENaC as alternative targets in CF lung disease, which remains the major cause of morbidity and mortality in patients with CF. Finally, we will focus on the hurdles that still need to be overcome to make effective ion transport modulation therapies available for all patients with CF irrespective of their CFTR genotype.
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Affiliation(s)
- Marcus A Mall
- Department of Translational Pulmonology, Translational Lung Research Center Heidelberg (TLRC), Member of the German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany; Division of Pediatric Pulmonology & Allergy and Cystic Fibrosis Center, Department of Pediatrics, University of Heidelberg, Heidelberg, Germany.
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Pranke IM, Sermet-Gaudelus I. Biosynthesis of cystic fibrosis transmembrane conductance regulator. Int J Biochem Cell Biol 2014; 52:26-38. [DOI: 10.1016/j.biocel.2014.03.020] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 03/19/2014] [Accepted: 03/20/2014] [Indexed: 01/19/2023]
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28
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Liu X, Li T, Riederer B, Lenzen H, Ludolph L, Yeruva S, Tuo B, Soleimani M, Seidler U. Loss of Slc26a9 anion transporter alters intestinal electrolyte and HCO3(-) transport and reduces survival in CFTR-deficient mice. Pflugers Arch 2014; 467:1261-75. [PMID: 24965066 PMCID: PMC4434866 DOI: 10.1007/s00424-014-1543-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 05/19/2014] [Accepted: 05/20/2014] [Indexed: 12/16/2022]
Abstract
Slc26a9 is an anion transporter that is strongly expressed in the stomach and lung. Slc26a9 variants were recently found associated with a higher incidence of meconium ileus in cystic fibrosis (CF) infants, raising the question whether Slc26a9 is expressed in the intestine and what its functional role is. Slc26a9 messenger RNA (mRNA) was found highly expressed in the mucosae of the murine and human upper gastrointestinal tract, with an abrupt decrease in expression levels beyond the duodenum. Absence of SLC26a9 expression strongly increased the intestinally related mortality in cystic fibrosis transmembrane conductance regulator (CFTR)-deficient mice. Proximal duodenal JHCO3(-) and fluid secretion were reduced in the absence of Slc26a9 expression. In the proximal duodenum of young Slc26a9 KO mice, the glands and villi/crypts were elongated and proliferation was enhanced. This difference was lost with ageing, as were the alterations in fluid movement, whereas the reduction in JHCO3(-) remained. Laser dissection followed by qPCR suggested Slc26a9 expression to be crypt-predominant in the duodenum. In summary, deletion of Slc26a9 caused bicarbonate secretory and fluid absorptive changes in the proximal duodenal mucosa and increased the postweaning death rates in CFTR-deficient mice. Functional alterations in the duodenum were most prominent at young ages. We assume that the association of meconium ileus and Slc26a9 variants may be related to maldigestion and impaired downstream signaling caused by loss of upper GI tract digestive functions, aggravating the situation of lack of secretion and sticky mucus at the site of obstruction in CF intestine.
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Affiliation(s)
- Xuemei Liu
- Department of Gastroenterology, Hannover Medical School, Hannover, Germany
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Abstract
Cystic fibrosis (CF) remains the most common fatal hereditary lung disease. The discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene 25 years ago set the stage for: 1) unravelling the molecular and cellular basis of CF lung disease; 2) the generation of animal models to study in vivo pathogenesis; and 3) the development of mutation-specific therapies that are now becoming available for a subgroup of patients with CF. This article highlights major advances in our understanding of how CFTR dysfunction causes chronic mucus obstruction, neutrophilic inflammation and bacterial infection in CF airways. Furthermore, we focus on recent breakthroughs and remaining challenges of novel therapies targeting the basic CF defect, and discuss the next steps to be taken to make disease-modifying therapies available to a larger group of patients with CF, including those carrying the most common mutation ΔF508-CFTR. Finally, we will summarise emerging evidence indicating that acquired CFTR dysfunction may be implicated in the pathogenesis of chronic obstructive pulmonary disease, suggesting that lessons learned from CF may be applicable to common airway diseases associated with mucus plugging.
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Affiliation(s)
- Marcus A Mall
- Dept of Translational Pulmonology, Translational Lung Research Center Heidelberg (TLRC), University of Heidelberg, Member of the German Center for Lung Research (DZL), Heidelberg, Germany Division of Paediatric Pulmonology and Allergy and Cystic Fibrosis Center, Dept of Paediatrics, University of Heidelberg, Member of the German Center for Lung Research (DZL), Heidelberg, Germany
| | - Dominik Hartl
- Paediatric Infectiology and Immunology, Dept of Pediatrics, University of Tübingen, Tübingen, Germany
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30
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Functional interaction of the cystic fibrosis transmembrane conductance regulator with members of the SLC26 family of anion transporters (SLC26A8 and SLC26A9): physiological and pathophysiological relevance. Int J Biochem Cell Biol 2014; 52:58-67. [PMID: 24530837 DOI: 10.1016/j.biocel.2014.02.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/29/2014] [Accepted: 02/01/2014] [Indexed: 12/21/2022]
Abstract
The solute carrier 26 (SLC26) proteins are transmembrane proteins located at the plasma membrane of the cells and transporting a variety of monovalent and divalent anions, including chloride, bicarbonate, sulfate and oxalate. In humans, 11 members have been identified (SLC26A1 to SLC26A11) and although part of them display a very restricted tissue expression pattern, altogether they are widely expressed in the epithelial cells of the body where they contribute to the composition and the pH regulation of the secreted fluids. Importantly, mutations in SLC26A2, A3, A4, and A5 have been associated with distinct human genetic recessive disorders (i.e. diastrophic dysplasia, congenital chloride diarrhea, Pendred syndrome and deafness, respectively), demonstrating their essential and non-redundant functions in many tissues. During the last decade, physical and functional interactions of SLC26 members with the cystic fibrosis transmembrane conductance regulator (CFTR) have been highly documented, leading to the model of a crosstalk based on the binding of the SLC26 STAS domain to the CFTR regulatory domain. In this review, we will focus on the functional interaction of SLC26A8 and SLC26A9 with the CFTR channel. In particular we will highlight the newly published studies indicating that mutations in SLC26A8 and SLC26A9 proteins are associated with a deregulation of the CFTR anion transport activity in the pathophysiological context of the sperm and the pulmonary cells. These studies confirm the physiological relevance of SLC26 and CFTR cross-regulation, opening new gates for the treatment of cystic fibrosis.
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