1
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Lee D, Hong JH. Chloride/Multiple Anion Exchanger SLC26A Family: Systemic Roles of SLC26A4 in Various Organs. Int J Mol Sci 2024; 25:4190. [PMID: 38673775 PMCID: PMC11050216 DOI: 10.3390/ijms25084190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 03/31/2024] [Accepted: 04/08/2024] [Indexed: 04/28/2024] Open
Abstract
Solute carrier family 26 member 4 (SLC26A4) is a member of the SLC26A transporter family and is expressed in various tissues, including the airway epithelium, kidney, thyroid, and tumors. It transports various ions, including bicarbonate, chloride, iodine, and oxalate. As a multiple-ion transporter, SLC26A4 is involved in the maintenance of hearing function, renal function, blood pressure, and hormone and pH regulation. In this review, we have summarized the various functions of SLC26A4 in multiple tissues and organs. Moreover, the relationships between SLC26A4 and other channels, such as cystic fibrosis transmembrane conductance regulator, epithelial sodium channel, and sodium chloride cotransporter, are highlighted. Although the modulation of SLC26A4 is critical for recovery from malfunctions of various organs, development of specific inducers or agonists of SLC26A4 remains challenging. This review contributes to providing a better understanding of the role of SLC26A4 and development of therapeutic approaches for the SLC26A4-associated hearing loss and SLC26A4-related dysfunction of various organs.
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Affiliation(s)
| | - Jeong Hee Hong
- Department of Health Sciences and Technology, GAIHST (Gachon Advanced Institute for Health Sciences and Technology), Lee Gil Ya Cancer and Diabetes Institute, Gachon University, 155 Getbeolro, Yeonsu-gu, Incheon 21999, Republic of Korea;
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2
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Geertsma ER, Oliver D. SLC26 Anion Transporters. Handb Exp Pharmacol 2024; 283:319-360. [PMID: 37947907 DOI: 10.1007/164_2023_698] [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] [Indexed: 11/12/2023]
Abstract
Solute carrier family 26 (SLC26) is a family of functionally diverse anion transporters found in all kingdoms of life. Anions transported by SLC26 proteins include chloride, bicarbonate, and sulfate, but also small organic dicarboxylates such as fumarate and oxalate. The human genome encodes ten functional homologs, several of which are causally associated with severe human diseases, highlighting their physiological importance. Here, we review novel insights into the structure and function of SLC26 proteins and summarize the physiological relevance of human members.
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Affiliation(s)
- Eric R Geertsma
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
| | - Dominik Oliver
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, Marburg, Germany.
- Center for Mind, Brain and Behavior (CMBB), Universities of Marburg and Giessen, Marburg, Giessen, Germany.
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3
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Haigis AC, Vergauwen L, LaLone CA, Villeneuve DL, O'Brien JM, Knapen D. Cross-species applicability of an adverse outcome pathway network for thyroid hormone system disruption. Toxicol Sci 2023; 195:1-27. [PMID: 37405877 DOI: 10.1093/toxsci/kfad063] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/07/2023] Open
Abstract
Thyroid hormone system disrupting compounds are considered potential threats for human and environmental health. Multiple adverse outcome pathways (AOPs) for thyroid hormone system disruption (THSD) are being developed in different taxa. Combining these AOPs results in a cross-species AOP network for THSD which may provide an evidence-based foundation for extrapolating THSD data across vertebrate species and bridging the gap between human and environmental health. This review aimed to advance the description of the taxonomic domain of applicability (tDOA) in the network to improve its utility for cross-species extrapolation. We focused on the molecular initiating events (MIEs) and adverse outcomes (AOs) and evaluated both their plausible domain of applicability (taxa they are likely applicable to) and empirical domain of applicability (where evidence for applicability to various taxa exists) in a THSD context. The evaluation showed that all MIEs in the AOP network are applicable to mammals. With some exceptions, there was evidence of structural conservation across vertebrate taxa and especially for fish and amphibians, and to a lesser extent for birds, empirical evidence was found. Current evidence supports the applicability of impaired neurodevelopment, neurosensory development (eg, vision) and reproduction across vertebrate taxa. The results of this tDOA evaluation are summarized in a conceptual AOP network that helps prioritize (parts of) AOPs for a more detailed evaluation. In conclusion, this review advances the tDOA description of an existing THSD AOP network and serves as a catalog summarizing plausible and empirical evidence on which future cross-species AOP development and tDOA assessment could build.
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Affiliation(s)
- Ann-Cathrin Haigis
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, 2610 Wilrijk, Belgium
| | - Lucia Vergauwen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, 2610 Wilrijk, Belgium
| | - Carlie A LaLone
- Great Lakes Toxicology and Ecology Division, United States Environmental Protection Agency, Duluth, Minnesota 55804, USA
| | - Daniel L Villeneuve
- Great Lakes Toxicology and Ecology Division, United States Environmental Protection Agency, Duluth, Minnesota 55804, USA
| | - Jason M O'Brien
- Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Carleton University, Ottawa, Ontario K1S 5B6, Canada
| | - Dries Knapen
- Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, 2610 Wilrijk, Belgium
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4
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Heneghan JF, Majmundar AJ, Rivera A, Wohlgemuth JG, Dlott JS, Snyder LM, Hildebrandt F, Alper SL. Activation of 2-oxoglutarate receptor 1 (OXGR1) by α-ketoglutarate (αKG) does not detectably stimulate Pendrin-mediated anion exchange in Xenopus oocytes. Physiol Rep 2022; 10:e15362. [PMID: 35851763 PMCID: PMC9294391 DOI: 10.14814/phy2.15362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Revised: 06/01/2022] [Accepted: 06/03/2022] [Indexed: 06/15/2023] Open
Abstract
SLC26A4/Pendrin is the major electroneutral Cl- /HCO3- exchanger of the apical membrane of the Type B intercalated cell (IC) of the connecting segment (CNT) and cortical collecting duct (CCD). Pendrin mediates both base secretion in response to systemic base load and Cl- reabsorption in response to systemic volume depletion, manifested as decreased nephron salt and water delivery to the distal nephron. Pendrin-mediated Cl- /HCO3- exchange in the apical membrane is upregulated through stimulation of the β-IC apical membrane G protein-coupled receptor, 2-oxoglutarate receptor 1 (OXGR1/GPR99), by its ligand α-ketoglutarate (αKG). αKG is both filtered by the glomerulus and lumenally secreted by proximal tubule apical membrane organic anion transporters (OATs). OXGR1-mediated regulation of Pendrin by αKG has been documented in transgenic mice and in isolated perfused CCD. However, aspects of the OXGR1 signaling pathway have remained little investigated since its original discovery in lymphocytes. Moreover, no ex vivo cellular system has been reported in which to study the OXGR1 signaling pathway of Type B-IC, a cell type refractory to survival in culture in its differentiated state. As Xenopus oocytes express robust heterologous Pendrin activity, we investigated OXGR1 regulation of Pendrin in oocytes. Despite functional expression of OXGR1 in oocytes, co-expression of Pendrin and OXGR1 failed to exhibit αKG-sensitive stimulation of Pendrin-mediated Cl- /anion exchange under a wide range of conditions. We conclude that Xenopus oocytes lack one or more essential molecular components or physical conditions required for OXGR1 to regulate Pendrin activity.
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Affiliation(s)
- John F. Heneghan
- Division of NephrologyBeth Israel Deaconess Medical CenterBostonMassachusettsUSA
- Department of MedicineHarvard Medical SchoolBostonMassachusettsUSA
| | - Amar J. Majmundar
- Division of NephrologyBoston Children's HospitalBostonMassachusettsUSA
- Department of PediatricsHarvard Medical SchoolBostonMassachusettsUSA
| | - Alicia Rivera
- Division of NephrologyBeth Israel Deaconess Medical CenterBostonMassachusettsUSA
- Department of MedicineHarvard Medical SchoolBostonMassachusettsUSA
| | | | | | | | - Friedhelm Hildebrandt
- Division of NephrologyBoston Children's HospitalBostonMassachusettsUSA
- Department of PediatricsHarvard Medical SchoolBostonMassachusettsUSA
- Department of GeneticsHarvard Medical SchoolBostonMassachusettsUSA
| | - Seth L. Alper
- Division of NephrologyBeth Israel Deaconess Medical CenterBostonMassachusettsUSA
- Department of MedicineHarvard Medical SchoolBostonMassachusettsUSA
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5
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Whittamore JM, Hatch M. Oxalate Flux Across the Intestine: Contributions from Membrane Transporters. Compr Physiol 2021; 12:2835-2875. [PMID: 34964122 DOI: 10.1002/cphy.c210013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Epithelial oxalate transport is fundamental to the role occupied by the gastrointestinal (GI) tract in oxalate homeostasis. The absorption of dietary oxalate, together with its secretion into the intestine, and degradation by the gut microbiota, can all influence the excretion of this nonfunctional terminal metabolite in the urine. Knowledge of the transport mechanisms is relevant to understanding the pathophysiology of hyperoxaluria, a risk factor in kidney stone formation, for which the intestine also offers a potential means of treatment. The following discussion presents an expansive review of intestinal oxalate transport. We begin with an overview of the fate of oxalate, focusing on the sources, rates, and locations of absorption and secretion along the GI tract. We then consider the mechanisms and pathways of transport across the epithelial barrier, discussing the transcellular, and paracellular components. There is an emphasis on the membrane-bound anion transporters, in particular, those belonging to the large multifunctional Slc26 gene family, many of which are expressed throughout the GI tract, and we summarize what is currently known about their participation in oxalate transport. In the final section, we examine the physiological stimuli proposed to be involved in regulating some of these pathways, encompassing intestinal adaptations in response to chronic kidney disease, metabolic acid-base disorders, obesity, and following gastric bypass surgery. There is also an update on research into the probiotic, Oxalobacter formigenes, and the basis of its unique interaction with the gut epithelium. © 2021 American Physiological Society. Compr Physiol 11:1-41, 2021.
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Affiliation(s)
- Jonathan M Whittamore
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Marguerite Hatch
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, Florida, USA
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6
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Structure and function of an Arabidopsis thaliana sulfate transporter. Nat Commun 2021; 12:4455. [PMID: 34294705 PMCID: PMC8298490 DOI: 10.1038/s41467-021-24778-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 07/01/2021] [Indexed: 02/06/2023] Open
Abstract
Plant sulfate transporters (SULTR) mediate absorption and distribution of sulfate (SO42-) and are essential for plant growth; however, our understanding of their structures and functions remains inadequate. Here we present the structure of a SULTR from Arabidopsis thaliana, AtSULTR4;1, in complex with SO42- at an overall resolution of 2.8 Å. AtSULTR4;1 forms a homodimer and has a structural fold typical of the SLC26 family of anion transporters. The bound SO42- is coordinated by side-chain hydroxyls and backbone amides, and further stabilized electrostatically by the conserved Arg393 and two helix dipoles. Proton and SO42- are co-transported by AtSULTR4;1 and a proton gradient significantly enhances SO42- transport. Glu347, which is ~7 Å from the bound SO42-, is required for H+-driven transport. The cytosolic STAS domain interacts with transmembrane domains, and deletion of the STAS domain or mutations to the interface compromises dimer formation and reduces SO42- transport, suggesting a regulatory function of the STAS domain.
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7
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Kanavy DM, McNulty SM, Jairath MK, Brnich SE, Bizon C, Powell BC, Berg JS. Comparative analysis of functional assay evidence use by ClinGen Variant Curation Expert Panels. Genome Med 2019; 11:77. [PMID: 31783775 PMCID: PMC6884856 DOI: 10.1186/s13073-019-0683-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 11/05/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The 2015 American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) guidelines for clinical sequence variant interpretation state that "well-established" functional studies can be used as evidence in variant classification. These guidelines articulated key attributes of functional data, including that assays should reflect the biological environment and be analytically sound; however, details of how to evaluate these attributes were left to expert judgment. The Clinical Genome Resource (ClinGen) designates Variant Curation Expert Panels (VCEPs) in specific disease areas to make gene-centric specifications to the ACMG/AMP guidelines, including more specific definitions of appropriate functional assays. We set out to evaluate the existing VCEP guidelines for functional assays. METHODS We evaluated the functional criteria (PS3/BS3) of six VCEPs (CDH1, Hearing Loss, Inherited Cardiomyopathy-MYH7, PAH, PTEN, RASopathy). We then established criteria for evaluating functional studies based on disease mechanism, general class of assay, and the characteristics of specific assay instances described in the primary literature. Using these criteria, we extensively curated assay instances cited by each VCEP in their pilot variant classification to analyze VCEP recommendations and their use in the interpretation of functional studies. RESULTS Unsurprisingly, our analysis highlighted the breadth of VCEP-approved assays, reflecting the diversity of disease mechanisms among VCEPs. We also noted substantial variability between VCEPs in the method used to select these assays and in the approach used to specify strength modifications, as well as differences in suggested validation parameters. Importantly, we observed discrepancies between the parameters VCEPs specified as required for approved assay instances and the fulfillment of these requirements in the individual assays cited in pilot variant interpretation. CONCLUSIONS Interpretation of the intricacies of functional assays often requires expert-level knowledge of the gene and disease, and current VCEP recommendations for functional assay evidence are a useful tool to improve the accessibility of functional data by providing a starting point for curators to identify approved functional assays and key metrics. However, our analysis suggests that further guidance is needed to standardize this process and ensure consistency in the application of functional evidence.
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Affiliation(s)
- Dona M Kanavy
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Shannon M McNulty
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Meera K Jairath
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Sarah E Brnich
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Chris Bizon
- Renaissance Computing Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Bradford C Powell
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Jonathan S Berg
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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8
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Oza AM, DiStefano MT, Hemphill SE, Cushman BJ, Grant AR, Siegert RK, Shen J, Chapin A, Boczek NJ, Schimmenti LA, Murry JB, Hasadsri L, Nara K, Kenna M, Booth KT, Azaiez H, Griffith A, Avraham KB, Kremer H, Rehm HL, Amr SS, Abou Tayoun AN. Expert specification of the ACMG/AMP variant interpretation guidelines for genetic hearing loss. Hum Mutat 2019; 39:1593-1613. [PMID: 30311386 DOI: 10.1002/humu.23630] [Citation(s) in RCA: 285] [Impact Index Per Article: 57.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 07/23/2018] [Accepted: 08/25/2018] [Indexed: 12/23/2022]
Abstract
Due to the high genetic heterogeneity of hearing loss (HL), current clinical testing includes sequencing large numbers of genes, which often yields a significant number of novel variants. Therefore, the standardization of variant interpretation is crucial to provide consistent and accurate diagnoses. The Hearing Loss Variant Curation Expert Panel was created within the Clinical Genome Resource to provide expert guidance for standardized genomic interpretation in the context of HL. As one of its major tasks, our Expert Panel has adapted the American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines for the interpretation of sequence variants in HL genes. Here, we provide a comprehensive illustration of the newly specified ACMG/AMP HL rules. Three rules remained unchanged, four rules were removed, and the remaining 21 rules were specified. These rules were further validated and refined using a pilot set of 51 variants assessed by curators and disease experts. Of the 51 variants evaluated in the pilot, 37% (19/51) changed category based upon application of the expert panel specified rules and/or aggregation of evidence across laboratories. These HL-specific ACMG/AMP rules will help standardize variant interpretation, ultimately leading to better care for individuals with HL.
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Affiliation(s)
- Andrea M Oza
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts.,Department of Otolaryngology and Communication Enhancement, Boston Children's Hospital, Boston, Massachusetts
| | - Marina T DiStefano
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts.,Harvard Medical School, Boston, Massachusetts
| | - Sarah E Hemphill
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts
| | - Brandon J Cushman
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts
| | - Andrew R Grant
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts
| | - Rebecca K Siegert
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts
| | - Jun Shen
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Department of Pathology, Brigham & Women's Hospital, Boston, Massachusetts
| | | | - Nicole J Boczek
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Lisa A Schimmenti
- Department of Otorhinolaryngology, Clinical Genomics and Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota
| | - Jaclyn B Murry
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts
| | - Linda Hasadsri
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Kiyomitsu Nara
- Division of Hearing and Balance Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Margaret Kenna
- Department of Otolaryngology and Communication Enhancement, Boston Children's Hospital, Boston, Massachusetts.,Harvard Medical School, Boston, Massachusetts
| | - Kevin T Booth
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology, University of Iowa Hospital and Clinics, Iowa City, Iowa.,The Interdisciplinary Graduate Program in Molecular Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Hela Azaiez
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology, University of Iowa Hospital and Clinics, Iowa City, Iowa
| | - Andrew Griffith
- Audiology Unit, National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland
| | - Karen B Avraham
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Hannie Kremer
- Department of Otorhinolaryngology and Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Heidi L Rehm
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Center for Genomic Medicine, Massachusetts General Hospital, Boston, Massachusetts.,The Broad Institute of MIT and Harvard, Cambridge, Massachusetts
| | - Sami S Amr
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Department of Pathology, Brigham & Women's Hospital, Boston, Massachusetts
| | - Ahmad N Abou Tayoun
- The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.,The University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
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9
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The role of intestinal oxalate transport in hyperoxaluria and the formation of kidney stones in animals and man. Urolithiasis 2016; 45:89-108. [PMID: 27913853 DOI: 10.1007/s00240-016-0952-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 11/22/2016] [Indexed: 12/26/2022]
Abstract
The intestine exerts a considerable influence over urinary oxalate in two ways, through the absorption of dietary oxalate and by serving as an adaptive extra-renal pathway for elimination of this waste metabolite. Knowledge of the mechanisms responsible for oxalate absorption and secretion by the intestine therefore have significant implications for understanding the etiology of hyperoxaluria, as well as offering potential targets for future treatment strategies for calcium oxalate kidney stone disease. In this review, we present the recent developments and advances in this area over the past 10 years, and put to the test some of the new ideas that have emerged during this time, using human and mouse models. A key focus for our discussion are the membrane-bound anion exchangers, belonging to the SLC26 gene family, some of which have been shown to participate in transcellular oxalate absorption and secretion. This has offered the opportunity to not only examine the roles of these specific transporters, revealing their importance to oxalate homeostasis, but to also probe the relative contributions made by the active transcellular and passive paracellular components of oxalate transport across the intestine. We also discuss some of the various physiological stimuli and signaling pathways which have been suggested to participate in the adaptation and regulation of intestinal oxalate transport. Finally, we offer an update on research into Oxalobacter formigenes, alongside recent investigations of other oxalate-degrading gut bacteria, in both laboratory animals and humans.
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10
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Extracellular Cl(-) regulates human SO4 (2-)/anion exchanger SLC26A1 by altering pH sensitivity of anion transport. Pflugers Arch 2016; 468:1311-32. [PMID: 27125215 DOI: 10.1007/s00424-016-1823-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 04/03/2016] [Accepted: 04/07/2016] [Indexed: 12/16/2022]
Abstract
Genetic deficiency of the SLC26A1 anion exchanger in mice is known to be associated with hyposulfatemia and hyperoxaluria with nephrolithiasis, but many aspects of human SLC26A1 function remain to be explored. We report here the functional characterization of human SLC26A1, a 4,4'-diisothiocyanato-2,2'-stilbenedisulfonic acid (DIDS)-sensitive, electroneutral sodium-independent anion exchanger transporting sulfate, oxalate, bicarbonate, thiosulfate, and (with divergent properties) chloride. Human SLC26A1-mediated anion exchange differs from that of its rodent orthologs in its stimulation by alkaline pHo and inhibition by acidic pHo but not pHi and in its failure to transport glyoxylate. SLC26A1-mediated transport of sulfate and oxalate is highly dependent on allosteric activation by extracellular chloride or non-substrate anions. Extracellular chloride stimulates apparent V max of human SLC26A1-mediated sulfate uptake by conferring a 2-log decrease in sensitivity to inhibition by extracellular protons, without changing transporter affinity for extracellular sulfate. In contrast to SLC26A1-mediated sulfate transport, SLC26A1-associated chloride transport is activated by acid pHo, shows reduced sensitivity to DIDS, and exhibits cation dependence of its DIDS-insensitive component. Human SLC26A1 resembles SLC26 paralogs in its inhibition by phorbol ester activation of protein kinase C (PKC), which differs in its undiminished polypeptide abundance at or near the oocyte surface. Mutation of SLC26A1 residues corresponding to candidate anion binding site-associated residues in avian SLC26A5/prestin altered anion transport in patterns resembling those of prestin. However, rare SLC26A1 polymorphic variants from a patient with renal Fanconi Syndrome and from a patient with nephrolithiasis/calcinosis exhibited no loss-of-function phenotypes consistent with disease pathogenesis.
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11
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Lazo-Fernandez Y, Aguilera G, Pham TD, Park AY, Beierwaltes WH, Sutliff RL, Verlander JW, Pacak K, Osunkoya AO, Ellis CL, Kim YH, Shipley GL, Wynne BM, Hoover RS, Sen SK, Plotsky PM, Wall SM. Pendrin localizes to the adrenal medulla and modulates catecholamine release. Am J Physiol Endocrinol Metab 2015; 309:E534-45. [PMID: 26173457 PMCID: PMC4572452 DOI: 10.1152/ajpendo.00035.2015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 07/09/2015] [Indexed: 02/02/2023]
Abstract
Pendrin (Slc26a4) is a Cl(-)/HCO3 (-) exchanger expressed in renal intercalated cells and mediates renal Cl(-) absorption. With pendrin gene ablation, blood pressure and vascular volume fall, which increases plasma renin concentration. However, serum aldosterone does not significantly increase in pendrin-null mice, suggesting that pendrin regulates adrenal zona glomerulosa aldosterone production. Therefore, we examined pendrin expression in the adrenal gland using PCR, immunoblots, and immunohistochemistry. Pendrin protein was detected in adrenal lysates from wild-type but not pendrin-null mice. However, immunohistochemistry and qPCR of microdissected adrenal zones showed that pendrin was expressed in the adrenal medulla, rather than in cortex. Within the adrenal medulla, pendrin localizes to both epinephrine- and norepinephrine-producing chromaffin cells. Therefore, we examined plasma catecholamine concentration and blood pressure in wild-type and pendrin-null mice under basal conditions and then after 5 and 20 min of immobilization stress. Under basal conditions, blood pressure was lower in the mutant than in the wild-type mice, although epinephrine and norepinephrine concentrations were similar. Catecholamine concentration and blood pressure increased markedly in both groups with stress. With 20 min of immobilization stress, epinephrine and norepinephrine concentrations increased more in pendrin-null than in wild-type mice, although stress produced a similar increase in blood pressure in both groups. We conclude that pendrin is expressed in the adrenal medulla, where it blunts stress-induced catecholamine release.
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Affiliation(s)
| | - Greti Aguilera
- Section on Endocrine Physiology, Developmental Endocrinology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Truyen D Pham
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Annie Y Park
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - William H Beierwaltes
- Hypertension and Vascular Research Division, Henry Ford Hospital and Wayne State School of Medicine, Detroit, Michigan
| | - Roy L Sutliff
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia; Atlanta Veterans Affairs Hospital, Atlanta, Georgia
| | - Jill W Verlander
- Department of Medicine, University of Florida, Gainesville, Florida
| | - Karel Pacak
- Program in Reproductive and Adult Endocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Adeboye O Osunkoya
- Department of Pathology, Emory University School of Medicine, Atlanta, Georgia
| | - Carla L Ellis
- Department of Pathology, Emory University School of Medicine, Atlanta, Georgia
| | - Young Hee Kim
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Gregory L Shipley
- Department of Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas
| | - Brandi M Wynne
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Robert S Hoover
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia; Atlanta Veterans Affairs Hospital, Atlanta, Georgia; Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
| | - Shurjo K Sen
- Cardiovascular Disease Section, and National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland
| | - Paul M Plotsky
- Department of Psychiatry, Emory University School of Medicine, Atlanta, Georgia; and
| | - Susan M Wall
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia; Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
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12
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Soleimani M. The multiple roles of pendrin in the kidney. Nephrol Dial Transplant 2014; 30:1257-66. [PMID: 25281699 DOI: 10.1093/ndt/gfu307] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/25/2014] [Indexed: 12/30/2022] Open
Abstract
The [Formula: see text] exchanger pendrin (SLC26A4, PDS) is located on the apical membrane of B-intercalated cells in the kidney cortical collecting duct and the connecting tubules and mediates the secretion of bicarbonate and the reabsorption of chloride. Given its dual function of bicarbonate secretion and chloride reabsorption in the distal tubules, it was thought that pendrin plays important roles in systemic acid-base balance and electrolyte and vascular volume homeostasis under basal conditions. Mice with the genetic deletion of pendrin or humans with inactivating mutations in PDS gene, however, do not display excessive salt and fluid wasting or altered blood pressure under baseline conditions. Very recent reports have unmasked the basis of incongruity between the mild phenotype in mutant mice and the role of pendrin as an important player in salt reabsorption in the distal tubule. These studies demonstrate that pendrin and the Na-Cl cotransporter (NCC; SLC12A3) cross compensate for the loss of each other, therefore masking the role that each transporter plays in salt reabsorption under baseline conditions. In addition, pendrin regulates calcium reabsorption in the distal tubules. Furthermore, combined deletion of pendrin and NCC not only causes severe volume depletion but also results in profound calcium wasting and luminal calcification in medullary collecting ducts. Based on studies in pathophysiological states and the examination of genetically engineered mouse models, the evolving picture points to important roles for pendrin (SLC26A4) in kidney physiology and in disease states. This review summarizes recent advances in the characterization of pendrin and the multiple roles it plays in the kidney, with emphasis on its essential roles in several diverse physiological processes, including chloride homeostasis, vascular volume and blood pressure regulation, calcium excretion and kidney stone formation.
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Affiliation(s)
- Manoocher Soleimani
- Center on Genetics of Transport and Epithelial Biology, University of Cincinnati, Cincinnati, OH, USA Research Services, Veterans Affairs Medical Center, Cincinnati, OH, USA Department of Medicine, University of Cincinnati, Cincinnati, OH, USA
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Alka K, Casey JR. Bicarbonate transport in health and disease. IUBMB Life 2014; 66:596-615. [PMID: 25270914 DOI: 10.1002/iub.1315] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 09/10/2014] [Indexed: 12/28/2022]
Abstract
Bicarbonate (HCO3(-)) has a central place in human physiology as the waste product of mitochondrial energy production and for its role in pH buffering throughout the body. Because bicarbonate is impermeable to membranes, bicarbonate transport proteins are necessary to enable control of bicarbonate levels across membranes. In humans, 14 bicarbonate transport proteins, members of the SLC4 and SLC26 families, function by differing transport mechanisms. In addition, some anion channels and ZIP metal transporters contribute to bicarbonate movement across membranes. Defective bicarbonate transport leads to diseases, including systemic acidosis, brain dysfunction, kidney stones, and hypertension. Altered expression levels of bicarbonate transporters in patients with breast, colon, and lung cancer suggest an important role of these transporters in cancer.
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Affiliation(s)
- Kumari Alka
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
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Kim D, Kim J, Burghardt B, Best L, Steward MC. Role of anion exchangers in Cl− and HCO3− secretion by the human airway epithelial cell line Calu-3. Am J Physiol Cell Physiol 2014; 307:C208-19. [DOI: 10.1152/ajpcell.00083.2014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Despite the importance of airway surface liquid pH in the lung's defenses against infection, the mechanism of airway HCO3− secretion remains unclear. Our aim was to assess the contribution of apical and basolateral Cl−/HCO3− exchangers to Cl− and HCO3− transport in the Calu-3 cell line, derived from human airway submucosal glands. Changes in intracellular pH (pHi) were measured following substitution of Cl− with gluconate. Apical Cl− substitution led to an alkalinization in forskolin-stimulated cells, indicative of Cl−/HCO3− exchange. This was unaffected by the anion exchange inhibitor DIDS but inhibited by the CFTR blocker CFTRinh-172, suggesting that the HCO3− influx might occur via CFTR, rather than a solute carrier family 26 (SLC26) exchanger, as recently proposed. The anion selectivity of the recovery process more closely resembled that of CFTR than an SLC26 exchanger, and quantitative RT-PCR showed only low levels of SLC26 exchanger transcripts relative to CFTR and anion exchanger 2 (AE2). For pHi to rise to observed values (∼7.8) through HCO3− entry via CFTR, the apical membrane potential must reverse to at least +20 mV following Cl− substitution; this was confirmed by perforated-patch recordings. Substitution of basolateral Cl− evoked a DIDS-sensitive alkalinization, attributed to Cl−/HCO3− exchange via AE2. This appeared to be abolished in forskolin-stimulated cells but was unmasked by blocking apical efflux of HCO3− via CFTR. We conclude that Calu-3 cells secrete HCO3− predominantly via CFTR, and, contrary to previous reports, the basolateral anion exchanger AE2 remains active during stimulation, providing an important pathway for basolateral Cl− uptake.
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Affiliation(s)
- Dusik Kim
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Juyeon Kim
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Beáta Burghardt
- Department of Oral Biology, Semmelweis University, Budapest, Hungary; and
| | - Len Best
- Faculty of Medicine and Human Sciences, University of Manchester, Manchester, United Kingdom
| | - Martin C. Steward
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
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Li J, Xia F, Reithmeier RAF. N-glycosylation and topology of the human SLC26 family of anion transport membrane proteins. Am J Physiol Cell Physiol 2014; 306:C943-60. [PMID: 24647542 DOI: 10.1152/ajpcell.00030.2014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The human solute carrier (SLC26) family of anion transporters consists of 10 members (SLCA1-11, SLCA10 being a pseudogene) that encode membrane proteins containing ~12 transmembrane (TM) segments with putative N-glycosylation sites (-NXS/T-) in extracellular loops and a COOH-terminal cytosolic STAS domain. All 10 members of the human SLC26 family, FLAG-tagged at the NH2 terminus, were transiently expressed in HEK-293 cells. While most proteins were observed to contain both high-mannose and complex oligosaccharides, SLC26A2 was mainly in the complex form, SLC26A4 in the high-mannose form, and SLC26A8 was not N-glycosylated. Mutation of the putative N-glycosylation sites showed that most members contain multiple N-glycosylation sites in the second extracytosolic (EC) loop, except SLC26A11, which was N-glycosylated in EC loop 4. Immunofluorescence staining of permeabilized cells localized the proteins to the plasma membrane and the endoplasmic reticulum, with SLC26A2 highly localized to the plasma membrane. N-glycosylation was not a necessary requirement for cell surface expression as the localization of nonglycosylated proteins was similar to their wild-type counterparts, although a lower level of cell-surface biotinylation was observed. No immunostaining of intact cells was observed for any SLC26 members, demonstrating that the NH2-terminal FLAG tag was located in the cytosol. Topological models of the SLC26 proteins that contain an even number of transmembrane segments with both the NH2 and COOH termini located in the cytosol and utilized N-glycosylation sites defining the positions of two EC loops are presented.
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Affiliation(s)
- Jing Li
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Fan Xia
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
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Cordat E, Reithmeier RA. Structure, Function, and Trafficking of SLC4 and SLC26 Anion Transporters. CURRENT TOPICS IN MEMBRANES 2014; 73:1-67. [DOI: 10.1016/b978-0-12-800223-0.00001-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Alper SL, Sharma AK. The SLC26 gene family of anion transporters and channels. Mol Aspects Med 2013; 34:494-515. [PMID: 23506885 DOI: 10.1016/j.mam.2012.07.009] [Citation(s) in RCA: 256] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 06/21/2012] [Indexed: 02/08/2023]
Abstract
The phylogenetically ancient SLC26 gene family encodes multifunctional anion exchangers and anion channels transporting a broad range of substrates, including Cl(-), HCO3(-), sulfate, oxalate, I(-), and formate. SLC26 polypeptides are characterized by N-terminal cytoplasmic domains, 10-14 hydrophobic transmembrane spans, and C-terminal cytoplasmic STAS domains, and appear to be homo-oligomeric. SLC26-related SulP proteins of marine bacteria likely transport HCO3(-) as part of oceanic carbon fixation. SulP genes present in antibiotic operons may provide sulfate for antibiotic biosynthetic pathways. SLC26-related Sultr proteins transport sulfate in unicellular eukaryotes and in plants. Mutations in three human SLC26 genes are associated with congenital or early onset Mendelian diseases: chondrodysplasias for SLC26A2, chloride diarrhea for SLC26A3, and deafness with enlargement of the vestibular aqueduct for SLC26A4. Additional disease phenotypes evident only in mouse knockout models include oxalate urolithiasis for Slc26a6 and Slc26a1, non-syndromic deafness for Slc26a5, gastric hypochlorhydria for Slc26a7 and Slc26a9, distal renal tubular acidosis for Slc26a7, and male infertility for Slc26a8. STAS domains are required for cell surface expression of SLC26 proteins, and contribute to regulation of the cystic fibrosis transmembrane regulator in complex, cell- and tissue-specific ways. The protein interactomes of SLC26 polypeptides are under active investigation.
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Affiliation(s)
- Seth L Alper
- Renal Division and Division of Molecular and Vascular Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
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18
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Mohebbi N, Perna A, van der Wijst J, Becker HM, Capasso G, Wagner CA. Regulation of two renal chloride transporters, AE1 and pendrin, by electrolytes and aldosterone. PLoS One 2013; 8:e55286. [PMID: 23383138 PMCID: PMC3561381 DOI: 10.1371/journal.pone.0055286] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Accepted: 12/21/2012] [Indexed: 01/14/2023] Open
Abstract
The renal handling of salt and protons and bicarbonate are intricately linked through shared transport mechanisms for sodium, chloride, protons, and bicarbonate. In the collecting duct, the regulated fine-tuning of salt and acid-base homeostasis is achieved by a series of transport proteins located in different cell types, intercalated and principal cells. Intercalated cells are considered to be of less importance for salt handling but recent evidence has suggested that the anion exchanger pendrin may participate in salt reabsorption and blood pressure regulation. Here, we examined the regulated expression of two functionally related but differentially expressed anion exchangers, AE1 and pendrin, by dietary electrolyte intake and aldosterone. Cortical expression of pendrin was regulated on mRNA and protein level. The combination of NaHCO3 and DOCA enhanced pendrin mRNA and protein levels, whereas DOCA or NaHCO3 alone had no effect. NaCl or KHCO3 increased pendrin mRNA, KCl decreased its mRNA abundance. On protein level, NH4Cl, NaCl, and KCl reduced pendrin expression, the other treatments were without effect. In contrast, AE1 mRNA or protein expression in kidney cortex was regulated by none of these treatments. In kidney medulla, NaHCO3/DOCA or NaHCO3 alone enhanced AE1 mRNA levels. AE1 protein abundance was increased by NH4Cl, NaHCO3/DOCA, and NaCl. Immunolocalization showed that during NH4Cl treatment the relative number of AE1 positive cells was increased and pendrin expressing cells reduced. Thus, pendrin and AE1 are differentially regulated with distinct mechanisms that separately affect mRNA and protein levels. Pendrin is regulated by acidosis and chloride intake, whereas AE1 is enhanced by acidosis, NaCl, and the combination of DOCA and NaHCO3.
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Affiliation(s)
- Nilufar Mohebbi
- Institute of Physiology and Zurich Center for Integrative Human Physiology-ZIHP, Zurich, Switzerland
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Pelzl L, Pakladok T, Pathare G, Fakhri H, Michael D, Wagner CA, Paulmichl M, Lang F. DOCA sensitive pendrin expression in kidney, heart, lung and thyroid tissues. Cell Physiol Biochem 2012; 30:1491-501. [PMID: 23235354 DOI: 10.1159/000343337] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2012] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND/AIMS Pendrin (SLC26A4), a transporter accomplishing anion exchange, is expressed in inner ear, thyroid gland, kidneys, lung, liver and heart. Loss or reduction of function mutations of SLC26A4 underlie Pendred syndrome, a disorder invariably leading to hearing loss with enlarged vestibular aqueducts and in some patients to hypothyroidism and goiter. Renal pendrin expression is up-regulated by mineralocorticoids such as aldosterone or deoxycorticosterone (DOCA). Little is known about the impact of mineralocorticoids on pendrin expression in extrarenal tissues. METHODS The present study utilized RT-qPCR and Western blotting to quantify the transcript levels and protein abundance of Slc26a4 in murine kidney, thyroid, heart and lung prior to and following subcutaneous administration of 100 mg/kg DOCA. RESULTS Slc26a4 transcript levels as compared to Gapdh transcript levels were significantly increased by DOCA treatment in kidney, heart, lung and thyroid. Accordingly pendrin protein expression was again significantly increased by DOCA treatment in kidney, heart, lung and thyroid. CONCLUSION The observations reveal mineralocorticoid sensitivity of pendrin expression in kidney, heart, thyroid and lung.
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Affiliation(s)
- Lisann Pelzl
- Department of Physiology, University of Tuebingen, Tuebingen, Germany
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Dossena S, Nofziger C, Lang F, Valenti G, Paulmichl M. The ESF meeting on "The proteomics, epigenetics and pharmacogenetics of pendrin". Cell Physiol Biochem 2011; 28:377-84. [PMID: 22116352 DOI: 10.1159/000335101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/10/2011] [Indexed: 12/25/2022] Open
Abstract
Human pendrin (SCL26A4, PDS) is a 780 amino acid integral membrane protein with transport function. It acts as an electroneutral, sodium-independent anion exchanger for a wide range of anions, such as iodide, chloride, formate, bicarbonate, hydroxide and thiocyanate. Pendrin expression was originally described in the thyroid gland, kidney and inner ear. Accordingly, pendrin mutations with reduction or loss of transport function result in thyroid and inner ear abnormalities, manifested as syndromic (Pendred syndrome) and non-syndromic hearing loss with an enlarged vestibular aqueduct (ns-EVA). Pendred syndrome, the most common form of syndromic deafness, is an autosomal recessive disease characterized by sensorineural deafness due to inner ear malformations and a partial iodide organification defect that may lead to thyroid goiter. Later, it became evident that not only pendrin loss of function, but also up-regulation could participate in the pathogenesis of human diseases. Indeed, despite the absence of kidney dysfunction in Pendred syndrome patients, evidence exists that pendrin also plays a crucial role in this organ, with a potential involvement in the pathogenesis of hypertension. In addition, recent data underscore the role of pendrin in exacerbations of respiratory distresses including bronchial asthma and chronic obstructive pulmonary disease (COPD). Pendrin expression in other organs such as mammary gland, testis, placenta, endometrium and liver point to new, underscored pendrin functions that deserve to be further investigated.
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Affiliation(s)
- Silvia Dossena
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
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