1
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Majmundar AJ, Widmeier E, Heneghan JF, Daga A, Wu CHW, Buerger F, Hugo H, Ullah I, Amar A, Ottlewski I, Braun DA, Jobst-Schwan T, Lawson JA, Zahoor MY, Rodig NM, Tasic V, Nelson CP, Khaliq S, Schönauer R, Halbritter J, Sayer JA, Fathy HM, Baum MA, Shril S, Mane S, Alper SL, Hildebrandt F. OXGR1 is a candidate disease gene for human calcium oxalate nephrolithiasis. Genet Med 2023; 25:100351. [PMID: 36571463 PMCID: PMC9992313 DOI: 10.1016/j.gim.2022.11.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 11/23/2022] [Accepted: 11/27/2022] [Indexed: 12/12/2022] Open
Abstract
PURPOSE Nephrolithiasis (NL) affects 1 in 11 individuals worldwide, leading to significant patient morbidity. NL is associated with nephrocalcinosis (NC), a risk factor for chronic kidney disease. Causative genetic variants are detected in 11% to 28% of NL and/or NC, suggesting that additional NL/NC-associated genetic loci await discovery. Therefore, we employed genomic approaches to discover novel genetic forms of NL/NC. METHODS Exome sequencing and directed sequencing of the OXGR1 locus were performed in a worldwide NL/NC cohort. Putatively deleterious, rare OXGR1 variants were functionally characterized. RESULTS Exome sequencing revealed a heterozygous OXGR1 missense variant (c.371T>G, p.L124R) cosegregating with calcium oxalate NL and/or NC disease in an autosomal dominant inheritance pattern within a multigenerational family with 5 affected individuals. OXGR1 encodes 2-oxoglutarate (α-ketoglutarate [AKG]) receptor 1 in the distal nephron. In response to its ligand AKG, OXGR1 stimulates the chloride-bicarbonate exchanger, pendrin, which also regulates transepithelial calcium transport in cortical connecting tubules. Strong amino acid conservation in orthologs and paralogs, severe in silico prediction scores, and extreme rarity in exome population databases suggested that the variant was deleterious. Interrogation of the OXGR1 locus in 1107 additional NL/NC families identified 5 additional deleterious dominant variants in 5 families with calcium oxalate NL/NC. Rare, potentially deleterious OXGR1 variants were enriched in patients with NL/NC compared with Exome Aggregation Consortium controls (χ2 = 7.117, P = .0076). Wild-type OXGR1-expressing Xenopus oocytes exhibited AKG-responsive Ca2+ uptake. Of 5 NL/NC-associated missense variants, 5 revealed impaired AKG-dependent Ca2+ uptake, demonstrating loss of function. CONCLUSION Rare, dominant loss-of-function OXGR1 variants are associated with recurrent calcium oxalate NL/NC disease.
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Affiliation(s)
- Amar J Majmundar
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Eugen Widmeier
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - John F Heneghan
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Ankana Daga
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Chen-Han Wilfred Wu
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Division of Genetics and Genomics, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Departments of Urology and Genetics and Genome Sciences, School of Medicine, Case Western Reserve University and University Hospitals, Cleveland, OH
| | - Florian Buerger
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Hannah Hugo
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Ihsan Ullah
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Molecular Biology Laboratory, Institute of Biochemistry and Biotechnology, University of Veterinary & Animal Sciences, Lahore, Pakistan
| | - Ali Amar
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Department of Human Genetics and Molecular Biology, University of Health Sciences Lahore, Lahore, Pakistan
| | - Isabel Ottlewski
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Daniela A Braun
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Tilman Jobst-Schwan
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Department of Nephrology and Hypertension, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jennifer A Lawson
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Muhammad Yasir Zahoor
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA; Molecular Biology Laboratory, Institute of Biochemistry and Biotechnology, University of Veterinary & Animal Sciences, Lahore, Pakistan
| | - Nancy M Rodig
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Velibor Tasic
- Medical Faculty Skopje, University Children's Hospital, Skopje, North Macedonia
| | - Caleb P Nelson
- Department of Urology, Boston Children's Hospital and Department of Surgery, Harvard Medical School, Boston, MA
| | - Shagufta Khaliq
- Department of Human Genetics and Molecular Biology, University of Health Sciences Lahore, Lahore, Pakistan
| | - Ria Schönauer
- Division of Nephrology, Department of Internal Medicine, University of Leipzig, Leipzig, Germany; Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jan Halbritter
- Division of Nephrology, Department of Internal Medicine, University of Leipzig, Leipzig, Germany; Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - John A Sayer
- Institute of Genetic Medicine, Newcastle University, Newcastle, United Kingdom; The Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle, United Kingdom; NIHR Newcastle Biomedical Research Centre, Newcastle, United Kingdom
| | - Hanan M Fathy
- Pediatric Nephrology Unit, Alexandria University, Alexandria, Egypt
| | - Michelle A Baum
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Shirlee Shril
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA
| | - Shrikant Mane
- Department of Genetics and Yale Center for Mendelian Genomics, Yale University School of Medicine, New Haven, CT
| | - Seth L Alper
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Friedhelm Hildebrandt
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA.
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2
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Vandorpe DH, Heneghan JF, Waitzman JS, McCarthy GM, Blasio A, Magraner JM, Donovan OG, Schaller LB, Shah SS, Subramanian B, Riella CV, Friedman DJ, Pollak MR, Alper SL. Apolipoprotein L1 (APOL1) cation current in HEK-293 cells and in human podocytes. Pflugers Arch 2023; 475:323-341. [PMID: 36449077 DOI: 10.1007/s00424-022-02767-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 10/14/2022] [Accepted: 10/25/2022] [Indexed: 12/05/2022]
Abstract
Two heterozygous missense variants (G1 and G2) of Apolipoprotein L1 (APOL1) found in individuals of recent African ancestry can attenuate the severity of infection by some forms of Trypanosoma brucei. However, these two variants within a broader African haplotype also increase the risk of kidney disease in Americans of African descent. Although overexpression of either variant G1 or G2 causes multiple pathogenic changes in cultured cells and transgenic mouse models, the mechanism(s) promoting kidney disease remain unclear. Human serum APOL1 kills trypanosomes through its cation channel activity, and cation channel activity of recombinant APOL1 has been reconstituted in lipid bilayers and proteoliposomes. Although APOL1 overexpression increases whole cell cation currents in HEK-293 cells, the ion channel activity of APOL1 has not been assessed in glomerular podocytes, the major site of APOL1-associated kidney diseases. We characterize APOL1-associated whole cell and on-cell cation currents in HEK-293 T-Rex cells and demonstrate partial inhibition of currents by anti-APOL antibodies. We detect in primary human podocytes a similar cation current inducible by interferon-γ (IFNγ) and sensitive to inhibition by anti-APOL antibody as well as by a fragment of T. brucei Serum Resistance-Associated protein (SRA). CRISPR knockout of APOL1 in human primary podocytes abrogates the IFNγ-induced, antibody-sensitive current. Our novel characterization in HEK-293 cells of heterologous APOL1-associated cation conductance inhibited by anti-APOL antibody and our documentation in primary human glomerular podocytes of endogenous IFNγ-stimulated, APOL1-mediated, SRA and anti-APOL-sensitive ion channel activity together support APOL1-mediated channel activity as a therapeutic target for treatment of APOL1-associated kidney diseases.
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Affiliation(s)
- David H Vandorpe
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - John F Heneghan
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Pathology, Brigham and Women's Hospital, Boston, MA, 02215, USA
| | - Joshua S Waitzman
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - Gizelle M McCarthy
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Vertex Pharmaceuticals, Boston, MA, 02210, USA
| | - Angelo Blasio
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Vertex Pharmaceuticals, Boston, MA, 02210, USA
| | - Jose M Magraner
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,, San Diego, CA, USA
| | - Olivia G Donovan
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA
| | - Lena B Schaller
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Ludwig-Maximilians-Universitaet, 80336, Munich, Germany
| | - Shrijal S Shah
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Chroma Medicine, Cambridge, MA, 02142, USA
| | - Balajikarthick Subramanian
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - Cristian V Riella
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - David J Friedman
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA.,Broad Institute of Harvard and MIT, Cambridge, MA, 02139, USA
| | - Martin R Pollak
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA.,Broad Institute of Harvard and MIT, Cambridge, MA, 02139, USA
| | - Seth L Alper
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA. .,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA. .,Broad Institute of Harvard and MIT, Cambridge, MA, 02139, USA.
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3
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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4
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Shashikanth N, Rizzo HE, Pongkorpsakol P, Heneghan JF, Turner JR. Correction: Electrophysiologic Analysis of Tight Junction Size and Charge Selectivity. Curr Protoc 2021; 1:e259. [PMID: 34495581 DOI: 10.1002/cpz1.259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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5
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Shashikanth N, Rizzo HE, Pongkorpsakol P, Heneghan JF, Turner JR. Electrophysiologic Analysis of Tight Junction Size and Charge Selectivity. Curr Protoc 2021; 1:e143. [PMID: 34106526 DOI: 10.1002/cpz1.143] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Tight junctions form selectively permeable barriers that limit paracellular flux across epithelial-lined surfaces. Rather than being absolute barriers, tight junctions in many tissues allow ions, water, and other small molecules to cross on the basis of size and charge selectivity via the high-capacity pore pathway. Most probes currently used to assess tight junction permeability exceed the maximum size capacity of the pore pathway. As a result, available analytical tools have generally been limited to measurement of transepithelial electrical resistances. These provide no information regarding size selectivity and, therefore, cannot be used to distinguish between the pore pathway and the leak pathway, a low-capacity route that accommodates larger macromolecules. This article describes use of dilution potential and bi-ionic potential measurements for analysis of tight junction size and charge selectivity within monolayers of cultured epithelial cells. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Culture of MDCK monolayers on semipermeable supports and induction of claudin-2 expression Basic Protocol 2: Configuring voltage/current clamp and other equipment Basic Protocol 3: Measuring dilution and bi-ionic potentials Basic Protocol 4: Calculating ion permeabilities and pore diameter Support Protocol: Preparation of agar bridges and electrophysiology rig setup.
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Affiliation(s)
- Nitesh Shashikanth
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Heather E Rizzo
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Pawin Pongkorpsakol
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.,Faculty of Medicine and Public Health, HRH Princess Chulabhorn College of Medical Science, Chulabhorn Royal Academy, Bangkok, Thailand
| | - John F Heneghan
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Jerrold R Turner
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
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6
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Abtahi S, Gliksman NR, Heneghan JF, Nilsen SP, Muhlich JL, Copeland J, Rozbicki E, Allan C, Dudeja PK, Turner JR. A Simple Method for Creating a High-Content Microscope for Imaging Multiplexed Tissue Microarrays. Curr Protoc 2021; 1:e68. [PMID: 33822482 DOI: 10.1002/cpz1.68] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
High-throughput, high-content imaging technologies and multiplex slide scanning have become widely used. Advantages of these approaches include the ability to archive digital copies of slides, review slides as teams using virtual microscopy software, and standardize analytical approaches. The cost and hardware and software inflexibility of dedicated slide scanning devices can, however, complicate implementation. Here, we describe a simple method that allows any microscope to be used for slide scanning. The only requirements are that the microscope be equipped with a motorized filter turret or wheels (for multi-channel fluorescence) and a motorized xyz stage. This example uses MetaMorph software, but the same principles can be used with any microscope control software that includes a few standard functions and allows programming of simple command routines, or journals. The series of journals that implement the method perform key functions, including assistance in defining an unlimited number of regions of interest (ROI) and imaging parameters. Fully automated acquisition is rapid, taking less than 3 hr to image fifty 2.5-mm ROIs in four channels. Following acquisition, images can be easily stitched and displayed using open-source or commercial image-processing and virtual microscope applications. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Hardware and software configuration Basic Protocol 2: Create a preliminary scan Basic Protocol 3: Select, save, and position ROIs Basic Protocol 4: Determine and set autofocus parameters Basic Protocol 5: Acquire tiled images Basic Protocol 6: Review the scans Basic Protocol 7: Reimage ROIs as needed Basic Protocol 8: Stitch, stack, and assemble images Basic Protocol 9: Repeat scanning for multiplex immunostaining or background subtraction.
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Affiliation(s)
- Shabnam Abtahi
- Department of Pathology, Laboratory of Mucosal Barrier Pathobiology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | | | - John F Heneghan
- Department of Pathology, Laboratory of Mucosal Barrier Pathobiology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Steven P Nilsen
- Department of Pathology, Laboratory of Mucosal Barrier Pathobiology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Jeremy L Muhlich
- Laboratory of Systems Pharmacology, Harvard Medical School, Boston, Massachusetts
| | - Jay Copeland
- Harvard Medical School Information Technology Department, Research Computing, Harvard Medical School, Boston, Massachusetts
| | | | - Chris Allan
- Glencoe Software, Dundee, Scotland, United Kingdom
| | - Pradeep K Dudeja
- Department of Medicine, Division of Gastroenterology and Hepatology, University of Illinois at Chicago, Chicago, Illinois.,Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Jerrold R Turner
- Department of Pathology, Laboratory of Mucosal Barrier Pathobiology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
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7
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Jobst-Schwan T, Klämbt V, Tarsio M, Heneghan JF, Majmundar AJ, Shril S, Buerger F, Ottlewski I, Shmukler BE, Topaloglu R, Hashmi S, Hafeez F, Emma F, Greco M, Laube GF, Fathy HM, Pohl M, Gellermann J, Milosevic D, Baum MA, Mane S, Lifton RP, Kane PM, Alper SL, Hildebrandt F. Whole exome sequencing identified ATP6V1C2 as a novel candidate gene for recessive distal renal tubular acidosis. Kidney Int 2019; 97:567-579. [PMID: 31959358 DOI: 10.1016/j.kint.2019.09.026] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 09/08/2019] [Accepted: 09/12/2019] [Indexed: 12/18/2022]
Abstract
Distal renal tubular acidosis is a rare renal tubular disorder characterized by hyperchloremic metabolic acidosis and impaired urinary acidification. Mutations in three genes (ATP6V0A4, ATP6V1B1 and SLC4A1) constitute a monogenic causation in 58-70% of familial cases of distal renal tubular acidosis. Recently, mutations in FOXI1 have been identified as an additional cause. Therefore, we hypothesized that further monogenic causes of distal renal tubular acidosis remain to be discovered. Panel sequencing and/or whole exome sequencing was performed in a cohort of 17 families with 19 affected individuals with pediatric onset distal renal tubular acidosis. A causative mutation was detected in one of the three "classical" known distal renal tubular acidosis genes in 10 of 17 families. The seven unsolved families were then subjected to candidate whole exome sequencing analysis. Potential disease causing mutations in three genes were detected: ATP6V1C2, which encodes another kidney specific subunit of the V-type proton ATPase (1 family); WDR72 (2 families), previously implicated in V-ATPase trafficking in cells; and SLC4A2 (1 family), a paralog of the known distal renal tubular acidosis gene SLC4A1. Two of these mutations were assessed for deleteriousness through functional studies. Yeast growth assays for ATP6V1C2 revealed loss-of-function for the patient mutation, strongly supporting ATP6V1C2 as a novel distal renal tubular acidosis gene. Thus, we provided a molecular diagnosis in a known distal renal tubular acidosis gene in 10 of 17 families (59%) with this disease, identified mutations in ATP6V1C2 as a novel human candidate gene, and provided further evidence for phenotypic expansion in WDR72 mutations from amelogenesis imperfecta to distal renal tubular acidosis.
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Affiliation(s)
- Tilman Jobst-Schwan
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Verena Klämbt
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Maureen Tarsio
- Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, NY
| | - John F Heneghan
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Amar J Majmundar
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Shirlee Shril
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Florian Buerger
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Isabel Ottlewski
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Boris E Shmukler
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Rezan Topaloglu
- Department of Pediatric Nephrology, Hacettepe University Faculty of Medicine, Ankara, Turkey
| | - Seema Hashmi
- Department of Pediatric Nephrology, Sindh Institute of Urology and Transplantation, Karachi, Pakistan
| | - Farkhanda Hafeez
- Department of Pediatric Nephrology, The Children's Hospital and Institute of Child Health, Lahore, Pakistan
| | - Francesco Emma
- Department of Pediatric Subspecialties, Division of Nephrology, Bambino Gesù Children's Hospital-IRCCS, Rome, Italy
| | - Marcella Greco
- Department of Pediatric Subspecialties, Division of Nephrology, Bambino Gesù Children's Hospital-IRCCS, Rome, Italy
| | - Guido F Laube
- Nephrology Unit, University Children's Hospital, Zürich, Switzerland
| | - Hanan M Fathy
- Pediatric Nephrology Unit, Alexandria Faculty of Medicine, University of Alexandria, Alexandria, Egypt
| | - Martin Pohl
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Jutta Gellermann
- Department of Pediatrics, University Children's Hospital of Berlin, University Hospital Berlin Charité, Berlin, Germany
| | - Danko Milosevic
- University of Zagreb School of Medicine, Zagreb University Hospital Center, Zagreb, Croatia
| | - Michelle A Baum
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Shrikant Mane
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA; Yale Center for Mendelian Genomics, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Richard P Lifton
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA; Yale Center for Mendelian Genomics, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, NY
| | - Seth L Alper
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
| | - Friedhelm Hildebrandt
- Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
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8
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Abstract
Apolipoprotein L1 (APOL1) protein is the human serum factor that protect human beings against Trypanosoma brucei brucei, the cause of trypanosomiasis. Subspecies of T b brucei that cause human sleeping sickness-T b gambiense and T b rhodesiense evolved molecular mechanisms that enabled them to evade killing by APOL1. Sequence changes (termed G1 and G2) in the APOL1 gene that restored its ability to kill T b rhodesiense also increase the risk of developing glomerular diseases and accelerate progression to end-stage kidney disease. To lyse trypanosome parasites, APOL1 forms pores in the trypanosome endolysosomal and mitochondrial membranes, resulting in rapid membrane depolarization. However, the molecular mechanism underlying APOL1 nephropathy is unknown. Recent experimental evidence has shown that aberrant efflux of intracellular potassium is an early event in APOL1-induced death of human embryonic kidney cells. Here, we discuss the possibility that abnormal efflux of cellular potassium or other cations may be relevant to the pathogenesis of APOL1 nephropathy.
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Affiliation(s)
- Opeyemi A Olabisi
- Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, MA; Harvard Medical School, Boston, MA.
| | - John F Heneghan
- Harvard Medical School, Boston, MA; Division of Nephrology, Vascular Biology Research Center, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA; Surgical Immunotherapy at Roger Williams Medical Center, Providence, RI
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9
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Knauf F, Thomson RB, Heneghan JF, Jiang Z, Adebamiro A, Thomson CL, Barone C, Asplin JR, Egan ME, Alper SL, Aronson PS. Loss of Cystic Fibrosis Transmembrane Regulator Impairs Intestinal Oxalate Secretion. J Am Soc Nephrol 2016; 28:242-249. [PMID: 27313231 DOI: 10.1681/asn.2016030279] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 05/16/2016] [Indexed: 11/03/2022] Open
Abstract
Patients with cystic fibrosis have an increased incidence of hyperoxaluria and calcium oxalate nephrolithiasis. Net intestinal absorption of dietary oxalate results from passive paracellular oxalate absorption as modified by oxalate back secretion mediated by the SLC26A6 oxalate transporter. We used mice deficient in the cystic fibrosis transmembrane conductance regulator gene (Cftr) to test the hypothesis that SLC26A6-mediated oxalate secretion is defective in cystic fibrosis. We mounted isolated intestinal tissue from C57BL/6 (wild-type) and Cftr-/- mice in Ussing chambers and measured transcellular secretion of [14C]oxalate. Intestinal tissue isolated from Cftr-/- mice exhibited significantly less transcellular oxalate secretion than intestinal tissue of wild-type mice. However, glucose absorption, another representative intestinal transport process, did not differ in Cftr-/- tissue. Compared with wild-type mice, Cftr-/- mice showed reduced expression of SLC26A6 in duodenum by immunofluorescence and Western blot analysis. Furthermore, coexpression of CFTR stimulated SLC26A6-mediated Cl--oxalate exchange in Xenopus oocytes. In association with the profound defect in intestinal oxalate secretion, Cftr-/- mice had serum and urine oxalate levels 2.5-fold greater than those of wild-type mice. We conclude that defective intestinal oxalate secretion mediated by SLC26A6 may contribute to the hyperoxaluria observed in this mouse model of cystic fibrosis. Future studies are needed to address whether similar mechanisms contribute to the increased risk for calcium oxalate stone formation observed in patients with cystic fibrosis.
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Affiliation(s)
- Felix Knauf
- Departments of Internal Medicine, .,Department of Nephrology and Hypertension, Friedrich Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | | | - John F Heneghan
- Division of Nephrology and Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts.,Department of Medicine, Harvard Medical School, Boston, Massachusetts; and
| | | | | | | | | | - John R Asplin
- Litholink Corporation, Laboratory Corporation of America Holdings, Chicago, Illinois
| | - Marie E Egan
- Pediatrics, and.,Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut
| | - Seth L Alper
- Division of Nephrology and Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts.,Department of Medicine, Harvard Medical School, Boston, Massachusetts; and
| | - Peter S Aronson
- Departments of Internal Medicine, .,Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut
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10
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Muskett JA, Chattaraj P, Heneghan JF, Reimold FR, Shmukler BE, Brewer CC, King KA, Zalewski CK, Shawker TH, Butman JA, Kenna MA, Chien WW, Alper SL, Griffith AJ. Atypical patterns of segregation of familial enlargement of the vestibular aqueduct. Laryngoscope 2015; 126:E240-7. [PMID: 26485571 DOI: 10.1002/lary.25737] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Revised: 09/18/2015] [Accepted: 09/23/2015] [Indexed: 12/19/2022]
Abstract
OBJECTIVES/HYPOTHESIS Hearing loss and enlarged vestibular aqueduct (EVA) can be inherited as an autosomal recessive trait caused by mutant alleles of the SLC26A4 gene. In some other families, EVA does not segregate in a typical autosomal recessive pattern. The goal of this study was to characterize the SLC26A4 genotypes and phenotypes of extended families with atypical segregation of EVA. STUDY DESIGN Prospective study of cohort of families ascertained between 1998 and 2014 at the National Institutes of Health Clinical Center. METHODS Study subjects were members of eight families segregating EVA in at least two members who were not related as siblings. Evaluations included pure-tone audiometry, temporal bone imaging, SLC26A4 nucleotide sequence analysis, SLC26A4-linked marker genotype and haplotype analysis, and pedigree analysis. RESULTS One family had members with EVA caused by different etiologies, and two families had pseudodominant inheritance of recessive mutations of SLC26A4. In five families, the etiology remained unknown and could include inheritance of mutant alleles at another genetic locus, nongenetic influences, or a combination of these factors. CONCLUSIONS Familial EVA can demonstrate a variety of atypical segregation patterns. Pseudodominant inheritance of SLC26A4 mutations or recessive alleles of other hearing loss genes may be more likely to occur in families in which deaf individuals have intermarried. The etiologic basis of atypical segregation of EVA without detectable SLC26A4 mutations remains unknown. Future studies of these families may reveal novel genes for EVA. LEVEL OF EVIDENCE NA Laryngoscope, 126:E240-E247, 2016.
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Affiliation(s)
- Julie A Muskett
- Otolaryngology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland
| | - Parna Chattaraj
- Otolaryngology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland
| | - John F Heneghan
- Renal Division, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Fabian R Reimold
- Renal Division, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Boris E Shmukler
- Renal Division, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Carmen C Brewer
- Otolaryngology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland
| | - Kelly A King
- Otolaryngology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland
| | - Christopher K Zalewski
- Otolaryngology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland
| | - Thomas H Shawker
- Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, Maryland
| | - John A Butman
- Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, Maryland
| | - Margaret A Kenna
- Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts.,Department of Otolaryngology and Communication Enhancement, Boston Children's Hospital, Boston, Massachusetts
| | - Wade W Chien
- Office of the Clinical Director, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - Seth L Alper
- Renal Division, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Andrew J Griffith
- Otolaryngology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland
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11
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Heneghan JF, Vandorpe DH, Shmukler BE, Giovinazzo JA, Giovinnazo JA, Raper J, Friedman DJ, Pollak MR, Alper SL. BH3 domain-independent apolipoprotein L1 toxicity rescued by BCL2 prosurvival proteins. Am J Physiol Cell Physiol 2015; 309:C332-47. [PMID: 26108665 DOI: 10.1152/ajpcell.00142.2015] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 06/18/2015] [Indexed: 12/12/2022]
Abstract
The potent trypanolytic properties of human apolipoprotein L1 (APOL1) can be neutralized by the trypanosome variant surface antigen gene product known as serum resistance-associated protein. However, two common APOL1 haplotypes present uniquely in individuals of West African ancestry each encode APOL1 variants resistant to serum resistance-associated protein, and each confers substantial resistance to human African sleeping sickness. In contrast to the dominantly inherited anti-trypanosomal activity of APOL1, recessive inheritance of these two trypanoprotective APOL1 alleles predisposes to kidney disease. Proposed mechanisms of APOL1 toxicity have included BH3 domain-dependent autophagy and/or ion channel activity. We probed these potential mechanisms by expressing APOL1 in Xenopus laevis oocytes. APOL1 expression in oocytes increased ion permeability and caused profound morphological deterioration (toxicity). Coexpression of BCL2 family members rescued APOL1-associated oocyte toxicity in the order MCL1 ∼ BCLW > BCLXL ∼ BCL2A1 ≫ BCL2. Deletion of nine nominal core BH3 domain residues abolished APOL1-associated toxicity, but missense substitution of the same residues abolished neither oocyte toxicity nor its rescue by coexpressed MCL1. The APOL1 BH3 domain was similarly dispensable for the ability of APOL1 to rescue intact mice from lethal trypanosome challenge. Replacement of most extracellular Na(+) by K(+) also reduced APOL1-associated oocyte toxicity, allowing demonstration of APOL1-associated increases in Ca(2+) and Cl(-) fluxes and oocyte ion currents, which were similarly reduced by MCL1 coexpression. Thus APOL1 toxicity in Xenopus oocytes is BH3-independent, but can nonetheless be rescued by some BCL2 family proteins.
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Affiliation(s)
- J F Heneghan
- Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and
| | - D H Vandorpe
- Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and
| | - B E Shmukler
- Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and
| | | | - J A Giovinnazo
- The Graduate Center and Department of Biological Sciences, Hunter College of the City University of New York, New York, New York
| | - J Raper
- The Graduate Center and Department of Biological Sciences, Hunter College of the City University of New York, New York, New York
| | - D J Friedman
- Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and
| | - M R Pollak
- Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and
| | - S L Alper
- Renal Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Medicine, Harvard Medical School, Boston, Massachusetts; and
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12
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Reimold FR, Stewart AK, Stolpe K, Heneghan JF, Shmukler BE, Alper SL. Substitution of transmembrane domain Cys residues alters pH(o)-sensitive anion transport by AE2/SLC4A2 anion exchanger. Pflugers Arch 2012; 465:839-51. [PMID: 23271450 DOI: 10.1007/s00424-012-1196-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 11/19/2012] [Accepted: 11/30/2012] [Indexed: 10/27/2022]
Abstract
AE2/SLC4A2 is the most widely expressed of the Na(+)-independent SLC4 Cl(-)/HCO3 (-) exchangers and is essential for postnatal survival, but its structure remains unknown. We have generated and expressed a mouse AE2 construct devoid of transmembrane domain cysteine (Cys) residues, mAE2Cys-less, to enhance the utility of Cys-substitution mutagenesis for structural and structure-function studies of mAE2. mAE2Cys-less expressed in Xenopus oocytes exhibited partial reduction of stilbene disulfonate-sensitive anion exchange activity. This activity was independent of the mAE2 N-terminal cytosolic domain and was accompanied by near-normal surface expression, without change in K 1/2 for extracellular Cl(-). mAE2Cys-less exhibited wildtype activation of anion exchange by hypertonicity and by NH4Cl, and wildtype inhibition of anion exchange by acidic intracellular pH (pHi) in the absence of NH4 (+). However, inhibition of anion exchange by extracellular pH (pHo) exhibited an alkaline shifted pHo(50) value of at least 0.6-0.7 pH units. Although SO4 (2-) transport by mAE2Cys-less resembled wildtype mAE2 in its stimulation by acidic pHo, the absence of transmembrane domain Cys residues abrogated activation of oxalate transport by acidic pHo. The contrasting enhancement of SO4 (2-) transport by alkaline pHo in the mAE1 anion translocation pathway mutant E699Q (Am J Physiol Cell Physiol 295: C302) was phenocopied by the corresponding mutant E1007Q in both AE2 and AE2Cys-less. However, the absence of transmembrane domain Cys residues exacerbated the reduced basal anion transport function exhibited by this and other missense substitutions at AE2 residue E1007. AE2Cys-less will be a valuable experimental tool for structure-function studies of the SLC4 gene family, but its utility for studies of AE2 regulation by extracellular pH must be evaluated in the context of its alkaline-shifted pHo sensitivity, resembling that of AE2 gastric parietal cell variant AE2c1.
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Affiliation(s)
- Fabian R Reimold
- Renal Division and Molecular and Vascular Medicine Division, Beth Israel Deaconess Medical Center, 99 Brookline Avenue, RN-380F, Boston, MA 02215, USA
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13
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Reimold FR, Heneghan JF, Stewart AK, Zelikovic I, Vandorpe DH, Shmukler BE, Alper SL. Pendrin function and regulation in Xenopus oocytes. Cell Physiol Biochem 2011; 28:435-50. [PMID: 22116357 DOI: 10.1159/000335106] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/19/2011] [Indexed: 01/24/2023] Open
Abstract
SLC26A4/PDS mutations cause Pendred Syndrome and non-syndromic deafness. but some aspects of function and regulation of the SLC26A4 polypeptide gene product, pendrin, remain controversial or incompletely understood. We have therefore extended the functional analysis of wildtype and mutant pendrin in Xenopus oocytes, with studies of isotopic flux, electrophysiology, and protein localization. Pendrin mediated electroneutral, pH-insensitive, DIDS-insensitive anion exchange, with extracellular K((1/2)) (in mM) of 1.9 (Cl(-)), 1.8 (I(-)), and 0.9 (Br(-)). The unusual phenotype of Pendred Syndrome mutation E303Q (loss-of-function with normal surface expression) prompted systematic mutagenesis at position 303. Only mutant E303K exhibited loss-of-function unrescued by forced overexpression. Mutant E303C was insensitive to charge modification by methanethiosulfonates. The corresponding mutants SLC26A2 E336Q, SLC26A3 E293Q, and SLC26A6 E298Q exhibited similar loss-of-function phenotypes, with wildtype surface expression also documented for SLC26A2 E336Q. The strong inhibition of wildtype SLC26A2, SLC26A3, and SLC26A6 by phorbol ester contrasts with its modest inhibition of pendrin. Phorbol ester inhibition of SLC26A2, SLC26A3, and SLC26A6 was blocked by coexpressed kinase-dead PKCδ but was without effect on pendrin. Mutation of SLC26A2 serine residues conserved in PKCδ -sensitive SLC26 proteins but absent from pendrin failed to reduce PKCδ sensitivity of SLC26A2 (190).
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Affiliation(s)
- Fabian R Reimold
- Renal Division and Molecular and Vascular Medicine Unit, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
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14
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Heneghan JF, Alper SL. This, too, shall pass--like a kidney stone: a possible path to prophylaxis of nephrolithiasis? Focus on "Cholinergic signaling inhibits oxalate transport by human intestinal T84 cells". Am J Physiol Cell Physiol 2011; 302:C18-20. [PMID: 22049207 DOI: 10.1152/ajpcell.00389.2011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Stewart AK, Shmukler BE, Vandorpe DH, Rivera A, Heneghan JF, Li X, Hsu A, Karpatkin M, O'Neill AF, Bauer DE, Heeney MM, John K, Kuypers FA, Gallagher PG, Lux SE, Brugnara C, Westhoff CM, Alper SL. Loss-of-function and gain-of-function phenotypes of stomatocytosis mutant RhAG F65S. Am J Physiol Cell Physiol 2011; 301:C1325-43. [PMID: 21849667 DOI: 10.1152/ajpcell.00054.2011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Four patients with overhydrated cation leak stomatocytosis (OHSt) exhibited the heterozygous RhAG missense mutation F65S. OHSt erythrocytes were osmotically fragile, with elevated Na and decreased K contents and increased cation channel-like activity. Xenopus oocytes expressing wild-type RhAG and RhAG F65S exhibited increased ouabain and bumetanide-resistant uptake of Li(+) and (86)Rb(+), with secondarily increased (86)Rb(+) influx sensitive to ouabain and to bumetanide. Increased RhAG-associated (14)C-methylammonium (MA) influx was severely reduced in RhAG F65S-expressing oocytes. RhAG-associated influxes of Li(+), (86)Rb(+), and (14)C-MA were pharmacologically distinct, and Li(+) uptakes associated with RhAG and RhAG F65S were differentially inhibited by NH(4)(+) and Gd(3+). RhAG-expressing oocytes were acidified and depolarized by 5 mM bath NH(3)/NH(4)(+), but alkalinized and depolarized by subsequent bath exposure to 5 mM methylammonium chloride (MA/MA(+)). RhAG F65S-expressing oocytes exhibited near-wild-type responses to NH(4)Cl, but MA/MA(+) elicited attenuated alkalinization and strong hyperpolarization. Expression of RhAG or RhAG F65S increased steady-state cation currents unaltered by bath Li(+) substitution or bath addition of 5 mM NH(4)Cl or MA/MA(+). These oocyte studies suggest that 1) RhAG expression increases oocyte transport of NH(3)/NH(4)(+) and MA/MA(+); 2) RhAG F65S exhibits gain-of-function phenotypes of increased cation conductance/permeability, and loss-of-function phenotypes of decreased and modified MA/MA(+) transport, and decreased NH(3)/NH(4)(+)-associated depolarization; and 3) RhAG transports NH(3)/NH(4)(+) and MA/MA(+) by distinct mechanisms, and/or the substrates elicit distinct cellular responses. Thus, RhAG F65S is a loss-of-function mutation for amine transport. The altered oocyte intracellular pH, membrane potential, and currents associated with RhAG or RhAG F65S expression may reflect distinct transport mechanisms.
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Affiliation(s)
- Andrew K Stewart
- Beth Israel Deaconess Medical Center, 330 Brookline Ave., Boston, MA 02215, USA
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16
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Stewart AK, Shmukler BE, Vandorpe DH, Reimold F, Heneghan JF, Nakakuki M, Akhavein A, Ko S, Ishiguro H, Alper SL. SLC26 anion exchangers of guinea pig pancreatic duct: molecular cloning and functional characterization. Am J Physiol Cell Physiol 2011; 301:C289-303. [PMID: 21593449 DOI: 10.1152/ajpcell.00089.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The secretin-stimulated human pancreatic duct secretes HCO(3)(-)-rich fluid essential for normal digestion. Optimal stimulation of pancreatic HCO(3)(-) secretion likely requires coupled activities of the cystic fibrosis transmembrane regulator (CFTR) anion channel and apical SLC26 Cl(-)/HCO(3)(-) exchangers. However, whereas stimulated human and guinea pig pancreatic ducts secrete ∼140 mM HCO(3)(-) or more, mouse and rat ducts secrete ∼40-70 mM HCO(3)(-). Moreover, the axial distribution and physiological roles of SLC26 anion exchangers in pancreatic duct secretory processes remain controversial and may vary among mammalian species. Thus the property of high HCO(3)(-) secretion shared by human and guinea pig pancreatic ducts prompted us to clone from guinea pig pancreatic duct cDNAs encoding Slc26a3, Slc26a6, and Slc26a11 polypeptides. We then functionally characterized these anion transporters in Xenopus oocytes and human embryonic kidney (HEK) 293 cells. In Xenopus oocytes, gpSlc26a3 mediated only Cl(-)/Cl(-) exchange and electroneutral Cl(-)/HCO(3)(-) exchange. gpSlc26a6 in Xenopus oocytes mediated Cl(-)/Cl(-) exchange and bidirectional exchange of Cl(-) for oxalate and sulfate, but Cl(-)/HCO(3)(-) exchange was detected only in HEK 293 cells. gpSlc26a11 in Xenopus oocytes exhibited pH-dependent Cl(-), oxalate, and sulfate transport but no detectable Cl(-)/HCO(3)(-) exchange. The three gpSlc26 anion transporters exhibited distinct pharmacological profiles of (36)Cl(-) influx, including partial sensitivity to CFTR inhibitors Inh-172 and GlyH101, but only Slc26a11 was inhibited by PPQ-102. This first molecular and functional assessment of recombinant SLC26 anion transporters from guinea pig pancreatic duct enhances our understanding of pancreatic HCO(3)(-) secretion in species that share a high HCO(3)(-) secretory output.
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Affiliation(s)
- Andrew K Stewart
- Renal Division and Vascular Biology Center, Beth Israel Deaconess Medical Center, Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
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Heneghan JF, Akhavein A, Salas MJ, Shmukler BE, Karniski LP, Vandorpe DH, Alper SL. Regulated transport of sulfate and oxalate by SLC26A2/DTDST. Am J Physiol Cell Physiol 2010; 298:C1363-75. [PMID: 20219950 PMCID: PMC2889644 DOI: 10.1152/ajpcell.00004.2010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Accepted: 03/04/2010] [Indexed: 12/25/2022]
Abstract
Nephrolithiasis in the Slc26a6(-/-) mouse is accompanied by 50-75% reduction in intestinal oxalate secretion with unchanged intestinal oxalate absorption. The molecular identities of enterocyte pathways for oxalate absorption and for Slc26a6-independent oxalate secretion remain undefined. The reported intestinal expression of SO(4)(2-) transporter SLC26A2 prompted us to characterize transport of oxalate and other anions by human SLC26A2 and mouse Slc26a2 expressed in Xenopus oocytes. We found that hSLC26A2-mediated [(14)C]oxalate uptake (K(1/2) of 0.65 +/- 0.08 mM) was cis-inhibited by external SO(4)(2-) (K(1/2) of 3.1 mM). hSLC26A2-mediated bidirectional oxalate/SO(4)(2-) exchange exhibited extracellular SO(4)(2-) K(1/2) of 1.58 +/- 0.44 mM for exchange with intracellular [(14)C]oxalate, and extracellular oxalate K(1/2) of 0.14 +/- 0.11 mM for exchange with intracellular (35)SO(4)(2-). Influx rates and K(1/2) values for mSlc26a2 were similar. hSLC26A2-mediated oxalate/Cl(-) exchange and bidirectional SO(4)(2-)/Cl(-) exchange were not detectably electrogenic. Both SLC26A2 orthologs exhibited nonsaturable extracellular Cl(-) dependence for efflux of intracellular [(14)C]oxalate, (35)SO(4)(2-), or (36)Cl(-). Rate constants for (36)Cl(-) efflux into extracellular Cl(-), SO(4)(2-), and oxalate were uniformly 10-fold lower than for oppositely directed exchange. Acidic extracellular pH (pH(o)) inhibited all modes of hSLC26A2-mediated anion exchange. In contrast, acidic intracellular pH (pH(i)) selectively activated exchange of extracellular Cl(-) for intracellular (35)SO(4)(2-) but not for intracellular (36)Cl(-) or [(14)C]oxalate. Protein kinase C inhibited hSLC26A2 by reducing its surface abundance. Diastrophic dysplasia mutants R279W and A386V of hSLC26A2 exhibited similar reductions in uptake of both (35)SO(4)(2-) and [(14)C]oxalate. A386V surface abundance was reduced, but R279W surface abundance was at wild-type levels.
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Heneghan JF, Mitra-Ganguli T, Stanish LF, Liu L, Zhao R, Rittenhouse AR. The Ca2+ channel beta subunit determines whether stimulation of Gq-coupled receptors enhances or inhibits N current. ACTA ACUST UNITED AC 2010; 134:369-84. [PMID: 19858357 PMCID: PMC2768801 DOI: 10.1085/jgp.200910203] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In superior cervical ganglion (SCG) neurons, stimulation of M1 receptors (M1Rs) produces a distinct pattern of modulation of N-type calcium (N-) channel activity, enhancing currents elicited with negative test potentials and inhibiting currents elicited with positive test potentials. Exogenously applied arachidonic acid (AA) reproduces this profile of modulation, suggesting AA functions as a downstream messenger of M1Rs. In addition, techniques that diminish AA's concentration during M1R stimulation minimize N-current modulation. However, other studies suggest depletion of phosphatidylinositol-4,5-bisphosphate during M1R stimulation suffices to elicit modulation. In this study, we used an expression system to examine the physiological mechanisms regulating modulation. We found the β subunit (CaVβ) acts as a molecular switch regulating whether modulation results in enhancement or inhibition. In human embryonic kidney 293 cells, stimulation of M1Rs or neurokinin-1 receptors (NK-1Rs) inhibited activity of N channels formed by CaV2.2 and coexpressed with CaVβ1b, CaVβ3, or CaVβ4 but enhanced activity of N channels containing CaVβ2a. Exogenously applied AA produced the same pattern of modulation. Coexpression of CaVβ2a, CaVβ3, and CaVβ4 recapitulated the modulatory response previously seen in SCG neurons, implying heterogeneous association of CaVβ with CaV2.2. Further experiments with mutated, chimeric CaVβ subunits and free palmitic acid revealed that palmitoylation of CaVβ2a is essential for loss of inhibition. The data presented here fit a model in which CaVβ2a blocks inhibition, thus unmasking enhancement. Our discovery that the presence or absence of palmitoylated CaVβ2a toggles M1R- or NK-1R–mediated modulation of N current between enhancement and inhibition identifies a novel role for palmitoylation. Moreover, these findings predict that at synapses, modulation of N-channel activity by M1Rs or NK-1Rs will fluctuate between enhancement and inhibition based on the presence of palmitoylated CaVβ2a.
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Affiliation(s)
- John F Heneghan
- Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655, USA
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Stewart AK, Vandorpe DH, Heneghan JF, Chebib F, Stolpe K, Akhavein A, Edelman EJ, Maksimova Y, Gallagher PG, Alper SL. The GPA-dependent, spherostomatocytosis mutant AE1 E758K induces GPA-independent, endogenous cation transport in amphibian oocytes. Am J Physiol Cell Physiol 2009; 298:C283-97. [PMID: 19907019 DOI: 10.1152/ajpcell.00444.2009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The previously undescribed heterozygous missense mutation E758K was discovered in the human AE1/SLC4A1/band 3 gene in two unrelated patients with well-compensated hereditary spherostomatocytic anemia (HSt). Oocyte surface expression of AE1 E758K, in contrast to that of wild-type AE1, required coexpressed glycophorin A (GPA). The mutant polypeptide exhibited, in parallel, strong GPA dependence of DIDS-sensitive (36)Cl(-) influx, trans-anion-dependent (36)Cl(-) efflux, and Cl(-)/HCO(3)(-) exchange activities at near wild-type levels. AE1 E758K expression was also associated with GPA-dependent increases of DIDS-sensitive pH-independent SO(4)(2-) uptake and oxalate uptake with altered pH dependence. In marked contrast, the bumetanide- and ouabain-insensitive (86)Rb(+) influx associated with AE1 E758K expression was largely GPA-independent in Xenopus oocytes and completely GPA-independent in Ambystoma oocytes. AE1 E758K-associated currents in Xenopus oocytes also exhibited little or no GPA dependence. (86)Rb(+) influx was higher but inward cation current was lower in oocytes expressing AE1 E758K than previously reported in oocytes expressing the AE1 HSt mutants S731P and H734R. The pharmacological inhibition profile of AE1 E758K-associated (36)Cl(-) influx differed from that of AE1 E758K-associated (86)Rb(+) influx, as well as from that of wild-type AE1-mediated Cl(-) transport. Thus AE1 E758K-expressing oocytes displayed GPA-dependent surface polypeptide expression and anion transport, accompanied by substantially GPA-independent, pharmacologically distinct Rb(+) flux and by small, GPA-independent currents. The data strongly suggest that most of the increased cation transport associated with the novel HSt mutant AE1 E758K reflects activation of endogenous oocyte cation permeability pathways, rather than cation translocation through the mutant polypeptide.
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Affiliation(s)
- Andrew K Stewart
- Division of Nephrology, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA
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Liu L, Heneghan JF, Michael GJ, Stanish LF, Egertová M, Rittenhouse AR. L- and N-current but not M-current inhibition by M1 muscarinic receptors requires DAG lipase activity. J Cell Physiol 2008; 216:91-100. [PMID: 18247369 DOI: 10.1002/jcp.21378] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Stimulation of postsynaptic M(1) muscarinic receptors (M(1)Rs) increases firing rates of both sympathetic and central neurons that underlie increases in vasomotor tone, heart rate, and cognitive memory functioning. At the cellular level, M(1)R stimulation modulates currents through various voltage-gated ion channels, including KCNQ K+ channels (M-current) and both L- and N-type Ca2+ channels (L- and N-current) by a pertussis toxin-insensitive, slow signaling pathway. Depletion of phosphatidylinositol-4,5-bisphosphate (PIP2) during M(1)R stimulation suffices to inhibit M-current. We found previously that following PIP2 hydrolysis by phospholipase C, activation of phospholipase A2 and liberation of a lipid metabolite, most likely arachidonic acid (AA) are necessary for L- and N-current modulation. Here we examined the involvement of a third lipase, diacylglycerol lipase (DAGL), in the slow pathway. We documented the presence of DAGL in superior cervical ganglion neurons, and then tested the highly selective DAGL inhibitor, RHC-80267, for its capacity to antagonize M(1)R-mediated modulation of whole-cell Ca2+ currents. RHC-80267 significantly reduced L- and N-current inhibition by the muscarinic agonist oxotremorine-M (Oxo-M) but did not affect their inhibition by exogenous AA. Moreover, voltage-dependent inhibition of N-current by Oxo-M remained in the presence of RHC-80267, indicating selective action on the slow pathway. RHC also blocked inhibition of recombinant N-current. In contrast, RHC-80267 had no effect on native M-current inhibition. These data are consistent with a role for DAGL in mediating L- and N-current inhibition. These results extend our previous findings that the signaling pathway mediating L- and N-current inhibition diverges from the pathway initiating M-current inhibition.
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Affiliation(s)
- Liwang Liu
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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Clark JS, Vandorpe DH, Chernova MN, Heneghan JF, Stewart AK, Alper SL. Species differences in Cl- affinity and in electrogenicity of SLC26A6-mediated oxalate/Cl- exchange correlate with the distinct human and mouse susceptibilities to nephrolithiasis. J Physiol 2008; 586:1291-306. [PMID: 18174209 DOI: 10.1113/jphysiol.2007.143222] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The mouse is refractory to lithogenic agents active in rats and humans, and so has been traditionally considered a poor experimental model for nephrolithiasis. However, recent studies have identified slc26a6 as an oxalate nephrolithiasis gene in the mouse. Here we extend our earlier demonstration of different anion selectivities of the orthologous mouse and human SLC26A6 polypeptides to investigate the correlation between species-specific differences in SLC26A6 oxalate/anion exchange properties as expressed in Xenopus oocytes and in reported nephrolithiasis susceptibility. We find that human SLC26A6 mediates minimal rates of Cl(-) exchange for Cl(-), sulphate or formate, but rates of oxalate/Cl(-) exchange roughly equivalent to those of mouse slc2a6. Both transporters exhibit highly cooperative dependence of oxalate efflux rate on extracellular [Cl(-)], but whereas the K(1/2) for extracellular [Cl(-)] is only 8 mM for mouse slc26a6, that for human SLC26A6 is 62 mM. This latter value approximates the reported mean luminal [Cl(-)] of postprandial human jejunal chyme, and reflects contributions from both transmembrane and C-terminal cytoplasmic domains of human SLC26A6. Human SLC26A6 variant V185M exhibits altered [Cl(-)] dependence and reduced rates of oxalate/Cl(-) exchange. Whereas mouse slc26a6 mediates bidirectional electrogenic oxalate/Cl(-) exchange, human SLC26A6-mediated oxalate transport appears to be electroneutral. We hypothesize that the low extracellular Cl(-) affinity and apparent electroneutrality of oxalate efflux characterizing human SLC26A6 may partially explain the high human susceptibility to nephrolithiasis relative to that of mouse. SLC26A6 sequence variant(s) are candidate risk modifiers for nephrolithiasis.
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Affiliation(s)
- Jeffrey S Clark
- Molecular and Vascular Medicine Unit and Renal Division, Beth Israel Deaconess Medical Center and Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
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Liu L, Heneghan JF, Mitra-Ganguli T, Roberts-Crowley ML, Rittenhouse AR. Role of PIP2 in regulating versus modulating Ca2+ channel activity. J Physiol 2007; 583:1165-6; author reply 1167. [PMID: 17673503 PMCID: PMC2277180 DOI: 10.1113/jphysiol.2007.141424] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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