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Bissonnette P, Lussier Y, Matar J, Leduc‐Nadeau A, Da Cal S, Arthus M, Unwin RJ, Steinke J, Rangaswamy D, Bichet DG. Further evidence for functional recovery of AQP2 mutations associated with nephrogenic diabetes insipidus. Physiol Rep 2021; 9:e14866. [PMID: 34120413 PMCID: PMC8198467 DOI: 10.14814/phy2.14866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 03/26/2021] [Accepted: 04/13/2021] [Indexed: 11/24/2022] Open
Abstract
Aquaporin-2 (AQP2) is a homotetrameric water channel responsible for the final water reuptake in the kidney. Disease-causing AQP2 mutations induce nephrogenic diabetes insipidus (NDI), a condition that challenges the bodily water balance by producing large urinary volumes. In this study, we characterize three new AQP2 mutations identified in our lab from NDI patients (A120D, A130V, T179N) along the previously reported A47V variant. Using Xenopus oocytes, we compared the key functional and biochemical features of these mutations against classical recessive (R187C) and dominant (R254Q) forms, and once again found clear functional recovery features (increased protein stability and function) for all mutations under study. This behaviour, attributed to heteromerization to wt-AQP2, challenge the classical model to NDI which often depicts recessive mutations as ill-structured proteins unable to oligomerize. Consequently, we propose a revised model to the cell pathophysiology of AQP2-related NDI which accounts for the functional recovery of recessive AQP2 mutations.
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Affiliation(s)
- Pierre Bissonnette
- Département de Pharmacologie et PhysiologieUniversité de MontréalMontréalQCCanada
| | - Yoann Lussier
- Département de Pharmacologie et PhysiologieUniversité de MontréalMontréalQCCanada
| | - Jessica Matar
- Département de Pharmacologie et PhysiologieUniversité de MontréalMontréalQCCanada
| | | | - Sandra Da Cal
- Département de Pharmacologie et PhysiologieUniversité de MontréalMontréalQCCanada
| | | | - Robert J. Unwin
- Department of Renal MedicineUniversity College LondonLondonUK
| | - Julia Steinke
- Division of Pediatric NephrologyHelen DeVos Children’s Hospital and ClinicsGrand RapidsMIUSA
| | - Dharshan Rangaswamy
- Department of NephrologyKasturba Medical CollegeKasturba HospitalManipal Academy of Higher EducationManipalKarnatakaIndia
| | - Daniel G. Bichet
- Département de Pharmacologie et PhysiologieUniversité de MontréalMontréalQCCanada
- Centre de RechercheHôpital du Sacré‐Cœur de MontréalMontréalQCCanada
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Ullah AKMS, Rumley AC, Peleh V, Fernandes D, Almomani EY, Berrini M, Lashhab R, Touret N, Alexander RT, Herrmann JM, Cordat E. SLC26A7 protein is a chloride/bicarbonate exchanger and its abundance is osmolarity- and pH-dependent in renal epithelial cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183238. [PMID: 32119864 DOI: 10.1016/j.bbamem.2020.183238] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 02/19/2020] [Accepted: 02/24/2020] [Indexed: 12/23/2022]
Abstract
Acid-secreting intercalated cells of the collecting duct express the chloride/bicarbonate kidney anion exchanger 1 (kAE1) as well as SLC26A7, two proteins that colocalize in the basolateral membrane. The latter protein has been reported to function either as a chloride/bicarbonate exchanger or a chloride channel. Both kAE1 and SLC26A7 are detected in the renal medulla, an environment hyper-osmotic to plasma. Individuals with mutations in the SLC4A1 gene encoding kAE1 and mice lacking Slc26a7 develop distal renal tubular acidosis (dRTA). Here, we aimed to (i) confirm that SLC26A7 can function as chloride/bicarbonate exchanger in Madin-Darby canine kidney (MDCK) cells, and (ii) examine the behavior of SLC26A7 relative to kAE1 wild type or carrying the dRTA mutation R901X in iso- or hyper-osmotic conditions mimicking the renal medulla. Although we found that SLC26A7 abundance increases in hyper-osmotic growth medium, it is reduced in low pH growth conditions mimicking acidosis when expressed at high levels in MDCK cells. In these cells, SLC26A7 exchange activity was independent from extracellular osmolarity. When SLC26A7 protein was co-expressed with kAE1 WT or the R901X dRTA mutant, the cellular chloride/bicarbonate exchange rate was not additive compared to when proteins are expressed individually, possibly reflecting a decreased overall protein expression. Furthermore, the cellular chloride/bicarbonate exchange rate was osmolarity-independent. Together, these results show that (i) in MDCK cells, SLC26A7 is a chloride/bicarbonate exchanger whose abundance is up-regulated by high osmolarity growth medium and (ii) acidic extracellular pH decreases the abundance of SLC26A7 protein.
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Affiliation(s)
| | - A Carly Rumley
- Department of Physiology, University of Alberta, Edmonton, AB, Canada
| | - Valentina Peleh
- Cell Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Daphne Fernandes
- Department of Physiology, University of Alberta, Edmonton, AB, Canada
| | - Ensaf Y Almomani
- Faculty of Pharmacy, Al-Zaytoonah University of Jordan, Amman, Jordan
| | - Mattia Berrini
- Department of Physiology, University of Alberta, Edmonton, AB, Canada
| | - Rawad Lashhab
- Department of Physiology, University of Alberta, Edmonton, AB, Canada
| | - Nicolas Touret
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
| | - R Todd Alexander
- Department of Physiology, University of Alberta, Edmonton, AB, Canada
| | | | - Emmanuelle Cordat
- Department of Physiology, University of Alberta, Edmonton, AB, Canada.
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Huang Y, Zhang Y, Chi Z, Huang R, Huang H, Liu G, Zhang Y, Yang H, Lin J, Yang T, Cao S. The Handling of Oxalate in the Body and the Origin of Oxalate in Calcium Oxalate Stones. Urol Int 2019; 104:167-176. [DOI: 10.1159/000504417] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 10/28/2019] [Indexed: 11/19/2022]
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4
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Takeuchi T, Hattori-Kato M, Okuno Y, Kanatani A, Zaitsu M, Mikami K. A single nucleotide polymorphism in kidney anion exchanger 1 gene is associated with incomplete type 1 renal tubular acidosis. Sci Rep 2016; 6:35841. [PMID: 27767102 PMCID: PMC5073285 DOI: 10.1038/srep35841] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 10/06/2016] [Indexed: 11/19/2022] Open
Abstract
Various conditions including distal renal tubular acidosis (dRTA) can induce stone formation in the kidney. dRTA is characterized by an impairment of urine acidification in the distal nephron. dRTA is caused by variations in genes functioning in intercalated cells including SLC4A1/AE1/Band3 transcribing two kinds of mRNAs encoding the Cl−/HCO3− exchanger in erythrocytes and that expressed in α-intercalated cells (kAE1). With the acid-loading test, 25% of urolithiasis patients were diagnosed with incomplete dRTA. In erythroid intron 3 containing the promoter region of kAE1, rs999716 SNP showed a significantly higher minor allele A frequency in incomplete dRTA compared with non-dRTA patients. The promoter regions of the kAE1 gene with the minor allele A at rs999716 downstream of the TATA box showed reduced promoter activities compared that with the major allele G. Patients with the A allele at rs999716 may express less kAE1 mRNA and protein in the intercalated cells, developing incomplete dRTA.
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Affiliation(s)
- Takumi Takeuchi
- Department of Urology, Japan Organization of Occupational Health and Safety, Kanto Rosai Hospital, 1-1 Kizukisumiyoshi-cho, Nakahara-ku, Kawasaki 211-8510, Japan
| | - Mami Hattori-Kato
- Department of Urology, Japan Organization of Occupational Health and Safety, Kanto Rosai Hospital, 1-1 Kizukisumiyoshi-cho, Nakahara-ku, Kawasaki 211-8510, Japan
| | - Yumiko Okuno
- Department of Urology, Japan Organization of Occupational Health and Safety, Kanto Rosai Hospital, 1-1 Kizukisumiyoshi-cho, Nakahara-ku, Kawasaki 211-8510, Japan
| | - Atsushi Kanatani
- Division of Molecular Pathology, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
| | - Masayoshi Zaitsu
- Department of Urology, Japan Organization of Occupational Health and Safety, Kanto Rosai Hospital, 1-1 Kizukisumiyoshi-cho, Nakahara-ku, Kawasaki 211-8510, Japan
| | - Koji Mikami
- Department of Urology, Japan Organization of Occupational Health and Safety, Kanto Rosai Hospital, 1-1 Kizukisumiyoshi-cho, Nakahara-ku, Kawasaki 211-8510, Japan
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Reithmeier RAF, Casey JR, Kalli AC, Sansom MSP, Alguel Y, Iwata S. Band 3, the human red cell chloride/bicarbonate anion exchanger (AE1, SLC4A1), in a structural context. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1507-32. [PMID: 27058983 DOI: 10.1016/j.bbamem.2016.03.030] [Citation(s) in RCA: 133] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 03/21/2016] [Accepted: 03/29/2016] [Indexed: 02/03/2023]
Abstract
The crystal structure of the dimeric membrane domain of human Band 3(1), the red cell chloride/bicarbonate anion exchanger 1 (AE1, SLC4A1), provides a structural context for over four decades of studies into this historic and important membrane glycoprotein. In this review, we highlight the key structural features responsible for anion binding and translocation and have integrated the following topological markers within the Band 3 structure: blood group antigens, N-glycosylation site, protease cleavage sites, inhibitor and chemical labeling sites, and the results of scanning cysteine and N-glycosylation mutagenesis. Locations of mutations linked to human disease, including those responsible for Southeast Asian ovalocytosis, hereditary stomatocytosis, hereditary spherocytosis, and distal renal tubular acidosis, provide molecular insights into their effect on Band 3 folding. Finally, molecular dynamics simulations of phosphatidylcholine self-assembled around Band 3 provide a view of this membrane protein within a lipid bilayer.
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Affiliation(s)
- Reinhart A F Reithmeier
- Department of Biochemistry, 1 King's College Circle, University of Toronto, Toronto M5S 1A8, Canada.
| | - Joseph R Casey
- Department of Biochemistry, Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Antreas C Kalli
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Yilmaz Alguel
- Division of Molecular Biosciences, Imperial College London, London, SW7 2AZ, UK
| | - So Iwata
- Division of Molecular Biosciences, Imperial College London, London, SW7 2AZ, UK
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6
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Adeva-Andany MM, Carneiro-Freire N, Donapetry-García C, Rañal-Muíño E, López-Pereiro Y. The importance of the ionic product for water to understand the physiology of the acid-base balance in humans. BIOMED RESEARCH INTERNATIONAL 2014; 2014:695281. [PMID: 24877130 PMCID: PMC4022011 DOI: 10.1155/2014/695281] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 03/31/2014] [Accepted: 04/04/2014] [Indexed: 12/13/2022]
Abstract
Human plasma is an aqueous solution that has to abide by chemical rules such as the principle of electrical neutrality and the constancy of the ionic product for water. These rules define the acid-base balance in the human body. According to the electroneutrality principle, plasma has to be electrically neutral and the sum of its cations equals the sum of its anions. In addition, the ionic product for water has to be constant. Therefore, the plasma concentration of hydrogen ions depends on the plasma ionic composition. Variations in the concentration of plasma ions that alter the relative proportion of anions and cations predictably lead to a change in the plasma concentration of hydrogen ions by driving adaptive adjustments in water ionization that allow plasma electroneutrality while maintaining constant the ionic product for water. The accumulation of plasma anions out of proportion of cations induces an electrical imbalance compensated by a fall of hydroxide ions that brings about a rise in hydrogen ions (acidosis). By contrast, the deficiency of chloride relative to sodium generates plasma alkalosis by increasing hydroxide ions. The adjustment of plasma bicarbonate concentration to these changes is an important compensatory mechanism that protects plasma pH from severe deviations.
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Affiliation(s)
| | | | | | - Eva Rañal-Muíño
- Hospital General Juan Cardona, C/ Pardo Bazán s/n, Ferrol, 15406 La Coruña, Spain
| | - Yosua López-Pereiro
- Hospital General Juan Cardona, C/ Pardo Bazán s/n, Ferrol, 15406 La Coruña, Spain
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8
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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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9
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Almomani EY, King JC, Netsawang J, Yenchitsomanus PT, Malasit P, Limjindaporn T, Alexander RT, Cordat E. Adaptor protein 1 complexes regulate intracellular trafficking of the kidney anion exchanger 1 in epithelial cells. Am J Physiol Cell Physiol 2012; 303:C554-66. [PMID: 22744004 DOI: 10.1152/ajpcell.00124.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Distal renal tubular acidosis (dRTA) can be caused by mutations in the gene encoding the anion exchanger 1 (AE1) and is characterized by defective urinary acidification, metabolic acidosis, and renal stones. AE1 is expressed at the basolateral membrane of type A intercalated cells in the renal cortical collecting duct (kAE1). Two dRTA mutations result in the carboxyl-terminal truncation of kAE1; in one case, the protein trafficked in a nonpolarized way in epithelial cells. A recent yeast two-hybrid assay showed that the carboxyl-terminal cytosolic domain of AE1 interacts with adaptor protein complex 1 (AP-1A) subunit μ1A (mu-1A; Sawasdee N, Junking M, Ngaojanlar P, Sukomon N, Ungsupravate D, Limjindaporn T, Akkarapatumwong V, Noisakran S, Yenchitsomanus PT. Biochem Biophys Res Commun 401: 85-91, 2010). Here, we show the interaction between kAE1 and mu-1A and B in vitro by reciprocal coimmunoprecipitation in epithelial cells and in vivo by coimmunoprecipitation from mouse kidney extract. When endogenous mu-1A (and to a lesser extent mu-1B) was reduced, kAE1 protein was unable to traffic to the plasma membrane and was rapidly degraded via a lysosomal pathway. Expression of either small interfering RNA-resistant mu-1A or mu-1B stabilized kAE1 in these cells. We also show that newly synthesized kAE1 does not traffic through recycling endosomes to the plasma membrane, suggesting that AP-1B, located in recycling endosomes, is not primarily involved in trafficking of newly synthesized kAE1 when AP-1A is present in the cells. Our data demonstrate that AP-1A regulates processing of the basolateral, polytopic membrane protein kAE1 to the cell surface and that both AP-1A and B adaptor complexes are required for normal kAE1 trafficking.
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Affiliation(s)
- Ensaf Y Almomani
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
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10
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Wu F, Satchwell TJ, Toye AM. Anion exchanger 1 in red blood cells and kidney: Band 3's in a pod. Biochem Cell Biol 2011; 89:106-14. [PMID: 21455263 DOI: 10.1139/o10-146] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The bicarbonate/chloride exchanger 1 (AE1, Band 3) is abundantly expressed in the red blood cell membrane, where it is involved in gas exchange and functions as a major site of cytoskeletal attachment to the erythrocyte membrane. A truncated kidney isoform (kAE1) is highly expressed in type A intercalated cells of the distal tubules, where it is vital for urinary acidification. Recently, kAE1 has emerged as a novel physiologically significant protein in the kidney glomerulus. This minireview will discuss the known interactions of kAE1 in the podocytes and the possible mechanisms whereby this important multispanning membrane protein may contribute to the function of the glomerular filtration barrier and prevent proteinuria.
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Affiliation(s)
- Fiona Wu
- School of Clinical Sciences, University of Bristol, Bristol, UK.
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11
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Almomani EY, Chu CY, Cordat E. Mis-trafficking of bicarbonate transporters: implications to human diseasesThis paper is one of a selection of papers published in a Special Issue entitled CSBMCB 53rd Annual Meeting — Membrane Proteins in Health and Disease, and has undergone the Journal’s usual peer review process. Biochem Cell Biol 2011; 89:157-77. [DOI: 10.1139/o10-153] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Bicarbonate is a waste product of mitochondrial respiration and one of the main buffers in the human body. Thus, bicarbonate transporters play an essential role in maintaining acid-base balance but also during fetal development as they ensure tight regulation of cytosolic and extracellular environments. Bicarbonate transporters belong to two gene families, SLC4A and SLC26A. Proteins from these two families are widely expressed, and thus mutations in their genes result in various diseases that affect bones, pancreas, reproduction, brain, kidneys, eyes, heart, thyroid, red blood cells, and lungs. In this minireview, we discuss the current state of knowledge regarding the effect of SLC4A and SLC26A mutants, with a special emphasis on mutants that have been studied in mammalian cell lines and how they correlate with phenotypes observed in mice models.
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Affiliation(s)
- Ensaf Y. Almomani
- Membrane Protein Research Group, Department of Physiology, School of Molecular and Systems Medicine, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Carmen Y.S. Chu
- Membrane Protein Research Group, Department of Physiology, School of Molecular and Systems Medicine, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Emmanuelle Cordat
- Membrane Protein Research Group, Department of Physiology, School of Molecular and Systems Medicine, University of Alberta, Edmonton, AB T6G 2H7, Canada
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12
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Band 3 Edmonton I, a novel mutant of the anion exchanger 1 causing spherocytosis and distal renal tubular acidosis. Biochem J 2010; 426:379-88. [DOI: 10.1042/bj20091525] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
dRTA (distal renal tubular acidosis) and HS (hereditary spherocytosis) are two diseases that can be caused by mutations in the gene encoding the AE1 (anion exchanger 1; Band 3). dRTA is characterized by defective urinary acidification, leading to metabolic acidosis, renal stones and failure to thrive. HS results in anaemia, which may require regular blood transfusions and splenectomy. Mutations in the gene encoding AE1 rarely cause both HS and dRTA. In the present paper, we describe a novel AE1 mutation, Band 3 Edmonton I, which causes dominant HS and recessive dRTA. The patient is a compound heterozygote with the new mutation C479W and the previously described mutation G701D. Red blood cells from the patient presented a reduced amount of AE1. Expression in a kidney cell line showed that kAE1 (kidney AE1) C479W is retained intracellularly. As kAE1 is a dimer, we performed co-expression studies and found that, in kidney cells, kAE1 C479W and G701D proteins traffic independently from each other despite their ability to form heterodimers. Therefore the patient carries one kAE1 mutant that is retained in the Golgi (G701D) and another kAE1 mutant (C479W) located in the endoplasmic reticulum of kidney cells, and is thus probably unable to reabsorb bicarbonate into the blood. We conclude that the C479W mutant is a novel trafficking mutant of AE1, which causes HS due to a decreased cell-surface AE1 protein and results in dRTA due to its intracellular retention in kidney.
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Ungsupravate D, Sawasdee N, Khositseth S, Udomchaiprasertkul W, Khoprasert S, Li J, Reithmeier RAF, Yenchitsomanus PT. Impaired trafficking and intracellular retention of mutant kidney anion exchanger 1 proteins (G701D and A858D) associated with distal renal tubular acidosis. Mol Membr Biol 2010; 27:92-103. [DOI: 10.3109/09687681003588020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Chang YH, Shaw CF, Jian SH, Hsieh KH, Chiou YH, Lu PJ. Compound mutations in human anion exchanger 1 are associated with complete distal renal tubular acidosis and hereditary spherocytosis. Kidney Int 2009; 76:774-83. [DOI: 10.1038/ki.2009.258] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Walsh S, Borgese F, Gabillat N, Guizouarn H. Southeast Asian AE1 associated renal tubular acidosis: cation leak is a class effect. Biochem Biophys Res Commun 2009; 382:668-72. [PMID: 19289107 DOI: 10.1016/j.bbrc.2009.03.062] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Accepted: 03/11/2009] [Indexed: 11/30/2022]
Abstract
Anion Exchanger 1 (AE1) is present in the erythrocyte and also in the alpha-intercalated cell; different mutations can cause either red cell disease or distal renal tubular acidosis (dRTA). Recently, we described a cation leak property in four dRTA-causing AE1 mutants, three autosomal dominant (AD) European mutants, one autosomal recessive (AR) from Southeast Asia, G701D. G701D had a very large leak property and is unusually common in SE Asia. We hypothesized that this property might confer a survival advantage. We characterized three other AR dRTA-associated AE1 mutants found in SE Asia, S773P, Delta850 and A858D via transport experiments in AE1-expressing Xenopus oocytes. These three SE Asian mutants also had cation leaks of similar magnitude to that seen in G701D, a property that distinguishes them as a discrete group. The clustering of these cation-leaky AE1 mutations to malarious areas of SE Asia suggests that they may confer malaria resistance.
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Affiliation(s)
- Stephen Walsh
- Laboratoire de Biologie et Physiopathologie des Systèmes Intégrés, FRE3094, CNRS-Université de Nice, Bâtiment de Sciences Naturelles, Nice Cedex 2, France.
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16
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Abstract
The family of mammalian bicarbonate transport proteins are involved in a wide-range of physiological processes. The importance of bicarbonate transport follows from the biochemistry of HCO(3)(-) itself. Bicarbonate is the waste product of mitochondrial respiration. HCO(3)(-) undergoes pH-dependent conversion into CO(2) and in doing so converts from a membrane impermeant anion into a gas that can diffuse across membranes. The CO(2)-HCO(3)(-) equilibrium forms the most important pH buffering system of our bodies. Bicarbonate transport proteins facilitate the movement of membrane-impermeant HCO(3)(-) across membranes to accelerate disposal of waste CO(2), control cellular and whole-body pH, and to regulate fluid movement and acid/base secretion. Defects of bicarbonate transport proteins manifest in diseases of most organ systems. Fourteen gene products facilitate mammalian bicarbonate transport, whose physiology and pathophysiology is discussed in the present review.
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17
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Williamson RC, Brown ACN, Mawby WJ, Toye AM. Human kidney anion exchanger 1 localisation in MDCK cells is controlled by the phosphorylation status of two critical tyrosines. J Cell Sci 2008; 121:3422-32. [PMID: 18827007 DOI: 10.1242/jcs.035584] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An important question in renal physiology is how the alpha-intercalated cells of the kidney regulate the distribution of the basolateral kidney anion exchanger 1 (kAE1) according to systemic acid-base status. Previous work using a MDCKI model system demonstrated that kAE1 basolateral targeting requires an N-terminal determinant and a critical C-terminal tyrosine (Y904). Here, we show that the N-terminal determinant is residue Y359, because a Y359A substitution mutant was mistargeted to the apical membrane. Further determinants might exist because a range of N-terminal kAE1 truncations that contained Y359 were incorrectly targeted to the TGN. Y359 and Y904 in kAE1 are phosphorylated upon pervanadate treatment and this phosphorylation is sensitive to specific Src kinase family inhibitors. We tested a range of stimuli on this model system and only the application of high nonphysiological concentrations of extracellular bicarbonate, and to a lesser extent hypertonicity or hyperosmolarity, induced tyrosine phosphorylation of kAE1. Treatment with pervanadate caused internalisation of kAE1 from the plasma membrane, but treatment with high concentrations of bicarbonate did not, because of the hypertonicity of the solution. We propose that alpha-intercalated cells control the distribution of kAE1 by reversible phosphorylation of tyrosine residues Y359 and Y904.
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Affiliation(s)
- Rosalind C Williamson
- University of Bristol, Department of Biochemistry, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK
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18
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Walsh S, Borgese F, Gabillat N, Unwin R, Guizouarn H. Cation transport activity of anion exchanger 1 mutations found in inherited distal renal tubular acidosis. Am J Physiol Renal Physiol 2008; 295:F343-50. [PMID: 18524859 DOI: 10.1152/ajprenal.00587.2007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Anion exchanger 1 (AE1) is encoded by SLC4A1 and mediates electroneutral anion exchange across cell membranes. It is the most abundant protein in the red cell membrane, but it is also found in the basolateral membrane of renal alpha-intercalated cells, where it is required for normal urinary acidification. Recently, four point mutations in red cell AE1 have been described that convert the anion exchanger to a cation conductance. SLC4A1 mutations can also cause type 1 hypokalemic distal renal tubular acidosis (dRTA). We investigated the properties of four dRTA-associated AE1 mutations (R589H, G609R, S613F, and G701D) by heterologous expression in Xenopus laevis oocytes. Although these AE1 mutants are functional anion exchangers, unlike the red cell disease mutants, we found that they also demonstrated a cation leak. We found a large cation leak in the G701D mutant. This mutant normally requires coexpression with glycophorin A for surface membrane expression in red blood cells and oocytes. However, we found that coexpressing wild-type kidney AE1 with G701D in oocytes still caused a cation leak, consistent with heterodimerized G701D reaching the cell membrane and retaining its cation conductance property. These findings have potential structural and functional implications for AE1, and they indicate that while anion exchange and cation conductance properties are distinct, they can coexist.
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Affiliation(s)
- Stephen Walsh
- Laboratoire de Physiologie des Membranes Cellulaires, UMR6548, Centre National de la Recherche Scientifique-Université de Nice, Bâtiment de Sciences Naturelles, Nice, France.
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Dominant-negative effect of Southeast Asian ovalocytosis anion exchanger 1 in compound heterozygous distal renal tubular acidosis. Biochem J 2008; 410:271-81. [PMID: 17941824 DOI: 10.1042/bj20070615] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 10/15/2007] [Accepted: 10/17/2007] [Indexed: 11/17/2022]
Abstract
The human chloride/bicarbonate AE1 (anion exchanger) is a dimeric glycoprotein expressed in the red blood cell membrane,and expressed as an N-terminal (Delta1-65) truncated form, kAE1(kidney AE1), in the basolateral membrane of alpha-intercalated cells in the distal nephron. Mutations in AE1 can cause SAO (Southeast Asian ovalocytosis) or dRTA (distal renal tubular acidosis), an inherited kidney disease resulting in impaired acid secretion. The dominant SAO mutation (Delta400-408) that results in an inactive transporter and altered erythrocyte shape occurs in manydRTA families, but does not itself result in dRTA. Compound heterozygotes of four dRTA mutations (R602H, G701D, DeltaV850 and A858D) with SAO exhibit dRTA and abnormal red blood cell properties. Co-expression of kAE1 and kAE1 SAO with the dRTAmutantswas studied in polarized epithelial MDCK(Madin-Darbycanine kidney) cells. Like SAO, the G701D and DeltaV850 mutants were predominantly retained intracellularly, whereas the R602H and A858D mutants could traffic to the basolateral membrane. When co-expressed in transfected cells, kAE1 WT (wild-type)and kAE1 SAO could interact with the dRTA mutants. MDCK cells co-expressing kAE1 SAO with kAE1 WT, kAE1 R602Hor kAE1 A858D showed a decrease in cell-surface expression of the co-expressed proteins. When co-expressed, kAE1 WT colocalized with the kAE1 R602H, kAE1 G701D, kAE1 DeltaV850 and kAE1 A858D mutants at the basolateral membrane, whereaskAE1 SAO co-localized with kAE1 WT, kAE1 R602H, kAE1 G701D, kAE1 DeltaV850 and kAE1 A858D in MDCK cells. The decrease in cell-surface expression of the dRTAmutants as a result of the interaction with kAE1 SAO would account for the impaired expression of functional kAE1 at the basolateral membrane of alpha-intercalated cells, resulting in dRTA in compound heterozygous patients.
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Williamson RC, Toye AM. Glycophorin A: Band 3 aid. Blood Cells Mol Dis 2008; 41:35-43. [PMID: 18304844 DOI: 10.1016/j.bcmd.2008.01.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2008] [Accepted: 01/04/2008] [Indexed: 11/24/2022]
Abstract
Band 3 (B3) is a major site of cytoskeletal attachment to the erythrocyte membrane and is important for gas exchange. A truncated isoform of B3 (kB3) is expressed in the alpha-intercalated cells of the kidney and its functional activity and basolateral localization are essential for acid secretion. B3 mutations generally lead to red blood cell (RBC) specific disease (hereditary spherocytosis (HS), Southeast Asian Ovalocytosis or hereditary stomatocytosis) or kidney disease (distal Renal Tubular Acidosis--dRTA). It is rare for both the RBC and kidney disease phenotypes to co-exist, but this does occur in knockout mice, and also in humans (B3 Coimbra and B3 Courcouronne) or cattle with homozygous HS mutations. This is because RBCs express a B3 chaperone-like molecule in the form of Glycophorin A that can rescue the majority of B3 mutations that cause dRTA but probably not the majority of HS mutations. The study of naturally occurring B3 variant blood and expression of B3 or kB3 mutants in heterologous expression systems has provided valuable information concerning B3 trafficking and interactions in the RBC and kidney. This article will review these studies and comment on our current understanding of the interaction between GPA with B3 and also on the proposed B3 centred macrocomplex.
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Affiliation(s)
- Rosalind C Williamson
- University of Bristol, Department of Biochemistry, School of Medical Sciences, University Walk, Bristol, BS8 1TD, UK
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Cordat E. Unraveling trafficking of the kidney anion exchanger 1 in polarized MDCK epithelial cells. Biochem Cell Biol 2007; 84:949-59. [PMID: 17215882 DOI: 10.1139/o06-200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Kidney anion exchanger 1 (kAE1) is a membrane glycoprotein expressed at the basolateral membrane of type A intercalated cells in the kidney collecting tubule. Mutations occurring in the gene encoding this protein can give rise to distal renal tubular acidosis (dRTA), a disease characterized by an impaired urine acidification, nephrocalcinosis, and renal failure. Here we review how the study of dRTA mutants in polarized epithelial cells has shed light on the cellular mechanisms resulting in this renal disease.
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Affiliation(s)
- Emmanuelle Cordat
- Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
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