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Yano-Sakamoto K, Kitai Y, Toriu N, Yamamoto S, Mizuta K, Saitou M, Tsukiyama T, Taniuchi I, Osato M, Yanagita M. Expression pattern of Runt-related transcription factor (RUNX) family members and the role of RUNX1 during kidney development. Biochem Biophys Res Commun 2024; 722:150155. [PMID: 38795454 DOI: 10.1016/j.bbrc.2024.150155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 05/19/2024] [Accepted: 05/21/2024] [Indexed: 05/28/2024]
Abstract
Runt-related transcription factor (RUNX) family members play critical roles in the development of multiple organs. Mammalian RUNX family members, consisting of RUNX1, RUNX2, and RUNX3, have distinct tissue-specific expression and function. In this study, we examined the spatiotemporal expression patterns of RUNX family members in developing kidneys and analyzed the role of RUNX1 during kidney development. In the developing mouse kidney, RUNX1 protein was strongly expressed in the ureteric bud (UB) tip and weakly expressed in the distal segment of the renal vesicle (RV), comma-shaped body (CSB), and S-shaped body (SSB). In contrast, RUNX2 protein was restricted to the stroma, and RUNX3 protein was only expressed in immune cells. We also analyzed the expression of RUNX family members in the cynomolgus monkey kidney. We found that expression patterns of RUNX2 and RUNX3 were conserved between rodents and primates, whereas RUNX1 was only expressed in the UB tip, not in the RV, CSB, or SSB of cynomolgus monkeys, suggesting a species differences. We further evaluated the roles of RUNX1 using two different conditional knockout mice: Runx1f/f:HoxB7-Cre and Runx1f/f:R26-CreERT2 and found no abnormalities in the kidney. Our findings showed that RUNX1, which is mainly expressed in the UB tip, is not essential for kidney development.
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Affiliation(s)
- Keiko Yano-Sakamoto
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
| | - Yuichiro Kitai
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
| | - Naoya Toriu
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan; Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University, Kyoto, 606-8501, Japan.
| | - Shinya Yamamoto
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan.
| | - Ken Mizuta
- Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University, Kyoto, 606-8501, Japan; Department of Anatomy and Cell Biology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan.
| | - Mitinori Saitou
- Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University, Kyoto, 606-8501, Japan; Department of Anatomy and Cell Biology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan; Center for iPS Cell Research and Application (CiRA), Kyoto University, Kyoto, 606-8397, Japan.
| | - Tomoyuki Tsukiyama
- Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University, Kyoto, 606-8501, Japan; Research Center for Animal Life Science, Shiga University of Medical Science, Shiga, 520-2192, Japan.
| | - Ichiro Taniuchi
- Laboratory for Transcriptional Regulation, RIKEN Center for Integrative Medical Sciences, Yokohama, 230-0045, Japan.
| | - Motomi Osato
- International Research Center for Medical Sciences, Kumamoto University, Kumamoto, 860-0811, Japan.
| | - Motoko Yanagita
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan; Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University, Kyoto, 606-8501, Japan.
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Wu Y, Ding J. Severe Hypokalemia and Poor Appetite in a 20-Month-Old Male. Clin Pediatr (Phila) 2024:99228241248975. [PMID: 38680022 DOI: 10.1177/00099228241248975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 05/01/2024]
Affiliation(s)
- Yuping Wu
- Children's Medical Ward I,Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Hospital), Tongji Medical College, Huazhong University of Science & Technology, Wuhan, Hubei, China
| | - Juanjuan Ding
- Children's Medical Ward I,Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Hospital), Tongji Medical College, Huazhong University of Science & Technology, Wuhan, Hubei, China
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Chu A, Yao Y, Glibowicka M, Deber CM, Manolson MF. The Human Mutation K237_V238del in a Putative Lipid Binding Motif within the V-ATPase a2 Isoform Suggests a Molecular Mechanism Underlying Cutis Laxa. Int J Mol Sci 2024; 25:2170. [PMID: 38396846 PMCID: PMC10889665 DOI: 10.3390/ijms25042170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 01/19/2024] [Accepted: 02/01/2024] [Indexed: 02/25/2024] Open
Abstract
Vacuolar ATPases (V-ATPases), proton pumps composed of 16 subunits, are necessary for a variety of cellular functions. Subunit "a" has four isoforms, a1-a4, each with a distinct cellular location. We identified a phosphoinositide (PIP) interaction motif, KXnK(R)IK(R), conserved in all four isoforms, and hypothesize that a/PIP interactions regulate V-ATPase recruitment/retention to different organelles. Among the four isoforms, a2 is enriched on Golgi with a2 mutations in the PIP motif resulting in cutis laxa. We hypothesize that the hydrophilic N-terminal (NT) domain of a2 contains a lipid-binding domain, and mutations in this domain prevent interaction with Golgi-enriched PIPs, resulting in cutis laxa. We recreated the cutis laxa-causing mutation K237_V238del, and a double mutation in the PIP-binding motif, K237A/V238A. Circular dichroism confirmed that there were no protein structure alterations. Pull-down assays with PIP-enriched liposomes revealed that wildtype a2NT preferentially binds phosphatidylinositol 4-phosphate (PI(4)P), while mutants decreased binding to PI(4)P. In HEK293 cells, wildtype a2NT was localized to Golgi and co-purified with microsomal membranes. Mutants reduced Golgi localization and membrane association. Rapamycin depletion of PI(4)P diminished a2NT-Golgi localization. We conclude that a2NT is sufficient for Golgi retention, suggesting the lipid-binding motif is involved in V-ATPase targeting and/or retention. Mutational analyses suggest a molecular mechanism underlying how a2 mutations result in cutis laxa.
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Affiliation(s)
- Anh Chu
- Faculty of Dentistry, University of Toronto, Toronto M5G 1G6, ON, Canada; (A.C.); (Y.Y.)
| | - Yeqi Yao
- Faculty of Dentistry, University of Toronto, Toronto M5G 1G6, ON, Canada; (A.C.); (Y.Y.)
| | - Miroslawa Glibowicka
- Division of Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto M5G 0A4, ON, Canada; (M.G.); (C.M.D.)
| | - Charles M. Deber
- Division of Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto M5G 0A4, ON, Canada; (M.G.); (C.M.D.)
- Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto M5S 1A8, ON, Canada
| | - Morris F. Manolson
- Faculty of Dentistry, University of Toronto, Toronto M5G 1G6, ON, Canada; (A.C.); (Y.Y.)
- Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto M5S 1A8, ON, Canada
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Bourgeois S, Kovacikova J, Bugarski M, Bettoni C, Gehring N, Hall A, Wagner CA. The B1 H + -ATPase ( Atp6v1b1 ) Subunit in Non-Type A Intercalated Cells is Required for Driving Pendrin Activity and the Renal Defense Against Alkalosis. J Am Soc Nephrol 2024; 35:7-21. [PMID: 37990364 PMCID: PMC10786613 DOI: 10.1681/asn.0000000000000259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 10/07/2023] [Indexed: 11/23/2023] Open
Abstract
SIGNIFICANCE STATEMENT In the kidney, the B1 H + -ATPase subunit is mostly expressed in intercalated cells (IC). Its importance in acid-secreting type A ICs is evident in patients with inborn distal renal tubular acidosis and ATP6V1B1 mutations. However, the protein is also highly expressed in alkali-secreting non-type A ICs where its function is incompletely understood. We demonstrate in Atp6v1b1 knock out mice that the B1 subunit is critical for the renal response to defend against alkalosis during an alkali load or chronic furosemide treatment. These findings highlight the importance of non-type A ICs in maintaining acid-base balance in response to metabolic challenges or commonly used diuretics. BACKGROUND Non-type A ICs in the collecting duct system express the luminal Cl - /HCO 3- exchanger pendrin and apical and/or basolateral H + -ATPases containing the B1 subunit isoform. Non-type A ICs excrete bicarbonate during metabolic alkalosis. Mutations in the B1 subunit (ATP6V1B1) cause distal renal tubular acidosis due to its role in acid secretory type A ICs. The function of B1 in non-type A ICs has remained elusive. METHODS We examined the responses of Atp6v1b1-/- and Atp6v1b1+/+ mice to an alkali load and to chronic treatment with furosemide. RESULTS An alkali load or 1 week of furosemide resulted in a more pronounced hypokalemic alkalosis in male ATP6v1b1-/- versus Atp6v1b1+/+ mice that could not be compensated by respiration. Total pendrin expression and activity in non-type A ICs of ex vivo microperfused cortical collecting ducts were reduced, and β2 -adrenergic stimulation of pendrin activity was blunted in ATP6v1b1-/- mice. Basolateral H + -ATPase activity was strongly reduced, although the basolateral expression of the B2 isoform was increased. Ligation assays for H + -ATPase subunits indicated impaired assembly of V 0 and V 1 H + -ATPase domains. During chronic furosemide treatment, ATP6v1b1-/- mice also showed polyuria and hyperchloremia versus Atp6v1b1+/+ . The expression of pendrin, the water channel AQP2, and subunits of the epithelial sodium channel ENaC were reduced. CONCLUSIONS Our data demonstrate a critical role of H + -ATPases in non-type A ICs function protecting against alkalosis and reveal a hitherto unrecognized need of basolateral B1 isoform for a proper H + -ATPase complexes assembly and ability to be stimulated.
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Affiliation(s)
- Soline Bourgeois
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Jana Kovacikova
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Milica Bugarski
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Carla Bettoni
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Nicole Gehring
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Andrew Hall
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
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Wagner CA, Unwin R, Lopez-Garcia SC, Kleta R, Bockenhauer D, Walsh S. The pathophysiology of distal renal tubular acidosis. Nat Rev Nephrol 2023; 19:384-400. [PMID: 37016093 DOI: 10.1038/s41581-023-00699-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2023] [Indexed: 04/06/2023]
Abstract
The kidneys have a central role in the control of acid-base homeostasis owing to bicarbonate reabsorption and production of ammonia and ammonium in the proximal tubule and active acid secretion along the collecting duct. Impaired acid excretion by the collecting duct system causes distal renal tubular acidosis (dRTA), which is characterized by the failure to acidify urine below pH 5.5. This defect originates from reduced function of acid-secretory type A intercalated cells. Inherited forms of dRTA are caused by variants in SLC4A1, ATP6V1B1, ATP6V0A4, FOXI1, WDR72 and probably in other genes that are yet to be discovered. Inheritance of dRTA follows autosomal-dominant and -recessive patterns. Acquired forms of dRTA are caused by various types of autoimmune diseases or adverse effects of some drugs. Incomplete dRTA is frequently found in patients with and without kidney stone disease. These patients fail to appropriately acidify their urine when challenged, suggesting that incomplete dRTA may represent an intermediate state in the spectrum of the ability to excrete acids. Unrecognized or insufficiently treated dRTA can cause rickets and failure to thrive in children, osteomalacia in adults, nephrolithiasis and nephrocalcinosis. Electrolyte disorders are also often present and poorly controlled dRTA can increase the risk of developing chronic kidney disease.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK.
| | - Robert Unwin
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
| | - Sergio C Lopez-Garcia
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
- Department of Paediatric Nephrology, Great Ormond Street Hospital for Children, NHS Foundation Trust, London, UK
| | - Robert Kleta
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
| | - Detlef Bockenhauer
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
- Department of Paediatric Nephrology, Great Ormond Street Hospital for Children, NHS Foundation Trust, London, UK
| | - Stephen Walsh
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
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Characterization of a PIP Binding Site in the N-Terminal Domain of V-ATPase a4 and Its Role in Plasma Membrane Association. Int J Mol Sci 2023; 24:ijms24054867. [PMID: 36902293 PMCID: PMC10002524 DOI: 10.3390/ijms24054867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 02/13/2023] [Accepted: 02/21/2023] [Indexed: 03/06/2023] Open
Abstract
Vacuolar ATPases (V-ATPases) are multi-subunit ATP-dependent proton pumps necessary for cellular functions, including pH regulation and membrane fusion. The evidence suggests that the V-ATPase a-subunit's interaction with the membrane signaling lipid phosphatidylinositol (PIPs) regulates the recruitment of V-ATPase complexes to specific membranes. We generated a homology model of the N-terminal domain of the human a4 isoform (a4NT) using Phyre2.0 and propose a lipid binding domain within the distal lobe of the a4NT. We identified a basic motif, K234IKK237, critical for interaction with phosphoinositides (PIP), and found similar basic residue motifs in all four mammalian and both yeast a-isoforms. We tested PIP binding of wildtype and mutant a4NT in vitro. In protein lipid overlay assays, the double mutation K234A/K237A and the autosomal recessive distal renal tubular-causing mutation K237del reduced both PIP binding and association with liposomes enriched with PI(4,5)P2, a PIP enriched within plasma membranes. Circular dichroism spectra of the mutant protein were comparable to wildtype, indicating that mutations affected lipid binding, not protein structure. When expressed in HEK293, wildtype a4NT localized to the plasma membrane in fluorescence microscopy and co-purified with the microsomal membrane fraction in cellular fractionation experiments. a4NT mutants showed reduced membrane association and decreased plasma membrane localization. Depletion of PI(4,5)P2 by ionomycin caused reduced membrane association of the WT a4NT protein. Our data suggest that information contained within the soluble a4NT is sufficient for membrane association and that PI(4,5)P2 binding capacity is involved in a4 V-ATPase plasma membrane retention.
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Zhang R, Chen Z, Song Q, Wang S, Liu Z, Zhao X, Shi X, Guo W, Lang Y, Bottillo I, Shao L. Identification of seven exonic variants in the SLC4A1, ATP6V1B1, and ATP6V0A4 genes that alter RNA splicing by minigene assay. Hum Mutat 2021; 42:1153-1164. [PMID: 34157794 DOI: 10.1002/humu.24246] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 06/02/2021] [Accepted: 06/19/2021] [Indexed: 12/25/2022]
Abstract
Primary distal renal tubular acidosis (dRTA) is a rare tubular disease associated with variants in SLC4A1, ATP6V0A4, ATP6V1B1, FOXⅠ1, or WDR72 genes. Currently, there is growing evidence that all types of exonic variants can alter splicing regulatory elements, affecting the precursor messenger RNA (pre-mRNA) splicing process. This study was to determine the consequences of variants associated with dRTA on pre-mRNA splicing combined with predictive bioinformatics tools and minigene assay. As a result, among the 15 candidate variants, 7 variants distributed in SLC4A1 (c.1765C>T, p.Arg589Cys), ATP6V1B1 (c.368G>T, p.Gly123Val; c.370C>T, p.Arg124Trp; c.484G>T, p.Glu162* and c.1102G>A, p.Glu368Lys) and ATP6V0A4 genes (c.322C>T, p.Gln108* and c.1572G>A, p.Pro524Pro) were identified to result in complete or incomplete exon skipping by either disruption of exonic splicing enhancers (ESEs) and generation of exonic splicing silencers, or interference with the recognition of the classic splicing site, or both. To our knowledge, this is the first study on pre-mRNA splicing of exonic variants in the dRTA-related genes. These results highlight the importance of assessing the effects of exonic variants at the mRNA level and suggest that minigene analysis is an effective tool for evaluating the effects of splicing on variants in vitro.
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Affiliation(s)
- Ruixiao Zhang
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Zeqing Chen
- Academy for Engineering and Technology, Fudan University, Shanghai, China
| | - Qijing Song
- Emergency Center, People's Hospital of Jimo District, Qingdao, China
| | - Sai Wang
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China.,Department of Dermatology, Peking University First Hospital, Beijing, China
| | - Zhiying Liu
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Xiangzhong Zhao
- Central Laboratory, The Affiliated Hospital of Qingdao University, Qingdao, China
| | - Xiaomeng Shi
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Wencong Guo
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Yanhua Lang
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
| | - Irene Bottillo
- Division of Medical Genetics, Department of Molecular Medicine, San Camillo-Forlanini Hospital, Sapienza University, Rome, Italy
| | - Leping Shao
- Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, Qingdao, China
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Khandelwal P, Mahesh V, Mathur VP, Raut S, Geetha TS, Nair S, Hari P, Sinha A, Bagga A. Phenotypic variability in distal acidification defects associated with WDR72 mutations. Pediatr Nephrol 2021; 36:881-887. [PMID: 33033857 DOI: 10.1007/s00467-020-04747-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 07/21/2020] [Accepted: 08/26/2020] [Indexed: 12/11/2022]
Abstract
BACKGROUND Distal renal tubular acidosis (RTA) is typically caused by defects in ATP6V0A4, ATP6V1B1, and SLC4A1, accounting for 60-80% of patients. Genes recently implicated include FOXI1, ATP6V1C2, and WDR72, of which WDR72 is associated with dental enamel defects. METHODS We describe 4 patients, from three unrelated consanguineous families, with RTA and amelogenesis imperfecta. Distal tubular acidification was evaluated by furosemide-fludrocortisone test, urine-to-blood PCO2 gradient and fractional excretion of bicarbonate. Exome sequencing was performed using a panel of genes implicated in human disease. RESULTS Patients had polyuria, hypokalemia, hypercalciuria, and nephrocalcinosis, but metabolic acidosis varied in severity. Although all patients acidified urine to pH < 5.3 during furosemide-fludrocortisone test, urine-to-blood PCO2 gradient was < 20 mmHg during bicarbonate loading. All patients had transient proximal tubular dysfunction with urinary losses of phosphate and beta-2-microglobulin, and generalized aminoaciduria. Homozygous pathogenic truncating variants in WDR72 was detected in all probands. CONCLUSION Patients with WDR72 mutations show mild rate-dependent distal RTA with variable metabolic acidosis, and intact ability to acidify the urine on provocative testing. Concomitant proximal tubular dysfunction may be present. Mutations in WDR72 should be considered in patients with suspected distal RTA, especially if associated with dental defects.
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Affiliation(s)
- Priyanka Khandelwal
- Division of Nephrology, Department of Pediatrics, ICMR Center for Advanced Research in Nephrology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
| | - Mahesh V
- Division of Nephrology, Department of Pediatrics, ICMR Center for Advanced Research in Nephrology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
| | - Vijay Prakash Mathur
- Center for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India
| | - Sumantra Raut
- Division of Nephrology, Department of Pediatrics, ICMR Center for Advanced Research in Nephrology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
| | | | | | - Pankaj Hari
- Division of Nephrology, Department of Pediatrics, ICMR Center for Advanced Research in Nephrology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
| | - Aditi Sinha
- Division of Nephrology, Department of Pediatrics, ICMR Center for Advanced Research in Nephrology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India.
| | - Arvind Bagga
- Division of Nephrology, Department of Pediatrics, ICMR Center for Advanced Research in Nephrology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
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Transcriptomic and metabolomic insights into the variety of sperm storage in oviduct of egg layers. Poult Sci 2021; 100:101087. [PMID: 33887680 PMCID: PMC8082553 DOI: 10.1016/j.psj.2021.101087] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 01/26/2021] [Accepted: 02/26/2021] [Indexed: 11/22/2022] Open
Abstract
In birds, the sperm storage tubules (SST) are dispersed in uterovaginal junction (UVJ) and highly correlated with differential capacity of sperm storage (SS) in and among species with unspecified mechanisms. Here, the SS duration of 252 egg layer breeders was evaluated in 5 rounds with 3 phenotypic traits to screen high- and low-SS individuals, respectively, followed with transcriptome of UVJ tissues and metabolome of serum (high-SS vs. low-SS) to decipher the candidate genes and biochemical markers correlated with differential SS capacity. Histological characterization suggested slightly higher density of SST in UVJ (high-SS vs. low-SS). Transcriptome analyses identified 596 differentially expressed genes (336 upregulated vs. 260 downregulated), which were mainly enriched in gene ontology terms of homeostasis, steroid and lipid metabolism and hormone activity, and 12 significant pathways (P < 0.05) represented by calcium, steroid, and lipid metabolism. Immunohistochemical staining of GNAQ, ST6GAL1, ADFP, and PCNA showed similar distribution in UVJ tissues between 2 groups. Several candidates (HSD11B2, DIO2, AQP3, GNAQ, NANS, ST6GAL1) combined with 4 (11β-prostaglandin F2α, prostaglandin B1, 7α-hydroxytestosterone, and N-acetylneuraminic acid) of 40 differential metabolites enriched in serum metabolome were considered as regulators and biomarkers of SS duration in egg layer breeders. The integrated transcriptome and metabolome analyses of chicken breeder hens will provide novel insights for exploration and improvement of differential SS capacity in birds.
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Santos-Pereira C, Rodrigues LR, Côrte-Real M. Emerging insights on the role of V-ATPase in human diseases: Therapeutic challenges and opportunities. Med Res Rev 2021; 41:1927-1964. [PMID: 33483985 DOI: 10.1002/med.21782] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/05/2020] [Accepted: 01/05/2021] [Indexed: 12/13/2022]
Abstract
The control of the intracellular pH is vital for the survival of all organisms. Membrane transporters, both at the plasma and intracellular membranes, are key players in maintaining a finely tuned pH balance between intra- and extracellular spaces, and therefore in cellular homeostasis. V-ATPase is a housekeeping ATP-driven proton pump highly conserved among prokaryotes and eukaryotes. This proton pump, which exhibits a complex multisubunit structure based on cell type-specific isoforms, is essential for pH regulation and for a multitude of ubiquitous and specialized functions. Thus, it is not surprising that V-ATPase aberrant overexpression, mislocalization, and mutations in V-ATPase subunit-encoding genes have been associated with several human diseases. However, the ubiquitous expression of this transporter and the high toxicity driven by its off-target inhibition, renders V-ATPase-directed therapies very challenging and increases the need for selective strategies. Here we review emerging evidence linking V-ATPase and both inherited and acquired human diseases, explore the therapeutic challenges and opportunities envisaged from recent data, and advance future research avenues. We highlight the importance of V-ATPases with unique subunit isoform molecular signatures and disease-associated isoforms to design selective V-ATPase-directed therapies. We also discuss the rational design of drug development pipelines and cutting-edge methodological approaches toward V-ATPase-centered drug discovery. Diseases like cancer, osteoporosis, and even fungal infections can benefit from V-ATPase-directed therapies.
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Affiliation(s)
- Cátia Santos-Pereira
- Department of Biology, Centre of Molecular and Environmental Biology (CBMA), University of Minho, Braga, Portugal.,Department of Biological Engineering, Centre of Biological Engineering (CEB), University of Minho, Braga, Portugal
| | - Lígia R Rodrigues
- Department of Biological Engineering, Centre of Biological Engineering (CEB), University of Minho, Braga, Portugal
| | - Manuela Côrte-Real
- Department of Biology, Centre of Molecular and Environmental Biology (CBMA), University of Minho, Braga, Portugal
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Adam RJ, Paterson MR, Wardecke L, Hoffmann BR, Kriegel AJ. Functionally Essential Tubular Proteins Are Lost to Urine-Excreted, Large Extracellular Vesicles during Chronic Renal Insufficiency. ACTA ACUST UNITED AC 2020; 1:1105-1115. [PMID: 34263177 DOI: 10.34067/kid.0001212020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Background The 5/6 nephrectomy (5/6Nx) rat model recapitulates many elements of human CKD. Within weeks of surgery, 5/6Nx rats spontaneously exhibit proximal tubular damage, including the production of very large extracellular vesicles and brush border shedding. We hypothesized that production and elimination of these structures, termed large renal tubular extracellular vesicles (LRT-EVs), into the urine represents a pathologic mechanism by which essential tubule proteins are lost. Methods LRT-EVs were isolated from 5/6Nx rat urine 10 weeks after surgery. LRT-EV diameters were measured. LRT-EV proteomic analysis was performed by tandem mass spectrometry. Data are available via the ProteomeXchange Consortium with identifier PXD019207. Kidney tissue pathology was evaluated by trichrome staining, TUNEL staining, and immunohistochemistry. Results LRT-EV size and a lack of TUNEL staining in 5/6Nx rats suggest LRT-EVs to be distinct from exosomes, microvesicles, and apoptotic bodies. LRT-EVs contained many proximal tubule proteins that, upon disruption, are known to contribute to CKD pathologic hallmarks. Select proteins included aquaporin 1, 16 members of the solute carrier family, basolateral Na+/K+-ATPase subunit ATP1A1, megalin, cubilin, and sodium-glucose cotransporters (SLC5A1 and SLC5A2). Histologic analysis confirmed the presence of apical membrane proteins in LRT-EVs and brush border loss in 5/6Nx rats. Conclusions This study provides comprehensive proteomic analysis of a previously unreported category of extracellular vesicles associated with chronic renal stress. Because LRT-EVs contain proteins responsible for essential renal functions known to be compromised in CKD, their formation and excretion may represent an underappreciated pathogenic mechanism.
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Affiliation(s)
- Ryan J Adam
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Mark R Paterson
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Lukus Wardecke
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Brian R Hoffmann
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.,Department of Biomedical Engineering, Medical College of Wisconsin, Milwaukee, Wisconsin.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin.,Max McGee National Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Alison J Kriegel
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.,Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin.,Center of Systems Molecular Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin
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12
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Abstract
Acid-base balance is critical for normal life. Acute and chronic disturbances impact cellular energy metabolism, endocrine signaling, ion channel activity, neuronal activity, and cardiovascular functions such as cardiac contractility and vascular blood flow. Maintenance and adaptation of acid-base homeostasis are mostly controlled by respiration and kidney. The kidney contributes to acid-base balance by reabsorbing filtered bicarbonate, regenerating bicarbonate through ammoniagenesis and generation of protons, and by excreting acid. This review focuses on acid-base disorders caused by renal processes, both inherited and acquired. Distinct rare inherited monogenic diseases affecting acid-base handling in the proximal tubule and collecting duct have been identified. In the proximal tubule, mutations of solute carrier 4A4 (SLC4A4) (electrogenic Na+/HCO3--cotransporter Na+/bicarbonate cotransporter e1 [NBCe1]) and other genes such as CLCN5 (Cl-/H+-antiporter), SLC2A2 (GLUT2 glucose transporter), or EHHADH (enoyl-CoA, hydratase/3-hydroxyacyl CoA dehydrogenase) causing more generalized proximal tubule dysfunction can cause proximal renal tubular acidosis resulting from bicarbonate wasting and reduced ammoniagenesis. Mutations in adenosine triphosphate ATP6V1 (B1 H+-ATPase subunit), ATPV0A4 (a4 H+-ATPase subunit), SLC4A1 (anion exchanger 1), and FOXI1 (forkhead transcription factor) cause distal renal tubular acidosis type I. Carbonic anhydrase II mutations affect several nephron segments and give rise to a mixed proximal and distal phenotype. Finally, mutations in genes affecting aldosterone synthesis, signaling, or downstream targets can lead to hyperkalemic variants of renal tubular acidosis (type IV). More common forms of renal acidosis are found in patients with advanced stages of chronic kidney disease and are owing, at least in part, to a reduced capacity for ammoniagenesis.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland; National Center for Competence in Research Kidney, Switzerland.
| | - Pedro H Imenez Silva
- Institute of Physiology, University of Zurich, Zurich, Switzerland; National Center for Competence in Research Kidney, Switzerland
| | - Soline Bourgeois
- Institute of Physiology, University of Zurich, Zurich, Switzerland; National Center for Competence in Research Kidney, Switzerland
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13
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Zhao X, Lu J, Gao Y, Wang X, Lang Y, Shao L. Novel compound heterozygous ATP6V1B1 mutations in a Chinese child patient with primary distal renal tubular acidosis: a case report. BMC Nephrol 2018; 19:364. [PMID: 30558562 PMCID: PMC6297984 DOI: 10.1186/s12882-018-1173-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 12/05/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Distal renal tubular acidosis (dRTA) is a heterogeneous disorder characterized by normal anion gap metabolic acidosis. Autosomal recessive dRTA is usually caused by mutations occurring in ATP6V1B1 and ATP6V0A4 genes,encoding subunits B1 and a4 of apical H+-ATPase, respectively. The heterogeneous clinical manifestations of dRTA have been described in different ethnic groups harboring distinct mutations. Most of the reported cases are from Europe and Africa. At present, the prevalence of primary dRTA is still poorly elucidated in Chinese population. CASE PRESENTATION A 2-year and six-month-old female patient was hospitalized because of recurrent hypokalemia, hyperchloremic metabolic acidosis and growth retardation. Laboratory investigations presented a normal anion gap hyperchloremic metabolic acidosis, hypokalemia, and inappropriate alkaline urine. Renal ultrasound indicated bilateral nephrocalcinosis. Bilateral sensorineural hearing loss (SNHL) was confirmed with moderately severe (45 dB) on the left ear and severe (80 dB) on the right ear, which was accompanied with enlarged vestibular aqueduct (EVA) on both sides. According to these findings, a diagnosis of dRTA was made. To identify the pathogenic gene mutation, all coding regions of ATP6V1B1 and ATP6V0A4 gene, including intron-exon boundaries, were analyzed using PCR followed by direct sequence analysis. The splicing variants were verified in peripheral blood leucocytes of the patient by RT-PCR. As a result, two novel heterozygous mutations in ATP6V1B1 were identified in the child. One mutation was a successive 2-nucleotide deletion in exon 2(c.133-134delTG), which caused a marked nonsense mediated mRNA decay. The other was a guanine to adenine substitution of the first nucleotide of intron 8(c.785 + 1 G > A), which led to the exclusion of exon 8. After treatment with sodium citrate, potassium citrateand citric acid, metabolic acidosis and hypokalemia were corrected, but her hearing decreased gradually during the 2 years and had to accept the use of bilateral hearing aids. CONCLUSIONS We described two novel dRTA associated mutations in ATP6V1B1 identified in a Chinese child patient accompanying with SNHL and EVA. Our study will help to expand the understanding of this rare disease in Chinese population.
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Affiliation(s)
- Xiangzhong Zhao
- Central Laboratory, The Affiliated Hospital of Qingdao University, 1677 Wutaishan Road, Qingdao, 266555, China
| | - Jingru Lu
- Central Laboratory, The Affiliated Hospital of Qingdao University, 1677 Wutaishan Road, Qingdao, 266555, China.,Department of Nephrology, The Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China
| | - Yanxia Gao
- Department of Nephrology, Qingdao Branch of Qilu Hospital of Shandong University, Qingdao, Shandong, 266000, People's Republic of China
| | - Xiaoling Wang
- Central Laboratory, The Affiliated Hospital of Qingdao University, 1677 Wutaishan Road, Qingdao, 266555, China.,Department of Nephrology, The Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China
| | - Yanhua Lang
- Central Laboratory, The Affiliated Hospital of Qingdao University, 1677 Wutaishan Road, Qingdao, 266555, China
| | - Leping Shao
- Central Laboratory, The Affiliated Hospital of Qingdao University, 1677 Wutaishan Road, Qingdao, 266555, China. .,Department of Nephrology, The Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China. .,Central Laboratory and Department of Nephrolog, the Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China.
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14
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Duan X, Yang S, Zhang L, Yang T. V-ATPases and osteoclasts: ambiguous future of V-ATPases inhibitors in osteoporosis. Theranostics 2018; 8:5379-5399. [PMID: 30555553 PMCID: PMC6276090 DOI: 10.7150/thno.28391] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 10/10/2018] [Indexed: 12/11/2022] Open
Abstract
Vacuolar ATPases (V-ATPases) play a critical role in regulating extracellular acidification of osteoclasts and bone resorption. The deficiencies of subunit a3 and d2 of V-ATPases result in increased bone density in humans and mice. One of the traditional drug design strategies in treating osteoporosis is the use of subunit a3 inhibitor. Recent findings connect subunits H and G1 with decreased bone density. Given the controversial effects of ATPase subunits on bone density, there is a critical need to review the subunits of V-ATPase in osteoclasts and their functions in regulating osteoclasts and bone remodeling. In this review, we comprehensively address the following areas: information about all V-ATPase subunits and their isoforms; summary of V-ATPase subunits associated with human genetic diseases; V-ATPase subunits and osteopetrosis/osteoporosis; screening of all V-ATPase subunits variants in GEFOS data and in-house data; spectrum of V-ATPase subunits during osteoclastogenesis; direct and indirect roles of subunits of V-ATPases in osteoclasts; V-ATPase-associated signaling pathways in osteoclasts; interactions among V-ATPase subunits in osteoclasts; osteoclast-specific V-ATPase inhibitors; perspective of future inhibitors or activators targeting V-ATPase subunits in the treatment of osteoporosis.
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Affiliation(s)
- Xiaohong Duan
- State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases, Department of Oral Biology, Clinic of Oral Rare and Genetic Diseases, School of Stomatology, the Fourth Military Medical University, 145 West Changle Road, Xi'an 710032, P. R. China
| | - Shaoqing Yang
- State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases, Department of Oral Biology, Clinic of Oral Rare and Genetic Diseases, School of Stomatology, the Fourth Military Medical University, 145 West Changle Road, Xi'an 710032, P. R. China
| | - Lei Zhang
- Center for Genetic Epidemiology and Genomics, School of Public Health, Medical College of Soochow University, 199 Renai Road, Suzhou, Jiangsu, P. R. China
| | - Tielin Yang
- Key Laboratory of Biomedical Information Engineering of Ministry of Education, and Institute of Molecular Genetics, School of Life Science and Technology, Xi'an Jiaotong University, 28 West Xianning Road, Xi'an 710049, People's Republic of China
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15
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Bourgeois S, Bounoure L, Mouro-Chanteloup I, Colin Y, Brown D, Wagner CA. The ammonia transporter RhCG modulates urinary acidification by interacting with the vacuolar proton-ATPases in renal intercalated cells. Kidney Int 2018; 93:390-402. [PMID: 29054531 PMCID: PMC6166241 DOI: 10.1016/j.kint.2017.07.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 07/08/2017] [Accepted: 07/27/2017] [Indexed: 12/19/2022]
Abstract
Ammonium, stemming from renal ammoniagenesis, is a major urinary proton buffer and is excreted along the collecting duct. This process depends on the concomitant secretion of ammonia by the ammonia channel RhCG and of protons by the vacuolar-type proton-ATPase pump. Thus, urinary ammonium content and urinary acidification are tightly linked. However, mice lacking Rhcg excrete more alkaline urine despite lower urinary ammonium, suggesting an unexpected role of Rhcg in urinary acidification. RhCG and the B1 and B2 proton-ATPase subunits could be co-immunoprecipitated from kidney. In ex vivo microperfused cortical collecting ducts (CCD) proton-ATPase activity was drastically reduced in the absence of Rhcg. Conversely, overexpression of RhCG in HEK293 cells resulted in higher proton secretion rates and increased B1 proton-ATPase mRNA expression. However, in kidneys from Rhcg-/- mice the expression of only B1 and B2 subunits was altered. Immunolocalization of proton-ATPase subunits together with immuno-gold detection of the A proton-ATPase subunit showed similar localization and density of staining in kidneys from Rhcg+/+ and Rhcg-/-mice. In order to test for a reciprocal effect of intercalated cell proton-ATPases on Rhcg activity, we assessed Rhcg and proton-ATPase activities in microperfused CCD from Atp6v1b1-/- mice and showed reduced proton-ATPase activity without altering Rhcg activity. Thus, RhCG and proton-ATPase are located within the same cellular protein complex. RhCG may modulate proton-ATPase function and urinary acidification, whereas proton-ATPase activity does not affect RhCG function. This mechanism may help to coordinate ammonia and proton secretion beyond physicochemical driving forces.
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Affiliation(s)
- Soline Bourgeois
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Lisa Bounoure
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | | | - Yves Colin
- UMR_S1134, INSERM, Université Paris Diderot, INTS, Labex GR-Ex, Paris, France
| | - Dennis Brown
- Center for Systems Biology, Program in Membrane Biology, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
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16
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Pathophysiology, diagnosis and treatment of inherited distal renal tubular acidosis. J Nephrol 2017; 31:511-522. [DOI: 10.1007/s40620-017-0447-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 09/21/2017] [Indexed: 10/18/2022]
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17
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Maier C, Schadock I, Haber PK, Wysocki J, Ye M, Kanwar Y, Flask CA, Yu X, Hoit BD, Adams GN, Schmaier AH, Bader M, Batlle D. Prolylcarboxypeptidase deficiency is associated with increased blood pressure, glomerular lesions, and cardiac dysfunction independent of altered circulating and cardiac angiotensin II. J Mol Med (Berl) 2017; 95:473-486. [PMID: 28160049 DOI: 10.1007/s00109-017-1513-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 12/20/2016] [Accepted: 01/20/2017] [Indexed: 12/28/2022]
Abstract
Prolylcarboxypeptidase (PRCP) is a carboxypeptidase that cleaves angiotensin II (AngII) forming Ang(1-7). The impact of genetic PRCP deficiency on AngII metabolism, blood pressure (BP), kidney histology, and cardiac phenotype was investigated in two lines of PRCP-deficient mice: KST302 derived in C57BL/6 background and GST090 derived in FVB/N background. The GST090 line had increased mean arterial pressure (MAP) (113.7 ± 2.07 vs. WT 105.0 ± 1.23 mmHg; p < 0.01) and left ventricular hypertrophy (LVH) (ratio of diastolic left ventricular posterior wall dimension to left ventricular diameter 0.239 ± 0.0163 vs. WT 0.193 ± 0.0049; p < 0.05). Mice in the KST302 line also had mild hypertension and LVH. Cardiac defects, increased glomerular size, and glomerular mesangial expansion were also observed. After infusion of AngII to mice in the KST302 line, both MAP and LVH increased, but the constitutive differences between the gene trap mice and controls were no longer observed. Plasma and cardiac AngII and Ang(1-7) were not significantly different between PRCP-deficient mice and controls. Thus, PRCP deficiency is associated with elevated blood pressure and cardiac alterations including LVH and cardiac defects independently of systemic or cardiac AngII and Ang(1-7). An ex vivo assay showed that recombinant PRCP, unlike recombinant ACE2, did not degrade AngII to form Ang(1-7) in plasma at pH 7.4. PRCP was localized in α-intercalated cells of the kidney collecting tubule. The low pH prevailing at this site and the acidic pH preference of PRCP suggest a role of this enzyme in regulating AngII degradation in the collecting tubule where this peptide increases sodium reabsorption and therfore BP. However, there are other potential mechanisms for increased BP in this model that need to be considered as well. PRCP converts AngII to Ang(1-7) but only at an acidic pH. Global PRCP deficiency causes heart and kidney alterations and a moderate rise in BP. PRCP is abundant in the kidney collecting tubules, where the prevailing pH is low. In collecting tubules, PRCP deficiency could result in impaired AngII degradation. Increased AngII at this nephron site stimulates Na reabsorption and increases BP. KEY MESSAGE Prolylcarboxypeptidase (PRCP) converts AngII to Ang (1-7) but only at an acidic pH. Global PRCP deficiency causes heart and kidney alterations and a moderate rise in BP. PRCP is abundant in the kidney collecting tubules, where the prevailing pH is low. In collecting tubules, PRCP deficiency could result in impaired AngII degradation. Increased AngII at this nephron site stimulates Na reabsorption and increases BP.
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Affiliation(s)
- Christoph Maier
- Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.,Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Ines Schadock
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Philipp K Haber
- Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.,Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Jan Wysocki
- Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Minghao Ye
- Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Yashpal Kanwar
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Christopher A Flask
- Department of Radiology, Case Western Reserve University, Cleveland, OH, USA.,Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Xin Yu
- Department of Radiology, Case Western Reserve University, Cleveland, OH, USA.,Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Brian D Hoit
- Department of Medicine, Division of Cardiology, University Hospitals Case Medical Center and Case Western Reserve University, Cleveland, OH, USA
| | - Gregory N Adams
- Department of Medicine, Division of Hematology and Oncology, University Hospitals Case Medical Center and Case Western Reserve University, Cleveland, OH, USA
| | - Alvin H Schmaier
- Department of Medicine, Division of Hematology and Oncology, University Hospitals Case Medical Center and Case Western Reserve University, Cleveland, OH, USA
| | - Michael Bader
- Charité-Universitätsmedizin Berlin, Berlin, Germany.,Max Delbrück Center for Molecular Medicine, Berlin, Germany.,National Institute of Science and Technology in Nanobiopharmaceutics, Federal University of Minas Gerais, Belo Horizonte, Brazil.,German Center for Cardiovascular Research (DZHK), Berlin site, Berlin, Germany
| | - Daniel Batlle
- Division of Nephrology and Hypertension, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
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18
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Mohebbi N, Ferraro PM, Gambaro G, Unwin R. Tubular and genetic disorders associated with kidney stones. Urolithiasis 2016; 45:127-137. [DOI: 10.1007/s00240-016-0945-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 11/22/2016] [Indexed: 02/08/2023]
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19
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Daryadel A, Bourgeois S, Figueiredo MFL, Gomes Moreira A, Kampik NB, Oberli L, Mohebbi N, Lu X, Meima ME, Danser AHJ, Wagner CA. Colocalization of the (Pro)renin Receptor/Atp6ap2 with H+-ATPases in Mouse Kidney but Prorenin Does Not Acutely Regulate Intercalated Cell H+-ATPase Activity. PLoS One 2016; 11:e0147831. [PMID: 26824839 PMCID: PMC4732657 DOI: 10.1371/journal.pone.0147831] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 01/08/2016] [Indexed: 12/11/2022] Open
Abstract
The (Pro)renin receptor (P)RR/Atp6ap2 is a cell surface protein capable of binding and non-proteolytically activate prorenin. Additionally, (P)RR is associated with H+-ATPases and alternative functions in H+-ATPase regulation as well as in Wnt signalling have been reported. Kidneys express very high levels of H+-ATPases which are involved in multiple functions such as endocytosis, membrane protein recycling as well as urinary acidification, bicarbonate reabsorption, and salt absorption. Here, we wanted to localize the (P)RR/Atp6ap2 along the murine nephron, exmaine whether the (P)RR/Atp6ap2 is coregulated with other H+-ATPase subunits, and whether acute stimulation of the (P)RR/Atp6ap2 with prorenin regulates H+-ATPase activity in intercalated cells in freshly isolated collecting ducts. We localized (P)PR/Atp6ap2 along the murine nephron by qPCR and immunohistochemistry. (P)RR/Atp6ap2 mRNA was detected in all nephron segments with highest levels in the collecting system coinciding with H+-ATPases. Further experiments demonstrated expression at the brush border membrane of proximal tubules and in all types of intercalated cells colocalizing with H+-ATPases. In mice treated with NH4Cl, NaHCO3, KHCO3, NaCl, or the mineralocorticoid DOCA for 7 days, (P)RR/Atp6ap2 and H+-ATPase subunits were regulated but not co-regulated at protein and mRNA levels. Immunolocalization in kidneys from control, NH4Cl or NaHCO3 treated mice demonstrated always colocalization of PRR/Atp6ap2 with H+-ATPase subunits at the brush border membrane of proximal tubules, the apical pole of type A intercalated cells, and at basolateral and/or apical membranes of non-type A intercalated cells. Microperfusion of isolated cortical collecting ducts and luminal application of prorenin did not acutely stimulate H+-ATPase activity. However, incubation of isolated collecting ducts with prorenin non-significantly increased ERK1/2 phosphorylation. Our results suggest that the PRR/Atp6ap2 may form a complex with H+-ATPases in proximal tubule and intercalated cells but that prorenin has no acute effect on H+-ATPase activity in intercalated cells.
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MESH Headings
- Ammonium Chloride/pharmacology
- Animals
- Anion Transport Proteins/genetics
- Anion Transport Proteins/metabolism
- Aquaporin 2/genetics
- Aquaporin 2/metabolism
- Cell Membrane/drug effects
- Cell Membrane/metabolism
- Dogs
- Gene Expression Regulation
- Kidney Cortex/cytology
- Kidney Cortex/drug effects
- Kidney Cortex/metabolism
- Kidney Medulla/cytology
- Kidney Medulla/drug effects
- Kidney Medulla/metabolism
- Kidney Tubules, Collecting/cytology
- Kidney Tubules, Collecting/drug effects
- Kidney Tubules, Collecting/metabolism
- Kidney Tubules, Proximal/cytology
- Kidney Tubules, Proximal/drug effects
- Kidney Tubules, Proximal/metabolism
- Madin Darby Canine Kidney Cells
- Male
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/metabolism
- Mice
- Mice, Inbred C57BL
- Proton-Translocating ATPases/genetics
- Proton-Translocating ATPases/metabolism
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Renin/pharmacology
- Renin-Angiotensin System/drug effects
- Signal Transduction
- Sodium Bicarbonate/pharmacology
- Sodium Chloride/pharmacology
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/metabolism
- Solute Carrier Family 12, Member 1/genetics
- Solute Carrier Family 12, Member 1/metabolism
- Solute Carrier Family 12, Member 3/genetics
- Solute Carrier Family 12, Member 3/metabolism
- Sulfate Transporters
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Affiliation(s)
- Arezoo Daryadel
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Soline Bourgeois
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | | | | | - Nicole B. Kampik
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Lisa Oberli
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Nilufar Mohebbi
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Divison of Nephrology, University Hospital Zurich, Zurich, Switzerland
| | - Xifeng Lu
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Marcel E. Meima
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - A. H. Jan Danser
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Carsten A. Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- * E-mail:
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20
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Wagner CA, Mohebbi N, Bourgeois S. The ugly duckling of urinary acidification: what is the contribution of the thick ascending limb of the loop of Henle to urinary acidification? Am J Physiol Renal Physiol 2015; 309:F431-3. [PMID: 26155846 DOI: 10.1152/ajprenal.00296.2015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 07/07/2015] [Indexed: 11/22/2022] Open
Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland; and
| | - Nilufar Mohebbi
- Division of Nephrology, University Hospital Zurich, Zurich, Switzerland
| | - Soline Bourgeois
- Institute of Physiology, University of Zurich, Zurich, Switzerland; and
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21
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Zhang J, Fuster DG, Cameron MA, Quiñones H, Griffith C, Xie XS, Moe OW. Incomplete distal renal tubular acidosis from a heterozygous mutation of the V-ATPase B1 subunit. Am J Physiol Renal Physiol 2014; 307:F1063-71. [PMID: 25164082 DOI: 10.1152/ajprenal.00408.2014] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Congenital distal renal tubular acidosis (RTA) from mutations of the B1 subunit of V-ATPase is considered an autosomal recessive disease. We analyzed a distal RTA kindred with a truncation mutation of B1 (p.Phe468fsX487) previously shown to have failure of assembly into the V1 domain of V-ATPase. All heterozygous carriers in this kindred have normal plasma HCO3- concentrations and thus evaded the diagnosis of RTA. However, inappropriately high urine pH, hypocitraturia, and hypercalciuria were present either individually or in combination in the heterozygotes at baseline. Two of the heterozygotes studied also had inappropriate urinary acidification with acute ammonium chloride loading and an impaired urine-blood Pco2 gradient during bicarbonaturia, indicating the presence of a H+ gradient and flux defects. In normal human renal papillae, wild-type B1 is located primarily on the plasma membrane, but papilla from one of the heterozygote who had kidney stones but not nephrocalcinosis showed B1 in both the plasma membrane as well as diffuse intracellular staining. Titration of increasing amounts of the mutant B1 subunit did not exhibit negative dominance over the expression, cellular distribution, or H+ pump activity of wild-type B1 in mammalian human embryonic kidney-293 cells and in V-ATPase-deficient Saccharomyces cerevisiae. This is the first demonstration of renal acidification defects and nephrolithiasis in heterozygous carriers of a mutant B1 subunit that cannot be attributable to negative dominance. We propose that heterozygosity may lead to mild real acidification defects due to haploinsufficiency. B1 heterozygosity should be considered in patients with calcium nephrolithiasis and urinary abnormalities such as alkalinuria or hypocitraturia.
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Affiliation(s)
- Jianning Zhang
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Daniel G Fuster
- Department of Nephrology and Hypertension and Institute of Biochemistry and Molecular Medicine, Inselspital, University of Bern, Bern, Switzerland
| | - Mary Ann Cameron
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Henry Quiñones
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Carolyn Griffith
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Xiao-Song Xie
- McDermott Center of Human Development, University of Texas Southwestern Medical Center, Dallas, Texas; and
| | - Orson W Moe
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas;
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Murine Joubert syndrome reveals Hedgehog signaling defects as a potential therapeutic target for nephronophthisis. Proc Natl Acad Sci U S A 2014; 111:9893-8. [PMID: 24946806 DOI: 10.1073/pnas.1322373111] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Nephronophthisis (NPHP) is the major cause of pediatric renal failure, yet the disease remains poorly understood, partly due to the lack of appropriate animal models. Joubert syndrome (JBTS) is an inherited ciliopathy giving rise to NPHP with cerebellar vermis aplasia and retinal degeneration. Among patients with JBTS and a cerebello-oculo-renal phenotype, mutations in CEP290 (NPHP6) are the most common genetic lesion. We present a Cep290 gene trap mouse model of JBTS that displays the kidney, eye, and brain abnormalities that define the syndrome. Mutant mice present with cystic kidney disease as neonates. Newborn kidneys contain normal amounts of lymphoid enhancer-binding factor 1 (Lef1) and transcription factor 1 (Tcf1) protein, indicating normal function of the Wnt signaling pathway; however, an increase in the protein Gli3 repressor reveals abnormal Hedgehog (Hh) signaling evident in newborn kidneys. Collecting duct cells from mutant mice have abnormal primary cilia and are unable to form spheroid structures in vitro. Treatment of mutant cells with the Hh agonist purmorphamine restored normal spheroid formation. Renal epithelial cells from a JBTS patient with CEP290 mutations showed similar impairments to spheroid formation that could also be partially rescued by exogenous stimulation of Hh signaling. These data implicate abnormal Hh signaling as the cause of NPHP and suggest that Hh agonists may be exploited therapeutically.
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23
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Vacuolar H+-ATPase: An Essential Multitasking Enzyme in Physiology and Pathophysiology. ACTA ACUST UNITED AC 2014. [DOI: 10.1155/2014/675430] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Vacuolar H+-ATPases (V-ATPases) are large multisubunit proton pumps that are required for housekeeping acidification of membrane-bound compartments in eukaryotic cells. Mammalian V-ATPases are composed of 13 different subunits. Their housekeeping functions include acidifying endosomes, lysosomes, phagosomes, compartments for uncoupling receptors and ligands, autophagosomes, and elements of the Golgi apparatus. Specialized cells, including osteoclasts, intercalated cells in the kidney and pancreatic beta cells, contain both the housekeeping V-ATPases and an additional subset of V-ATPases, which plays a cell type specific role. The specialized V-ATPases are typically marked by the inclusion of cell type specific isoforms of one or more of the subunits. Three human diseases caused by mutations of isoforms of subunits have been identified. Cancer cells utilize V-ATPases in unusual ways; characterization of V-ATPases may lead to new therapeutic modalities for the treatment of cancer. Two accessory proteins to the V-ATPase have been identified that regulate the proton pump. One is the (pro)renin receptor and data is emerging that indicates that V-ATPase may be intimately linked to renin/angiotensin signaling both systemically and locally. In summary, V-ATPases play vital housekeeping roles in eukaryotic cells. Specialized versions of the pump are required by specific organ systems and are involved in diseases.
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Christensen EI, Wagner CA, Kaissling B. Uriniferous tubule: structural and functional organization. Compr Physiol 2013; 2:805-61. [PMID: 23961562 DOI: 10.1002/cphy.c100073] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The uriniferous tubule is divided into the proximal tubule, the intermediate (thin) tubule, the distal tubule and the collecting duct. The present chapter is based on the chapters by Maunsbach and Christensen on the proximal tubule, and by Kaissling and Kriz on the distal tubule and collecting duct in the 1992 edition of the Handbook of Physiology, Renal Physiology. It describes the fine structure (light and electron microscopy) of the entire mammalian uriniferous tubule, mainly in rats, mice, and rabbits. The structural data are complemented by recent data on the location of the major transport- and transport-regulating proteins, revealed by morphological means(immunohistochemistry, immunofluorescence, and/or mRNA in situ hybridization). The structural differences along the uriniferous tubule strictly coincide with the distribution of the major luminal and basolateral transport proteins and receptors and both together provide the basis for the subdivision of the uriniferous tubule into functional subunits. Data on structural adaptation to defined functional changes in vivo and to genetical alterations of specified proteins involved in transepithelial transport importantly deepen our comprehension of the correlation of structure and function in the kidney, of the role of each segment or cell type in the overall renal function,and our understanding of renal pathophysiology.
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25
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Gueutin V, Vallet M, Jayat M, Peti-Peterdi J, Cornière N, Leviel F, Sohet F, Wagner CA, Eladari D, Chambrey R. Renal β-intercalated cells maintain body fluid and electrolyte balance. J Clin Invest 2013; 123:4219-31. [PMID: 24051376 DOI: 10.1172/jci63492] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 06/28/2013] [Indexed: 12/11/2022] Open
Abstract
Inactivation of the B1 proton pump subunit (ATP6V1B1) in intercalated cells (ICs) leads to type I distal renal tubular acidosis (dRTA), a disease associated with salt- and potassium-losing nephropathy. Here we show that mice deficient in ATP6V1B1 (Atp6v1b1-/- mice) displayed renal loss of NaCl, K+, and water, causing hypovolemia, hypokalemia, and polyuria. We demonstrated that NaCl loss originated from the cortical collecting duct, where activity of both the epithelial sodium channel (ENaC) and the pendrin/Na(+)-driven chloride/bicarbonate exchanger (pendrin/NDCBE) transport system was impaired. ENaC was appropriately increased in the medullary collecting duct, suggesting a localized inhibition in the cortex. We detected high urinary prostaglandin E2 (PGE2) and ATP levels in Atp6v1b1-/- mice. Inhibition of PGE2 synthesis in vivo restored ENaC protein levels specifically in the cortex. It also normalized protein levels of the large conductance calcium-activated potassium channel and the water channel aquaporin 2, and improved polyuria and hypokalemia in mutant mice. Furthermore, pharmacological inactivation of the proton pump in β-ICs induced release of PGE2 through activation of calcium-coupled purinergic receptors. In the present study, we identified ATP-triggered PGE2 paracrine signaling originating from β-ICs as a mechanism in the development of the hydroelectrolytic imbalance associated with dRTA. Our data indicate that in addition to principal cells, ICs are also critical in maintaining sodium balance and, hence, normal vascular volume and blood pressure.
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26
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Lu X, Garrelds IM, Wagner CA, Danser AHJ, Meima ME. (Pro)renin receptor is required for prorenin-dependent and -independent regulation of vacuolar H+-ATPase activity in MDCK.C11 collecting duct cells. Am J Physiol Renal Physiol 2013; 305:F417-25. [DOI: 10.1152/ajprenal.00037.2013] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Prorenin binding to the prorenin receptor [(P)RR] results in nonproteolytic activation of prorenin but also directly (i.e., independent of angiotensin generation) activates signal transduction cascades that can lead to the upregulation of profibrotic factors. The (P)RR is an accessory protein of vacuolar-type H+-ATPase (V-ATPase) and is required for V-ATPase integrity. In addition, in collecting duct cells, prorenin-induced activation of Erk depends on V-ATPase activity. However, whether prorenin binding to the (P)RR directly regulates V-ATPase activity is as yet unknown. Here, we studied the effect of prorenin on plasma membrane V-ATPase activity in Madin-Darby canine kidney clone 11 (MDCK.C11) cells, which resemble intercalated cells of the collecting duct. Prorenin increased V-ATPase activity at low nanomolar concentrations, and the V-ATPase inhibitor bafilomycin A1, but not the angiotensin II type 1 and 2 receptor blockers irbesartan and PD-123319, prevented this. Increased, but not basal, V-ATPase activity was abolished by small interfering RNA depletion of the (P)RR. Unexpectedly, the putative peptidic (P)RR blocker handle region peptide also increasedV-ATPase activity in a (P)RR-dependent manner. Finally, [Arg8]-vasopressin-stimulated V-ATPase activity and cAMP production were also abolished by (P)RR depletion. Our results show that in MDCK.C11 cells, the (P)RR is required for prorenin-dependent and -independent regulation of V-ATPase activity.
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Affiliation(s)
- Xifeng Lu
- Division of Pharmacology and Vascular Medicine, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands; and
| | - Ingrid M. Garrelds
- Division of Pharmacology and Vascular Medicine, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands; and
| | | | - A. H. Jan Danser
- Division of Pharmacology and Vascular Medicine, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands; and
| | - Marcel E. Meima
- Division of Pharmacology and Vascular Medicine, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands; and
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Sulfatides are required for renal adaptation to chronic metabolic acidosis. Proc Natl Acad Sci U S A 2013; 110:9998-10003. [PMID: 23716689 DOI: 10.1073/pnas.1217775110] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Urinary ammonium excretion by the kidney is essential for renal excretion of sufficient amounts of protons and to maintain stable blood pH. Ammonium secretion by the collecting duct epithelia accounts for the majority of urinary ammonium; it is driven by an interstitium-to-lumen NH3 gradient due to the accumulation of ammonium in the medullary and papillary interstitium. Here, we demonstrate that sulfatides, highly charged anionic glycosphingolipids, are important for maintaining high papillary ammonium concentration and increased urinary acid elimination during metabolic acidosis. We disrupted sulfatide synthesis by a genetic approach along the entire renal tubule. Renal sulfatide-deficient mice had lower urinary pH accompanied by lower ammonium excretion. Upon acid diet, they showed impaired ammonuria, decreased ammonium accumulation in the papilla, and chronic hyperchloremic metabolic acidosis. Expression levels of ammoniagenic enzymes and Na(+)-K(+)/NH4(+)-2Cl(-) cotransporter 2 were higher, and transepithelial NH3 transport, examined by in vitro microperfusion of cortical and outer medullary collecting ducts, was unaffected in mutant mice. We therefore suggest that sulfatides act as counterions for interstitial ammonium facilitating its retention in the papilla. This study points to a seminal role of sulfatides in renal ammonium handling, urinary acidification, and acid-base homeostasis.
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Yasuoka Y, Kobayashi M, Sato Y, Zhou M, Abe H, Okamoto H, Nonoguchi H, Tanoue A, Kawahara K. The intercalated cells of the mouse kidney OMCD(is) are the target of the vasopressin V1a receptor axis for urinary acidification. Clin Exp Nephrol 2013; 17:783-92. [PMID: 23456233 DOI: 10.1007/s10157-013-0783-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Accepted: 01/31/2013] [Indexed: 12/31/2022]
Abstract
BACKGROUND Vasopressin V1a receptor (V1aR) null mice have insufficient acid-base balance, but the target cell for V1aR signaling which results in the urinary acidification has not been identified. METHODS By using a quantitative in situ hybridization technique and a double-staining technique with an anti-AQP3 antibody in mice, we investigated the axial distribution and acidosis-induced expression of V1aR mRNA along the nephron. We also investigated the acidosis-induced morphological change in the tubule cells from wild-type and V1aR-null (V1aR(-/-)) mice. RESULTS In the normal condition, V1aR mRNA was moderately expressed in the medullary thick ascending limb (MTAL) and highly expressed in the intercalated cell (IC) throughout the collecting duct (CD). However, no expression was observed in the proximal tubule, thin limbs of Henle's loop, and the principal cell of the CD. Importantly, V1aR mRNA was upregulated significantly both in the TAL and the IC of the CD in the inner stripe of the outer medulla (MTALis and IC of OMCDis, respectively) when mice were treated with NH4Cl (0.28 mol/L) for 6 days. Acidosis-induced hypertrophy, which was completely attenuated in V1aR(-/-) mice, was observed only in the IC of OMCDis (P < 0.005). In addition, urinary excretion of ammonia (NH3/NH4 (+)) was significantly decreased on day 3 (P < 0.05) and day 6 (P < 0.005) in the V1aR(-/-) mice treated with NH4Cl. CONCLUSION In conclusion, the IC of OMCDis may be the target cell stimulated by the vasopressin V1aR axis and contribute to urinary acidification, at least during metabolic acidosis.
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Affiliation(s)
- Yukiko Yasuoka
- Department of Physiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, 252-0374, Japan
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29
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Mohebbi N, Perna A, van der Wijst J, Becker HM, Capasso G, Wagner CA. Regulation of two renal chloride transporters, AE1 and pendrin, by electrolytes and aldosterone. PLoS One 2013; 8:e55286. [PMID: 23383138 PMCID: PMC3561381 DOI: 10.1371/journal.pone.0055286] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Accepted: 12/21/2012] [Indexed: 01/14/2023] Open
Abstract
The renal handling of salt and protons and bicarbonate are intricately linked through shared transport mechanisms for sodium, chloride, protons, and bicarbonate. In the collecting duct, the regulated fine-tuning of salt and acid-base homeostasis is achieved by a series of transport proteins located in different cell types, intercalated and principal cells. Intercalated cells are considered to be of less importance for salt handling but recent evidence has suggested that the anion exchanger pendrin may participate in salt reabsorption and blood pressure regulation. Here, we examined the regulated expression of two functionally related but differentially expressed anion exchangers, AE1 and pendrin, by dietary electrolyte intake and aldosterone. Cortical expression of pendrin was regulated on mRNA and protein level. The combination of NaHCO3 and DOCA enhanced pendrin mRNA and protein levels, whereas DOCA or NaHCO3 alone had no effect. NaCl or KHCO3 increased pendrin mRNA, KCl decreased its mRNA abundance. On protein level, NH4Cl, NaCl, and KCl reduced pendrin expression, the other treatments were without effect. In contrast, AE1 mRNA or protein expression in kidney cortex was regulated by none of these treatments. In kidney medulla, NaHCO3/DOCA or NaHCO3 alone enhanced AE1 mRNA levels. AE1 protein abundance was increased by NH4Cl, NaHCO3/DOCA, and NaCl. Immunolocalization showed that during NH4Cl treatment the relative number of AE1 positive cells was increased and pendrin expressing cells reduced. Thus, pendrin and AE1 are differentially regulated with distinct mechanisms that separately affect mRNA and protein levels. Pendrin is regulated by acidosis and chloride intake, whereas AE1 is enhanced by acidosis, NaCl, and the combination of DOCA and NaHCO3.
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Affiliation(s)
- Nilufar Mohebbi
- Institute of Physiology and Zurich Center for Integrative Human Physiology-ZIHP, Zurich, Switzerland
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30
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Hennings JC, Picard N, Huebner AK, Stauber T, Maier H, Brown D, Jentsch TJ, Vargas-Poussou R, Eladari D, Hübner CA. A mouse model for distal renal tubular acidosis reveals a previously unrecognized role of the V-ATPase a4 subunit in the proximal tubule. EMBO Mol Med 2012; 4:1057-71. [PMID: 22933323 PMCID: PMC3491836 DOI: 10.1002/emmm.201201527] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2012] [Revised: 06/19/2012] [Accepted: 07/10/2012] [Indexed: 11/09/2022] Open
Abstract
The V-ATPase is a multisubunit complex that transports protons across membranes. Mutations of its B1 or a4 subunit are associated with distal renal tubular acidosis and deafness. In the kidney, the a4 subunit is expressed in intercalated cells of the distal nephron, where the V-ATPase controls acid/base secretion, and in proximal tubule cells, where its role is less clear. Here, we report that a4 KO mice suffer not only from severe acidosis but also from proximal tubule dysfunction with defective endocytic trafficking, proteinuria, phosphaturia and accumulation of lysosomal material and we provide evidence that these findings may be also relevant in patients. In the inner ear, the a4 subunit co-localized with pendrin at the apical side of epithelial cells lining the endolymphatic sac. As a4 KO mice were profoundly deaf and displayed enlarged endolymphatic fluid compartments mirroring the alterations in pendrin KO mice, we propose that pendrin and the proton pump co-operate in endolymph homeostasis. Thus, our mouse model gives new insights into the divergent functions of the V-ATPase and the pathophysiology of a4-related symptoms.
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31
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Bhargava A, Voronov I, Wang Y, Glogauer M, Kartner N, Manolson MF. Osteopetrosis mutation R444L causes endoplasmic reticulum retention and misprocessing of vacuolar H+-ATPase a3 subunit. J Biol Chem 2012; 287:26829-39. [PMID: 22685294 DOI: 10.1074/jbc.m112.345702] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Osteopetrosis is a genetic bone disease characterized by increased bone density and fragility. The R444L missense mutation in the human V-ATPase a3 subunit (TCIRG1) is one of several known mutations in a3 and other proteins that can cause this disease. The autosomal recessive R444L mutation results in a particularly malignant form of infantile osteopetrosis that is lethal in infancy, or early childhood. We have studied this mutation using the pMSCV retroviral vector system to integrate the cDNA construct for green fluorescent protein (GFP)-fused a3(R445L) mutant protein into the RAW 264.7 mouse osteoclast differentiation model. In comparison with wild-type a3, the mutant glycoprotein localized to the ER instead of lysosomes and its oligosaccharide moiety was misprocessed, suggesting inability of the core-glycosylated glycoprotein to traffic to the Golgi. Reduced steady-state expression of the mutant protein, in comparison with wild type, suggested that the former was being degraded, likely through the endoplasmic reticulum-associated degradation pathway. In differentiated osteoclasts, a3(R445L) was found to degrade at an increased rate over the course of osteoclastogenesis. Limited proteolysis studies suggested that the R445L mutation alters mouse a3 protein conformation. Together, these data suggest that Arg-445 plays a role in protein folding, or stability, and that infantile malignant osteopetrosis caused by the R444L mutation in the human V-ATPase a3 subunit is another member of the growing class of protein folding diseases. This may have implications for early-intervention treatment, using protein rescue strategies.
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Affiliation(s)
- Ajay Bhargava
- Dental Research Institute, Faculty of Dentistry, University of Toronto, Toronto, Ontario M5G 1G6, Canada
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32
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Gröger N, Vitzthum H, Fröhlich H, Krüger M, Ehmke H, Braun T, Boettger T. Targeted mutation of SLC4A5 induces arterial hypertension and renal metabolic acidosis. Hum Mol Genet 2011; 21:1025-36. [PMID: 22082831 DOI: 10.1093/hmg/ddr533] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The human SLC4A5 gene has been identified as a hypertension susceptibility gene based on the association of single nucleotide polymorphisms with blood pressure (BP) levels and hypertension status. The biochemical basis of this association is unknown particularly since no single gene variant was linked to hypertension in humans. SLC4A5 (NBCe2, NBC4) is expressed in the collecting duct of the kidney and acts as an electrogenic ion-transporter that transports sodium and bicarbonate with a 1:2 or 1:3 stoichiometry allowing bicarbonate reabsorption with relatively minor concurrent sodium uptake. We have mutated the Slc4a5 gene in mice, which caused a persistent increase in systolic and diastolic BP. Slc4a5 mutant mice also displayed a compensated metabolic acidosis and hyporeninemic hypoaldosteronism. Analysis of kidney physiology revealed elevated fluid intake and urine excretion and increased glomerular filtration rate. Transcriptome analysis uncovers possible compensatory mechanisms induced by SLC4A5 mutation, including upregulation of SLC4A7 and pendrin as well as molecular mechanisms associated with hypertension. Induction of metabolic alkalosis eliminated the BP difference between wild-type and Slc4a5 mutant mice. We conclude that the impairment of the function of SLC4A5 favors development of a hypertensive state. We reason that the loss of sodium-sparing bicarbonate reabsorption by SLC4A5 initiates a regulatory cascade consisting of compensatory bicarbonate reabsorption via other sodium-bicarbonate transporters (e.g. SLC4A7) at the expense of an increased sodium uptake. This will ultimately raise BP and cause hypoaldosteronism, thus providing a mechanistic explanation for the linkage of the SLC4A5 locus to hypertension in humans.
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Affiliation(s)
- Nicole Gröger
- Department of Cardiac Development and Remodelling, Max Planck Institute for Heart and Lung Research, Ludwigstrasse 43, D-61231 Bad Nauheim, Germany
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Welsh-Bacic D, Nowik M, Kaissling B, Wagner CA. Proliferation of acid-secretory cells in the kidney during adaptive remodelling of the collecting duct. PLoS One 2011; 6:e25240. [PMID: 22039408 PMCID: PMC3200326 DOI: 10.1371/journal.pone.0025240] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 08/29/2011] [Indexed: 01/07/2023] Open
Abstract
The renal collecting duct adapts to changes in acid-base metabolism by remodelling and altering the relative number of acid or alkali secreting cells, a phenomenon termed plasticity. Acid secretory A intercalated cells (A-IC) express apical H(+)-ATPases and basolateral bicarbonate exchanger AE1 whereas bicarbonate secretory B intercalated cells (B-IC) express basolateral (and apical) H(+)-ATPases and the apical bicarbonate exchanger pendrin. Intercalated cells were thought to be terminally differentiated and unable to proliferate. However, a recent report in mouse kidney suggested that intercalated cells may proliferate and that this process is in part dependent on GDF-15. Here we extend these observations to rat kidney and provide a detailed analysis of regional differences and demonstrate that differentiated A-IC proliferate massively during adaptation to systemic acidosis. We used markers of proliferation (PCNA, Ki67, BrdU incorporation) and cell-specific markers for A-IC (AE1) and B-IC (pendrin). Induction of remodelling in rats with metabolic acidosis (with NH(4)Cl for 12 hrs, 4 and 7 days) or treatment with acetazolamide for 10 days resulted in a larger fraction of AE1 positive cells in the cortical collecting duct. A large number of AE1 expressing A-IC was labelled with proliferative markers in the cortical and outer medullary collecting duct whereas no labeling was found in B-IC. In addition, chronic acidosis also increased the rate of proliferation of principal collecting duct cells. The fact that both NH(4)Cl as well as acetazolamide stimulated proliferation suggests that systemic but not urinary pH triggers this response. Thus, during chronic acidosis proliferation of AE1 containing acid-secretory cells occurs and may contribute to the remodelling of the collecting duct or replace A-IC due to a shortened life span under these conditions.
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Affiliation(s)
- Desa Welsh-Bacic
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Marta Nowik
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | | | - Carsten A. Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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Quigley IK, Stubbs JL, Kintner C. Specification of ion transport cells in the Xenopus larval skin. Development 2011; 138:705-14. [PMID: 21266406 DOI: 10.1242/dev.055699] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Specialized epithelial cells in the amphibian skin play important roles in ion transport, but how they arise developmentally is largely unknown. Here we show that proton-secreting cells (PSCs) differentiate in the X. laevis larval skin soon after gastrulation, based on the expression of a `kidney-specific' form of the H(+)v-ATPase that localizes to the plasma membrane, orthologs of the Cl(-)/HCO(-)(3) antiporters ae1 and pendrin, and two isoforms of carbonic anhydrase. Like PSCs in other species, we show that the expression of these genes is likely to be driven by an ortholog of foxi1, which is also sufficient to promote the formation of PSC precursors. Strikingly, the PSCs form in the skin as two distinct subtypes that resemble the alpha- and beta-intercalated cells of the kidney. The alpha-subtype expresses ae1 and localizes H(+)v-ATPases to the apical plasma membrane, whereas the beta-subtype expresses pendrin and localizes the H(+)v-ATPase cytosolically or basolaterally. These two subtypes are specified during early PSC differentiation by a binary switch that can be regulated by Notch signaling and by the expression of ubp1, a transcription factor of the grainyhead family. These results have implications for how PSCs are specified in vertebrates and become functionally heterogeneous.
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Affiliation(s)
- Ian K Quigley
- The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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35
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Vivante A, Lotan D, Pode-Shakked N, Landau D, Svec P, Nampoothiri S, Verma I, Abu-Libdeh A, Bockenhauer D, Dekel B, Anikster Y. Familial Autosomal Recessive Renal Tubular Acidosis: Importance of Early Diagnosis. ACTA ACUST UNITED AC 2011; 119:p31-9. [DOI: 10.1159/000329668] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 05/24/2011] [Indexed: 01/01/2023]
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36
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Nowik M, Kampik NB, Mihailova M, Eladari D, Wagner CA. Induction of Metabolic Acidosis with Ammonium Chloride (NH 4Cl) in Mice and Rats – Species Differences and Technical Considerations. Cell Physiol Biochem 2010; 26:1059-72. [DOI: 10.1159/000323984] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/04/2010] [Indexed: 11/19/2022] Open
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Dos Santos PM, Freitas FP, Mendes J, Tararthuch AL, Fernandez R. Differential regulation of H+-ATPases in MDCK-C11 cells by aldosterone and vasopressin. Can J Physiol Pharmacol 2009; 87:653-65. [DOI: 10.1139/y09-057] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objective of the present work was to characterize the biochemical activity of the proton pumps present in the C11 clone of Madin–Darby canine kidney (MDCK) cells, akin to intercalated cells of the collecting duct, as well as to study their regulation by hormones like aldosterone and vasopressin. MDCK-C11 cells from passages 78 to 86 were utilized. The reaction to determine H+-ATPase activity was started by addition of cell homogenates to tubes contained the assay medium. The inorganic phosphate (Pi) released was determined by a colorimetric method modified from that described by Fiske and Subbarow. Changes in intracellular calcium concentration in the cells was determined using the Ca2+-sensing dye fluo-4 AM. Homogenates of MDCK-C11 cells present a bafilomycin-sensitive activity (vacuolar H+-ATPase), and a vanadate-sensitive activity (H+/K+-ATPase). The bafilomycin-sensitive activity showed a pH optimum of 6.12. ATPase activity was also stimulated in a dose-dependent fashion as K+ concentration was increased between 0 and 50 mmol·L–1, with an apparent Km for the release of Pi of 0.13 mmol·L–1 and Vmax of 22.01 nmol·mg–1·min–1. Incubation of cell monolayers with 10−8 mol·L–1 aldosterone for 24 h significantly increased vacuolar H+-ATPase activity, an effect prevented by 10−5 mol·L–1 spironolactone. Vacuolar H+-ATPase activity was also stimulated by 10−11 mol·L–1 vasopressin, an effect prevented by a V1 receptor-specific antagonist. This dose of vasopressin determined a sustained rise of cytosolic ionized calcium. We conclude that (i) homogenates of MDCK-C11 cells present a bafilomycin-sensitive (H+-ATPase) activity and a vanadate-sensitive (H+/K+-ATPase) activity, and (ii) vacuolar H+-ATPase activity is activated by aldosterone through a genomic pathway and by vasopressin through V1 receptors.
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Affiliation(s)
- Priscilla M.C. Dos Santos
- Department of Physiology, Division of Biological Sciences, Federal University of Paraná (UFPR), Paraná, Brazil
| | - Fabio P. Freitas
- Department of Physiology, Division of Biological Sciences, Federal University of Paraná (UFPR), Paraná, Brazil
| | - Jeane Mendes
- Department of Physiology, Division of Biological Sciences, Federal University of Paraná (UFPR), Paraná, Brazil
| | - Ana Lucia Tararthuch
- Department of Physiology, Division of Biological Sciences, Federal University of Paraná (UFPR), Paraná, Brazil
| | - Ricardo Fernandez
- Department of Physiology, Division of Biological Sciences, Federal University of Paraná (UFPR), Paraná, Brazil
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Mohebbi N, Mihailova M, Wagner CA. The calcineurin inhibitor FK506 (tacrolimus) is associated with transient metabolic acidosis and altered expression of renal acid-base transport proteins. Am J Physiol Renal Physiol 2009; 297:F499-509. [DOI: 10.1152/ajprenal.90489.2008] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Calcineurin inhibitors like FK506 (tacrolimus) are routinely used for immunosuppression following transplantation. Its use is limited by many side effects, including renal tubular acidosis (RTA), mainly of the distal type. In this study, rats were treated with FK506 and at baseline (after 9 days) systemic acid-base status was similar to that in control animals. However, FK506-treated rats given NH4Cl in the drinking water for 2 days developed a more severe metabolic acidosis than control animals. Urine pH was more alkaline, but net acid excretion was normal. After 7 days of acid load, all differences related to acid-base homeostasis were equalized in both groups. Protein abundance of type IIa Na-Pi cotransporter, type 3 Na+/H+ exchanger, and electrogenic Na+-bicarbonate cotransporter, and both a4 and B2 subunits of the vacuolar H+-ATPase were reduced under baseline conditions, while induction of metabolic acidosis enhanced protein abundance of these transporters in FK506-treated animals. In parallel, protein expression of AE1 was reduced at baseline and increased together with pendrin during NH4Cl loading in FK506 rats. Protein abundance of the Na+-bicarbonate cotransporter NBCn1 was reduced under baseline conditions but remained downregulated during metabolic acidosis. Morphological analysis revealed an increase in the relative number of non-type A intercalated cells in the connecting tubule and cortical collecting duct at the expense of principal cells. Additionally, subcellular distribution of the a4 subunit of the vacuolar H+-ATPase was affected by FK506 with less luminal localization in the connecting tubule and outer medullary collecting duct. These data suggest that FK506 impacts on several major acid-base transport proteins in the kidney, and its use is associated with transient metabolic acidosis and altered expression of key renal acid-base transport proteins.
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Busque SM, Wagner CA. Potassium restriction, high protein intake, and metabolic acidosis increase expression of the glutamine transporter SNAT3 (Slc38a3) in mouse kidney. Am J Physiol Renal Physiol 2009; 297:F440-50. [PMID: 19458124 DOI: 10.1152/ajprenal.90318.2008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Kidneys produce ammonium to buffer and excrete acids through metabolism of glutamine. Expression of the glutamine transporter Slc38a3 (SNAT3) increases in kidney during metabolic acidosis (MA), suggesting a role during ammoniagenesis. Potassium depletion and high dietary protein intake are known to elevate renal ammonium excretion. In this study, we examined SNAT3, phosphate-dependent glutaminase (PDG), and phosphoenolpyruvate carboxykinase (PEPCK) regulation during a control (0.36%) or low-K(+) (0.02%) diet for 7 or 14 days or a control (20%) or high-protein (50%) diet for 7 days. MA was induced in control and low-K(+) groups by addition of NH(4)Cl. Urinary ammonium excretion increased during MA, after 14-day K(+) restriction alone, and during high protein intake. SNAT3, PDG, and PEPCK mRNA abundance were elevated during MA and after 14-day K(+) restriction but not during high protein intake. SNAT3 protein abundance was enhanced during MA (both control and low K(+)), after 14-day low-K(+) treatment alone, and during high protein intake. Seven-day dietary K(+) depletion alone had no effect. Immunohistochemistry showed SNAT3 staining in earlier parts of the proximal tubule during 14-day K(+) restriction with and without NH(4)Cl treatment and during high protein intake. In summary, SNAT3, PDG, and PEPCK mRNA expression were congruent with urinary ammonium excretion during MA. Chronic dietary K(+) restriction, high protein intake, and MA enhance ammoniagenesis, an effect that may involve enhanced SNAT3 mRNA and protein expression. Our data suggest that SNAT3 plays an important role as the glutamine uptake mechanism in ammoniagenesis under these conditions.
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Affiliation(s)
- Stephanie M Busque
- Institute of Physiology, Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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Günzel D, Stuiver M, Kausalya PJ, Haisch L, Krug SM, Rosenthal R, Meij IC, Hunziker W, Fromm M, Müller D. Claudin-10 exists in six alternatively spliced isoforms that exhibit distinct localization and function. J Cell Sci 2009; 122:1507-17. [DOI: 10.1242/jcs.040113] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The tight junction protein claudin-10 is known to exist in two isoforms, resulting from two alternative exons, 1a and 1b (Cldn10a, Cldn10b). Here, we identified and characterized another four claudin-10 splice variants in mouse and human. One (Cldn10a_v1) results from an alternative splice donor site, causing a deletion of the last 57 nucleotides of exon 1a. For each of these three variants one further splice variant was identified (Cldn10a_v2, Cldn10a_v3, Cldn10b_v1), lacking exon 4. When transfected into MDCK cells, Cldn10a, Cldn10a_v1 and Cldn10b were inserted into the tight junction, whereas isoforms of splice variants lacking exon 4 were retained in the endoplasmic reticulum. Cldn10a transfection into MDCK cells confirmed the previously described increase in paracellular anion permeability. Cldn10a_v1 transfection had no direct effect, but modulated Cldn10a-induced organic anion permeability. At variance with previous reports in MDCK-II cells, transfection of high-resistance MDCK-C7 cells with Cldn10b dramatically decreased transepithelial resistance, increased cation permeability, and changed monovalent cation selectivity from Eisenman sequence IV to X, indicating the presence of a high field-strength binding site that almost completely removes the hydration shell of the permeating cations. The extent of all these effects strongly depended on the endogenous claudins of the transfected cells.
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Affiliation(s)
- Dorothee Günzel
- Institute of Clinical Physiology, Charité, 12200 Berlin, Germany
| | - Marchel Stuiver
- Department of Pediatric Nephrology, Charité, 13535 Berlin, Germany
| | - P. Jaya Kausalya
- Institute of Molecular and Cell Biology (IMCB), Singapore 138673
| | - Lea Haisch
- Department of Pediatric Nephrology, Charité, 13535 Berlin, Germany
| | - Susanne M. Krug
- Institute of Clinical Physiology, Charité, 12200 Berlin, Germany
| | - Rita Rosenthal
- Institute of Clinical Physiology, Charité, 12200 Berlin, Germany
| | - Iwan C. Meij
- Max-Delbrueck-Center for Molecular Medicine, 13125 Berlin, Germany
| | - Walter Hunziker
- Institute of Molecular and Cell Biology (IMCB), Singapore 138673
| | - Michael Fromm
- Institute of Clinical Physiology, Charité, 12200 Berlin, Germany
| | - Dominik Müller
- Department of Pediatric Nephrology, Charité, 13535 Berlin, Germany
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Wagner CA, Devuyst O, Bourgeois S, Mohebbi N. Regulated acid–base transport in the collecting duct. Pflugers Arch 2009; 458:137-56. [DOI: 10.1007/s00424-009-0657-z] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 02/22/2009] [Accepted: 02/24/2009] [Indexed: 02/07/2023]
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Hafner P, Grimaldi R, Capuano P, Capasso G, Wagner CA. Pendrin in the mouse kidney is primarily regulated by Cl− excretion but also by systemic metabolic acidosis. Am J Physiol Cell Physiol 2008; 295:C1658-67. [DOI: 10.1152/ajpcell.00419.2008] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Cl−/anion exchanger pendrin (SLC26A4) is expressed on the apical side of renal non-type A intercalated cells. The abundance of pendrin is reduced during metabolic acidosis induced by oral NH4Cl loading. More recently, it has been shown that pendrin expression is increased during conditions associated with decreased urinary Cl− excretion and decreased upon Cl− loading. Hence, it is unclear if pendrin regulation during NH4Cl-induced acidosis is primarily due the Cl− load or acidosis. Therefore, we treated mice to increase urinary acidification, induce metabolic acidosis, or provide an oral Cl− load and examined the systemic acid-base status, urinary acidification, urinary Cl− excretion, and pendrin abundance in the kidney. NaCl or NH4Cl increased urinary Cl− excretion, whereas (NH4)2SO4, Na2SO4, and acetazolamide treatments decreased urinary Cl− excretion. NH4Cl, (NH4)2SO4, and acetazolamide caused metabolic acidosis and stimulated urinary net acid excretion. Pendrin expression was reduced under NaCl, NH4Cl, and (NH4)2SO4 loading and increased with the other treatments. (NH4)2SO4 and acetazolamide treatments reduced the relative number of pendrin-expressing cells in the collecting duct. In a second series, animals were kept for 1 and 2 wk on a low-protein (20%) diet or a high-protein (50%) diet. The high-protein diet slightly increased urinary Cl− excretion and strongly stimulated net acid excretion but did not alter pendrin expression. Thus, pendrin expression is primarily correlated with urinary Cl− excretion but not blood Cl−. However, metabolic acidosis caused by acetazolamide or (NH4)2SO4 loading prevented the increase or even reduced pendrin expression despite low urinary Cl− excretion, suggesting an independent regulation by acid-base status.
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Abstract
H(+)-ATPases mediate urinary acidification along the collecting duct, and mutations in their B1 and a4 subunits result in distal renal tubular acidosis. The pathomechanisms by which these mutations affect pump activity are only poorly understood. Common polymorphisms may impair pump activity and may link the pump to a higher risk for alkaline urine and the development of kidney stones.
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Affiliation(s)
- C A Wagner
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
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44
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Su Y, Blake-Palmer KG, Sorrell S, Javid B, Bowers K, Zhou A, Chang SH, Qamar S, Karet FE. Human H+ATPase a4 subunit mutations causing renal tubular acidosis reveal a role for interaction with phosphofructokinase-1. Am J Physiol Renal Physiol 2008; 295:F950-8. [PMID: 18632794 PMCID: PMC2576143 DOI: 10.1152/ajprenal.90258.2008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The vacuolar-type ATPase (H+ATPase) is a ubiquitously expressed multisubunit pump whose regulation is poorly understood. Its membrane-integral a-subunit is involved in proton translocation and in humans has four forms, a1-a4. This study investigated two naturally occurring point mutations in a4's COOH terminus that cause recessive distal renal tubular acidosis (dRTA), R807Q and G820R. Both lie within a domain that binds the glycolytic enzyme phosphofructokinase-1 (PFK-1). We recreated these disease mutations in yeast to investigate effects on protein expression, H+ATPase assembly, targeting and activity, and performed in vitro PFK-1 binding and activity studies of mammalian proteins. Mammalian studies revealed complete loss of binding between the COOH terminus of a4 containing the G-to-R mutant and PFK-1, without affecting PFK-1's catalytic activity. In yeast expression studies, protein levels, H+ATPase assembly, and targeting of this mutant were all preserved. However, severe (78%) loss of proton transport but less decrease in ATPase activity (36%) were observed in mutant vacuoles, suggesting a requirement for the a-subunit/PFK-1 binding to couple these two functions. This role for PFK in H+ATPase function was supported by similar functional losses and uncoupling ratio between the two proton pump domains observed in vacuoles from a PFK-null strain, which was also unable to grow at alkaline pH. In contrast, the R-to-Q mutation dramatically reduced a-subunit production, abolishing H+ATPase function completely. Thus in the context of dRTA, stability and function of the metabolon composed of H+ATPase and glycolytic components can be compromised by either loss of required PFK-1 binding (G820R) or loss of pump protein (R807Q).
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Affiliation(s)
- Ya Su
- Department of Medical Genetics, Cambridge University, Cambridge Institute for Medical Research, Addenbrooke's Hospital Box 139, Cambridge, CB2 0XY, UK
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Sun X, Soleimani M, Petrovic S. Decreased expression of Slc26a4 (Pendrin) and Slc26a7 in the kidneys of carbonic anhydrase II-deficient mice. Cell Physiol Biochem 2008; 21:95-108. [PMID: 18209476 DOI: 10.1159/000113751] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2007] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Intercalated cells (ICs) of the kidney collecting duct are rich in carbonic anhydrase II (CAII), which facilitates proton and bicarbonate transport. Bicarbonate secretion is mediated via Pendrin (Slc26a4), which is expressed on the apical membrane of B-ICs and nonA-nonB ICs in the cortical collecting ducts (CCD). Bicarbonate absorption is mediated via anion exchanger 1 (AE1-Slc4a1) in the CCD and via AE1 and possibly Slc26a7 in the OMCD. Both exchangers are expressed on the basolateral membrane of A-ICs. The aim of this study was to examine the expression of pendrin, Slc26a7, and AE1 in the kidneys of CAII-deficient (CAR2-null) mice. METHODS For the expression studies, we used real-time RT-PCR, Northern hybridization, immunolabeling, and immunoblotting. RESULTS Pendrin mRNA expression was reduced 63% along with decreased pendrin immunolabeling in the cortex of CAR2-null mice present predominantly in nonA-nonB ICs. Slc26a7 mRNA expression was decreases by 73% and Slc26a7 immunolabeling, present in A-ICs, severely reduced in the outer medulla of CAR2-null mice. AE1 mRNA expression was decreased to a similar degree (62%) along with reduced AE1 immunolabeling. The expression of aquaporin 2 (AQP2) water channel, exclusively present in principal cells of the collecting duct, was comparable in the wild type and CAR2-null mice. CONCLUSION CAII deficiency results in a significant decrease in the gene and protein expression of bicarbonate transport proteins from Slc26 gene family - Slc26a4 (pendrin) and Slc26a7. These results emphasize the critical role of CAII for the maintenance of the intercalated cell phenotype.
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Affiliation(s)
- Xuming Sun
- Department of Medicine, University of Cincinnati, Cincinnati, OH 45267-0585, USA
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Nowik M, Lecca MR, Velic A, Rehrauer H, Brändli AW, Wagner CA. Genome-wide gene expression profiling reveals renal genes regulated during metabolic acidosis. Physiol Genomics 2007; 32:322-34. [PMID: 18056784 DOI: 10.1152/physiolgenomics.00160.2007] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Production and excretion of acids are balanced to maintain systemic acid-base homeostasis. During metabolic acidosis (MA) excess acid accumulates and is removed from the body, a process achieved, at least in part, by increasing renal acid excretion. This acid-secretory process requires the concerted regulation of metabolic and transport pathways, which are only partially understood. Chronic MA causes also morphological remodeling of the kidney. Therefore, we characterized transcriptional changes in mammalian kidney during MA to gain insights into adaptive pathways. Total kidney RNA from control and 2- and 7-days NH(4)Cl treated mice was subjected to microarray gene profiling. We identified 4,075 transcripts significantly (P < 0.05) regulated after 2 and/or 7 days of treatment. Microarray results were confirmed by qRT-PCR. Analysis of candidate genes revealed that a large group of regulated transcripts was represented by different solute carrier transporters, genes involved in cell growth, proliferation, apoptosis, water homeostasis, and ammoniagenesis. Pathway analysis revealed that oxidative phosphorylation was the most affected pathway. Interestingly, the majority of acutely regulated genes after 2 days, returned to normal values after 7 days suggesting that adaptation had occurred. Besides these temporal changes, we detected also differential regulation of selected genes (SNAT3, PEPCK, PDG) between early and late proximal tubule. In conclusion, the mammalian kidney responds to MA by temporally and spatially altering the expression of a large number of genes. Our analysis suggests that many of these genes may participate in various processes leading to adaptation and restoration of normal systemic acid-base and electrolyte homeostasis.
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Affiliation(s)
- Marta Nowik
- Institute of Physiology and Zurich Center for Human Integrative Physiology (ZIHP), University of Zurich
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Abstract
PURPOSE OF REVIEW Metabolic acidosis is a severe disturbance of extracellular pH homeostasis that can be caused both by inborn or acquired defects in renal acid excretion or metabolic acid production. Chronic metabolic acidosis causes osteomalacia with nephrocalcinosis and urolithiasis. In the setting of end-stage renal disease, metabolic acidosis is often associated with increased peripheral insulin resistance, and represents an additional independent morbidity risk factor. This review summarizes recent insight, gained primarily from mouse models, into the mechanisms whereby the kidney regulates and adapts acid excretion. RECENT FINDINGS Human genetics and various mouse models have shed new light on mechanisms that contribute to the kidney's ability to excrete acid and adapt appropriately to metabolism. Progress in four specific areas will be highlighted: mechanisms contributing to the synthesis and excretion of ammonia; insights into adaptive processes during acidosis; mechanisms by which the kidney may sense acidosis; and the pathophysiology of acquired and inborn errors of renal acid handling. SUMMARY Genetic mouse models and various messenger RNA and proteome profiling and screening technologies demonstrate the importance of various acid-base transporting proteins and a metabolic and regulatory network that contributes to the kidney's ability to maintain the systemic acid-base balance.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology and Zurich Center for Human Integrative Physiology (ZIHP), University of Zurich, Zurich, Switzerland.
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Abstract
Inherited acidosis may result from a primary renal defect in acid-base handling, emphasizing the central role of the kidney in control of body pH; as a secondary phenomenon resulting from abnormal renal electrolyte handling; or from excess production of acid elsewhere in the body. Here, we review our current understanding of the inherited renal acidoses at a genetic and molecular level.
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Affiliation(s)
- Andrew C Fry
- Department of Medical Genetics and Division of Renal Medicine, University of Cambridge, Cambridge Institute for Medical Research, UK
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Stehberger PA, Shmukler BE, Stuart-Tilley AK, Peters LL, Alper SL, Wagner CA. Distal renal tubular acidosis in mice lacking the AE1 (band3) Cl-/HCO3- exchanger (slc4a1). J Am Soc Nephrol 2007; 18:1408-18. [PMID: 17409310 DOI: 10.1681/asn.2006101072] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Mutations in the human gene that encodes the AE1 Cl(-)/HCO(3)(-) exchanger (SLC4A1) cause autosomal recessive and dominant forms of distal renal tubular acidosis (dRTA). A mouse model that lacks AE1/slc4a1 (slc4a1-/-) exhibited dRTA characterized by spontaneous hyperchloremic metabolic acidosis with low net acid excretion and, inappropriately, alkaline urine without bicarbonaturia. Basolateral Cl(-)/HCO(3)(-) exchange activity in acid-secretory intercalated cells of isolated superfused slc4a1-/- medullary collecting duct was reduced, but alternate bicarbonate transport pathways were upregulated. Homozygous mice had nephrocalcinosis associated with hypercalciuria, hyperphosphaturia, and hypocitraturia. A severe urinary concentration defect in slc4a1-/- mice was accompanied by dysregulated expression and localization of the aquaporin-2 water channel. Mice that were heterozygous for the AE1-deficient allele had no apparent defect. Thus, the slc4a1-/- mouse is the first genetic model of complete dRTA and demonstrates that the AE1/slc4a1 Cl(-)/HCO(3)(-) exchanger is required for maintenance of normal acid-base homeostasis by distal renal regeneration of bicarbonate in the mouse as well as in humans.
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Affiliation(s)
- Paul A Stehberger
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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Mohebbi N, Kovacikova J, Nowik M, Wagner CA. Thyroid hormone deficiency alters expression of acid-base transporters in rat kidney. Am J Physiol Renal Physiol 2007; 293:F416-27. [PMID: 17409279 DOI: 10.1152/ajprenal.00391.2006] [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
Hypothyroidism in humans is associated with incomplete distal renal tubular acidosis, presenting as the inability to respond appropriately to an acid challenge by excreting less acid. Here, we induced hypothyroidism in rats with methimazole (HYPO) and in one group substituted with l-thyroxine (EU). After 4 wk, acid-base status was similar in both groups. However, after 24 h acid loading with NH(4)Cl HYPO rats displayed a more pronounced metabolic acidosis. The expression of the Na(+)/H(+) exchanger NHE3, the Na(+)-phosphate cotransporter NaPi-IIa, and the B2 subunit of the vacuolar H(+)-ATPase was reduced in the brush-border membrane of the proximal tubule of the HYPO group, paralleled by a lower abundance of the Na(+)/HCO(3)(-) cotransporter NBCe1 and a higher expression of the acid-secretory type A intercalated cell-specific Cl(-)/HCO(3)(-) exchanger AE1. In contrast to control conditions, the expression of NBCe1 was increased in the HYPO group during metabolic acidosis. In addition, net acid excretion was similar in both groups. The relative number of type A intercalated cells was increased in the connecting tubule and cortical collecting duct of the HYPO group during acidosis. Thus thyroid hormones modulate the renal response to an acid challenge and alter the expression of several key acid-base transporters. Mild hypothyroidism is associated only with a very mild defect in renal acid handling, which appears to be mainly located in the proximal tubule and is compensated by the distal nephron.
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Affiliation(s)
- Nilufar Mohebbi
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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