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Daryadel A, Küng CJ, Haykir B, Sabrautzki S, de Angelis MH, Hernando N, Rubio-Aliaga I, Wagner CA. The calcium-sensing receptor has only a parathyroid hormone-dependent role in the acute response of renal phosphate transporters to phosphate intake. Am J Physiol Renal Physiol 2024; 326:F792-F801. [PMID: 38545651 DOI: 10.1152/ajprenal.00009.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 03/22/2024] [Accepted: 03/22/2024] [Indexed: 05/04/2024] Open
Abstract
The kidney controls systemic inorganic phosphate (Pi) levels by adapting reabsorption to Pi intake. Renal Pi reabsorption is mostly mediated by sodium-phosphate cotransporters NaPi-IIa (SLC34A1) and NaPi-IIc (SLC34A3) that are tightly controlled by various hormones including parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23). PTH and FGF23 rise in response to Pi intake and decrease NaPi-IIa and NaPi-IIc brush border membrane abundance enhancing phosphaturia. Phosphaturia and transporter regulation occurs even in the absence of PTH and FGF23 signaling. The calcium-sensing receptor (CaSR) regulates PTH and FGF23 secretion, and may also directly affect renal Pi handling. Here, we combined pharmacological and genetic approaches to examine the role of the CaSR in the acute phosphaturic response to Pi loading. Animals pretreated with the calcimimetic cinacalcet were hyperphosphatemic, had blunted PTH levels upon Pi administration, a reduced Pi-induced phosphaturia, and no Pi-induced NaPi-IIa downregulation. The calcilytic NPS-2143 exaggerated the PTH response to Pi loading but did not abolish Pi-induced downregulation of NaPi-IIa. In mice with a dominant inactivating mutation in the Casr (CasrBCH002), baseline NaPi-IIa expression was higher, whereas downregulation of transporter expression was blunted in double CasrBCH002/PTH knockout (KO) transgenic animals. Thus, in response to an acute Pi load, acute modulation of the CaSR affects the endocrine and renal response, whereas chronic genetic inactivation, displays only subtle differences in the downregulation of NaPi-IIa and NaPi-IIc renal expression. We did not find evidence that the CaSR impacts on the acute renal response to oral Pi loading beyond its role in regulating PTH secretion.NEW & NOTEWORTHY Consumption of phosphate-rich diets causes an adaptive response of the body leading to the urinary excretion of phosphate. The underlying mechanisms are still poorly understood. Here, we examined the role of the calcium-sensing receptor (CaSR) that senses both calcium and phosphate. We confirmed that the receptor increases the secretion of parathyroid hormone involved in stimulating urinary phosphate excretion. However, we did not find any evidence for a role of the receptor beyond this function.
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Affiliation(s)
- Arezoo Daryadel
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Catharina J Küng
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Betül Haykir
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Sibylle Sabrautzki
- Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Martin Hrabĕ de Angelis
- Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
- Lehrstuhl für Experimentelle Genetik, Technische Universität München, Freising, Germany
- Member of German Center for Diabetes Research, Neuherberg, Germany
| | - Nati Hernando
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | | | - Carsten A Wagner
- Institute of Physiology, University of Zürich, Zürich, Switzerland
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Haykir B, Moser SO, Pastor-Arroyo EM, Schnitzbauer U, Radvanyi Z, Prucker I, Qiu D, Fiedler D, Saiardi A, Jessen HJ, Hernando N, Wagner CA. The Ip6k1 and Ip6k2 Kinases Are Critical for Normal Renal Tubular Function. J Am Soc Nephrol 2024; 35:441-455. [PMID: 38317282 PMCID: PMC11000740 DOI: 10.1681/asn.0000000000000303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 12/24/2023] [Indexed: 02/07/2024] Open
Abstract
SIGNIFICANCE STATEMENT Kidneys are gatekeepers of systemic inorganic phosphate balance because they control urinary phosphate excretion. In yeast and plants, inositol hexakisphosphate kinases (IP6Ks) are central to regulate phosphate metabolism, whereas their role in mammalian phosphate homeostasis is mostly unknown. We demonstrate in a renal cell line and in mice that Ip6k1 and Ip6k2 are critical for normal expression and function of the major renal Na + /Pi transporters NaPi-IIa and NaPi-IIc. Moreover, Ip6k1/2-/- mice also show symptoms of more generalized kidney dysfunction. Thus, our results suggest that IP6Ks are essential for phosphate metabolism and proper kidney function in mammals. BACKGROUND Inorganic phosphate is an essential mineral, and its plasma levels are tightly regulated. In mammals, kidneys are critical for maintaining phosphate homeostasis through mechanisms that ultimately regulate the expression of the Na + /Pi cotransporters NaPi-IIa and NaPi-IIc in proximal tubules. Inositol pyrophosphate 5-IP 7 , generated by IP6Ks, is a main regulator of phosphate metabolism in yeast and plants. IP6Ks are conserved in mammals, but their role in phosphate metabolism in vivo remains unexplored. METHODS We used in vitro (opossum kidney cells) and in vivo (renal tubular-specific Ip6k1/2-/- mice) models to analyze the role of IP6K1/2 in phosphate homeostasis in mammals. RESULTS In both systems, Ip6k1 and Ip6k2 are responsible for synthesis of 5-IP 7 . Depletion of Ip6k1/2 in vitro reduced phosphate transport and mRNA expression of Na + /Pi cotransporters, and it blunts phosphate transport adaptation to changes in ambient phosphate. Renal ablation of both kinases in mice also downregulates the expression of NaPi-IIa and NaPi-IIc and lowered the uptake of phosphate into proximal renal brush border membranes. In addition, the absence of Ip6k1 and Ip6k2 reduced the plasma concentration of fibroblast growth factor 23 and increased bone resorption, despite of which homozygous males develop hypophosphatemia. Ip6k1/2-/- mice also show increased diuresis, albuminuria, and hypercalciuria, although the morphology of glomeruli and proximal brush border membrane seemed unaffected. CONCLUSIONS Depletion of renal Ip6k1/2 in mice not only altered phosphate homeostasis but also dysregulated other kidney functions.
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Affiliation(s)
- Betül Haykir
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Seraina Olivia Moser
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Eva Maria Pastor-Arroyo
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Udo Schnitzbauer
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Zsuzsa Radvanyi
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Isabel Prucker
- The Center for Integrative Biological Signalling Studies, Institute of Organic Chemistry and CIBSS, University of Freiburg, Freiburg, Germany
| | - Danye Qiu
- The Center for Integrative Biological Signalling Studies, Institute of Organic Chemistry and CIBSS, University of Freiburg, Freiburg, Germany
| | - Dorothea Fiedler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Henning J. Jessen
- The Center for Integrative Biological Signalling Studies, Institute of Organic Chemistry and CIBSS, University of Freiburg, Freiburg, Germany
| | - Nati Hernando
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Carsten A. Wagner
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
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Wang Q, Chen JJ, Wei LY, Ding Y, Liu M, Li WJ, Su C, Gong CX. Biallelic and monoallelic pathogenic variants in CYP24A1 and SLC34A1 genes cause idiopathic infantile hypercalcemia. Orphanet J Rare Dis 2024; 19:126. [PMID: 38504242 PMCID: PMC10953066 DOI: 10.1186/s13023-024-03135-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 03/11/2024] [Indexed: 03/21/2024] Open
Abstract
OBJECTIVE Idiopathic infantile hypercalcemia (IIH) is a rare disorder of PTH-independent hypercalcemia. CYP24A1 and SLC34A1 gene mutations cause two forms of hereditary IIH. In this study, the clinical manifestations and molecular aspects of six new Chinese patients were investigated. METHODS The clinical manifestations and laboratory study of six patients with idiopathic infantile hypercalcemia were analyzed retrospectively. RESULTS Five of the patients were diagnosed with hypercalcemia, hypercalciuria, and bilateral medullary nephrocalcinosis. Their clinical symptoms and biochemical abnormalities improved after treatment. One patient presented at age 11 years old with arterial hypertension, hypercalciuria and nephrocalcinosis, but normal serum calcium. Gene analysis showed that two patients had compound heterozygous mutations of CYP24A1, one patient had a monoallelic CYP24A1 variant, and three patients had a monoallelic SLC34A1 variant. Four novel CYP24A1 variants (c.116G > C, c.287T > A, c.476G > A and c.1349T > C) and three novel SLC34A1 variants (c.1322 A > G, c.1697_1698insT and c.1726T > C) were found in these patients. CONCLUSIONS A monoallelic variant of CYP24A1 or SLC34A1 gene contributes to symptomatic hypercalcemia, hypercalciuria and nephrocalcinosis. Manifestations of IIH vary with onset age. Hypercalcemia may not necessarily present after infancy and IIH should be considered in patients with nephrolithiasis either in older children or adults.
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Affiliation(s)
- Qiao Wang
- Department of Endocrinology, Genetics and Metabolism, Beijing Children's Hospital, 56# Nan Lishi Road, west district, Beijing, 100045, China
| | - Jia-Jia Chen
- Department of Endocrinology, Genetics and Metabolism, Beijing Children's Hospital, 56# Nan Lishi Road, west district, Beijing, 100045, China
| | - Li-Ya Wei
- Department of Endocrinology, Genetics and Metabolism, Beijing Children's Hospital, 56# Nan Lishi Road, west district, Beijing, 100045, China
| | - Yuan Ding
- Department of Endocrinology, Genetics and Metabolism, Beijing Children's Hospital, 56# Nan Lishi Road, west district, Beijing, 100045, China
| | - Min Liu
- Department of Endocrinology, Genetics and Metabolism, Beijing Children's Hospital, 56# Nan Lishi Road, west district, Beijing, 100045, China
| | - Wen-Jing Li
- Department of Endocrinology, Genetics and Metabolism, Beijing Children's Hospital, 56# Nan Lishi Road, west district, Beijing, 100045, China
| | - Chang Su
- Department of Endocrinology, Genetics and Metabolism, Beijing Children's Hospital, 56# Nan Lishi Road, west district, Beijing, 100045, China
| | - Chun-Xiu Gong
- Department of Endocrinology, Genetics and Metabolism, Beijing Children's Hospital, 56# Nan Lishi Road, west district, Beijing, 100045, China.
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Friedman PA, Sneddon WB, Mamonova T, Montanez-Miranda C, Ramineni S, Harbin NH, Squires KE, Gefter JV, Magyar CE, Emlet DR, Hepler JR. RGS14 regulates PTH- and FGF23-sensitive NPT2A-mediated renal phosphate uptake via binding to the NHERF1 scaffolding protein. J Biol Chem 2022; 298:101836. [PMID: 35307350 PMCID: PMC9035407 DOI: 10.1016/j.jbc.2022.101836] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 03/04/2022] [Accepted: 03/06/2022] [Indexed: 02/06/2023] Open
Abstract
Phosphate homeostasis, mediated by dietary intake, renal absorption, and bone deposition, is incompletely understood because of the uncharacterized roles of numerous implicated protein factors. Here, we identified a novel role for one such element, regulator of G protein signaling 14 (RGS14), suggested by genome-wide association studies to associate with dysregulated Pi levels. We show that human RGS14 possesses a carboxy-terminal PDZ ligand required for sodium phosphate cotransporter 2a (NPT2A) and sodium hydrogen exchanger regulatory factor-1 (NHERF1)-mediated renal Pi transport. In addition, we found using isotope uptake measurements combined with bioluminescence resonance energy transfer assays, siRNA knockdown, pull-down and overlay assays, and molecular modeling that secreted proteins parathyroid hormone (PTH) and fibroblast growth factor 23 inhibited Pi uptake by inducing dissociation of the NPT2A-NHERF1 complex. PTH failed to affect Pi transport in cells expressing RGS14, suggesting that it suppresses hormone-sensitive but not basal Pi uptake. Interestingly, RGS14 did not affect PTH-directed G protein activation or cAMP formation, implying a postreceptor site of action. Further pull-down experiments and direct binding assays indicated that NPT2A and RGS14 bind distinct PDZ domains on NHERF1. We showed that RGS14 expression in human renal proximal tubule epithelial cells blocked the effects of PTH and fibroblast growth factor 23 and stabilized the NPT2A-NHERF1 complex. In contrast, RGS14 genetic variants bearing mutations in the PDZ ligand disrupted RGS14 binding to NHERF1 and subsequent PTH-sensitive Pi transport. In conclusion, these findings identify RGS14 as a novel regulator of hormone-sensitive Pi transport. The results suggest that changes in RGS14 function or abundance may contribute to the hormone resistance and hyperphosphatemia observed in kidney diseases.
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Affiliation(s)
- Peter A Friedman
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA; Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
| | - W Bruce Sneddon
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Tatyana Mamonova
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Carolina Montanez-Miranda
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Suneela Ramineni
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Nicholas H Harbin
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Katherine E Squires
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Julia V Gefter
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Clara E Magyar
- Department of Pathology and Laboratory Medicine, The David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - David R Emlet
- Center for Critical Care Nephrology, Department of Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - John R Hepler
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, Georgia, USA.
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5
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Lenherr-Taube N, Young EJ, Furman M, Elia Y, Assor E, Chitayat D, Uster T, Kirwin S, Robbins K, Vinette KMB, Daneman A, Marshall CR, Collins C, Thummel K, Sochett E, Levine MA. Mild Idiopathic Infantile Hypercalcemia-Part 1: Biochemical and Genetic Findings. J Clin Endocrinol Metab 2021; 106:2915-2937. [PMID: 34125233 PMCID: PMC8475208 DOI: 10.1210/clinem/dgab431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Indexed: 11/19/2022]
Abstract
CONTEXT Idiopathic infantile hypercalcemia (IIH), an uncommon disorder characterized by elevated serum concentrations of 1,25 dihydroxyvitamin D (1,25(OH)2D) and low parathyroid hormone (PTH) levels, may present with mild to severe hypercalcemia during the first months of life. Biallelic variants in the CYP24A1 or SLC34A1 genes are associated with severe IIH. Little is known about milder forms. OBJECTIVE This work aims to characterize the genetic associations and biochemical profile of mild IIH. METHODS This is a cross-sectional study including children between age 6 months and 17 years with IIH who were followed in the Calcium Clinic at the Hospital for Sick Children (SickKids), Toronto, Canada. Twenty children with mild IIH on calcium-restricted diets were evaluated. We performed a dietary assessment and analyzed biochemical measures including vitamin D metabolites and performed a stepwise molecular genetic analysis. Complementary biochemical assessments and renal ultrasounds were offered to first-degree family members of positive probands. RESULTS The median age was 16 months. Median serum levels of calcium (2.69 mmol/L), urinary calcium:creatinine ratio (0.72 mmol/mmol), and 1,25(OH)2D (209 pmol/L) were elevated, whereas intact PTH was low normal (22.5 ng/L). Mean 1,25(OH)2D/PTH and 1,25(OH)2D/25(OH)D ratios were increased by comparison to healthy controls. Eleven individuals (55%) had renal calcification. Genetic variants were common (65%), with the majority being heterozygous variants in SLC34A1 and SLC34A3, while a minority showed variants of CYP24A1 and other genes related to hypercalciuria. CONCLUSION The milder form of IIH has a distinctive vitamin D metabolite profile and is primarily associated with heterozygous SLC34A1 and SLC34A3 variants.
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Affiliation(s)
- Nina Lenherr-Taube
- Department of Pediatrics, Division of Endocrinology, The Hospital for Sick Children, University of Toronto, M5G 1X8 Toronto, Ontario, Canada
| | - Edwin J Young
- Genome Diagnostics, Department of Paediatric Medicine, The Hospital for Sick Children, M5G 1X8 Toronto, Ontario, Canada
| | - Michelle Furman
- Department of Pediatrics, Division of Endocrinology, The Hospital for Sick Children, University of Toronto, M5G 1X8 Toronto, Ontario, Canada
| | - Yesmino Elia
- Department of Pediatrics, Division of Endocrinology, The Hospital for Sick Children, University of Toronto, M5G 1X8 Toronto, Ontario, Canada
| | - Esther Assor
- Department of Pediatrics, Division of Endocrinology, The Hospital for Sick Children, University of Toronto, M5G 1X8 Toronto, Ontario, Canada
| | - David Chitayat
- Department of Obstetrics and Gynecology, The Prenatal Diagnosis and Medical Genetics Program, Mount Sinai Hospital, University of Toronto, M5G 1X8 Toronto, Ontario, Canada
- Department of Pediatrics, Division of Clinical Genetics and Metabolism, The Hospital for Sick Children, University of Toronto, M5G 1X8 Toronto, Ontario, Canada
| | - Tami Uster
- Department of Obstetrics and Gynecology, The Prenatal Diagnosis and Medical Genetics Program, Mount Sinai Hospital, University of Toronto, M5G 1X8 Toronto, Ontario, Canada
| | - Susan Kirwin
- Nemours Molecular Diagnostics Laboratory, Nemours Children’s Health System, Wilmington, Delaware 19802, USA
| | - Katherine Robbins
- Nemours Molecular Diagnostics Laboratory, Nemours Children’s Health System, Wilmington, Delaware 19802, USA
| | - Kathleen M B Vinette
- Nemours Molecular Diagnostics Laboratory, Nemours Children’s Health System, Wilmington, Delaware 19802, USA
| | - Alan Daneman
- Department of Diagnostic Imaging, Division of General Radiology and Body Imaging, The Hospital for Sick Children, University of Toronto, M5G 1X8 Toronto, Ontario, Canada
| | - Christian R Marshall
- Genome Diagnostics, Department of Paediatric Medicine, The Hospital for Sick Children, M5G 1X8 Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, M5S 1A8 Toronto, Ontario, Canada
| | - Carol Collins
- Department of Pharmaceutics, University of Washington, Seattle, Washington 98195, USA
| | - Kenneth Thummel
- Department of Pharmaceutics, University of Washington, Seattle, Washington 98195, USA
| | - Etienne Sochett
- Department of Pediatrics, Division of Endocrinology, The Hospital for Sick Children, University of Toronto, M5G 1X8 Toronto, Ontario, Canada
| | - Michael A Levine
- Division of Endocrinology and Diabetes and Center for Bone Health, Children’s Hospital of Philadelphia and Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA
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6
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Kowalska E, Rola R, Wójcik M, Łaszcz N, Płudowski P, Wierzbicka A, Janiec A, Książyk J, Halat P, Ciara E, Obrycki Ł, Pronicka E, Litwin M. Analysis of vitamin D 3 metabolites in survivors of infantile idiopathic hypercalcemia caused by CYP24A1 mutation or SLC34A1 mutation. J Steroid Biochem Mol Biol 2021; 208:105824. [PMID: 33516786 DOI: 10.1016/j.jsbmb.2021.105824] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 12/06/2020] [Accepted: 01/14/2021] [Indexed: 12/24/2022]
Abstract
UNLABELLED Infantile hypercalcemia (IH), is a rare disorder caused by CYP24A1 or SLC34A1 variants which lead to disturbed catabolism of 25(OH)D3 and 125(OH)2D3 or increased generation of 125(OH)2D3. AIM OF STUDY To assess the status of 2425(OH)2D3 and other markers of vitamin D in IH survivors, in whom variants of CYP24A1 or SLC34A1 gene were found and to compare these unique biochemical features with those obtained from subjects who were diagnosed in the first year of life with hypercalcemia, elevated 25(OH)D3 and low PTH but in whom neither CYP24A1 nor SLC34A1 variant was found. PATIENTS AND METHODS 16 IH survivors in whom CYP24A1 (n = 13) or SLC34A1 (n = 3) variants were found and 41 subjects in whom hypercalcemia was diagnosed in the first year of life but in whom CYP24A1 or SLC34A1 variants were not found were included in the study. 25(OH)D3, 3-epi-25(OH)D3, 25(OH)D2, 2425(OH)2D3 were assessed by liquid chromatography coupled with tandem mass spectrometry. 125(OH)2D3 concentrations were assessed by chemiluminescence. RESULTS Subjects with CYP24A1 variants, despite normal 25(OH)D3 levels, had higher 25(OH)D3/2425(OH)2D3 ratio values (487; 265-1073 ng/mL) when compared to subjects with SLC34A1 variants (16; 16-23 ng/mL) and with subjects in whom CYP24A1 or SLC34A1 were not found (56; 9-56 ng/mL) (p = 0.00003). Separation of interfering metabolite further increased differences between subjects with and without CYP24A1 mutation. CONCLUSIONS Survivors of IH with CYP24A1 variant, despite being normocalcemic, still presented extremely high 25(OH)D3/2425(OH)2D3 ratio values. Separation of interfering compound further increased differences between subjects with CYP24A1 mutation and without this mutation.
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Affiliation(s)
- Ewa Kowalska
- Department of Biochemistry, Radioimmunology and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland
| | - Rafał Rola
- Department of Biochemistry, Radioimmunology and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland
| | - Marek Wójcik
- Department of Biochemistry, Radioimmunology and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland
| | - Natalia Łaszcz
- Department of Biochemistry, Radioimmunology and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland
| | - Paweł Płudowski
- Department of Biochemistry, Radioimmunology and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland
| | - Aldona Wierzbicka
- Department of Biochemistry, Radioimmunology and Experimental Medicine, The Children's Memorial Health Institute, Warsaw, Poland
| | - Agnieszka Janiec
- Department of Pediatrics and Nutrition, The Children's Memorial Health Institute, Warsaw, Poland
| | - Janusz Książyk
- Department of Pediatrics and Nutrition, The Children's Memorial Health Institute, Warsaw, Poland
| | - Paulina Halat
- Department of Medical Genetics, The Children's Memorial Health Institute, Warsaw, Poland
| | - Elżbieta Ciara
- Department of Medical Genetics, The Children's Memorial Health Institute, Warsaw, Poland
| | - Łukasz Obrycki
- Department of Nephrology and Arterial Hypertension, The Children's Memorial Health Institute, Warsaw, Poland
| | - Ewa Pronicka
- Department of Medical Genetics, The Children's Memorial Health Institute, Warsaw, Poland
| | - Mieczysław Litwin
- Department of Nephrology and Arterial Hypertension, The Children's Memorial Health Institute, Warsaw, Poland.
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7
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Molin A, Lemoine S, Kaufmann M, Breton P, Nowoczyn M, Ballandonne C, Coudray N, Mittre H, Richard N, Ryckwaert A, Lavillaureix A, Jones G, Bacchetta J, Kottler ML. Overlapping Phenotypes Associated With CYP24A1, SLC34A1, and SLC34A3 Mutations: A Cohort Study of Patients With Hypersensitivity to Vitamin D. Front Endocrinol (Lausanne) 2021; 12:736240. [PMID: 34721296 PMCID: PMC8548709 DOI: 10.3389/fendo.2021.736240] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Accepted: 09/07/2021] [Indexed: 12/14/2022] Open
Abstract
Mutations in CYP24A1 (vitamin D 24-hydroxylase) and SLC34A1 (renal phosphate transporter NPT2a) cause autosomal recessive Infantile Hypercalcemia type 1 and 2, illustrating links between vitamin D and phosphate metabolism. Patients may present with hypercalciuria and alternate between chronic phases with normal serum calcium but inappropriately high 1,25-(OH)2D and appropriately low PTH, and acute phases with hypercalcemia with suppressed PTH. Mutations in SLC34A3 and SLC9A3R1 have been associated with phosphate wasting without hypercalcemia. The aims of this study were to evaluate the frequency of mutations in these genes in patients with a medical history suggestive of CYP24A1 mutation to search for a specific pattern. Using next generation sequencing, we screened for mutations in 185 patients with PTH levels < 20 pg/mL, hypercalcemia and/or hypercalciuria, and relatives. Twenty-eight (15%) patients harbored biallelic mutations in CYP24A1 (25) and SLC34A3 (3), mostly associated with renal disease (lithiasis, nephrocalcinosis) (86%). Hypophosphatemia was found in 7 patients with biallelic mutations in CYP24A1 and a normal phosphatemia was reported in 2 patients with biallelic mutations in SLC34A3. Rare variations in SLC34A1 and SLC34A3 were mostly of uncertain significance. Fifteen patients (8%) carried only one heterozygous mutation. Heterozygous relatives carrying SLC34A1 or SLC34A3 variation may present with biochemical changes in mineral metabolism. Two patients' genotype may suggest digenism (heterozygous variations in different genes). No variation was found in SLC9A3R1. As no specific pattern can be found, patients with medical history suggestive of CYP24A1 mutation should benefit from SLC34A1 and SLC34A3 analysis.
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Affiliation(s)
- Arnaud Molin
- Caen University Hospital, Department of Genetics, Molecular Genetics Laboratory and Reference Center for Rare Diseases of Calcium and Phosphorus Metabolism (OSCAR), Caen, France
- Caen Normandy University, Medical School, Caen, France
- BioTARGEN, Caen Normandy University, Caen, France
- OeReCa, Caen Normandy University, Caen, France
- *Correspondence: Arnaud Molin,
| | - Sandrine Lemoine
- Department of Nephrology and Renal Functional Explorations, Edouard Herriot Hospital, Lyon, France
- University of Lyon, University of Lyon 1, Villeurbanne, France
| | - Martin Kaufmann
- Queen’s University, Department of Biomedical and Molecular Sciences, Kingston, ON, Canada
| | - Pierre Breton
- Caen University Hospital, Department of Genetics, Molecular Genetics Laboratory and Reference Center for Rare Diseases of Calcium and Phosphorus Metabolism (OSCAR), Caen, France
| | - Marie Nowoczyn
- Caen Normandy University, Medical School, Caen, France
- Caen University Hospital, Department of Biochemistry, Caen, France
| | | | - Nadia Coudray
- Caen University Hospital, Department of Genetics, Molecular Genetics Laboratory and Reference Center for Rare Diseases of Calcium and Phosphorus Metabolism (OSCAR), Caen, France
| | - Hervé Mittre
- Caen University Hospital, Department of Genetics, Molecular Genetics Laboratory and Reference Center for Rare Diseases of Calcium and Phosphorus Metabolism (OSCAR), Caen, France
- Caen Normandy University, Medical School, Caen, France
- OeReCa, Caen Normandy University, Caen, France
| | - Nicolas Richard
- Caen University Hospital, Department of Genetics, Molecular Genetics Laboratory and Reference Center for Rare Diseases of Calcium and Phosphorus Metabolism (OSCAR), Caen, France
- BioTARGEN, Caen Normandy University, Caen, France
| | - Amélie Ryckwaert
- Department of Pediatrics, Rennes University Hospital, Rennes, France
| | | | - Glenville Jones
- Queen’s University, Department of Biomedical and Molecular Sciences, Kingston, ON, Canada
| | - Justine Bacchetta
- University of Lyon, University of Lyon 1, Villeurbanne, France
- Reference Center for Rare Kidney Diseases (ORKID), Department of Pediatric Nephrology, Rhumatology and Dermatology, Woman Mother Children Hospital, Bron, France
- Reference Center for Rare Diseases of Calcium and Phosphorus Metabolism (OSCAR), Department of Pediatric Nephrology, Rhumatology and Dermatology, Woman Mother Children Hospital, Bron, France
- INSERM 1033, Bone Diseases Prevention, Lyon, France
| | - Marie-Laure Kottler
- Caen University Hospital, Department of Genetics, Molecular Genetics Laboratory and Reference Center for Rare Diseases of Calcium and Phosphorus Metabolism (OSCAR), Caen, France
- Caen Normandy University, Medical School, Caen, France
- BioTARGEN, Caen Normandy University, Caen, France
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8
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Clerin V, Saito H, Filipski KJ, Nguyen AH, Garren J, Kisucka J, Reyes M, Jüppner H. Selective pharmacological inhibition of the sodium-dependent phosphate cotransporter NPT2a promotes phosphate excretion. J Clin Invest 2020; 130:6510-6522. [PMID: 32853180 PMCID: PMC7685737 DOI: 10.1172/jci135665] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 08/20/2020] [Indexed: 12/16/2022] Open
Abstract
The sodium-phosphate cotransporter NPT2a plays a key role in the reabsorption of filtered phosphate in proximal renal tubules, thereby critically contributing to phosphate homeostasis. Inadequate urinary phosphate excretion can lead to severe hyperphosphatemia as in tumoral calcinosis and chronic kidney disease (CKD). Pharmacological inhibition of NPT2a may therefore represent an attractive approach for treating hyperphosphatemic conditions. The NPT2a-selective small-molecule inhibitor PF-06869206 was previously shown to reduce phosphate uptake in human proximal tubular cells in vitro. Here, we investigated the acute and chronic effects of the inhibitor in rodents and report that administration of PF-06869206 was well tolerated and elicited a dose-dependent increase in fractional phosphate excretion. This phosphaturic effect lowered plasma phosphate levels in WT mice and in rats with CKD due to subtotal nephrectomy. PF-06869206 had no effect on Npt2a-null mice, but promoted phosphate excretion and reduced phosphate levels in normophophatemic mice lacking Npt2c and in hyperphosphatemic mice lacking Fgf23 or Galnt3. In CKD rats, once-daily administration of PF-06869206 for 8 weeks induced an unabated acute phosphaturic and hypophosphatemic effect, but had no statistically significant effect on FGF23 or PTH levels. Selective pharmacological inhibition of NPT2a thus holds promise as a therapeutic option for genetic and acquired hyperphosphatemic disorders.
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Affiliation(s)
- Valerie Clerin
- Pfizer Inc., Worldwide Research, Development and Medical, Cambridge, Massachusetts, USA
| | | | - Kevin J. Filipski
- Pfizer Inc., Worldwide Research, Development and Medical, Cambridge, Massachusetts, USA
| | - An Hai Nguyen
- Pfizer Inc., Worldwide Research, Development and Medical, Cambridge, Massachusetts, USA
| | - Jeonifer Garren
- Pfizer Inc., Worldwide Research, Development and Medical, Cambridge, Massachusetts, USA
| | - Janka Kisucka
- Pfizer Inc., Worldwide Research, Development and Medical, Cambridge, Massachusetts, USA
| | | | - Harald Jüppner
- Endocrine Unit and
- Pediatric Nephrology Unit, Massachusetts General Hospital (MGH) and Harvard Medical School, Boston, Massachusetts, USA
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9
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De Paolis E, Scaglione GL, De Bonis M, Minucci A, Capoluongo E. CYP24A1 and SLC34A1 genetic defects associated with idiopathic infantile hypercalcemia: from genotype to phenotype. Clin Chem Lab Med 2020; 57:1650-1667. [PMID: 31188746 DOI: 10.1515/cclm-2018-1208] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 02/22/2019] [Indexed: 02/07/2023]
Abstract
Loss of function mutations in the CYP24A1 gene, involved in vitamin D catabolism and in calcium homeostasis, are known to be the genetic drivers of both idiopathic infantile hypercalcemia (IIH) and adult renal stone disease. Recently, also defects in the SLC34A1 gene, encoding for the renal sodium-phosphate transporter NaPi-IIa, were associated with the disease. IIH typically affects infants and pediatric patients with a syndrome characterized by severe hypercalcemia, hypercalciuria, suppressed parathyroid hormone level and nephrolithiasis. In SLC34A1 mutated carriers, hypophosphatemia is also a typical biochemical tract. IIH may also persist undiagnosed into adulthood, causing an increased risk of nephrocalcinosis and renal complication. To note, a clinical heterogeneity characterizes IIH manifestation, principally due to the controversial gene-dose effect and, to the strong influence of environmental factors. The present review is aimed to provide an overview of the current molecular findings on the IIH disorder, giving a comprehensive description of the association between genotype and biochemical and clinical phenotype of the affected patients. We also underline that patients may benefit from genetic testing into a targeted diagnostic and therapeutic workflow.
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Affiliation(s)
- Elisa De Paolis
- Laboratory of Molecular Diagnostics and Genomics, Teaching and Research Hospital "Fondazione Policlinico Agostino Gemelli" - IRCCS, Catholic University of the Sacred Heart, Rome, Italy
| | - Giovanni Luca Scaglione
- Laboratory of Molecular Oncology, "Fondazione Giovanni Paolo II", Catholic University of Sacred Heart, Campobasso, Italy
| | - Maria De Bonis
- Laboratory of Molecular Diagnostics and Genomics, Teaching and Research Hospital "Fondazione Policlinico Agostino Gemelli" - IRCCS, Catholic University of the Sacred Heart, Rome, Italy
| | - Angelo Minucci
- Laboratory of Molecular Diagnostics and Genomics, Teaching and Research Hospital "Fondazione Policlinico Agostino Gemelli" - IRCCS, Catholic University of the Sacred Heart, Rome, Italy
| | - Ettore Capoluongo
- Laboratory of Molecular Diagnostics and Genomics, Teaching and Research Hospital "Fondazione Policlinico Agostino Gemelli" - IRCCS, Catholic University of the Sacred Heart, Rome, Italy
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10
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Gordon RJ, Li D, Doyle D, Zaritsky J, Levine MA. Digenic Heterozygous Mutations in SLC34A3 and SLC34A1 Cause Dominant Hypophosphatemic Rickets with Hypercalciuria. J Clin Endocrinol Metab 2020; 105:dgaa217. [PMID: 32311027 PMCID: PMC7448300 DOI: 10.1210/clinem/dgaa217] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 04/16/2020] [Indexed: 12/13/2022]
Abstract
CONTEXT Hypophosphatemia and metabolic bone disease are associated with hereditary hypophosphatemic rickets with hypercalciuria (HHRH) due to biallelic mutations of SLC34A3 encoding the NPT2C sodium-phosphate cotransporter and nephrolithiasis/osteoporosis, hypophosphatemic 1 (NPHLOP1) due to monoallelic mutations in SLC34A1 encoding the NPT2A sodium-phosphate cotransporter. OBJECTIVE To identify a genetic cause of apparent dominant transmission of HHRH. DESIGN AND SETTING Retrospective and prospective analysis of clinical and molecular characteristics of patients studied in 2 academic medical centers. METHODS We recruited 4 affected and 3 unaffected members of a 4-generation family in which the proband presented with apparent HHRH. We performed clinical examinations, biochemical and radiological analyses, and molecular studies of genomic DNA. RESULTS The proband and her affected sister and mother carried pathogenic heterozygous mutations in 2 related genes, SLC34A1 (exon 13, c.1535G>A; p.R512H) and SLC34A3 (exon 13, c.1561dupC; L521Pfs*72). The proband and her affected sister inherited both gene mutations from their mother, while their clinically less affected brother, father, and paternal grandmother carried only the SLC34A3 mutation. Renal phosphate-wasting exhibited both a gene dosage-effect and an age-dependent attenuation of severity. CONCLUSIONS We describe a kindred with autosomal dominant hypophosphatemic rickets in which whole exome analysis identified digenic heterozygous mutations in SLC34A1 and SLC34A3. Subjects with both mutations were more severely affected than subjects carrying only one mutation. These findings highlight the challenges of assigning causality to plausible genetic variants in the next generation sequencing era.
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Affiliation(s)
- Rebecca J Gordon
- Division of Endocrinology, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts
- Division of Endocrinology and Diabetes and the Center for Bone Health, The Children’s Hospital of Philadelphia, and the Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Dong Li
- Center for Applied Genomics, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Daniel Doyle
- Division of Pediatric Endocrinology, Sidney Kimmel Medical College of Thomas Jefferson University and Nemours Alfred I. duPont Hospital for Children, Wilmington, Delaware
| | - Joshua Zaritsky
- Division of Pediatric Nephrology, Sidney Kimmel Medical College of Thomas Jefferson University and Nemours Alfred I. duPont Hospital for Children, Wilmington, Delaware
| | - Michael A Levine
- Division of Endocrinology and Diabetes and the Center for Bone Health, The Children’s Hospital of Philadelphia, and the Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
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11
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Martins JS, Liu ES, Sneddon WB, Friedman PA, Demay MB. 1,25-Dihydroxyvitamin D Maintains Brush Border Membrane NaPi2a and Attenuates Phosphaturia in Hyp Mice. Endocrinology 2019; 160:2204-2214. [PMID: 31237611 PMCID: PMC6735734 DOI: 10.1210/en.2019-00186] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 06/19/2019] [Indexed: 12/21/2022]
Abstract
Phosphate homeostasis is critical for many cellular processes and is tightly regulated. The sodium-dependent phosphate cotransporter, NaPi2a, is the major regulator of urinary phosphate reabsorption in the renal proximal tubule. Its activity is dependent upon its brush border localization that is regulated by fibroblast growth factor 23 (FGF23) and PTH. High levels of FGF23, as are seen in the Hyp mouse model of human X-linked hypophosphatemia, lead to renal phosphate wasting. Long-term treatment of Hyp mice with 1,25-dihydroxyvitamin D (1,25D) or 1,25D analogues has been shown to improve renal phosphate wasting in the setting of increased FGF23 mRNA expression. Studies were undertaken to define the cellular and molecular basis for this apparent FGF23 resistance. 1,25D increased FGF23 protein levels in the cortical bone and circulation of Hyp mice but did not impair FGF23 cleavage. 1,25D attenuated urinary phosphate wasting as early as one hour postadministration, without suppressing FGF23 receptor/coreceptor expression. Although 1,25D treatment induced expression of early growth response 1, an early FGF23 responsive gene required for its phosphaturic effects, it paradoxically enhanced renal phosphate reabsorption and NaPi2a protein expression in renal brush border membranes (BBMs) within one hour. The Na-H+ exchange regulatory factor 1 (NHERF1) is a scaffolding protein thought to anchor NaPi2a to the BBM. Although 1,25D did not alter NHERF1 protein levels acutely, it enhanced NHERF1-NaPi2a interactions in Hyp mice. 1,25D also prevented the decrease in NHERF1/NaPi2a interactions in PTH-treated wild-type mice. Thus, these investigations identify a novel role for 1,25D in the hormonal regulation of renal phosphate handling.
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Affiliation(s)
- Janaina S Martins
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
| | - Eva S Liu
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
- Division of Endocrinology Diabetes and Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts
| | - W Bruce Sneddon
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Peter A Friedman
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Marie B Demay
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
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12
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Chen X, Xie Y, Wan S, Xu J, Cai B, Zhang Y, Yu X. A novel heterozygous mutation c.680A>G (p. N227S) in SLC34A1 gene leading to autosomal dominant hypophosphatemia: A case report. Medicine (Baltimore) 2019; 98:e15617. [PMID: 31096470 PMCID: PMC6531229 DOI: 10.1097/md.0000000000015617] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
RATIONALE Currently, the relationship between heterozygous mutations in SLC34A1 and hypophosphatemia is controversial. Here we report an autosomal dominant hypophosphatemia pedigree carrying a novel heterozygous mutation in SLC34A1. PATIENT CONCERNS The proband is a 32-year old young man, presented with progressive pain and weakness in his lower extremities for more than 5 years. The proband showed persistent hypophosphatemia and low TmPO4/GFR values, indicating renal phosphate leak. His grandfather, father, and one of his uncles showed the similar symptoms. DIAGNOSES Autosomal dominant hypophosphatemia. INTERVENTIONS AND OUTCOMES Phosphorus supplement was prescribed to the proband and his affected uncle. Both their serum phosphorus levels recovered to normal and their symptoms such as back pain and lower extremity weakness were completely relieved. Whole exome sequencing was performed to identify disease-causing mutations in proband. LESSONS A novel heterozygous missense mutation c.680A>G (p. N227S) in exon 7 of SLC34A1 was found in proband by whole exome sequencing, which was also found in other 4 family members of this pedigree. Our report of an autosomal dominant hypophosphatemia pedigree with 5 mutant carriers enriches the clinical phenotype caused by the SLC34A1 mutations and further affirms the heterozygous mutations are causative for hypophosphatemia.
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Affiliation(s)
- Xiang Chen
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University
| | - Ying Xie
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University
| | - Shan Wan
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University
| | - Jin Xu
- Department of Laboratory Medicine, West China Hospital, Sichuan University
| | - Bei Cai
- Department of Laboratory Medicine, West China Hospital, Sichuan University
| | - Yi Zhang
- Core Facility of West China Hospital, Sichuan University, Chengdu, China
| | - Xijie Yu
- Laboratory of Endocrinology and Metabolism, Department of Endocrinology and Metabolism, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University
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13
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Amar A, Majmundar AJ, Ullah I, Afzal A, Braun DA, Shril S, Daga A, Jobst-Schwan T, Ahmad M, Sayer JA, Gee HY, Halbritter J, Knöpfel T, Hernando N, Werner A, Wagner C, Khaliq S, Hildebrandt F. Gene panel sequencing identifies a likely monogenic cause in 7% of 235 Pakistani families with nephrolithiasis. Hum Genet 2019; 138:211-219. [PMID: 30778725 PMCID: PMC6426152 DOI: 10.1007/s00439-019-01978-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 02/07/2019] [Indexed: 12/11/2022]
Abstract
Nephrolithiasis (NL) affects 1 in 11 individuals worldwide and causes significant patient morbidity. We previously demonstrated a genetic cause of NL can be identified in 11-29% of pre-dominantly American and European stone formers. Pakistan, which resides within the Afro-Asian stone belt, has a high prevalence of nephrolithiasis (12%) as well as high rate of consanguinity (> 50%). We recruited 235 Pakistani subjects hospitalized for nephrolithiasis from five tertiary hospitals in the Punjab province of Pakistan. Subjects were surveyed for age of onset, NL recurrence, and family history. We conducted high-throughput exon sequencing of 30 NL disease genes and variant analysis to identify monogenic causative mutations in each subject. We detected likely causative mutations in 4 of 30 disease genes, yielding a likely molecular diagnosis in 7% (17 of 235) of NL families. Only 1 of 17 causative mutations was identified in an autosomal recessive disease gene. 10 of the 12 detected mutations were novel mutations (83%). SLC34A1 was most frequently mutated (12 of 17 solved families). We observed a higher frequency of causative mutations in subjects with a positive NL family history (13/109, 12%) versus those with a negative family history (4/120, 3%). Five missense SLC34A1 variants identified through genetic analysis demonstrated defective phosphate transport. We examined the monogenic causes of NL in a novel geographic cohort and most frequently identified dominant mutations in the sodium-phosphate transporter SLC34A1 with functional validation.
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Affiliation(s)
- Ali Amar
- Division of Nephrology, Department of Medicine, Harvard Medical School, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA, 02115, USA
- Department of Human Genetics and Molecular Biology, University of Health Sciences, Lahore, Pakistan
| | - Amar J Majmundar
- Division of Nephrology, Department of Medicine, Harvard Medical School, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Ihsan Ullah
- Division of Nephrology, Department of Medicine, Harvard Medical School, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Ayesha Afzal
- Department of Human Genetics and Molecular Biology, University of Health Sciences, Lahore, Pakistan
| | - Daniela A Braun
- Division of Nephrology, Department of Medicine, Harvard Medical School, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Shirlee Shril
- Division of Nephrology, Department of Medicine, Harvard Medical School, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Ankana Daga
- Division of Nephrology, Department of Medicine, Harvard Medical School, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Tilman Jobst-Schwan
- Division of Nephrology, Department of Medicine, Harvard Medical School, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - Mumtaz Ahmad
- Ganga Ram Hospital and Fatima Jinnah Medical University, Lahore, Pakistan
| | - John A Sayer
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle, NE1 3BZ, UK
- The Newcastle upon Tyne Hospitals NHS Foundation Trust, Freeman Road, Newcastle, NE7 7DN, UK
- NIHR Newcastle Biomedical Research Centre, Newcastle, NE4 5PL, UK
| | - Heon Yung Gee
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul, South Korea
| | - Jan Halbritter
- Division of Nephrology, Department of Internal Medicine, University of Leipzig, Leipzig, Germany
| | - Thomas Knöpfel
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Andreas Werner
- Institute for Cell and Molecular Biosciences Newcastle University, Newcastle upon Tyne, UK
| | - Carsten Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Shagufta Khaliq
- Department of Human Genetics and Molecular Biology, University of Health Sciences, Lahore, Pakistan
| | - Friedhelm Hildebrandt
- Division of Nephrology, Department of Medicine, Harvard Medical School, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA, 02115, USA.
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14
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Fearn A, Allison B, Rice SJ, Edwards N, Halbritter J, Bourgeois S, Pastor‐Arroyo EM, Hildebrandt F, Tasic V, Wagner CA, Hernando N, Sayer JA, Werner A. Clinical, biochemical, and pathophysiological analysis of SLC34A1 mutations. Physiol Rep 2018; 6:e13715. [PMID: 29924459 PMCID: PMC6010730 DOI: 10.14814/phy2.13715] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 04/30/2018] [Accepted: 05/01/2018] [Indexed: 12/11/2022] Open
Abstract
Mutations in SLC34A1, encoding the proximal tubular sodium-phosphate transporter NaPi-IIa, may cause a range of clinical phenotypes including infantile hypercalcemia, a proximal renal Fanconi syndrome, which are typically autosomal recessive, and hypophosphatemic nephrolithiasis, which may be an autosomal dominant trait. Here, we report two patients with mixed clinical phenotypes, both with metabolic acidosis, hyperphosphaturia, and renal stones. Patient A had a single heterozygous pathogenic missense mutation (p.I456N) in SLC34A1, consistent with the autosomal dominant pattern of renal stone disease in this family. Patient B, with an autosomal recessive pattern of disease, was compound heterozygous for SLC34A1 variants; a missense variant (p.R512C) together with a relatively common in-frame deletion p.V91A97del7 (91del7). Xenopus oocyte and renal (HKC-8) cell line transfection studies of the variants revealed limited cell surface localization, consistent with trafficking defects. Co-expression of wild-type and I456N and 91del7 appeared to cause intracellular retention in HKC-8, whereas the R512C mutant had a less dominant effect. Expression in Xenopus oocytes failed to demonstrate a significant dominant negative effect for I456N and R512C; however, a negative impact of 91del7 on [32 P]phosphate transport was found. In conclusion, we have investigated pathogenic alleles of SLC34A1 which contribute to both autosomal dominant and autosomal recessive renal stone disease.
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Affiliation(s)
- Amy Fearn
- Institute for Cell and Molecular BiosciencesMedical SchoolNewcastle UniversityNewcastleUnited Kingdom
| | - Benjamin Allison
- Institute for Cell and Molecular BiosciencesMedical SchoolNewcastle UniversityNewcastleUnited Kingdom
| | - Sarah J. Rice
- Institute of Genetic MedicineNewcastle UniversityNewcastleUnited Kingdom
| | - Noel Edwards
- Institute of Genetic MedicineNewcastle UniversityNewcastleUnited Kingdom
| | - Jan Halbritter
- Division of NephrologyDepartment of Internal MedicineUniversity Clinic LeipzigLeipzigGermany
| | | | | | - Friedhelm Hildebrandt
- Department of MedicineBoston Children's HospitalHarvard Medical SchoolBostonMassachusetts
| | - Velibor Tasic
- Medical Faculty SkopjeUniversity Children's HospitalSkopjeMacedonia
| | | | - Nati Hernando
- Institute of PhysiologyUniversity of ZurichZurichSwitzerland
| | - John A. Sayer
- Institute of Genetic MedicineNewcastle UniversityNewcastleUnited Kingdom
- Renal ServicesNewcastle Upon Tyne NHS Foundation TrustNewcastleUnited Kingdom
| | - Andreas Werner
- Institute for Cell and Molecular BiosciencesMedical SchoolNewcastle UniversityNewcastleUnited Kingdom
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15
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Demir K, Yildiz M, Bahat H, Goldman M, Hassan N, Tzur S, Ofir A, Magen D. Clinical Heterogeneity and Phenotypic Expansion of NaPi-IIa-Associated Disease. J Clin Endocrinol Metab 2017; 102:4604-4614. [PMID: 29029121 DOI: 10.1210/jc.2017-01592] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Accepted: 09/22/2017] [Indexed: 12/21/2022]
Abstract
CONTEXT NaPi-IIa, encoded by SLC34A1, is a key phosphate transporter in the mammalian proximal tubule and plays a cardinal role in renal phosphate handling. NaPi-IIa impairment has been linked to various overlapping clinical syndromes, including hypophosphatemic nephrolithiasis with osteoporosis, renal Fanconi syndrome with chronic kidney disease, and, most recently, idiopathic infantile hypercalcemia and nephrocalcinosis. OBJECTIVES We studied the molecular basis of idiopathic infantile hypercalcemia with partial proximal tubulopathy in two apparently unrelated patients of Israeli and Turkish descent. DESIGN Genetic analysis in two affected children and their close relatives was performed using whole-exome sequencing, followed by in vitro localization and trafficking analysis of mutant NaPi-IIa. RESULTS Mutation and haplotype analyses in both patients revealed a previously described homozygous loss-of-function inserted duplication (p.I154_V160dup) in NaPi-IIa, which is inherited identical-by-descent from a common ancestor. The shared mutation was originally reported by our team in two adult siblings with renal Fanconi syndrome, hypophosphatemic bone disease, and progressive renal failure who are family members of one of the infants reported herein. In vitro localization assays and biochemical analysis of p.I154_V160dup and of additional NaPi-IIa mutants harboring a trafficking defect indicate aberrant retention at the endoplasmic reticulum in an immature and underglycosylated state, leading to premature proteasomal degradation. CONCLUSIONS Our findings expand the phenotypic spectrum of NaPi-IIa disruption, reinforce its link with proximal tubular impairment, enable longitudinal study of the natural history of the disease, and shed light on cellular pathways associated with loss of function and impaired trafficking of NaPi-IIa mutants.
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Affiliation(s)
- Korcan Demir
- Division of Pediatric Endocrinology, Faculty of Medicine, Dokuz Eylül University, Turkey
| | - Melek Yildiz
- Division of Pediatric Endocrinology, Dr. Behçet Uz Children's Hospital, Turkey
| | - Hilla Bahat
- Department of Pediatrics, Assaf Harofeh Medical Center, Israel, and Sackler Faculty of Medicine, Tel Aviv University, Israel
| | - Michael Goldman
- Department of Pediatrics, Assaf Harofeh Medical Center, Israel, and Sackler Faculty of Medicine, Tel Aviv University, Israel
| | - Nisreen Hassan
- Laboratory of Molecular Medicine, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Israel
| | - Shay Tzur
- Laboratory of Molecular Medicine, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Israel
- Genomic Research Department, Emedgene Technologies, Israel
| | - Ayala Ofir
- Laboratory of Molecular Medicine, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Israel
| | - Daniella Magen
- Laboratory of Molecular Medicine, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Israel
- Pediatric Nephrology Institute, Ruth Children's Hospital, Rambam Health Care Campus, Israel
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16
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Caballero D, Li Y, Fetene J, Ponsetto J, Chen A, Zhu C, Braddock DT, Bergwitz C. Intraperitoneal pyrophosphate treatment reduces renal calcifications in Npt2a null mice. PLoS One 2017; 12:e0180098. [PMID: 28704395 PMCID: PMC5509111 DOI: 10.1371/journal.pone.0180098] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 06/09/2017] [Indexed: 12/12/2022] Open
Abstract
Mutations in the proximal tubular sodium-dependent phosphate co-transporters NPT2a and NPT2c have been reported in patients with renal stone disease and nephrocalcinosis, however the relative contribution of genotype, dietary calcium and phosphate, and modifiers of mineralization such as pyrophosphate (PPi) to the formation of renal mineral deposits is unclear. In the present study, we used Npt2a-/- mice to model the renal calcifications observed in these disorders. We observed elevated urinary excretion of PPi in Npt2a-/- mice when compared to WT mice. Presence of two hypomorphic Extracellular nucleotide pyrophosphatase phosphodiesterase 1 (Enpp1asj/asj) alleles decreased urine PPi and worsened renal calcifications in Npt2a-/- mice. These studies suggest that PPi is a thus far unrecognized factor protecting Npt2a-/- mice from the development of renal mineral deposits. Consistent with this conclusion, we next showed that renal calcifications in these mice can be reduced by intraperitoneal administration of sodium pyrophosphate. If confirmed in humans, urine PPi could therefore be of interest for developing new strategies to prevent the nephrocalcinosis and nephrolithiasis seen in phosphaturic disorders.
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Affiliation(s)
- Daniel Caballero
- Department of Medicine, Section Endocrinology, Yale University School of Medicine, New Haven, CT, United States of America
| | - Yuwen Li
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, United States of America
- Department of Pediatrics, The First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu Province, China
| | - Jonathan Fetene
- Department of Medicine, Section Endocrinology, Yale University School of Medicine, New Haven, CT, United States of America
| | - Julian Ponsetto
- Department of Medicine, Section Endocrinology, Yale University School of Medicine, New Haven, CT, United States of America
| | - Alyssa Chen
- Department of Medicine, Section Endocrinology, Yale University School of Medicine, New Haven, CT, United States of America
| | - Chuanlong Zhu
- Gastroenterology Unit, Massachusetts General Hospital and Harvard Medical School, Boston, United States of America
- Department of Infectious Diseases, The First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu Province, China
| | - Demetrios T. Braddock
- Department of Pathology, Yale University School of Medicine, New Haven, CT, United States of America
| | - Clemens Bergwitz
- Department of Medicine, Section Endocrinology, Yale University School of Medicine, New Haven, CT, United States of America
- * E-mail:
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17
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Pokharel BB, Regassa A, Nyachoti CM, Kim WK. Effect of low levels of dietary available phosphorus on phosphorus utilization, bone mineralization, phosphorus transporter mRNA expression and performance in growing pigs. J Environ Sci Health B 2017; 52:395-401. [PMID: 28277077 DOI: 10.1080/03601234.2017.1292096] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A study was conducted to examine the effects of different dietary levels of available phosphorus (aP) on P excretion, bone mineralization, performance and the mRNA expression of sodium-dependent P transporters in growing pigs. Sixty-day old growing pigs (n = 54) with an average initial BW of 19.50 ± 1.11 kg were randomly allocated to a control diet (C) containing 0.23% available phosphorus (aP), T1 containing 0.17% aP and T2 containing 0.11% aP. There were 6 pens per treatment with 3 pigs per pen. Body weight and feed intake were measured weekly. At the end of each week, one pig from each pen was housed in a metabolic crate for 24 h to collect fecal and urine samples and then sacrificed to obtain third metacarpal (MC3) bones and jejunal and kidney samples. Bones were scanned by Dual Energy X-ray Absorptiometry (DEXA). Fecal and urine samples were sub-sampled and analyzed for P content. The expression of P transporter mRNA in jejunum and kidney samples was measured using quantitative real-time polymerase chain reaction (qRT-PCR). Data were analyzed using GLM procedure of the Statistical Analysis System (SAS Institute version 9.2). Pigs fed the T2 diet had reduced (P < 0.05) average daily gain (ADG) and gain to feed (G:F) compared to those fed the C diet during week 2. Overall, ADG and G:F were also reduced (P < 0.05) in pigs fed the T2 diet compared to those fed the C and T1 diets. Bone mineral density (BMD) and bone mineral content (BMC) were reduced (P < 0.05) in pigs fed the T2 diet compared to those fed the C diet throughout the experiment. At week 1, jejunal mRNA expression of Na (+)-dependent phosphate transporter 2 (SLC34A2) was increased (P < 0.01) in pigs fed the T2 diet compared to C diet. Renal mRNA expression of Na(+)-dependent phosphate transporter 1 (SLC34A1) and SLC34A3 were increased (P < 0.05) in pigs fed the T2 diet compared to those fed the C diet at week 2 and was accompanied by lower (P < 0.05) urinary P in pigs fed the T2 diet during week 2 and week 3. In conclusion, growing pigs are highly sensitive to low dietary P as shown by reduced ADG, bone mineralization and urinary P level, but moderate reduction in dietary P up to 0.17% aP in the diet has the potential to reduce environmental pollution by reducing P concentration in swine manure and without compromising performance.
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Affiliation(s)
- Bishwo B Pokharel
- a Department of Animal Science , University of Manitoba , Winnipeg , Manitoba , Canada
| | - Alemu Regassa
- a Department of Animal Science , University of Manitoba , Winnipeg , Manitoba , Canada
| | - Charles M Nyachoti
- a Department of Animal Science , University of Manitoba , Winnipeg , Manitoba , Canada
| | - Woo K Kim
- b Department of Poultry Science , University of Georgia , Athens , Georgia , USA
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18
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Li Y, Caballero D, Ponsetto J, Chen A, Zhu C, Guo J, Demay M, Jüppner H, Bergwitz C. Response of Npt2a knockout mice to dietary calcium and phosphorus. PLoS One 2017; 12:e0176232. [PMID: 28448530 PMCID: PMC5407772 DOI: 10.1371/journal.pone.0176232] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 04/08/2017] [Indexed: 01/08/2023] Open
Abstract
Mutations in the renal sodium-dependent phosphate co-transporters NPT2a and NPT2c have been reported in patients with renal stone disease and nephrocalcinosis, but the relative contribution of genotype, dietary calcium and phosphate to the formation of renal mineral deposits is unclear. We previously reported that renal calcium phosphate deposits persist and/or reappear in older Npt2a-/- mice supplemented with phosphate despite resolution of hypercalciuria while no deposits are seen in wild-type (WT) mice on the same diet. Addition of calcium to their diets further increased calcium phosphate deposits in Npt2a-/-, but not WT mice. The response of PTH to dietary phosphate of Npt2a-/- was blunted when compared to WT mice and the response of the urinary calcium x phosphorus product to the addition of calcium and phosphate to the diet of Npt2a-/- was increased. These finding suggests that Npt2a-/- mice respond differently to dietary phosphate when compared to WT mice. Further evaluation in the Npt2a-/- cohort on different diets suggests that urinary calcium excretion, plasma phosphate and FGF23 levels appear to be positively correlated to renal mineral deposit formation while urine phosphate levels and the urine anion gap, an indirect measure of ammonia excretion, appear to be inversely correlated. Our observations in Npt2a-/- mice, if confirmed in humans, may be relevant for the optimization of existing and the development of novel therapies to prevent nephrolithiasis and nephrocalcinosis in human carriers of NPT2a and NPT2c mutations.
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Affiliation(s)
- Yuwen Li
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Pediatrics, The First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu Province, China
| | - Daniel Caballero
- Section Endocrinology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Julian Ponsetto
- Section Endocrinology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Alyssa Chen
- Section Endocrinology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Chuanlong Zhu
- Gastroenterology Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Infectious Diseases, The First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu Province, China
| | - Jun Guo
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Marie Demay
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Harald Jüppner
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
- Pediatric Nephrology Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Clemens Bergwitz
- Section Endocrinology, Yale University School of Medicine, New Haven, Connecticut, United States of America
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19
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Mahajan A, Rodan AR, Le TH, Gaulton KJ, Haessler J, Stilp AM, Kamatani Y, Zhu G, Sofer T, Puri S, Schellinger JN, Chu PL, Cechova S, van Zuydam N, Arnlov J, Flessner MF, Giedraitis V, Heath AC, Kubo M, Larsson A, Lindgren CM, Madden PAF, Montgomery GW, Papanicolaou GJ, Reiner AP, Sundström J, Thornton TA, Lind L, Ingelsson E, Cai J, Martin NG, Kooperberg C, Matsuda K, Whitfield JB, Okada Y, Laurie CC, Morris AP, Franceschini N. Trans-ethnic Fine Mapping Highlights Kidney-Function Genes Linked to Salt Sensitivity. Am J Hum Genet 2016; 99:636-646. [PMID: 27588450 PMCID: PMC5011075 DOI: 10.1016/j.ajhg.2016.07.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 07/08/2016] [Indexed: 01/09/2023] Open
Abstract
We analyzed genome-wide association studies (GWASs), including data from 71,638 individuals from four ancestries, for estimated glomerular filtration rate (eGFR), a measure of kidney function used to define chronic kidney disease (CKD). We identified 20 loci attaining genome-wide-significant evidence of association (p < 5 × 10(-8)) with kidney function and highlighted that allelic effects on eGFR at lead SNPs are homogeneous across ancestries. We leveraged differences in the pattern of linkage disequilibrium between diverse populations to fine-map the 20 loci through construction of "credible sets" of variants driving eGFR association signals. Credible variants at the 20 eGFR loci were enriched for DNase I hypersensitivity sites (DHSs) in human kidney cells. DHS credible variants were expression quantitative trait loci for NFATC1 and RGS14 (at the SLC34A1 locus) in multiple tissues. Loss-of-function mutations in ancestral orthologs of both genes in Drosophila melanogaster were associated with altered sensitivity to salt stress. Renal mRNA expression of Nfatc1 and Rgs14 in a salt-sensitive mouse model was also reduced after exposure to a high-salt diet or induced CKD. Our study (1) demonstrates the utility of trans-ethnic fine mapping through integration of GWASs involving diverse populations with genomic annotation from relevant tissues to define molecular mechanisms by which association signals exert their effect and (2) suggests that salt sensitivity might be an important marker for biological processes that affect kidney function and CKD in humans.
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Affiliation(s)
- Anubha Mahajan
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Aylin R Rodan
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75229, USA
| | - Thu H Le
- Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA
| | - Kyle J Gaulton
- Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA
| | - Jeffrey Haessler
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Adrienne M Stilp
- Department of Biostatistics, University of Washington, Seattle, WA 98195, USA
| | - Yoichiro Kamatani
- Laboratory for Statistical Analysis, RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan
| | - Gu Zhu
- Genetic Epidemiology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane 4006, Australia
| | - Tamar Sofer
- Department of Biostatistics, University of Washington, Seattle, WA 98195, USA
| | - Sanjana Puri
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75229, USA
| | - Jeffrey N Schellinger
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75229, USA
| | - Pei-Lun Chu
- Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA
| | - Sylvia Cechova
- Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA
| | - Natalie van Zuydam
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Johan Arnlov
- Department of Medical Sciences, Cardiovascular Epidemiology, Uppsala University, Uppsala 751 85, Sweden; School of Health and Social Studies, Dalarna University, Falun 791 88, Sweden
| | - Michael F Flessner
- National Institute of Diabetes, Digestive, and Kidney Disease, NIH, Bethesda, MD 20892, USA
| | - Vilmantas Giedraitis
- Department of Public Health and Caring Sciences, Molecular Geriatrics, Uppsala University, Uppsala 752 37, Sweden
| | - Andrew C Heath
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Michiaki Kubo
- Laboratory for Genotyping Development, RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan
| | - Anders Larsson
- Department of Medical Sciences, Cardiovascular Epidemiology, Uppsala University, Uppsala 751 85, Sweden
| | - Cecilia M Lindgren
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK; Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford OX3 7BN, UK
| | - Pamela A F Madden
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Grant W Montgomery
- Molecular Epidemiology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane 4006, Australia
| | - George J Papanicolaou
- Epidemiology Branch, Division of Cardiovascular Sciences, National Heart, Lung and Blood Institute, Bethesda, MD 20892, USA
| | - Alex P Reiner
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Johan Sundström
- Department of Medical Sciences, Cardiovascular Epidemiology, Uppsala University, Uppsala 751 85, Sweden
| | - Timothy A Thornton
- Department of Biostatistics, University of Washington, Seattle, WA 98195, USA
| | - Lars Lind
- Department of Medical Sciences, Cardiovascular Epidemiology, Uppsala University, Uppsala 751 85, Sweden
| | - Erik Ingelsson
- Department of Medical Sciences, Molecular Epidemiology and Science for Life Laboratory, Uppsala University, Uppsala 752 37, Sweden; Department of Medicine, Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Jianwen Cai
- Collaborative Studies Coordinating Center, Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Nicholas G Martin
- Genetic Epidemiology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane 4006, Australia
| | - Charles Kooperberg
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Koichi Matsuda
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
| | - John B Whitfield
- Genetic Epidemiology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane 4006, Australia
| | - Yukinori Okada
- Laboratory for Statistical Analysis, RIKEN Center for Integrative Medical Sciences, Yokohama 230-0045, Japan; Department of Statistical Genetics, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Cathy C Laurie
- Department of Biostatistics, University of Washington, Seattle, WA 98195, USA
| | - Andrew P Morris
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK; Department of Biostatistics, University of Liverpool, Liverpool L69 3GL, UK.
| | - Nora Franceschini
- Department of Epidemiology, University of North Carolina, Chapel Hill, NC 27514, USA.
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20
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Webster R, Sheriff S, Faroqui R, Siddiqui F, Hawse JR, Amlal H. Klotho/fibroblast growth factor 23- and PTH-independent estrogen receptor-α-mediated direct downregulation of NaPi-IIa by estrogen in the mouse kidney. Am J Physiol Renal Physiol 2016; 311:F249-59. [PMID: 27194721 PMCID: PMC5008677 DOI: 10.1152/ajprenal.00542.2015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 05/16/2016] [Indexed: 01/26/2023] Open
Abstract
Estrogen treatment causes renal phosphate (Pi) wasting and hypophosphatemia in rats and humans; however, the signaling mechanisms mediating this effect are still poorly understood. To determine the specific roles of estrogen receptor isoforms (ERα and ERβ) and the Klotho pathway in mediating these effects, we studied the effects of estrogen on renal Pi handling in female mice with null mutations of ERα or ERβ or Klotho and their wild type (WT) using balance studies in metabolic cages. Estrogen treatment of WT and ERβ knockout (KO) mice caused a significant reduction in food intake along with increased renal phosphate wasting. The latter resulted from a significant downregulation of NaPi-IIa and NaPi-IIc protein abundance. The mRNA expression levels of both transporters were unchanged in estrogen-treated mice. These effects on both food intake and renal Pi handling were absent in ERα KO mice. Estrogen treatment of Klotho KO mice or parathyroid hormone (PTH)-depleted thyroparathyroidectomized mice exhibited a significant downregulation of NaPi-IIa with no change in the abundance of NaPi-IIc. Estrogen treatment of a cell line (U20S) stably coexpressing both ERα and ERβ caused a significant downregulation of NaPi-IIa protein when transiently transfected with a plasmid containing full-length or open-reading frame (ORF) 3'-untranslated region (UTR) but not 5'-UTR ORF of mouse NaPi-IIa transcript. In conclusion, estrogen causes phosphaturia and hypophosphatemia in mice. These effects result from downregulation of NaPi-IIa and NaPi-IIc proteins in the proximal tubule through the activation of ERα. The downregulation of NaPi-IIa by estrogen involves 3'-UTR of its mRNA and is independent of Klotho/fibroblast growth factor 23 and PTH signaling pathways.
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Affiliation(s)
- Rose Webster
- Division of Nephrology and Hypertension, Department of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Sulaiman Sheriff
- Department of Surgery, University of Cincinnati, Cincinnati, Ohio; and
| | - Rashma Faroqui
- Division of Nephrology and Hypertension, Department of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Faraaz Siddiqui
- Division of Nephrology and Hypertension, Department of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - John R Hawse
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota
| | - Hassane Amlal
- Division of Nephrology and Hypertension, Department of Medicine, University of Cincinnati, Cincinnati, Ohio;
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21
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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22
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Arcidiacono T, Mingione A, Macrina L, Pivari F, Soldati L, Vezzoli G. Idiopathic calcium nephrolithiasis: a review of pathogenic mechanisms in the light of genetic studies. Am J Nephrol 2014; 40:499-506. [PMID: 25504362 DOI: 10.1159/000369833] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Calcium nephrolithiasis is a multifactorial disease with a polygenic milieu. Association studies identified genetic polymorphisms potentially implicated in the pathogenesis of calcium nephrolithiasis. The present article reviews the mechanisms of calcium stone formation and the potential contribution of gene polymorphisms to lithogenic mechanisms. SUMMARY Endoscopy observations suggested that precipitation of calcium-oxalate on the Randall's plaque at the papilla surface may cause idiopathic calcium-oxalate stones. The Randall's plaque is a hydroxyapatite deposit in the interstitium of the kidney medulla, which resembles a soft tissue calcification. Conversely, calcium-phosphate stones may develop from crystalline deposits located at the tip of the Bellini duct. Polymorphisms of eleven genes have been associated with stones in genome-wide association studies and replicated candidate-gene association studies: VDR, SLC34A1, SLC34A4, CLDN14, and CaSR genes coding for proteins regulating tubular phosphate and calcium reabsorption; CaSR, MGP, OPN, PLAU, and UMOD genes coding for proteins preventing calcium salt precipitation; AQP1 gene coding for a water channel in the proximal tubule. The renal activity of the last gene, DGKH, is unknown. Polymorphisms in these genes may predispose to calcium-oxalate and -phosphate stones by increasing the risk of calcium-phosphate precipitation in the tubular fluid. Key Messages: Genetic findings suggest that tubular fluid supersaturation with respect to calcium and phosphate predisposes to calcium-oxalate stones by triggering cellular mechanisms that lead to the Randall's plaque formation.
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Affiliation(s)
- Teresa Arcidiacono
- Nephrology and Dialysis Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy
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23
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Rajagopal A, Braslavsky D, Lu JT, Kleppe S, Clément F, Cassinelli H, Liu DS, Liern JM, Vallejo G, Bergadá I, Gibbs RA, Campeau PM, Lee BH. Exome sequencing identifies a novel homozygous mutation in the phosphate transporter SLC34A1 in hypophosphatemia and nephrocalcinosis. J Clin Endocrinol Metab 2014; 99:E2451-6. [PMID: 25050900 PMCID: PMC4223446 DOI: 10.1210/jc.2014-1517] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Two Argentinean siblings (a boy and a girl) from a nonconsanguineous family presented with hypercalcemia, hypercalciuria, hypophosphatemia, low parathyroid hormone (PTH), and nephrocalcinosis. OBJECTIVE The goal of this study was to identify genetic causes of the clinical findings in the two siblings. DESIGN Whole exome sequencing was performed to identify disease-causing mutations in the youngest sibling, and a candidate variant was screened in other family members by Sanger sequencing. In vitro experiments were conducted to determine the effects of the mutation that was identified. PATIENTS AND OTHER PARTICIPANTS Affected siblings (2 y.o. female and 10 y.o male) and their parents were included in the study. Informed consent was obtained for genetic studies. RESULTS A novel homozygous mutation in the gene encoding the renal sodium-dependent phosphate transporter SLC34A1 was identified in both siblings (c.1484G>A, p.Arg495His). In vitro studies showed that the p.Arg495His mutation resulted in decreased phosphate uptake when compared to wild-type SLC34A1. CONCLUSIONS The homozygous G>A transition that results in the substitution of histidine for arginine at position 495 of the renal sodium-dependent phosphate transporter, SLC34A1, is involved in disease pathogenesis in these patients. Our report of the second family with two mutated SLC34A1 alleles expands the known phenotype of this rare condition.
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Affiliation(s)
- Abbhirami Rajagopal
- Department of Molecular and Human Genetics (A.R., D.L., R.G., P.C., B.L.), Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030; Centro de Investigaciones Endocrinológicas "Dr. César Bergadá" (CEDIE) (D.B., F.C., H.C., I.B.), CONICET - FEI - División de Endocrinología, Hospital de Niños Ricardo Gutiérrez, C1425FD Buenos Aires, Argentina; Human Genome Sequencing Center (J.T.L., R.G.), Department of Structural and Computational Biology and Molecular Biophysics (J.T.L.), Baylor College of Medicine, Houston, Texas 77030; Unidad de Metabolismo (S.K.), Hospital de Niños Ricardo Gutiérrez, C1425FD Buenos Aires, Argentina; Unidad de Nefrología (J.M.L., G.V.), Hospital de Niños Ricardo Gutiérrez, C1425FD Buenos Aires, Argentina; Howard Hughes Medical Institute (B.L.), Houston, Texas 77030
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Pantelic J, Ajdzanovic V, Medigovic I, Mojic M, Trifunovic S, Milosevic V, Filipovic B. Genistein affects parathyroid gland and NaPi 2a cotransporter in an animal model of the andropause. J Physiol Pharmacol 2013; 64:361-368. [PMID: 23959733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 05/29/2013] [Indexed: 06/02/2023]
Abstract
This study aimed to examine the effects of genistein on the structural and functional changes in parathyroid glands (PTG) and sodium phosphate cotransporter 2a (NaPi 2a) in orchidectomized rats. Sixteen-month-old Wistar rats were divided into sham-operated (SO), orchidectomized (Orx) and genistein-treated orchidectomized (Orx+G) groups. Genistein (30 mg/kg/day) was administered subcutaneously for 3 weeks, while the controls received vehicle alone. PTG was analyzed histomorphometrically, while the expressions of NaPi 2a mRNA/protein levels from kidneys were determined by real time PCR and Western blots. Serum and urine parameters were determined biochemically. The PTG volume in Orx rats was increased by 30% (p<0.05), compared to the SO group. Orx+G treatment increased the PTG volume by 35% and 75% (p<0.05) respectively, comparing to Orx and SO animals. Orchidectomy led to increment of serum PTH by 27% (p<0.05) compared to the SO group, Orx+G decreased it by 18% (p<0.05) comparing to Orx animals. NaPi 2a expression in Orx animals was reduced in regards to its abundance in SO animals, although it was increased in Orx+G group compared to the Orx. Phosphorus urine content of Orx animals was raised by 12% (p<0.05) compared to that for the SO group, while Orx+G induced a 17% reduction (p<0.05) in regards to Orx animals. Our study shows that Orx increases PTG volume and serum PTH level, while protein expression of NaPi 2a is reduced. Application of genistein attenuates the orchidectomy-induced changes in serum PTH level, stimulates the expression of NaPi 2a and reduces urinary Pi excretion, implying potential beneficial effects on andropausal symptoms.
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Affiliation(s)
- J Pantelic
- Department of Cytology, Institute for Biological Research Sinisa Stankovic, University of Belgrade, Belgrade, Serbia.
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Guo J, Song L, Liu M, Segawa H, Miyamoto KI, Bringhurst FR, Kronenberg HM, Jüppner H. Activation of a non-cAMP/PKA signaling pathway downstream of the PTH/PTHrP receptor is essential for a sustained hypophosphatemic response to PTH infusion in male mice. Endocrinology 2013; 154:1680-9. [PMID: 23515284 PMCID: PMC3628020 DOI: 10.1210/en.2012-2240] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
PTH increases urinary Pi excretion by reducing expression of two renal cotransporters [NaPi-IIa (Npt2a) and NaPi-IIc (Npt2c)]. In contrast to acute transporter regulation that is cAMP/protein kinase A dependent, long-term effects require phospholipase C (PLC) signaling by the PTH/PTHrP receptor (PPR). To determine whether the latter pathway regulates Pi through Npt2a and/or Npt2c, wild-type mice (Wt) and animals expressing a mutant PPR incapable of PLC activation (DD) were tested in the absence of one (Npt2a(-/-) or Npt2c(-/-)) or both phosphate transporters (2a/2c-dko). PTH infusion for 8 days caused a rapid and persistent decrease in serum Pi in Wt mice, whereas serum Pi in DD mice fell only transiently for the first 2 days. Consistent with these findings, fractional Pi excretion index was increased initially in both animals, but this increase persisted only when the PPR Wt was present. The hypophosphatemic response to PTH infusion was impaired only slightly in PPR Wt/Npt2c(-/-) or DD/Npt2c(-/-) mice. Despite lower baselines, PTH infusion in PPR Wt/Npt2a(-/-) mice decreased serum Pi further, an effect that was attenuated in DD/Npt2a(-/-) mice. Continuous PTH had no effect on serum Pi in 2a/2c-dko mice. PTH administration increased serum 1,25 dihydroxyvitamin D3 levels in Wt and DD mice and increased levels above the elevated baseline with ablation of either but not of both transporters. Continuous PTH elevated serum fibroblast growth factor 23 and blood Ca(2+) equivalently in all groups of mice. Our data indicate that PLC signaling at the PPR contributes to the long-term effect of PTH on Pi homeostasis but not to the regulation of 1,25 dihydroxyvitamin D3, fibroblast growth factor 23, or blood Ca(2+).
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MESH Headings
- Animals
- Cyclic AMP/metabolism
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Hypophosphatemia/chemically induced
- Hypophosphatemia/genetics
- Hypophosphatemia/metabolism
- Infusions, Intravenous
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mutation/physiology
- Parathyroid Hormone/administration & dosage
- Parathyroid Hormone/adverse effects
- Parathyroid Hormone/metabolism
- Receptor, Parathyroid Hormone, Type 1/genetics
- Receptor, Parathyroid Hormone, Type 1/metabolism
- Receptor, Parathyroid Hormone, Type 1/physiology
- Signal Transduction/genetics
- Signal Transduction/physiology
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type IIc/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIc/metabolism
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Affiliation(s)
- Jun Guo
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
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Mannstadt M, Magen D, Segawa H, Stanley T, Sharma A, Sasaki S, Bergwitz C, Mounien L, Boepple P, Thorens B, Zelikovic I, Jüppner H. Fanconi-Bickel syndrome and autosomal recessive proximal tubulopathy with hypercalciuria (ARPTH) are allelic variants caused by GLUT2 mutations. J Clin Endocrinol Metab 2012; 97:E1978-86. [PMID: 22865906 PMCID: PMC3462928 DOI: 10.1210/jc.2012-1279] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
CONTEXT Many inherited disorders of calcium and phosphate homeostasis are unexplained at the molecular level. OBJECTIVE The objective of the study was to identify the molecular basis of phosphate and calcium abnormalities in two unrelated, consanguineous families. PATIENTS The affected members in family 1 presented with rickets due to profound urinary phosphate-wasting and hypophosphatemic rickets. In the previously reported family 2, patients presented with proximal renal tubulopathy and hypercalciuria yet normal or only mildly increased urinary phosphate excretion. METHODS Genome-wide linkage scans and direct nucleotide sequence analyses of candidate genes were performed. Transport of glucose and phosphate by glucose transporter 2 (GLUT2) was assessed using Xenopus oocytes. Renal sodium-phosphate cotransporter 2a and 2c (Npt2a and Npt2c) expressions were evaluated in transgenically rescued Glut2-null mice (tgGlut2-/-). RESULTS In both families, genetic mapping and sequence analysis of candidate genes led to the identification of two novel homozygous mutations (IVS4-2A>G and R124S, respectively) in GLUT2, the gene mutated in Fanconi-Bickel syndrome, a rare disease usually characterized by renal tubulopathy, impaired glucose homeostasis, and hepatomegaly. Xenopus oocytes expressing the [R124S]GLUT2 mutant showed a significant reduction in glucose transport, but neither wild-type nor mutant GLUT2 facilitated phosphate import or export; tgGlut2-/- mice demonstrated a profound reduction of Npt2c expression in the proximal renal tubules. CONCLUSIONS Homozygous mutations in the facilitative glucose transporter GLUT2, which cause Fanconi-Bickel syndrome, can lead to very different clinical and biochemical findings that are not limited to mild proximal renal tubulopathy but can include significant hypercalciuria and highly variable degrees of urinary phosphate-wasting and hypophosphatemia, possibly because of the impaired proximal tubular expression of Npt2c.
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Affiliation(s)
- Michael Mannstadt
- Massachusetts General Hospital, Endocrine Unit, Harvard Medical School, Thier 1051, 55 Fruit Street, Boston Massachusetts 02114, USA.
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Courbebaisse M, Leroy C, Bakouh N, Salaün C, Beck L, Grandchamp B, Planelles G, Hall RA, Friedlander G, Prié D. A new human NHERF1 mutation decreases renal phosphate transporter NPT2a expression by a PTH-independent mechanism. PLoS One 2012; 7:e34764. [PMID: 22506049 PMCID: PMC3323571 DOI: 10.1371/journal.pone.0034764] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 03/05/2012] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The sodium-hydrogen exchanger regulatory factor 1 (NHERF1) binds to the main renal phosphate transporter NPT2a and to the parathyroid hormone (PTH) receptor. We have recently identified mutations in NHERF1 that decrease renal phosphate reabsorption by increasing PTH-induced cAMP production in the renal proximal tubule. METHODS We compared relevant parameters of phosphate homeostasis in a patient with a previously undescribed mutation in NHERF1 and in control subjects. We expressed the mutant NHERF1 protein in Xenopus Oocytes and in cultured cells to study its effects on phosphate transport and PTH-induced cAMP production. RESULTS We identified in a patient with inappropriate renal phosphate reabsorption a previously unidentified mutation (E68A) located in the PDZ1 domain of NHERF1.We report the consequences of this mutation on NHERF1 function. E68A mutation did not modify cAMP production in the patient. PTH-induced cAMP synthesis and PKC activity were not altered by E68A mutation in renal cells in culture. In contrast to wild-type NHERF1, expression of the E68A mutant in Xenopus oocytes and in human cells failed to increase phosphate transport. Pull down experiments showed that E68A mutant did not interact with NPT2a, which robustly interacted with wild type NHERF1 and previously identified mutants. Biotinylation studies revealed that E68A mutant was unable to increase cell surface expression of NPT2a. CONCLUSIONS Our results indicate that the PDZ1 domain is critical for NHERF1-NPT2a interaction in humans and for the control of NPT2a expression at the plasma membrane. Thus we have identified a new mechanism of renal phosphate loss and shown that different mutations in NHERF1 can alter renal phosphate reabsorption via distinct mechanisms.
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Affiliation(s)
- Marie Courbebaisse
- Faculté de Médecine, Université Paris Descartes, Paris, France
- Research Center, Growth and Signaling, INSERM U845, Paris, France
- Service de Physiologie - Explorations Fonctionnelles, Hôpital Necker-Enfants Malades, Paris, France
| | - Christine Leroy
- Research Center, Growth and Signaling, INSERM U845, Paris, France
| | - Naziha Bakouh
- Research Center, Growth and Signaling, INSERM U845, Paris, France
| | - Christine Salaün
- Research Center, Growth and Signaling, INSERM U845, Paris, France
| | - Laurent Beck
- Research Center, Growth and Signaling, INSERM U845, Paris, France
| | - Bernard Grandchamp
- Hôpital Bichat Claude Bernard, Institut Fédératif de Recherche 02, INSERM, Université Paris Diderot, Paris, France
| | | | - Randy A. Hall
- Department of Pharmacology, School of Medicine, Emory University, Atlanta, Georgia, United States of America
| | - Gérard Friedlander
- Faculté de Médecine, Université Paris Descartes, Paris, France
- Research Center, Growth and Signaling, INSERM U845, Paris, France
- Service de Physiologie - Explorations Fonctionnelles, Hôpital Européen Georges Pompidou, Paris, France
| | - Dominique Prié
- Faculté de Médecine, Université Paris Descartes, Paris, France
- Research Center, Growth and Signaling, INSERM U845, Paris, France
- Service de Physiologie - Explorations Fonctionnelles, Hôpital Necker-Enfants Malades, Paris, France
- * E-mail:
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28
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Seki G, Horita S, Suzuki M, Yamada H. [Renal tubular acidosis]. Nihon Jinzo Gakkai Shi 2011; 53:173-176. [PMID: 21516702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
MESH Headings
- Acidosis, Renal Tubular/genetics
- Amino Acid Transport Systems, Neutral/genetics
- Amino Acid Transport Systems, Neutral/physiology
- Anion Exchange Protein 1, Erythrocyte/genetics
- Anion Exchange Protein 1, Erythrocyte/physiology
- Fanconi Syndrome/etiology
- Genes, Recessive
- Humans
- Lysosomes/metabolism
- Mutation
- Sodium-Bicarbonate Symporters/genetics
- Sodium-Bicarbonate Symporters/physiology
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/physiology
- Sodium-Phosphate Cotransporter Proteins, Type IIc/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIc/physiology
- Vacuolar Proton-Translocating ATPases/genetics
- Vacuolar Proton-Translocating ATPases/physiology
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Abstract
Fibroblast growth factor-23 (FGF23), a hormone central to renal phosphate handling, is elevated in multiple hypophosphatemic disorders. Initial FGF23-dependent Erk1/2 activity in the kidney localizes to the distal convoluted tubule (DCT) with the co-receptor α-Klotho (KL), distinct from Npt2a in proximal tubules (PT). The Hyp mouse model of X-linked hypophosphatemic rickets (XLH) is characterized by hypophosphatemia with increased Fgf23, and patients with XLH elevate FGF23 following combination therapy of phosphate and calcitriol. The molecular signaling underlying renal FGF23 activity, and whether these pathways are altered in hypophosphatemic disorders, is unknown. To examine Npt2a in vivo, mice were injected with FGF23. Initial p-Erk1/2 activity in the DCT occurred within 10 min; however, Npt2a protein was latently reduced in the PT at 30-60 min, and was independent of Npt2a mRNA changes. KL-null mice had no DCT p-Erk1/2 staining following FGF23 delivery. Under basal conditions in Hyp mice, c-Fos and Egr1, markers of renal Fgf23 activity, were increased; however, KL mRNA was reduced 60% (P<0.05). Despite the prevailing hypophosphatemia and elevated Fgf23, FGF23 injections into Hyp mice activated p-Erk1/2 in the DCT. FGF23 injection also resulted in phospho-β-catenin (p-β-cat) co-localization with KL in wild-type mice, and Hyp mice demonstrated strong p-β-cat staining under basal conditions, indicating potential crosstalk between mitogen-activated protein kinase and Wnt signaling. Collectively, these studies refine the mechanisms for FGF23 bioactivity, and demonstrate novel suppression of Wnt signaling in a KL-dependent DCT-PT axis, which is likely altered in XLH. Finally, the current treatment of phosphate and calcitriol for hypophosphatemic disorders may increase FGF23 activity.
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Affiliation(s)
- Emily G. Farrow
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Lelia J. Summers
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
| | | | | | | | - Kenneth E. White
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
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31
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Miedlich SU, Zhu ED, Sabbagh Y, Demay MB. The receptor-dependent actions of 1,25-dihydroxyvitamin D are required for normal growth plate maturation in NPt2a knockout mice. Endocrinology 2010; 151:4607-12. [PMID: 20685875 PMCID: PMC2946147 DOI: 10.1210/en.2010-0354] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Rickets is a growth plate abnormality observed in growing animals and humans. Rachitic expansion of the hypertrophic chondrocyte layer of the growth plate, in the setting of hypophosphatemia, is due to impaired apoptosis of these cells. Rickets is observed in humans and mice with X-linked hypophosphatemia that is associated with renal phosphate wasting secondary to elevated levels of fibroblast growth factor-23. Rickets is also seen in settings of impaired vitamin D action, due to elevated PTH levels that increase renal phosphate excretion. However, mice with hypophosphatemia secondary to ablation of the renal sodium-dependent phosphate transport protein 2a (Npt2a), have not been reported to develop rickets. Because activation of the mitochondrial apoptotic pathway by phosphate is required for hypertrophic chondrocyte apoptosis in vivo, investigations were undertaken to address this paradox. Analyses of the Npt2a null growth plate demonstrate expansion of the hypertrophic chondrocyte layer at 2 wk of age, with resolution of this abnormality by 5 wk of age. This is temporally associated with an increase in circulating levels of 1,25-dihydroxyvitamin D. To address whether the receptor-dependent actions of this steroid hormone are required for normalization of the growth plate phenotype, the Npt2a null mice were mated with mice lacking the vitamin D receptor or were rendered vitamin D deficient. These studies demonstrate that the receptor-dependent actions of 1,25-dihydroxyvitamin D are required for maintenance of a normal growth plate phenotype in the Npt2a null mice.
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Affiliation(s)
- Susanne U Miedlich
- Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA
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32
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Affiliation(s)
- Richard S Bockman
- Division of Endocrinology, Weill Cornell Medical College of Cornell University and Hospital for Special Surgery, 535 East 70th Street, New York, New York 10021, USA.
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33
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Kempe DS, Ackermann TF, Boini KM, Klaus F, Umbach AT, Dërmaku-Sopjani M, Judenhofer MS, Pichler BJ, Capuano P, Stange G, Wagner CA, Birnbaum MJ, Pearce D, Föller M, Lang F. Akt2/PKBbeta-sensitive regulation of renal phosphate transport. Acta Physiol (Oxf) 2010; 200:75-85. [PMID: 20236253 DOI: 10.1111/j.1748-1716.2010.02109.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
AIM The protein kinase B (PKB)/Akt is known to stimulate the cellular uptake of glucose and amino acids. The kinase is expressed in proximal renal tubules. The present study explored the influence of Akt/PKB on renal tubular phosphate transport. METHODS The renal phosphate transporter NaPi-IIa was expressed in Xenopus oocytes with or without PKB/Akt and Na(+) phosphate cotransport determined using dual electrode voltage clamp. Renal phosphate excretion was determined in Akt2/PKBbeta knockout mice (akt2(-/-)) and corresponding wild-type mice (akt2(+/+)). Transporter protein abundance was determined using Western blotting and phosphate transport by (32)P uptake into brush border membrane vesicles. RESULTS The phosphate-induced current in NaPi-IIa-expressing Xenopus oocytes was significantly increased by the coexpression of Akt/PKB. Phosphate excretion [micromol per 24 h per g BW] was higher by 91% in akt2(-/-) than in akt2(+/+) mice. The phosphaturia of akt2(-/-) mice occurred despite normal transport activity and expression of the renal phosphate transporters NaPi-IIa, NaPi-IIc and Pit2 in the brush border membrane, a significantly decreased plasma PTH concentration (by 46%) and a significantly enhanced plasma 1,25-dihydroxyvitamin D(3) concentration (by 46%). Moreover, fractional renal Ca(2+) excretion was significantly enhanced (by 53%) and bone density significantly reduced (by 11%) in akt2(-/-) mice. CONCLUSIONS Akt2/PKBbeta plays a role in the acute regulation of renal phosphate transport and thus contributes to the maintenance of phosphate balance and adequate mineralization of bone.
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Affiliation(s)
- D S Kempe
- Department of Physiology, University of Tübingen, Tübingen, Germany
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34
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Guttmann-Rubinstein L, Lichtstein D, Ilani A, Gal-Moscovici A, Scherzer P, Rubinger D. Evidence of a parathyroid hormone-independent chronic effect of estrogen on renal phosphate handling and sodium-dependent phosphate cotransporter type IIa expression. Horm Metab Res 2010; 42:230-6. [PMID: 20119884 DOI: 10.1055/s-0029-1246182] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The effects of estrogen on phosphate metabolism are not well understood. To better define the chronic effects of estrogen on phosphate balance and on renal phosphate handling, the following groups were examined: A. young male and female rats, age- and weight-matched (age 8-10 weeks, 1 (st) study), and B. ovariectomized female rats (OVX), 22 weeks old, ovariectomized aged-matched rats receiving estrogen replacement (15 micromol x 3/week) for 14 weeks (OVX+E), control female rats (intact ovaries), and male rats, both age matched to OVX and OVX+E (2 (nd) Study). In younger females (1 (st) study), plasma phosphate was lower, whereas the urinary excretion of phosphate was higher than in males. In adult intact females and in OVX+E urinary excretion of phosphate was higher than in males and OVX (2 (nd) Study). In these rats, a significant correlation between plasma phosphate and estrogen level was found. Sodium-dependent phosphate cotransporter (NaPiIIa) mRNA expression and protein abundance were higher in the renal cortex of younger male rats than in age- and weight-matched females. In adult rats, NaPiIIa mRNA and protein abundance were higher in OVX than in OVX+E, and in mature males as compared with age-matched females. These differences were not related to the parathyroid hormone (PTH) levels. Chronic estrogen administration was also associated with increased plasma calcium level and urinary calcium excretion. These results suggest that chronic estrogen treatment is associated with an inhibitory, PTH-independent effect on the expression of NaPiIIa in the kidney, leading to sex-related differences in phosphate balance.
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Affiliation(s)
- L Guttmann-Rubinstein
- Department of Medicine, Hadassah University Medical Center, The Hebrew University Hadassah Medical School, Jerusalem, Israel
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35
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Magen D, Berger L, Coady MJ, Ilivitzki A, Militianu D, Tieder M, Selig S, Lapointe JY, Zelikovic I, Skorecki K. A loss-of-function mutation in NaPi-IIa and renal Fanconi's syndrome. N Engl J Med 2010; 362:1102-9. [PMID: 20335586 DOI: 10.1056/nejmoa0905647] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We describe two siblings from a consanguineous family with autosomal recessive Fanconi's syndrome and hypophosphatemic rickets. Genetic analysis revealed a homozygous in-frame duplication of 21 bp in SLC34A1, which encodes the renal sodium-inorganic phosphate cotransporter NaPi-IIa, as the causative mutation. Functional studies in Xenopus laevis oocytes and in opossum kidney cells indicated complete loss of function of the mutant NaPi-IIa, resulting from failure of the transporter to reach the plasma membrane. These findings show that disruption of the human NaPi-IIa profoundly impairs overall renal phosphate reabsorption and proximal-tubule function and provide evidence of the critical role of NaPi-IIa in human renal phosphate handling.
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Affiliation(s)
- Daniella Magen
- Pediatric Nephrology Unit, Rambam Health Care Campus, Haifa, Israel.
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36
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Lorenz-Depiereux B, Schnabel D, Tiosano D, Häusler G, Strom TM. Loss-of-function ENPP1 mutations cause both generalized arterial calcification of infancy and autosomal-recessive hypophosphatemic rickets. Am J Hum Genet 2010; 86:267-72. [PMID: 20137773 PMCID: PMC2820166 DOI: 10.1016/j.ajhg.2010.01.006] [Citation(s) in RCA: 248] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 01/04/2010] [Accepted: 01/08/2010] [Indexed: 01/08/2023] Open
Abstract
The analysis of rare genetic disorders affecting phosphate homeostasis led to the identification of several proteins that are essential for the renal regulation of phosphate homeostasis; for example, fibroblast growth factor 23 (FGF23), which inhibits renal phosphate reabsorption and 1,25-dihydroxyvitamin D synthesis. Here, we report presumable loss-of-function mutations in the ENPP1 gene (ectonucleotide pyrophosphatase/phosphodiesterase) in members of four families affected with hypophosphatemic rickets. We provide evidence for the conclusion that ENPP1 is the fourth gene-in addition to PHEX, FGF23, and DMP1-that, if mutated, causes hypophosphatemic rickets resulting from elevated FGF23 levels. Surprisingly, ENPP1 loss-of-function mutations have previously been described in generalized arterial calcification of infancy, suggesting an as yet elusive mechanism that balances arterial calcification with bone mineralization.
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Affiliation(s)
- Bettina Lorenz-Depiereux
- Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
| | - Dirk Schnabel
- Department of Pediatric Endocrinology, Charité-Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Dov Tiosano
- Pediatric Endocrinology, Meyer Children's Hospital, Rambam Medical Center, 31096 Haifa, Israel
- Faculty of Medicine, Technion-Israel Institute of Technology, 31096 Haifa, Israel
| | - Gabriele Häusler
- Department of Pediatrics, Medizinische Universität Wien, 1090 Vienna, Austria
| | - Tim M. Strom
- Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
- Institute of Human Genetics, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany
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37
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Reining SC, Gisler SM, Fuster D, Moe OW, O'Sullivan GA, Betz H, Biber J, Murer H, Hernando N. GABARAP deficiency modulates expression of NaPi-IIa in renal brush-border membranes. Am J Physiol Renal Physiol 2009; 296:F1118-28. [PMID: 19225049 PMCID: PMC2681362 DOI: 10.1152/ajprenal.90492.2008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Accepted: 02/13/2009] [Indexed: 01/04/2023] Open
Abstract
Renal reabsorption of inorganic phosphate (P(i)) is mainly mediated by the Na(+)-dependent P(i)-cotransporter NaPi-IIa that is expressed in the brush-border membrane (BBM) of renal proximal tubules. Regulation and apical expression of NaPi-IIa are known to depend on a network of interacting proteins. Most of the interacting partners identified so far associate with the COOH-terminal PDZ-binding motif (TRL) of NaPi-IIa. In this study GABA(A) receptor-associated protein (GABARAP) was identified as a novel interacting partner of NaPi-IIa applying a membrane yeast-two-hybrid system (MYTH 2.0) to screen a mouse kidney library with the TRL-truncated cotransporter as bait. GABARAP mRNA and protein are present in renal tubules, and the interaction of NaPi-IIa and GABARAP was confirmed by using glutathione S-transferase pulldowns from BBM and coimmunoprecipitations from transfected HEK293 cells. Amino acids 36-68 of GABARAP were identified as the determinant for the described interaction. The in vivo effects of this interaction were studied in a murine model. GABARAP(-/-) mice have reduced urinary excretion of P(i), higher Na(+)-dependent (32)P(i) uptake in BBM vesicles, and increased expression of NaPi-IIa in renal BBM compared with GABARAP(+/+) mice. The expression of Na(+)/H(+) exchanger regulatory factor (NHERF)1, an important scaffold for the apical expression of NaPi-IIa, is also increased in GABARAP(-/-) mice. The absence of GABARAP does not interfere with the regulation of the cotransporter by either parathyroid hormone or acute changes of dietary P(i) content.
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Affiliation(s)
- Sonja C Reining
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland
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Sitara D, Kim S, Razzaque MS, Bergwitz C, Taguchi T, Schüler C, Erben RG, Lanske B. Genetic evidence of serum phosphate-independent functions of FGF-23 on bone. PLoS Genet 2008; 4:e1000154. [PMID: 18688277 PMCID: PMC2483943 DOI: 10.1371/journal.pgen.1000154] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Accepted: 07/08/2008] [Indexed: 12/21/2022] Open
Abstract
Maintenance of physiologic phosphate balance is of crucial biological importance, as it is fundamental to cellular function, energy metabolism, and skeletal mineralization. Fibroblast growth factor-23 (FGF-23) is a master regulator of phosphate homeostasis, but the molecular mechanism of such regulation is not yet completely understood. Targeted disruption of the Fgf-23 gene in mice (Fgf-23−/−) elicits hyperphosphatemia, and an increase in renal sodium/phosphate co-transporter 2a (NaPi2a) protein abundance. To elucidate the pathophysiological role of augmented renal proximal tubular expression of NaPi2a in Fgf-23−/− mice and to examine serum phosphate–independent functions of Fgf23 in bone, we generated a new mouse line deficient in both Fgf-23 and NaPi2a genes, and determined the effect of genomic ablation of NaPi2a from Fgf-23−/− mice on phosphate homeostasis and skeletal mineralization. Fgf-23−/−/NaPi2a−/− double mutant mice are viable and exhibit normal physical activities when compared to Fgf-23−/− animals. Biochemical analyses show that ablation of NaPi2a from Fgf-23−/− mice reversed hyperphosphatemia to hypophosphatemia by 6 weeks of age. Surprisingly, despite the complete reversal of serum phosphate levels in Fgf-23−/−/NaPi2a−/−, their skeletal phenotype still resembles the one of Fgf23−/− animals. The results of this study provide the first genetic evidence of an in vivo pathologic role of NaPi2a in regulating abnormal phosphate homeostasis in Fgf-23−/− mice by deletion of both NaPi2a and Fgf-23 genes in the same animal. The persistence of the skeletal anomalies in double mutants suggests that Fgf-23 affects bone mineralization independently of systemic phosphate homeostasis. Finally, our data support (1) that regulation of phosphate homeostasis is a systemic effect of Fgf-23, while (2) skeletal mineralization and chondrocyte differentiation appear to be effects of Fgf-23 that are independent of phosphate homeostasis. Regulation of phosphate homeostasis is a tightly controlled hormonal process involving the intestine, kidneys, and bone, and imbalance of this homeostasis may influence overall mineralization. Fibroblast growth factor-23 (FGF-23) is a circulating hormone produced in the bone that mainly targets the kidneys to control the activity of the sodium/phosphate co-transporters NaPi2a and NaPi2c. These transporters are responsible for actively reabsorbing phosphate ions into the body to maintain physiological serum phosphate levels. Changes in FGF-23 activity lead to human disorders associated with either phosphate wasting or retention. Genetically altered mice in which Fgf-23 activity is lost exhibit severe hyperphosphatemia accompanied by increased NaPi2a activity, and they develop abnormal bone mineralization. Here we describe a new mouse model in which we eliminated NaPi2a from Fgf-23 null mice and show reversal of hyperphosphatemia to hypophosphatemia, suggesting that NaPi2a is the major regulator of phosphate homeostasis. However, the skeletal mineralization defect observed in mice lacking Fgf-23 function remained unchanged in the absence of NaPi2a in these mice. Thus our data indicate that Fgf-23 has a role in controlling bone mineralization independent of systemic phosphate levels.
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Affiliation(s)
- Despina Sitara
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts, United States of America
| | - Somi Kim
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts, United States of America
| | - Mohammed S. Razzaque
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts, United States of America
| | - Clemens Bergwitz
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Takashi Taguchi
- Department of Pathology, Nagasaki University School of Biomedical Sciences, Nagasaki, Japan
| | - Christiane Schüler
- Department of Natural Sciences, University of Veterinary Medicine, Vienna, Austria
| | - Reinhold G. Erben
- Department of Natural Sciences, University of Veterinary Medicine, Vienna, Austria
| | - Beate Lanske
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts, United States of America
- * E-mail:
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Marsell R, Krajisnik T, Göransson H, Ohlsson C, Ljunggren O, Larsson TE, Jonsson KB. Gene expression analysis of kidneys from transgenic mice expressing fibroblast growth factor-23. Nephrol Dial Transplant 2007; 23:827-33. [PMID: 17911089 DOI: 10.1093/ndt/gfm672] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Fibroblast growth factor-23 (FGF23), a circulating protein produced in bone, causes decreased renal inorganic phosphate (Pi) reabsorption by reducing the expression of the sodium phosphate cotransporter type 2a (Npt2a). We have previously generated transgenic mice expressing human wild-type (WT) FGF23 under the control of the alpha1 (I) collagen promoter. METHODS In this study, we performed a large-scale gene expression study of kidneys from FGF23 transgenic mice and WT littermates. Microarray expression data of key transcripts were verified by real-time RT-PCR analysis. RESULTS Several genes that play a role in Pi regulation revealed decreased expression levels in the transgenic mice, such as Npt2a and Pdzk1, a scaffolding protein known to interact with Npt2a. Importantly, Klotho, a suggested FGF23 receptor cofactor, was the most significantly decreased transcript and alpha2-Na(+)/K(+)-ATPase (Atp1a2), a gene isoform of alpha1-Na(+)/K(+)-ATPase (Atp1a1) which has recently been shown to interact with Klotho and regulate calcium metabolism, was the most increased transcript. In contrast, other genes proposed to regulate Pi levels, such as secreted frizzled-related protein-4 (sFrp4) and Na(+)/H(+) exchanger regulatory factor-1 (Nherf1) revealed no changes. CONCLUSIONS FGF23 transgenic mice display differentially expressed transcript levels of several genes essential in renal Pi regulation. These findings may lead to further understanding of how FGF23 mediates its actions on renal Pi regulation.
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Affiliation(s)
- Richard Marsell
- Department of Surgical Sciences, Uppsala University Hospital, Uppsala 751 85, Sweden.
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40
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Solomon DH, Wilkins RJ, Meredith D, Browning JA. Characterisation of inorganic phosphate transport in bovine articular chondrocytes. Cell Physiol Biochem 2007; 20:99-108. [PMID: 17595520 DOI: 10.1159/000104158] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2007] [Indexed: 11/19/2022] Open
Abstract
In mineralising tissues such as growth plate cartilage extracellular organelles derived from the chondrocyte membrane are present. These matrix vesicles (MV) possess membrane transporters that accumulate Ca(2+) and inorganic phosphate (P(i)), and initiate the formation of hydroxyapatite crystals. MV are also present in articular cartilage, and hydroxyapatite crystals are believed to promote cartilage degradation in osteoarthritic joints. In the present study, P(i) transport pathways in isolated bovine articular chondrocytes have been characterised. P(i) uptake was temperature-sensitive and could be resolved into Na(+)-dependent and Na(+)-independent components. The Na(+)-dependent component saturated at high concentrations of extracellular P(i), with a K(m) for P(i) of 0.17 mM. In solutions lacking Na(+), uptake did not fully saturate, implying that under these conditions carrier-mediated uptake is supplemented by a diffusive pathway. Both Na(+)-dependent and Na(+)-independent components were sensitive to the P(i) transport inhibitors phosphonoacetate and arsenate, although a fraction of Na(+)-independent P(i) uptake was resistant to these anions. Total P(i) uptake was optimal at pH 7.4, and reduced as pH was made more acidic or more alkaline, an effect that represented reduced Na(+)-dependent influx. RT-PCR analysis confirmed that two members of the NaPi III family, Pit-1 and Pit-2, are expressed, but that NaPi II transporters are not.
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MESH Headings
- Animals
- Arsenates/pharmacology
- Base Sequence
- Biological Transport, Active/drug effects
- Cartilage, Articular/cytology
- Cartilage, Articular/drug effects
- Cartilage, Articular/metabolism
- Cattle
- Chondrocytes/drug effects
- Chondrocytes/metabolism
- DNA Primers/genetics
- Hydrogen-Ion Concentration
- In Vitro Techniques
- Kinetics
- Male
- Phosphate Transport Proteins/metabolism
- Phosphates/metabolism
- Phosphonoacetic Acid/pharmacology
- RNA/genetics
- RNA/metabolism
- Sodium/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type III/genetics
- Sodium-Phosphate Cotransporter Proteins, Type III/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type IIb/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIb/metabolism
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Affiliation(s)
- Daniel H Solomon
- Department of Physiology, Anatomy and Genetics, Sherrington Building, Oxford, UK
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41
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Abstract
Inorganic phosphate (Pi) is fundamental to cellular metabolism and skeletal mineralization. Ingested Pi is absorbed by the small intestine, deposited in bone, and filtered by the kidney where it is reabsorbed and excreted in amounts determined by the specific needs of the organism. Two distinct renal Na-dependent Pi transporters, type IIa (NPT2a, SLC34A1) and type IIc (NPT2c, SLC34A3), are expressed in brush border membrane of proximal tubular cells where the bulk of filtered Pi is reabsorbed. Both are regulated by dietary Pi intake and parathyroid hormone. Regulation is achieved by changes in transporter protein abundance in the brush border membrane and requires the interaction of the transporter with scaffolding and signaling proteins. The demonstration of hypophosphatemia secondary to decreased renal Pi reabsorption in mice homozygous for the disrupted type IIa gene underscores its crucial role in the maintenance of Pi homeostasis. Moreover, the recent identification of mutations in the type IIc gene in patients with hereditary hypophosphatemic rickets with hypercalciuria attests to the importance of this transporter in Pi conservation and subsequent skeletal mineralization. Two novel Pi regulating genes, PHEX and FGF23, play a role in the pathophysiology of inherited and acquired hypophosphatemic skeletal disorders and studies are underway to define their mechanism of action on renal Pi handling in health and disease.
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42
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Rosenberg T, Shachaf C, Tzukerman M, Skorecki K. A murine transgenic model for transcriptional regulation of the Na/Pi-IIa major renal phosphate cotransporter. Am J Physiol Renal Physiol 2007; 292:F1617-25. [PMID: 17287201 DOI: 10.1152/ajprenal.00412.2006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Levels of the type IIa Na/P(i) (Na/Pi-IIa) cotransporter, which serves as the principal mediator of phosphate reabsorption in the kidney, can be modulated through posttranscriptional or posttranslational mechanisms by dietary, hormonal, and pharmacological influences. Previous studies have not demonstrated clear-cut evidence for modulation of Na/Pi-IIa cotransporter levels through transcriptional mechanisms. We have previously demonstrated that a 4.7-kb rat genomic fragment upstream of the rodent Npt2 gene encoding the Na/Pi-IIa cotransporter, is sufficient to mediate its transcriptional activity in vitro (Shachaf C, Skorecki KL, Tzukerman M. Am J Physiol Renal Physiol 278: F406-F416, 2000). Accordingly, we have established an in vivo experimental model in which this Npt2 genomic fragment fused upstream of a Lac Z reporter gene was expressed as a transgene in mice. The nine independent transgenic founder lines generated exhibited Lac Z reporter gene expression specifically in the renal cortex. This renal cortical-specific expression driven by the Npt2 promoter was confirmed at the mRNA and protein levels using RT-PCR, histochemistry, and Lac Z enzymatic activity. Furthermore, the expression of the transgene correlated with expression of the endogenous Npt2 gene during embryonic and early postnatal development. Thus we have generated a transgenic mouse model which will enable in vivo investigation of the contribution of transcriptional mechanisms to the overall regulation of Na/Pi-IIa expression under physiological and pathophysiological conditions.
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Affiliation(s)
- Tzur Rosenberg
- Rambam Medical Center, Technion-Israel Institute of Technology, Haifa, Israel
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43
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Abstract
The type IIa Na(+)/P(i) cotransporter (NaPi-IIa) plays a key role in the reabsorption of inorganic phosphate (P(i)) in the renal proximal tubule. The rat NaPi-IIa isoform is a protein of 637 residues for which different algorithms predict 8-12 transmembrane domains (TMDs). Epitope tagging experiments demonstrated that both the N and the C termini of NaPi-IIa are located intracellularly. Site-directed mutagenesis revealed two N-glycosylation sites in a large putative extracellular loop. Results from structure-function studies suggested the assembly of two similar opposed regions that possibly constitute part of the substrate translocation pathway for one phosphate ion together with three sodium ions. Apart from these topological aspects, other structural features of NaPi-IIa are not known. In this study, we have addressed the topology of NaPi-IIa using in vitro transcription/translation of HK-M0 and HK-M1 fusion vectors designed to test membrane insertion properties of cDNA sequences encoding putative NaPi-IIa TMDs. Based on the results of in vitro transcription/translation analyses, we propose a model of NaPi-IIa comprising 12 TMDs, with both N and C termini orientated intracellularly and a large hydrophilic extracellular loop between the fifth and sixth TMDs. The proposed model is in good agreement with the prediction of the NaPi-IIa structure obtained by the hidden Markov algorithm HMMTOP.
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Affiliation(s)
- Tamara Radanovic
- Institute of Physiology and Center for Integrative Human Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
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Nakagawa T, Yamaguchi M. Overexpression of regucalcin enhances its nuclear localization and suppresses L-type Ca2+ channel and calcium-sensing receptor mRNA expressions in cloned normal rat kidney proximal tubular epithelial NRK52E cells. J Cell Biochem 2006; 99:1064-77. [PMID: 16767692 DOI: 10.1002/jcb.20863] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The effect of regucalcin (RC), a regulatory protein in intracellular signaling pathway, on the gene expression of various mineral ion transport-related proteins was investigated using the cloned normal rat kidney proximal tubular epithelial NRK52E cells overexpressing RC. NRK52E cells (wild-type) and stable RC/pCXN2 transfectant were cultured for 72 h in medium containing 5% bovine serum (BS) to obtain subconfluent monolayers. After culture for 72 h, cells were further cultured 24-72 h in a medium containing either vehicle, aldosterone (10(-8) or 10(-7) M), or parathyroid hormone (PTH) (1-34) (10(-8) or 10(-7) M) without BS. RC was markedly localized in the nucleus of transfectants. Overexpression of RC caused a significant increase in rat outer medullary K(+) channel (ROMK) mRNA expression, while it caused a remarkable decrease in L-type Ca(2+) channel and calcium-sensing receptor (CaR) mRNA expressions. Overexpression of RC did not have an effect on epithelial sodium channel (ENaC), Na, K-ATPase (alpha-subunit), Type II Na-Pi cotransporter (NaPi-IIa), angiotensinogen, Na(+)-Ca(2+) exchanger, and glyceroaldehyde-3-phosphate dehydrogenase (G3PDH) mRNA expressions. Hormonal effect on gene expression, moreover, was examined. Culture with aldosterone (10(-8) or 10(-7) M) caused a significant increase in ENaC, Na, K-ATPase, and ROMK mRNA expressions in the wild-type cells. Those increases were weakened in the transfectants. Culture with PTH (10(-8) or 10(-7) M) significantly decreased NaPi-IIa mRNA expression in the wild-type cells. This effect was not altered in the transfectants. PTH significantly decreased angiotensinogen mRNA expression in the wild-type cells and the transfectants, while aldosterone had no effect. Culture with PTH (10(-8) or 10(-7) M) caused a significant decrease in L-type Ca(2+) channel and CaR mRNA expressions in the wild-type cells, while the hormone significantly increased Na(+)-Ca(2+) exchanger mRNA expression. The effects of PTH on L-type Ca(2+) channel, CaR, and Na(+)-Ca(2+) exchanger mRNA expressions were also seen in the transfectants. This study demonstrates that overexpression of RC caused a remarkable increase in its nuclear localization, and that it has suppressive effects on the gene expression of L-type Ca(2+) channel or CaR, which regulates intracellular Ca(2+) signaling, among various regulator proteins for mineral ions in NRK52E cells.
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Affiliation(s)
- Taeko Nakagawa
- Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
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Patzer L, Hernando N, Ziegler U, Beck-Schimmer B, Biber J, Murer H. Ifosfamide metabolites CAA, 4-OH-Ifo and Ifo-mustard reduce apical phosphate transport by changing NaPi-IIa in OK cells. Kidney Int 2006; 70:1725-34. [PMID: 17003823 DOI: 10.1038/sj.ki.5001803] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Renal Fanconi syndrome occurs in about 1-5% of all children treated with Ifosfamide (Ifo) and impairment of renal phosphate reabsorption in about 20-30% of them. Pathophysiological mechanisms of Ifo-induced nephropathy are ill defined. The aim has been to investigate whether Ifo metabolites affect the type IIa sodium-dependent phosphate transporter (NaPi-IIa) in viable opossum kidney cells. Ifo did not influence viability of cells or NaPi-IIa-mediated transport up to 1 mM/24 h. Incubation of confluent cells with chloroacetaldehyde (CAA) and 4-hydroperoxyIfosfamide (4-OH-Ifo) led to cell death by necrosis in a concentration-dependent manner. At low concentrations (50-100 microM/24 h), cell viability was normal but apical phosphate transport, NaPi-IIa protein, and -mRNA expression were significantly reduced. Coincubation with sodium-2-mercaptoethanesulfonate (MESNA) prevented the inhibitory action of CAA but not of 4-OH-Ifo; DiMESNA had no effect. Incubation with Ifosfamide-mustard (Ifo-mustard) did alter cell viability at concentrations above 500 microM/24 h. At lower concentrations (50-100 microM/24 h), it led to significant reduction in phosphate transport, NaPi-IIa protein, and mRNA expression. MESNA did not block these effects. The effect of Ifo-mustard was due to internalization of NaPi-IIa. Cyclophosphamide-mustard (CyP-mustard) did not have any influence on cell survival up to 1000 microM, but the inhibitory effect on phosphate transport and on NaPi-IIa protein was the same as found after Ifo-mustard. In conclusion, CAA, 4-OH-Ifo, and Ifo- and CyP-mustard are able to inhibit sodium-dependent phosphate cotransport in viable opossum kidney cells. The Ifo-mustard effect took place via internalization and reduction of de novo synthesis of NaPi-IIa. Therefore, it is possible that Ifo-mustard plays an important role in pathogenesis of Ifo-induced nephropathy.
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Affiliation(s)
- L Patzer
- Department of Pediatrics, Friedrich-Schiller-University, Jena, Germany.
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46
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Abstract
Members of the SLC34 gene family of solute carriers encode for three Na+-dependent phosphate (P i) cotransporter proteins, two of which (NaPi-IIa/SLC34A1 and NaPi-IIc/SLC34A3) control renal reabsorption of P i in the proximal tubule of mammals, whereas NaPi-IIb/SCLC34A2 mediates P i transport in organs other than the kidney. The P i transport mechanism has been extensively studied in heterologous expression systems and structure-function studies have begun to reveal the intricacies of the transport cycle at the molecular level using techniques such as cysteine scanning mutagenesis, and voltage clamp fluorometry. Moreover, sequence differences between the three types of cotransporters have been exploited to obtain information about the molecular determinants of hormonal sensitivity and electrogenicity. Renal handling of P i is regulated by hormonal and non-hormonal factors. Changes in urinary excretion of P i are almost invariably mirrored by changes in the apical expression of NaPi-IIa and NaPi-IIc in proximal tubules. Therefore, understanding the mechanisms that control the apical expression of NaPi-IIa and NaPi-IIc as well as their functional properties is critical to understanding how an organism achieves P i homeostasis.
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MESH Headings
- Animals
- Homeostasis
- Humans
- Kidney Tubules, Proximal/metabolism
- Mice
- Parathyroid Hormone/physiology
- Phosphates/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type IIa/chemistry
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type IIb/chemistry
- Sodium-Phosphate Cotransporter Proteins, Type IIb/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIb/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type IIc/chemistry
- Sodium-Phosphate Cotransporter Proteins, Type IIc/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIc/metabolism
- Structure-Activity Relationship
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Affiliation(s)
- I C Forster
- Institute of Physiology and ZIHP, Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
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47
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Lanaspa MA, Giral H, Breusegem SY, Halaihel N, Baile G, Catalán J, Carrodeguas JA, Barry NP, Levi M, Sorribas V. Interaction of MAP17 with NHERF3/4 induces translocation of the renal Na/Pi IIa transporter to the trans-Golgi. Am J Physiol Renal Physiol 2006; 292:F230-42. [PMID: 16926447 DOI: 10.1152/ajprenal.00075.2006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The function of the NaPiIIa renal sodium-phosphate transporter is regulated through a complex network of interacting proteins. Several PDZ domain-containing proteins interact with its COOH terminus while the small membrane protein MAP17 interacts with its NH(2) end. To elucidate the function of MAP17, we identified its interacting proteins using both bacterial and mammalian two-hybrid systems. Several PDZ domain-containing proteins, including the four NHERF proteins, as well as NaPiIIa and NHE3, were found to bind to MAP17. The interactions of MAP17 with the NHERF proteins and with NaPiIIa were further analyzed in opossum kidney (OK) cells. Expression of MAP17 alone had no effect on the NaPiIIa apical membrane distribution, but coexpression of MAP17 and NHERF3 or NHERF4 induced internalization of NaPiIIa, MAP17, and the PDZ protein to the trans-Golgi network (TGN). This effect was not observed when MAP17 was cotransfected with NHERF1/2 proteins. Inhibition of protein kinase C (PKC) prevented expression of the three proteins in the TGN. Activation of PKC in OK cells transfected only with MAP17 induced complete degradation of MAP17 and NaPiIIa. When lysosomal degradation was prevented, both proteins accumulated in the TGN. When the dopamine D1-like receptor was activated with fenoldopam, both NaPiIIa and MAP17 also accumulated in the TGN. Finally, cotransfection of MAP17 and NHERF3 prevented the adaptive upregulation of phosphate transport activity in OK cells in response to low extracellular phosphate. Therefore, the interaction between MAP17, NHERF3/4, and NaPiIIa in the TGN could be an important intermediate or alternate path in the internalization of NaPiIIa.
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MESH Headings
- Animals
- Cells, Cultured
- Cloning, Molecular
- Cycloheximide/pharmacology
- DNA, Complementary/biosynthesis
- DNA, Complementary/genetics
- Dopamine/pharmacology
- Glutathione/metabolism
- Golgi Apparatus/metabolism
- Male
- Membrane Proteins/genetics
- Membrane Proteins/physiology
- Membranes/metabolism
- Mice
- Microscopy, Fluorescence
- Microvilli/metabolism
- Mutagenesis, Site-Directed
- Nucleic Acid Hybridization
- Opossums/metabolism
- Phosphoproteins/genetics
- Phosphoproteins/physiology
- Protein Synthesis Inhibitors/pharmacology
- Rats
- Rats, Wistar
- Sodium-Hydrogen Exchangers/genetics
- Sodium-Hydrogen Exchangers/physiology
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/physiology
- Subcellular Fractions/metabolism
- Transfection
- Translocation, Genetic
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Affiliation(s)
- Miguel A Lanaspa
- Laboratory of Molecular Toxicology, Univ. of Zaragoza, Veterinary Faculty, Calle Miguel Servet 177, 50013 Zaragoza, Spain
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48
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Yamamoto H, Tani Y, Kobayashi K, Taketani Y, Sato T, Arai H, Morita K, Miyamoto KI, Pike JW, Kato S, Takeda E. Alternative promoters and renal cell-specific regulation of the mouse type IIa sodium-dependent phosphate cotransporter gene. ACTA ACUST UNITED AC 2005; 1732:43-52. [PMID: 16380173 DOI: 10.1016/j.bbaexp.2005.11.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2005] [Revised: 10/06/2005] [Accepted: 11/08/2005] [Indexed: 10/25/2022]
Abstract
The type IIa sodium-dependent phosphate cotransporter (NPT2a) expressed in renal proximal tubules represents an important determinant in maintaining inorganic phosphate (Pi) homeostasis. In the present study, we identified two variant transcripts of the mouse NPT2a gene, Npt2a-v1 and Npt2a-v2, characterized by the presence of alternative first exons (either exon 1A or exon 1B). The chromosomal structure analysis revealed that the Npt2a gene comprises of two promoters (promoters 1 and 2) and 14 exons, and spans approximately 17 kb. Quantitative PCR analysis showed that renal mRNA levels of both the variants markedly decreased in X-linked vitamin D-resistant hypophosphatemic rickets (Hyp) mice compared to normal littermates. Interestingly, transcriptional activity of a reporter gene, containing Npt2a promoters 1 and 2, was renal cell-specifically increased by 1alpha, 25(OH)2D3 and its analogs. The deletion analysis revealed that the CAAT box in the Npt2a promoter 2 is important for the 1alpha, 25(OH)2D3-dependent renal cell-specific activation of the reporter gene. These data suggested that two alternative promoters control the renal expression of Npt2a gene and both Npt2a variant transcripts are down regulated in Hyp mice.
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Affiliation(s)
- Hironori Yamamoto
- Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, Kuramoto-Cho 3-18-15, Tokushima City 770-8503, Japan.
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Nashiki K, Taketani Y, Takeichi T, Sawada N, Yamamoto H, Ichikawa M, Arai H, Miyamoto KI, Takeda E. Role of membrane microdomains in PTH-mediated down-regulation of NaPi-IIa in opossum kidney cells. Kidney Int 2005; 68:1137-47. [PMID: 16105044 DOI: 10.1111/j.1523-1755.2005.00505.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Parathyroid hormone (PTH) rapidly down-regulates type IIa sodium-dependent phosphate transporter (NaPi-IIa) via an endocytic pathway. Since the relationship between PTH signaling and NaPi-IIa endocytosis has not been explored, we investigated the role of membrane microdomains in this process. METHODS We examined the submembrane localization of NaPi-IIa in opossum kidney (OK-N2) cells that stably expressed human NaPi-IIa, and searched for a PTH-induced specific phosphorylating substrate on their membrane microdomains by immunoblotting with specific antibody against phospho substrates of protein kinases. RESULTS We found that NaPi-IIa was primarily localized in low-density membrane (LDM) domains of the plasma membrane; PTH reduced the levels of immunoreactive NaPi-IIa in these domains. Furthermore, PTH activated both protein kinase A (PKA) and protein kinase Calpha (PKCa) and increased the phosphorylation of 250 kD and 80 kD substrates; this latter substrate was identified as ezrin, which a member of the ezrin-radixin-moesin (ERM) protein family. In response to PTH, ezrin was phosphorylated by both PKA and PKC. Dominant negative ezrin blocked the reduction in NaPi-IIa expression in the LDM domains that was induced by PTH. CONCLUSION These data suggest that NaPi-IIa and PTH-induced phosphorylated proteins that include ezrin are compartmentalized in LDM microdomains. This compartmentalization may play an important role in the down-regulation of NaPi-IIa via endocytosis.
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Affiliation(s)
- Kunitaka Nashiki
- Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, Tokushima, Japan
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Rubinger D, Wald H, Gimelreich D, Halaihel N, Rogers T, Levi M, Popovtzer MM. Regulation of the renal sodium-dependent phosphate cotransporter NaPi2 (Npt2) in acute renal failure due to ischemia and reperfusion. Nephron Clin Pract 2005; 100:p1-12. [PMID: 15775707 DOI: 10.1159/000084463] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2003] [Accepted: 01/12/2005] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND Acute renal failure (ARF) is associated with hyperphosphatemia and decreased urinary phosphate excretion. The present study was undertaken to characterize the effects of ARF due to ischemia and reperfusion on renal phosphate transport and on gene and protein expression of type IIa NaPi cotransporter (Npt2) the physiologically most relevant renal sodium-dependent phosphate cotransporter. METHODS The following groups of rats with intact parathyroid glands were studied: (1) sham operated (sham); (2) after 1 h ischemia by bilateral renal artery clamping (I), and after 1 h ischemia and reperfusion of 1 h (I + R 1 h); (3) 24 h (I + R 24 h); (4) 48 h (I + R 48 h), and (5) 72 h (I + R 72 h) duration. The effect of ARF on Npt2 mRNA and protein expression was also examined after parathyroidectomy (PTX) of 2 and 4 days' duration. RESULTS Ischemia and reperfusion were associated with increases in plasma creatinine, hyperphosphatemia, and with decreased tubular phosphate reabsorption. Npt2 mRNA was significantly downregulated in the cortex, maximal at 24 and 48 h of reperfusion. The degree of Npt2 mRNA downregulation was not affected by PTX of 2-4 days' duration. The abundance of Npt2 protein in proximal tubular apical brush border membrane was markedly decreased after reperfusion. Npt2 protein, however, was more abundant in PTX animals than in those with intact parathyroids and a similar degree of renal insufficiency. The immunohistochemical analysis of proximal tubular apical brush border membrane showed a progressive decrease of Npt2 protein labeling after ischemia and reperfusion, with progressive regeneration after 72 h. CONCLUSION These results suggest that downregulation of Npt2 protein may contribute to the decreased tubular reabsorption of phosphate in acute ischemic renal failure and hyperphosphatemia.
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