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Gefen AM, Zaritsky JJ. Review of childhood genetic nephrolithiasis and nephrocalcinosis. Front Genet 2024; 15:1381174. [PMID: 38606357 PMCID: PMC11007102 DOI: 10.3389/fgene.2024.1381174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Accepted: 03/04/2024] [Indexed: 04/13/2024] Open
Abstract
Nephrolithiasis (NL) is a common condition worldwide. The incidence of NL and nephrocalcinosis (NC) has been increasing, along with their associated morbidity and economic burden. The etiology of NL and NC is multifactorial and includes both environmental components and genetic components, with multiple studies showing high heritability. Causative gene variants have been detected in up to 32% of children with NL and NC. Children with NL and NC are genotypically heterogenous, but often phenotypically relatively homogenous, and there are subsequently little data on the predictors of genetic childhood NL and NC. Most genetic diseases associated with NL and NC are secondary to hypercalciuria, including those secondary to hypercalcemia, renal phosphate wasting, renal magnesium wasting, distal renal tubular acidosis (RTA), proximal tubulopathies, mixed or variable tubulopathies, Bartter syndrome, hyperaldosteronism and pseudohyperaldosteronism, and hyperparathyroidism and hypoparathyroidism. The remaining minority of genetic diseases associated with NL and NC are secondary to hyperoxaluria, cystinuria, hyperuricosuria, xanthinuria, other metabolic disorders, and multifactorial etiologies. Genome-wide association studies (GWAS) in adults have identified multiple polygenic traits associated with NL and NC, often involving genes that are involved in calcium, phosphorus, magnesium, and vitamin D homeostasis. Compared to adults, there is a relative paucity of studies in children with NL and NC. This review aims to focus on the genetic component of NL and NC in children.
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Affiliation(s)
- Ashley M. Gefen
- Phoenix Children’s Hospital, Department of Pediatrics, Division of Nephrology, Phoenix, AZ, United States
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2
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Friedman P, Mamonova T. The molecular sociology of NHERF1 PDZ proteins controlling renal hormone-regulated phosphate transport. Biosci Rep 2024; 44:BSR20231380. [PMID: 38465463 PMCID: PMC10987488 DOI: 10.1042/bsr20231380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 03/07/2024] [Accepted: 03/08/2024] [Indexed: 03/12/2024] Open
Abstract
Parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF23) control extracellular phosphate levels by regulating renal NPT2A-mediated phosphate transport by a process requiring the PDZ scaffold protein NHERF1. NHERF1 possesses two PDZ domains, PDZ1 and PDZ2, with identical core-binding GYGF motifs explicitly recognizing distinct binding partners that play different and specific roles in hormone-regulated phosphate transport. The interaction of PDZ1 and the carboxy-terminal PDZ-binding motif of NPT2A (C-TRL) is required for basal phosphate transport. PDZ2 is a regulatory domain that scaffolds multiple biological targets, including kinases and phosphatases involved in FGF23 and PTH signaling. FGF23 and PTH trigger disassembly of the NHERF1-NPT2A complex through reversible hormone-stimulated phosphorylation with ensuing NPT2A sequestration, down-regulation, and cessation of phosphate absorption. In the absence of NHERF1-NPT2A interaction, inhibition of FGF23 or PTH signaling results in disordered phosphate homeostasis and phosphate wasting. Additional studies are crucial to elucidate how NHERF1 spatiotemporally coordinates cellular partners to regulate extracellular phosphate levels.
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Affiliation(s)
- Peter A. Friedman
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, U.S.A
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, U.S.A
| | - Tatyana Mamonova
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, U.S.A
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Bosman W, Franken GAC, de Las Heras J, Madariaga L, Barakat TS, Oostenbrink R, van Slegtenhorst M, Perdomo-Ramírez A, Claverie-Martín F, van Eerde AM, Vargas-Poussou R, Dubourg LD, González-Recio I, Martínez-Cruz LA, de Baaij JHF, Hoenderop JGJ. Hypomagnesaemia with varying degrees of extrarenal symptoms as a consequence of heterozygous CNNM2 variants. Sci Rep 2024; 14:6917. [PMID: 38519529 PMCID: PMC10959950 DOI: 10.1038/s41598-024-57061-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 03/14/2024] [Indexed: 03/25/2024] Open
Abstract
Variants in the CNNM2 gene are causative for hypomagnesaemia, seizures and intellectual disability, although the phenotypes can be variable. This study aims to understand the genotype-phenotype relationship in affected individuals with CNNM2 variants by phenotypic, functional and structural analysis of new as well as previously reported variants. This results in the identification of seven variants that significantly affect CNNM2-mediated Mg2+ transport. Pathogenicity of these variants is further supported by structural modelling, which predicts CNNM2 structure to be affected by all of them. Strikingly, seizures and intellectual disability are absent in 4 out of 7 cases, indicating these phenotypes are caused either by specific CNNM2 variant only or by additional risk factors. Moreover, in line with sporadic observations from previous reports, CNNM2 variants might be associated with disturbances in parathyroid hormone and Ca2+ homeostasis.
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Affiliation(s)
- Willem Bosman
- Department of Medical BioSciences, Radboudumc, Nijmegen, The Netherlands
| | - Gijs A C Franken
- Department of Medical BioSciences, Radboudumc, Nijmegen, The Netherlands
| | - Javier de Las Heras
- Division of Pediatric Metabolism, Cruces University Hospital, CIBER-ER, Metab-ERN, University of the Basque Country (UPV/EHU), Biobizkaia Health Research Institute, Barakaldo, Spain
| | - Leire Madariaga
- Pediatric Nephrology Department, Cruces University Hospital, CIBERDEM, CIBER-ER, Endo-ERN, Biocruces Bizkaia Health Research Institute and University of the Basque Country (UPV/EHU), Barakaldo, Spain
| | - Tahsin Stefan Barakat
- Deparment of Clinical Genetics, Erasmus MC, Rotterdam, The Netherlands
- Discovery Unit, Department of Clinical Genetics, Erasmus MC, Rotterdam, The Netherlands
- ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus MC, Rotterdam, The Netherlands
| | - Rianne Oostenbrink
- ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus MC, Rotterdam, The Netherlands
- Department of General Pediatrics, Erasmus Medical Center Sophia Children's Hospital, Rotterdam, The Netherlands
| | | | - Ana Perdomo-Ramírez
- Unidad de Investigación, Renal Tube Group, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Félix Claverie-Martín
- Unidad de Investigación, Renal Tube Group, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | | | - Rosa Vargas-Poussou
- Service de medecine genomique des maladies rares, AP-HP, universite Paris Cité, Paris, France
- Centre de reference des maladies renales hereditaires de l'enfant et de l'adulte MARHEA, hopital Européen Georges Pompidou, Paris, France
- CNRS, centre de recherche des Cordeliers, Inserm UMRS 1138, Sorbonne universite, universite Paris Cité, Paris, France
| | - Laurence Derain Dubourg
- Hôpital Édouard Herriot, Hospices civils de Lyon, service de nephrologie, dialyse, hypertension et exploration fonctionnelle renale, Lyon, France
- Centre de reference des maladies renales rares et phosphocalciques, Nephrogones, Hôpital Femme-Mère-Enfant Bron, Bron, France
- Faculté de medecine Lyon est, Université Claude Bernard Lyon 1, Villeurbanne, France
| | - Irene González-Recio
- Center for Cooperative Research in Biosciences (CIC bioGUNE), Bizkaia Science and Technology Park, Derio, Bizkaia, Spain
| | - Luis Alfonso Martínez-Cruz
- Center for Cooperative Research in Biosciences (CIC bioGUNE), Bizkaia Science and Technology Park, Derio, Bizkaia, Spain
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Sneddon WB, Friedman PA, Mamonova T. Mutations in an unrecognized internal NPT2A PDZ motif disrupt phosphate transport and cause congenital hypophosphatemia. Biochem J 2023; 480:685-699. [PMID: 37132631 PMCID: PMC10442799 DOI: 10.1042/bcj20230020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 05/02/2023] [Accepted: 05/03/2023] [Indexed: 05/04/2023]
Abstract
The Na+-dependent phosphate cotransporter-2A (NPT2A, SLC34A1) is a primary regulator of extracellular phosphate homeostasis. Its most prominent structural element is a carboxy-terminal PDZ ligand that binds Na+/H+ Exchanger Regulatory Factor-1 (NHERF1, SLC9A3R1). NHERF1, a multidomain PDZ protein, establishes NPT2A membrane localization and is required for hormone-inhibitable phosphate transport. NPT2A also possesses an uncharacterized internal PDZ ligand. Two recent clinical reports describe congenital hypophosphatemia in children harboring Arg495His or Arg495Cys variants within the internal PDZ motif. The wild-type internal 494TRL496 PDZ ligand binds NHERF1 PDZ2, which we consider a regulatory domain. Ablating the internal PDZ ligand with a 494AAA496 substitution blocked hormone-inhibitable phosphate transport. Complementary approaches, including CRISPR/Cas9 technology, site-directed mutagenesis, confocal microscopy, and modeling, showed that NPT2A Arg495His or Arg495Cys variants do not support PTH or FGF23 action on phosphate transport. Coimmunoprecipitation experiments indicate that both variants bind NHERF1 similarly to WT NPT2A. However, in contrast with WT NPT2A, NPT2A Arg495His, or Arg495Cys variants remain at the apical membrane and are not internalized in response to PTH. We predict that Cys or His substitution of the charged Arg495 changes the electrostatics, preventing phosphorylation of the upstream Thr494, interfering with phosphate uptake in response to hormone action, and inhibiting NPT2A trafficking. We advance a model wherein the carboxy-terminal PDZ ligand defines apical localization NPT2A, while the internal PDZ ligand is essential for hormone-triggered phosphate transport.
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Affiliation(s)
- W. Bruce Sneddon
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, U.S.A
| | - Peter A. Friedman
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, U.S.A
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, U.S.A
| | - Tatyana Mamonova
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, U.S.A
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Petzold F, Schönauer R, Werner A, Halbritter J. Clinical and Functional Assessment of Digenicity in Renal Phosphate Wasting. Nutrients 2023; 15:2081. [PMID: 37432176 DOI: 10.3390/nu15092081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 04/21/2023] [Accepted: 04/24/2023] [Indexed: 07/12/2023] Open
Abstract
Apart from increased fluid intake, patients with kidney stone disease (KSD) due to renal phosphate wasting require specific metaphylaxis. NaPi2a, NaPi2c, and NHERF1 regulate plasma phosphate concentration by reabsorbing phosphate in proximal kidney tubules and have been found altered in monogenic hypophosphatemia with a risk of KSD. In this study, we aimed at assessing the combined genetic alterations impacting NaPi2a, NaPi2c, and NHERF1. Therefore, we screened our hereditary KSD registry for cases of oligo- and digenicity, conducted reverse phenotyping, and undertook functional studies. As a result, we identified three patients from two families with digenic alterations in NaPi2a, NaPi2c, and NHERF1. In family 1, the index patient, who presented with severe renal calcifications and a bone mineralization disorder, carried digenic alterations affecting both NaPi transporter 2a and 2c. Functional analysis confirmed an additive genetic effect. In family 2, the index patient presented with kidney function decline, distinct musculature-related symptoms, and intracellular ATP depletion. Genetically, this individual was found to harbor variants in both NaPi2c and NHERF1 pointing towards genetic interaction. In summary, digenicity and gene dosage are likely to impact the severity of renal phosphate wasting and should be taken into account in terms of metaphylaxis through phosphate substitution.
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Affiliation(s)
- Friederike Petzold
- Division of Nephrology, University of Leipzig Medical Center, 04103 Leipzig, Germany
| | - Ria Schönauer
- Division of Nephrology, University of Leipzig Medical Center, 04103 Leipzig, Germany
- Department of Nephrology, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany
| | - Andreas Werner
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
| | - Jan Halbritter
- Division of Nephrology, University of Leipzig Medical Center, 04103 Leipzig, Germany
- Department of Nephrology, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany
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Sneddon WB, Friedman PA, Mamonova T. Mutations in an unrecognized internal NPT2A PDZ motif disrupt phosphate transport causing congenital hypophosphatemia. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.06.531332. [PMID: 36945373 PMCID: PMC10028803 DOI: 10.1101/2023.03.06.531332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
The Na + -dependent phosphate cotransporter-2A (NPT2A, SLC34A1) is a primary regulator of extracellular phosphate homeostasis. Its most prominent structural element is a carboxy-terminal PDZ ligand that binds Na + /H + Exchanger Regulatory Factor-1 (NHERF1, SLC9A3R1). NHERF1, a multidomain PDZ protein,establishes NPT2A membrane localization and is required for hormone-sensitive phosphate transport. NPT2A also possesses an uncharacterized internal PDZ ligand. Two recent clinical reports describe congenital hypophosphatemia in children harboring Arg 495 His or Arg 495 Cys variants within the internal PDZ motif. The wild-type internal 494 TRL 496 PDZ ligand binds NHERF1 PDZ2, which we consider a regulatory domain. Ablating the internal PDZ ligand with a 494 AAA 496 substitution blocked hormone-sensitive phosphate transport. Complementary approaches, including CRISPR/Cas9 technology, site-directed mutagenesis, confocal microscopy, and modeling, showed that NPT2A Arg 495 His or Arg 495 Cys variants do not support PTH or FGF23 action on phosphate transport. Coimmunoprecipitation experiments indicate that both variants bind NHERF1 similarly to WT NPT2A. However, in contrast to WT NPT2A, NPT2A Arg 495 His or Arg 495 Cys variants remain at the apical membrane and are not internalized in response to PTH. We predict that Cys or His substitution of the charged Arg 495 changes the electrostatics, preventing phosphorylation of the upstream Thr 494 , interfering with phosphate uptake in response to hormone action, and inhibiting NPT2A trafficking. We advance a model wherein the carboxyterminal PDZ ligand defines apical localization NPT2A, while the internal PDZ ligand is essential for hormone-triggered phosphate transport.
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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] [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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Abstract
Phosphate is an essential nutrient for life and is a critical component of bone formation, a major signaling molecule, and structural component of cell walls. Phosphate is also a component of high-energy compounds (i.e., AMP, ADP, and ATP) and essential for nucleic acid helical structure (i.e., RNA and DNA). Phosphate plays a central role in the process of mineralization, normal serum levels being associated with appropriate bone mineralization, while high and low serum levels are associated with soft tissue calcification. The serum concentration of phosphate and the total body content of phosphate are highly regulated, a process that is accomplished by the coordinated effort of two families of sodium-dependent transporter proteins. The three isoforms of the SLC34 family (SLC34A1-A3) show very restricted tissue expression and regulate intestinal absorption and renal excretion of phosphate. SLC34A2 also regulates the phosphate concentration in multiple lumen fluids including milk, saliva, pancreatic fluid, and surfactant. Both isoforms of the SLC20 family exhibit ubiquitous expression (with some variation as to which one or both are expressed), are regulated by ambient phosphate, and likely serve the phosphate needs of the individual cell. These proteins exhibit similarities to phosphate transporters in nonmammalian organisms. The proteins are nonredundant as mutations in each yield unique clinical presentations. Further research is essential to understand the function, regulation, and coordination of the various phosphate transporters, both the ones described in this review and the phosphate transporters involved in intracellular transport.
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Affiliation(s)
- Nati Hernando
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
| | - Kenneth Gagnon
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
| | - Eleanor Lederer
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
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Song GJ, Gupta DP, Rahman MH, Park HT, Al Ghouleh I, Bisello A, Lee MG, Park JY, Park HH, Jun JH, Chung KW, Choi BO, Suk K. Loss-of-function of EBP50 is a new cause of hereditary peripheral neuropathy: EBP50 functions in peripheral nerve system. Glia 2020; 68:1794-1809. [PMID: 32077526 DOI: 10.1002/glia.23805] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 02/04/2020] [Accepted: 02/07/2020] [Indexed: 12/12/2022]
Abstract
Finding causative genetic mutations is important in the diagnosis and treatment of hereditary peripheral neuropathies. This study was conducted to find new genes involved in the pathophysiology of hereditary peripheral neuropathy. We identified a new mutation in the EBP50 gene, which is co-segregated with neuropathic phenotypes, including motor and sensory deficit in a family with Charcot-Marie-Tooth disease. EBP50 is known to be important for the formation of microvilli in epithelial cells, and the discovery of this gene mutation allowed us to study the function of EBP50 in the nervous system. EBP50 was strongly expressed in the nodal and paranodal regions of sciatic nerve fibers, where Schwann cell microvilli contact the axolemma, and at the growth tips of primary Schwann cells. In addition, EBP50 expression was decreased in mouse models of peripheral neuropathy. Knockout mice were used to study EBP50 function in the peripheral nervous system. Interestingly motor function deficit and abnormal histology of nerve fibers were observed in EBP50+/- heterozygous mice at 12 months of age, but not 3 months. in vitro studies using Schwann cells showed that NRG1-induced AKT activation and migration were significantly reduced in cells overexpressing the I325V mutant of EBP50 or cells with knocked-down EBP50 expression. In conclusion, we show for the first time that loss of function due to EBP50 gene deficiency or mutation can cause peripheral neuropathy.
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Affiliation(s)
- Gyun Jee Song
- Department of Medical Science, Institute for Bio-Medical Convergence, Catholic Kwandong University, International St. Mary's Hospital, Incheon, Republic of Korea
| | - Deepak Prasad Gupta
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Md Habibur Rahman
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Hwan Tae Park
- Department of Molecular Neuroscience, College of Medicine, Dong-A University, Busan, Republic of Korea
| | - Imad Al Ghouleh
- Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Alessandro Bisello
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Maan-Gee Lee
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
| | - Jae-Yong Park
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul, Republic of Korea
| | - Hyun Ho Park
- College of Pharmacy, Chung-Ang University, Seoul, Republic of Korea
| | - Jin Hyun Jun
- Department of Senior Healthcare, BK21 Plus Program, Graduate School of Eulji University, Department of Biomedical Laboratory Science, College of Health Science, Eulji University, Seongnam, Republic of Korea
| | - Ki Wha Chung
- Department of Biological Sciences, Kongju National University, Gongju, Republic of Korea
| | - Byung-Ok Choi
- Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Kyoungho Suk
- Department of Pharmacology, Brain Science and Engineering Institute, BK21 Plus KNU Biomedical Convergence Program, School of Medicine, Kyungpook National University, Daegu, Republic of Korea
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Bertholet-Thomas A, Tram N, Dubourg L, Lemoine S, Molin A, Bacchetta J. Fluconazole as a New Therapeutic Tool to Manage Patients With NPTIIc (SLC34A3) Mutation: A Case Report. Am J Kidney Dis 2019; 73:886-889. [DOI: 10.1053/j.ajkd.2018.12.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 12/06/2018] [Indexed: 11/11/2022]
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Wagner CA, Rubio-Aliaga I, Hernando N. Renal phosphate handling and inherited disorders of phosphate reabsorption: an update. Pediatr Nephrol 2019; 34:549-559. [PMID: 29275531 DOI: 10.1007/s00467-017-3873-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 12/08/2017] [Accepted: 12/12/2017] [Indexed: 01/12/2023]
Abstract
Renal phosphate handling critically determines plasma phosphate and whole body phosphate levels. Filtered phosphate is mostly reabsorbed by Na+-dependent phosphate transporters located in the brush border membrane of the proximal tubule: NaPi-IIa (SLC34A1), NaPi-IIc (SLC34A3), and Pit-2 (SLC20A2). Here we review new evidence for the role and relevance of these transporters in inherited disorders of renal phosphate handling. The importance of NaPi-IIa and NaPi-IIc for renal phosphate reabsorption and mineral homeostasis has been highlighted by the identification of mutations in these transporters in a subset of patients with infantile idiopathic hypercalcemia and patients with hereditary hypophosphatemic rickets with hypercalciuria. Both diseases are characterized by disturbed calcium homeostasis secondary to elevated 1,25-(OH)2 vitamin D3 as a consequence of hypophosphatemia. In vitro analysis of mutated NaPi-IIa or NaPi-IIc transporters suggests defective trafficking underlying disease in most cases. Monoallelic pathogenic mutations in both SLC34A1 and SLC34A3 appear to be very frequent in the general population and have been associated with kidney stones. Consistent with these findings, results from genome-wide association studies indicate that variants in SLC34A1 are associated with a higher risk to develop kidney stones and chronic kidney disease, but underlying mechanisms have not been addressed to date.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland. .,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland.
| | - Isabel Rubio-Aliaga
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland
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12
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Zhang Q, Xiao K, Paredes JM, Mamonova T, Sneddon WB, Liu H, Wang D, Li S, McGarvey JC, Uehling D, Al-Awar R, Joseph B, Jean-Alphonse F, Orte A, Friedman PA. Parathyroid hormone initiates dynamic NHERF1 phosphorylation cycling and conformational changes that regulate NPT2A-dependent phosphate transport. J Biol Chem 2019; 294:4546-4571. [PMID: 30696771 PMCID: PMC6433080 DOI: 10.1074/jbc.ra119.007421] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 01/25/2019] [Indexed: 12/30/2022] Open
Abstract
Na+-H+ exchanger regulatory factor-1 (NHERF1) is a PDZ protein that scaffolds membrane proteins, including sodium-phosphate co-transport protein 2A (NPT2A) at the plasma membrane. NHERF1 is a phosphoprotein with 40 Ser and Thr residues. Here, using tandem MS analysis, we characterized the sites of parathyroid hormone (PTH)-induced NHERF1 phosphorylation and identified 10 high-confidence phosphorylation sites. Ala replacement at Ser46, Ser162, Ser181, Ser269, Ser280, Ser291, Thr293, Ser299, and Ser302 did not affect phosphate uptake, but S290A substitution abolished PTH-dependent phosphate transport. Unexpectedly, Ser290 was rapidly dephosphorylated and rephosphorylated after PTH stimulation, and we found that protein phosphatase 1α (PP1α), which binds NHERF1 through a conserved VxF/W PP1 motif, dephosphorylates Ser290 Mutating 257VPF259 eliminated PP1 binding and blunted dephosphorylation. Tautomycetin blocked PP1 activity and abrogated PTH-sensitive phosphate transport. Using fluorescence lifetime imaging (FLIM), we observed that PTH paradoxically and transiently elevates intracellular phosphate. Added phosphate blocked PP1α-mediated Ser290 dephosphorylation of recombinant NHERF1. Hydrogen-deuterium exchange MS revealed that β-sheets in NHERF1's PDZ2 domain display lower deuterium uptake than those in the structurally similar PDZ1, implying that PDZ1 is more cloistered. Dephosphorylated NHERF1 exhibited faster exchange at C-terminal residues suggesting that NHERF1 dephosphorylation precedes Ser290 rephosphorylation. Our results show that PP1α and NHERF1 form a holoenzyme and that a multiprotein kinase cascade involving G protein-coupled receptor kinase 6A controls the Ser290 phosphorylation status of NHERF1 and regulates PTH-sensitive, NPT2A-mediated phosphate uptake. These findings reveal how reversible phosphorylation modifies protein conformation and function and the biochemical mechanisms underlying PTH control of phosphate transport.
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Affiliation(s)
- Qiangmin Zhang
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology
| | - Kunhong Xiao
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology.,Vascular Medicine Institute, and.,Biomedical Mass Spectrometry Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - José M Paredes
- the Department of Physical Chemistry, Faculty of Pharmacy, University of Granada, 18071-Granada, Spain
| | - Tatyana Mamonova
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology
| | - W Bruce Sneddon
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology
| | - Hongda Liu
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology
| | - Dawei Wang
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology
| | - Sheng Li
- the Department of Medicine, University of California San Diego, La Jolla, California 92093, and
| | - Jennifer C McGarvey
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology
| | - David Uehling
- the Department of Drug Discovery, Ontario Institute for Cancer Research, Toronto, Ontario M5G 0A3, Canada
| | - Rima Al-Awar
- the Department of Drug Discovery, Ontario Institute for Cancer Research, Toronto, Ontario M5G 0A3, Canada
| | - Babu Joseph
- the Department of Drug Discovery, Ontario Institute for Cancer Research, Toronto, Ontario M5G 0A3, Canada
| | | | - Angel Orte
- the Department of Physical Chemistry, Faculty of Pharmacy, University of Granada, 18071-Granada, Spain
| | - Peter A Friedman
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, .,Department of Structural Biology
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13
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Oliveira B, Unwin R, Walsh SB. Inherited proximal tubular disorders and nephrolithiasis. Urolithiasis 2019; 47:35-42. [PMID: 30673801 DOI: 10.1007/s00240-018-01103-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 12/08/2018] [Indexed: 12/20/2022]
Abstract
The proximal tubule is responsible for reclaiming water, phosphates and amino acids from the tubular filtrate. There are genetic defects in both phosphate and amino acid transporters leading to nephrolithiasis. This review also explores genetic defects in regulators of phosphate and calcium transport in this nephron segment that lead to stone formation.
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Affiliation(s)
- Ben Oliveira
- Royal Free Hospital/Medical School, Centre for Nephrology, University College London, London, NW3 2PF, UK
| | - Robert Unwin
- Royal Free Hospital/Medical School, Centre for Nephrology, University College London, London, NW3 2PF, UK.,AstraZeneca IMED ECD CVRM R&D, Gothenburg, Sweden
| | - Stephen B Walsh
- Royal Free Hospital/Medical School, Centre for Nephrology, University College London, London, NW3 2PF, UK.
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14
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Abstract
Calcium kidney stones are common worldwide. Most are idiopathic and composed of calcium oxalate. Calcium phosphate is present in around 80% and may initiate stone formation. Stone production is multifactorial with a polygenic genetic contribution. Phosphaturia is found frequently among stone formers but until recently received scant attention. This review examines possible mechanisms for the phosphaturia and its relevance to stone formation from a wide angle. There is a striking lack of clinical data. Phosphaturia is associated, but not correlated, with hypercalciuria, increased 1,25 dihydroxy-vitamin D [1,25 (OH)2D], and sometimes evidence of disturbances in proximal renal tubular function. Phosphate reabsorption in the proximal renal tubules requires tightly regulated interaction of many proteins. Paracellular flow through intercellular tight junctions is the major route of phosphate absorption from the intestine and can be reduced therapeutically in hyperphosphatemic patients. In monogenic defects stones develop when phosphaturia is associated with hypercalciuria, generally explained by increased 1,25 (OH)2D production in response to hypophosphatemia. Calcification does not occur in disorders with increased FGF23 when phosphaturia occurs in isolation and 1,25 (OH)2D is suppressed. Candidate gene studies have identified mutations in the phosphate transporters, but in few individuals. One genome-wide study identified a polymorphism of the phosphate transporter gene SLC34A4 associated with stones. Others did not find mutations obviously linked to phosphate reabsorption. Future genetic studies should have a wide trawl and should focus initially on groups of patients with clearly defined phenotypes. The global data should be pooled.
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Affiliation(s)
- Valerie Walker
- Department of Clinical Biochemistry, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom.
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15
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Emerging Roles of Diacylglycerol-Sensitive TRPC4/5 Channels. Cells 2018; 7:cells7110218. [PMID: 30463370 PMCID: PMC6262340 DOI: 10.3390/cells7110218] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 11/15/2018] [Accepted: 11/16/2018] [Indexed: 12/31/2022] Open
Abstract
Transient receptor potential classical or canonical 4 (TRPC4) and TRPC5 channels are members of the classical or canonical transient receptor potential (TRPC) channel family of non-selective cation channels. TRPC4 and TRPC5 channels are widely accepted as receptor-operated cation channels that are activated in a phospholipase C-dependent manner, following the Gq/11 protein-coupled receptor activation. However, their precise activation mechanism has remained largely elusive for a long time, as the TRPC4 and TRPC5 channels were considered as being insensitive to the second messenger diacylglycerol (DAG) in contrast to the other TRPC channels. Recent findings indicate that the C-terminal interactions with the scaffolding proteins Na+/H+ exchanger regulatory factor 1 and 2 (NHERF1 and NHERF2) dynamically regulate the DAG sensitivity of the TRPC4 and TRPC5 channels. Interestingly, the C-terminal NHERF binding suppresses, while the dissociation of NHERF enables, the DAG sensitivity of the TRPC4 and TRPC5 channels. This leads to the assumption that all of the TRPC channels are DAG sensitive. The identification of the regulatory function of the NHERF proteins in the TRPC4/5-NHERF protein complex offers a new starting point to get deeper insights into the molecular basis of TRPC channel activation. Future studies will have to unravel the physiological and pathophysiological functions of this multi-protein channel complex.
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16
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Fujii T, Shiozaki Y, Segawa H, Nishiguchi S, Hanazaki A, Noguchi M, Kirino R, Sasaki S, Tanifuji K, Koike M, Yokoyama M, Arima Y, Kaneko I, Tatsumi S, Ito M, Miyamoto KI. Analysis of opossum kidney NaPi-IIc sodium-dependent phosphate transporter to understand Pi handling in human kidney. Clin Exp Nephrol 2018; 23:313-324. [PMID: 30317447 DOI: 10.1007/s10157-018-1653-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 09/24/2018] [Indexed: 01/17/2023]
Abstract
BACKGROUND The role of Na+-dependent inorganic phosphate (Pi) transporters in the human kidney is not fully clarified. Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is caused by loss-of-function mutations in the IIc Na+-dependent Pi transporter (NPT2c/Npt2c/NaPi-IIc) gene. Another Na+-dependent type II transporter, (NPT2A/Npt2a/NaPi-IIa), is also important for renal Pi reabsorption in humans. In mice, Npt2c deletion does not lead to hypophosphatemia and rickets because Npt2a compensates for the impaired Pi reabsorption. To clarify the differences between mouse and human, we investigated the relation between NaPi-IIa and NaPi-IIc functions in opossum kidney (OK) cells. METHODS We cloned NaPi-IIc from OK cells and created opossum NaPi-IIc (oNaPi-IIc) antibodies. We used oNaPi-IIc small interference (si)RNA and investigated the role of NaPi-IIc in Pi transport in OK cells. RESULTS We cloned opossum kidney NaPi-IIc cDNAs encoding 622 amino acid proteins (variant1) and examined their pH- and sodium-dependency. The antibodies reacted specifically with 75-kDa and 150-kDa protein bands, and the siRNA of NaPi-IIc markedly suppressed endogenous oNaPi-IIc in OK cells. Treatment with siRNA significantly suppressed the expression of NaPi-4 (NaPi-IIa) protein and mRNA. oNaPi-IIc siRNA also suppressed Na+/H+ exchanger regulatory factor 1 expression in OK cells. CONCLUSION These findings suggest that NaPi-IIc is important for the expression of NaPi-IIa (NaPi-4) protein in OK cells. Suppression of Npt2c may downregulate Npt2a function in HHRH patients.
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Affiliation(s)
- Toru Fujii
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Yuji Shiozaki
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Hiroko Segawa
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Shiori Nishiguchi
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ai Hanazaki
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Miwa Noguchi
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ruri Kirino
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Sumire Sasaki
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Kazuya Tanifuji
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Megumi Koike
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Mizuki Yokoyama
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Yuki Arima
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ichiro Kaneko
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Sawako Tatsumi
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Mikiko Ito
- Human Science and Environment, University of Hyogo Graduate School, Hyogo, Japan
| | - Ken-Ichi Miyamoto
- Department of Molecular Nutrition, Institute of Biomedical Sciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan.
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17
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Abstract
Our understanding of the regulation of phosphate balance has benefited tremendously from the molecular identification and characterization of genetic defects leading to a number of rare inherited or acquired disorders affecting phosphate homeostasis. The identification of the key phosphate-regulating hormone, fibroblast growth factor 23 (FGF23), as well as other molecules that control its production, such as the glycosyltransferase GALNT3, the endopeptidase PHEX, and the matrix protein DMP1, and molecules that function as downstream effectors of FGF23 such as the longevity factor Klotho and the phosphate transporters NPT2a and NPT2c, has permitted us to understand the complex interplay that exists between the kidneys, bone, parathyroid, and gut. Such insights from genetic disorders have allowed not only the design of potent targeted treatment of FGF23-dependent hypophosphatemic conditions, but also provide clinically relevant observations related to the dysregulation of mineral ion homeostasis in health and disease.
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Affiliation(s)
- Marta Christov
- Division of Nephrology, Department of Medicine, New York Medical College, Valhalla, NY, USA
| | - Harald Jüppner
- Endocrine Unit and Pediatric Nephrology Unit, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
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18
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Hernando N. NaPi-IIa interacting partners and their (un)known functional roles. Pflugers Arch 2018; 471:67-82. [PMID: 30022249 DOI: 10.1007/s00424-018-2176-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 06/26/2018] [Indexed: 01/14/2023]
Abstract
The sorting and stabilization of proteins at specific subcellular domains depend upon the formation of networks build up by specific protein-protein interactions. In addition, protein networks also ensure the specificity of many regulatory processes by bringing together regulatory molecules with their targets. Whereas the success on the identification of protein-protein interactions is (up to a point) technology-driven, the assignment of functional roles to specific partners remains a major challenge. This review summarizes the work that led to the identification of partners of the Na+/phosphate cotransporter NaPi-IIa as well as the effects of the interactions in the expression and/or regulation of the cotransporter.
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Affiliation(s)
- Nati Hernando
- Institute of Physiology, University Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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19
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Marik B, Bagga A, Sinha A, Hari P, Sharma A. Genetics of Refractory Rickets: Identification of Novel PHEX Mutations in Indian Patients and a Literature Update. J Pediatr Genet 2018; 7:47-59. [PMID: 29707405 PMCID: PMC5916800 DOI: 10.1055/s-0038-1624577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 12/25/2017] [Indexed: 10/18/2022]
Abstract
Refractory rickets is a genetic disorder that cannot be treated by vitamin D supplementation and adequate dietary calcium and phosphorus. Hereditary hypophosphatemic rickets is one of the major forms of refractory rickets in Indian children and caused due to mutations in the PHEX , FGF23 , DMP1 , ENPP1 , and SLC34A3 genes. This is the first study in India on a large number of patients reporting on mutational screening of the PHEX gene. Direct sequencing in 37 patients with refractory rickets revealed eight mutations in 13 patients of which 1 was nonsense, 2 were deletions, 1 was a deletion-insertion, and 4 were missense mutations. Of these mutations, four (c.566_567 delAG, c.651_654delACAT, c.1337delinsAATAA, and c.2048T > A) were novel mutations. This article discusses the mutations in Indian patients, collates information on the genetic causes of refractory rickets, and emphasizes the significance of genetic testing for precise diagnosis, timely treatment, and management of the condition, especially in developing countries.
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Affiliation(s)
- Binata Marik
- Division of Genetics, Department of Anatomy, All India Institute of Medical Sciences, New Delhi, India
| | - Arvind Bagga
- Department of Paediatrics, All India Institute of Medical Sciences, New Delhi, India
| | - Aditi Sinha
- Department of Paediatrics, All India Institute of Medical Sciences, New Delhi, India
| | - Pankaj Hari
- Department of Paediatrics, All India Institute of Medical Sciences, New Delhi, India
| | - Arundhati Sharma
- Division of Genetics, Department of Anatomy, All India Institute of Medical Sciences, New Delhi, India
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20
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Bergsland KJ, Coe FL, Parks JH, Asplin JR, Worcester EM. Evidence for a role of PDZ domain-containing proteins to mediate hypophosphatemia in calcium stone formers. Nephrol Dial Transplant 2018; 33:759-770. [PMID: 29126251 DOI: 10.1093/ndt/gfx284] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 08/29/2017] [Indexed: 01/26/2023] Open
Abstract
Background Hypophosphatemia (HYP) is common among calcium stone formers (SFs) and in rare cases is associated with mutations in sodium-phosphate cotransporters or in Na+/H+ exchanger regulatory factor 1 (NHERF1), but the majority of cases are unexplained. We hypothesized that reduced sodium-phosphate cotransporter activity mediated via NHERF1 or a similar PDZ domain-containing protein, causes HYP. If so, other transport activities controlled by NHERF1, such as NHE3 and URAT1, might be reduced in HYP. Methods To test this idea, we analyzed two large but separate sets of 24-h urine samples and paired serums of 2700 SFs from the University of Chicago and 11 073 SFs from Litholink, a national laboratory. Patients were divided into quintiles based on serum phosphate. Results Males were more common in the lowest phosphate tiles in both datasets. Phosphate excretion did not vary across the quintiles, excluding diet as a cause of HYP. Tubule maximum (Tm) phosphate per unit glomerular filtration rate decreased and fractional excretion increased with decreasing phosphate quintiles, indicating reduced tubule phosphate reabsorption was responsible for HYP. Urine pH and serum chloride increased with decreasing serum phosphate, suggesting a coordinate change in NHE3 activity. Serum uric acid and Tm uric acid decreased significantly with decreasing serum phosphate, while uric acid excretion did not vary. Conclusion. HYP in SFs results from decreased tubule phosphate reabsorption and, being associated with related changes in other proximal tubule transporters, may arise from alterations in or signaling to PDZ-containing proteins.
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Affiliation(s)
| | - Fredric L Coe
- Department of Medicine, University of Chicago, Chicago, IL, USA
| | - Joan H Parks
- Department of Medicine, University of Chicago, Chicago, IL, USA
| | - John R Asplin
- Litholink Corporation, Laboratory Corporation of America Holdings, Chicago, IL, USA
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21
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Tachikawa M, Yokoyama R, Akanuma SI, Hosoya KI. Assembly of Taurine Transporter (Slc6a6) with Na +-H + Exchanger Regulatory Factor 1 (Slc9a3r1) Improves GABA Transport Activity by Increasing the Maximum Transport Velocity. Biol Pharm Bull 2018; 41:338-341. [PMID: 29491210 DOI: 10.1248/bpb.b17-00664] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Regulating γ-aminobutyric acid (GABA) uptake transport on the plasma membranes is required for its efficient clearance from the brain interstitial fluid. The purpose of this study was to clarify the assembly of taurine transporter (TauT/Slc6a6) and PSD-95/Disc-large/Zo-1 (PDZ) domain of Na+-H+ exchanger regulatory factor 1 (NHERF1) as a regulatory mechanism of TauT-mediated GABA transport activity. In vitro glutathione S-transferase (GST)-pull down assay and immunoblotting with anti-NHERF1 antibody revealed that NHERF1 protein was present in rat brain lysates as the binding protein of the GST-fusion TauT C-terminal protein with the PDZ-binding ETMM motif but not its corresponding deletion mutant lacking the motif. [3H]GABA uptake by TauT-NHERF1-coexpressing oocytes and TauT-singly expressing oocytes exhibited saturable kinetics with Michaelis-Menten constant values of 0.835±0.288 and 0.982±0.569 mM and a maximal transport velocity of 206±37 and 283±28 pmol/(h·oocyte), respectively. These results suggest that the assembly of TauT PDZ-binding motif and NHERF1 increases the maximal transport velocity of GABA rather than changes the affinity.
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Affiliation(s)
- Masanori Tachikawa
- Division of Membrane Transport and Drug Targeting, Graduate School of Pharmaceutical Sciences, Tohoku University.,Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama
| | - Reiji Yokoyama
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama
| | - Shin-Ichi Akanuma
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama
| | - Ken-Ichi Hosoya
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama
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22
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Abstract
Rickets is a metabolic bone disease that develops as a result of inadequate mineralization of growing bone due to disruption of calcium, phosphorus and/or vitamin D metabolism. Nutritional rickets remains a significant child health problem in developing countries. In addition, several rare genetic causes of rickets have also been described, which can be divided into two groups. The first group consists of genetic disorders of vitamin D biosynthesis and action, such as vitamin D-dependent rickets type 1A (VDDR1A), vitamin D-dependent rickets type 1B (VDDR1B), vitamin D-dependent rickets type 2A (VDDR2A), and vitamin D-dependent rickets type 2B (VDDR2B). The second group involves genetic disorders of excessive renal phosphate loss (hereditary hypophosphatemic rickets) due to impairment in renal tubular phosphate reabsorption as a result of FGF23-related or FGF23-independent causes. In this review, we focus on clinical, laboratory and genetic characteristics of various types of hereditary rickets as well as differential diagnosis and treatment approaches.
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Affiliation(s)
- Sezer Acar
- Dokuz Eylül University Faculty of Medicine, Department of Pediatric Endocrinology, İzmir, Turkey
| | - Korcan Demir
- Dokuz Eylül University Faculty of Medicine, Department of Pediatric Endocrinology, İzmir, Turkey
| | - Yufei Shi
- King Faisal Specialist Hospital & Research Centre, Department of Genetics, Riyadh, Saudi Arabia
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23
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Abstract
Rickets is a bone disease associated with abnormal serum calcium and phosphate levels. The clinical presentation is heterogeneous and depends on the age of onset and pathogenesis but includes bowing deformities of the legs, short stature and widening of joints. The disorder can be caused by nutritional deficiencies or genetic defects. Mutations in genes encoding proteins involved in vitamin D metabolism or action, fibroblast growth factor 23 (FGF23) production or degradation, renal phosphate handling or bone mineralization have been identified. The prevalence of nutritional rickets has substantially declined compared with the prevalence 200 years ago, but the condition has been re-emerging even in some well-resourced countries; prematurely born infants or breastfed infants who have dark skin types are particularly at risk. Diagnosis is usually established by medical history, physical examination, biochemical tests and radiography. Prevention is possible only for nutritional rickets and includes supplementation or food fortification with calcium and vitamin D either alone or in combination with sunlight exposure. Treatment of typical nutritional rickets includes calcium and/or vitamin D supplementation, although instances infrequently occur in which phosphate repletion may be necessary. Management of heritable types of rickets associated with defects in vitamin D metabolism or activation involves the administration of vitamin D metabolites. Oral phosphate supplementation is usually indicated for FGF23-independent phosphopenic rickets, whereas the conventional treatment of FGF23-dependent types of rickets includes a combination of phosphate and activated vitamin D; an anti-FGF23 antibody has shown promising results and is under further study.
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24
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Lee JJ, Plain A, Beggs MR, Dimke H, Alexander RT. Effects of phospho- and calciotropic hormones on electrolyte transport in the proximal tubule. F1000Res 2017; 6:1797. [PMID: 29043081 PMCID: PMC5627579 DOI: 10.12688/f1000research.12097.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/04/2017] [Indexed: 12/17/2022] Open
Abstract
Calcium and phosphate are critical for a myriad of physiological and cellular processes within the organism. Consequently, plasma levels of calcium and phosphate are tightly regulated. This occurs through the combined effects of the phospho- and calciotropic hormones, parathyroid hormone (PTH), active vitamin D
3, and fibroblast growth factor 23 (FGF23). The organs central to this are the kidneys, intestine, and bone. In the kidney, the proximal tubule reabsorbs the majority of filtered calcium and phosphate, which amounts to more than 60% and 90%, respectively. The basic molecular mechanisms responsible for phosphate reclamation are well described, and emerging work is delineating the molecular identity of the paracellular shunt wherein calcium permeates the proximal tubular epithelium. Significant experimental work has delineated the molecular effects of PTH and FGF23 on these processes as well as their regulation of active vitamin D
3 synthesis in this nephron segment. The integrative effects of both phospho- and calciotropic hormones on proximal tubular solute transport and subsequently whole body calcium-phosphate balance thus have been further complicated. Here, we first review the molecular mechanisms of calcium and phosphate reabsorption from the proximal tubule and how they are influenced by the phospho- and calciotropic hormones acting on this segment and then consider the implications on both renal calcium and phosphate handling as well as whole body mineral balance.
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Affiliation(s)
- Justin J Lee
- Department of Physiology, University of Alberta, Edmonton, Canada.,The Women and Children's Health Research Institute, Edmonton, Canada
| | - Allein Plain
- Department of Physiology, University of Alberta, Edmonton, Canada.,The Women and Children's Health Research Institute, Edmonton, Canada
| | - Megan R Beggs
- Department of Physiology, University of Alberta, Edmonton, Canada.,The Women and Children's Health Research Institute, Edmonton, Canada
| | - Henrik Dimke
- Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - R Todd Alexander
- Department of Physiology, University of Alberta, Edmonton, Canada.,The Women and Children's Health Research Institute, Edmonton, Canada.,Department of Pediatrics, Edmonton Clinic Health Academy, University of Alberta, Edmonton, Canada
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25
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Broadbent D, Ahmadzai MM, Kammala AK, Yang C, Occhiuto C, Das R, Subramanian H. Roles of NHERF Family of PDZ-Binding Proteins in Regulating GPCR Functions. Adv Immunol 2017; 136:353-385. [PMID: 28950951 DOI: 10.1016/bs.ai.2017.05.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Multicellular organisms are equipped with an array of G-protein-coupled receptors (GPCRs) that mediate cell-cell signaling allowing them to adapt to environmental cues and ultimately survive. This is mechanistically possible through complex intracellular GPCR machinery that encompasses a vast network of proteins. Within this network, there is a group called scaffolding proteins that facilitate proper localization of signaling proteins for a quick and robust GPCR response. One protein family within this scaffolding group is the PSD-95/Dlg/ZO-1 (PDZ) family which is important for GPCR localization, internalization, recycling, and downstream signaling. Although the PDZ family of proteins regulate the functions of several receptors, this chapter focuses on a subfamily within the PDZ protein family called the Na+/H+ exchanger regulatory factors (NHERFs). Here we extensively review the predominantly characterized roles of NHERFs in renal phosphate absorption, intestinal ion regulation, cancer progression, and immune cell functions. Finally, we discuss the future perspectives and possible clinical application of targeting NHERFs in several disorders.
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Affiliation(s)
| | | | | | - Canchai Yang
- Michigan State University, East Lansing, MI, United States
| | | | - Rupali Das
- Michigan State University, East Lansing, MI, United States
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Fakhar M, Rashid S. Targeted inhibition of Klotho binding to fibroblast growth factor 23 prevents hypophosphetemia. J Mol Graph Model 2017; 75:9-19. [PMID: 28501532 DOI: 10.1016/j.jmgm.2017.04.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 04/13/2017] [Accepted: 04/18/2017] [Indexed: 02/08/2023]
Abstract
Klotho is a transmembrane protein which plays significant role in the pathogenesis of phosphate ion (Pi)-related disorders. Pi accumulation in human kidney tissues results in the major metabolic disorders due to malfunctioning of Klotho-FGFR1-FGF23 trimeric complex. The potential role of Klotho in Pi metabolism was elaborated through modeling and interaction analysis of glycosyl hydrolase (GS1 and GS2) domains with Fibroblast growth factor 23 (FGF23). In order to inhibit the association of Klotho and FGF23, binding patterns of three reported hits (N-(2-chlorophenyl)-1H-indole-3-carboxamide, N-[2-(1-cyclohexen-1-yl)ethyl]-6,7,8,9-tetrahydropyrido[1,2-e]purin-4-amine and 2-(1-propyl)amino-11-chlorothiazolo[5,4-a]acridine) were evaluated through molecular docking analysis. These inhibitors effectively targeted both GS1 and GS2 domains of Klotho at the similar sites required for FGF23 binding. To further characterize the comparative binding profile of these compounds, molecular dynamics simulation assays were performed. Taken together, current study emphasizes that Klotho may be anticipated as a target molecule in familial hypophosphatemic rickets and mentioned compounds may prove to be effective therapeutic targets against hypophosphetemia induced disorders.
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Affiliation(s)
- Muhammad Fakhar
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan
| | - Sajid Rashid
- National Center for Bioinformatics, Quaid-i-Azam University, Islamabad, Pakistan.
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Mamonova T, Zhang Q, Chandra M, Collins BM, Sarfo E, Bu Z, Xiao K, Bisello A, Friedman PA. Origins of PDZ Binding Specificity. A Computational and Experimental Study Using NHERF1 and the Parathyroid Hormone Receptor. Biochemistry 2017; 56:2584-2593. [PMID: 28376304 DOI: 10.1021/acs.biochem.7b00078] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Na+/H+ exchanger regulatory factor-1 (NHERF1) is a scaffolding protein containing two PSD95/discs large protein/ZO1 (PDZ) domains that modifies the signaling, trafficking, and function of the parathyroid hormone receptor (PTHR), a family B G-protein-coupled receptor. PTHR and NHERF1 bind through a PDZ-ligand-recognition mechanism. We show that PTH elicits phosphorylation of Thr591 in the canonical -ETVM binding motif of PTHR. Conservative substitution of Thr591 with Cys does not affect PTH(1-34)-induced cAMP production or binding of PTHR to NHERF1. The findings suggested the presence of additional sites upstream of the PDZ-ligand motif through which the two proteins interact. Structural determinants outside the canonical NHERF1 PDZ-PTHR interface that influence binding have not been characterized. We used molecular dynamics (MD) simulation to predict residues involved in these interactions. Simulation data demonstrate that the negatively charged Glu side chains at positions -3, -5, and -6 upstream of the PDZ binding motif are involved in PDZ-PTHR recognition. Engineered mutant peptides representing the PTHR C-terminal region were used to measure the binding affinity with NHERF1 PDZ domains. Comparable micromolar affinities for peptides of different length were confirmed by fluorescence polarization, isothermal titration calorimetry, and surface plasmon resonance. Binding affinities measured for Ala variants validate MD simulations. The linear relation between the change in enthalpy and entropy following Ala substitutions at upstream positions -3, -5, and -6 of the PTHR peptide provides a clear example of the thermodynamic compensation rule. Overall, our data highlight sequences in PTHR that contribute to NHERF1 interaction and can be altered to prevent phosphorylation-mediated inhibition.
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Affiliation(s)
| | | | - Mintu Chandra
- Institute for Molecular Bioscience, The University of Queensland , St. Lucia, Brisbane, Queensland 4072, Australia
| | - Brett M Collins
- Institute for Molecular Bioscience, The University of Queensland , St. Lucia, Brisbane, Queensland 4072, Australia
| | - Edward Sarfo
- Department of Chemistry, City College of New York , New York, New York 10031, United States
| | - Zimei Bu
- Department of Chemistry, City College of New York , New York, New York 10031, United States
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Dynamic NHERF interaction with TRPC4/5 proteins is required for channel gating by diacylglycerol. Proc Natl Acad Sci U S A 2016; 114:E37-E46. [PMID: 27994151 DOI: 10.1073/pnas.1612263114] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The activation mechanism of the classical transient receptor potential channels TRPC4 and -5 via the Gq/11 protein-phospholipase C (PLC) signaling pathway has remained elusive so far. In contrast to all other TRPC channels, the PLC product diacylglycerol (DAG) is not sufficient for channel activation, whereas TRPC4/5 channel activity is potentiated by phosphatidylinositol 4,5-bisphosphate (PIP2) depletion. As a characteristic structural feature, TRPC4/5 channels contain a C-terminal PDZ-binding motif allowing for binding of the scaffolding proteins Na+/H+ exchanger regulatory factor (NHERF) 1 and 2. PKC inhibition or the exchange of threonine for alanine in the C-terminal PDZ-binding motif conferred DAG sensitivity to the channel. Altogether, we present a DAG-mediated activation mechanism for TRPC4/5 channels tightly regulated by NHERF1/2 interaction. PIP2 depletion evokes a C-terminal conformational change of TRPC5 proteins leading to dynamic dissociation of NHERF1/2 from the C terminus of TRPC5 as a prerequisite for DAG sensitivity. We show that NHERF proteins are direct regulators of ion channel activity and that DAG sensitivity is a distinctive hallmark of TRPC channels.
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Abstract
PTH and Vitamin D are two major regulators of mineral metabolism. They play critical roles in the maintenance of calcium and phosphate homeostasis as well as the development and maintenance of bone health. PTH and Vitamin D form a tightly controlled feedback cycle, PTH being a major stimulator of vitamin D synthesis in the kidney while vitamin D exerts negative feedback on PTH secretion. The major function of PTH and major physiologic regulator is circulating ionized calcium. The effects of PTH on gut, kidney, and bone serve to maintain serum calcium within a tight range. PTH has a reciprocal effect on phosphate metabolism. In contrast, vitamin D has a stimulatory effect on both calcium and phosphate homeostasis, playing a key role in providing adequate mineral for normal bone formation. Both hormones act in concert with the more recently discovered FGF23 and klotho, hormones involved predominantly in phosphate metabolism, which also participate in this closely knit feedback circuit. Of great interest are recent studies demonstrating effects of both PTH and vitamin D on the cardiovascular system. Hyperparathyroidism and vitamin D deficiency have been implicated in a variety of cardiovascular disorders including hypertension, atherosclerosis, vascular calcification, and kidney failure. Both hormones have direct effects on the endothelium, heart, and other vascular structures. How these effects of PTH and vitamin D interface with the regulation of bone formation are the subject of intense investigation.
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Affiliation(s)
- Syed Jalal Khundmiri
- Department of Medicine, University of Louisville, Louisville, Kentucky, USA
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky, USA
| | - Rebecca D. Murray
- Department of Medicine, University of Louisville, Louisville, Kentucky, USA
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky, USA
| | - Eleanor Lederer
- Department of Medicine, University of Louisville, Louisville, Kentucky, USA
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky, USA
- Robley Rex VA Medical Center, University of Louisville, Louisville, Kentucky, USA
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Abstract
Phosphate is essential for growth and maintenance of the skeleton and for generating high-energy phosphate compounds. Evolutionary adaptation to high dietary phosphorous in humans and other terrestrial vertebrates involves regulated mechanisms assuring the efficient renal elimination of excess phosphate. These mechanisms prominently include PTH, FGF23, and Vitamin D, which directly and indirectly regulate phosphate transport. Disordered phosphate homeostasis is associated with pathologies ranging from kidney stones to kidney failure. Chronic kidney disease results in hyperphosphatemia, an elevated calcium×phosphate product with considerable morbidity and mortality, mostly associated with adverse cardiovascular events. This chapter highlights recent findings and insights regarding the hormonal regulation of renal phosphate transport along with imbalances of phosphate balance due to acquired or inherited diseases states.
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D. Murray R, D. Lederer E, J. Khundmiri S. Role of PTH in the Renal Handling of Phosphate. AIMS MEDICAL SCIENCE 2015. [DOI: 10.3934/medsci.2015.3.162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Abstract
The regulation of serum phosphate, an acknowledged risk factor for chronic kidney disease and cardiovascular mortality, is poorly understood. The discovery of fibroblast growth factor 23 (FGF23) as a key regulator of renal phosphate handling and activation of vitamin D has revolutionized our comprehension of phosphate homeostasis. Through as yet undetermined mechanisms, circulating and dietary phosphate appear to have a direct effect on FGF23 release by bone cells that, in turn, causes renal phosphate excretion and decreases intestinal phosphate absorption through a decrease in vitamin D production. Thus, the two major phosphaturic hormones, PTH and FGF23, have opposing effects on vitamin D production, placing vitamin D at the nexus of phosphate homeostasis. While our understanding of phosphate homeostasis has advanced, the factors determining regulation of serum phosphate level remain enigmatic. Diet, time of day, season, gender, age and genetics have all been identified as significant contributors to serum phosphate level. The effects of these factors on serum phosphate have major implications for what is understood as 'normal' and for studies of phosphate homeostasis and metabolism. Moreover, other hormonal mediators such as dopamine, insulin-like growth factor, and angiotensin II also affect renal handling of phosphate. How the major hormone effects on phosphate handling are regulated and how the effect of these other factors are integrated to yield the measurable serum phosphate are only now beginning to be studied.
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Affiliation(s)
- Eleanor Lederer
- Medical Services, Robley Rex VA Medical Center, Department of Medicine, University of Louisville School of Medicine, Louisville, KY, 40202, USA
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Fabbri S, Ciuffi S, Nardone V, Gomes AR, Mavilia C, Zonefrati R, Galli G, Luzi E, Tanini A, Brandi ML. PTH-C1: a rat continuous cell line expressing the parathyroid phenotype. Endocrine 2014; 47:90-9. [PMID: 24627164 DOI: 10.1007/s12020-014-0229-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 02/26/2014] [Indexed: 01/17/2023]
Abstract
The lack of a continuous cell line of epithelial parathyroid cells able to produce parathyroid hormone (PTH) has hampered the studies on in vitro evaluation of the mechanisms involved in the control of parathyroid cell function and proliferation. The PT-r cell line was first established from rat parathyroid tissue in 1987, but these cells were known to express the parathyroid hormone-related peptide (Pthrp) gene, but not the Pth gene. In an attempt to subclone the PT-r cell line, a rat parathyroid cell strain was isolated and named PTH-C1. During 3 years, in culture, PTH-C1 cells maintained an epithelioid morphology, displaying a diploid chromosome number, a doubling time around 15 h during the exponential phase of growth, and parathyroid functional features. PTH-C1 cell line produces PTH and expresses the calcium sensing receptor (Casr) gene and other genes known to be involved in parathyroid function. Most importantly, the PTH-C1 cells also exhibit an in vitro secretory response to calcium. Altogether these findings indicate the uniqueness of the PTH-C1 cell line as an in vitro model for cellular and molecular studies on parathyroid physiopathology.
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Affiliation(s)
- Sergio Fabbri
- Department of Surgery and Translational Medicine, University of Florence, Largo Brambilla 3, 50134, Florence, Italy
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Wagner CA, Rubio-Aliaga I, Biber J, Hernando N. Genetic diseases of renal phosphate handling. Nephrol Dial Transplant 2014; 29:iv45-iv54. [DOI: 10.1093/ndt/gfu217] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
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Interstitial calcinosis in renal papillae of genetically engineered mouse models: relation to Randall's plaques. Urolithiasis 2014; 43 Suppl 1:65-76. [PMID: 25096800 DOI: 10.1007/s00240-014-0699-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 07/22/2014] [Indexed: 02/08/2023]
Abstract
Genetically engineered mouse models (GEMMs) have been highly instrumental in elucidating gene functions and molecular pathogenesis of human diseases, although their use in studying kidney stone formation or nephrolithiasis remains relatively limited. This review intends to provide an overview of several knockout mouse models that develop interstitial calcinosis in the renal papillae. Included herein are mice deficient for Tamm-Horsfall protein (THP; also named uromodulin), osteopontin (OPN), both THP and OPN, Na(+)-phosphate cotransporter Type II (Npt2a) and Na(+)/H(+) exchanger regulatory factor (NHERF-1). The baseline information of each protein is summarized, along with key morphological features of the interstitial calcium deposits in mice lacking these proteins. Attempts are made to correlate the papillary interstitial deposits found in GEMMs with Randall's plaques, the latter considered precursors of idiopathic calcium stones in patients. The pathophysiology that underlies the renal calcinosis in the knockout mice is also discussed wherever information is available. Not all the knockout models are allocated equal space because some are more extensively characterized than others. Despite the inroads already made, the exact physiological underpinning, origin, evolution and fate of the papillary interstitial calcinosis in the GEMMs remain incompletely defined. Greater investigative efforts are warranted to pin down the precise role of the papillary interstitial calcinosis in nephrolithiasis using the existing models. Additionally, more sophisticated, second-generation GEMMs that allow gene inactivation in a time-controlled manner and "compound mice" that bear several genetic alterations are urgently needed, in light of mounting evidence that nephrolithiasis is a multifactorial, multi-stage and polygenic disease.
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Wang B, Yang Y, Liu L, Blair HC, Friedman PA. NHERF1 regulation of PTH-dependent bimodal Pi transport in osteoblasts. Bone 2013; 52:268-77. [PMID: 23046970 PMCID: PMC3513631 DOI: 10.1016/j.bone.2012.10.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 09/18/2012] [Accepted: 10/01/2012] [Indexed: 02/01/2023]
Abstract
Control of systemic inorganic phosphate (Pi) levels is crucial for osteoid mineralization. Parathyroid hormone (PTH) mediates actions on phosphate homeostasis mostly by regulating the activity of the type 2 sodium-phosphate cotransporter (Npt2), and this action requires the PDZ protein NHERF1. Osteoblasts express Npt2 and in response to PTH enhance osteogenesis by increasing mineralized matrix. The regulation of Pi transport in osteoblasts is poorly understood. To address this gap we characterized PTH-dependent Pi transport and the role of NHERF1 in primary mouse calvarial osteoblasts. Under proliferating conditions osteoblasts express Npt2a, Npt2b, PTH receptor, and NHERF1. Npt2a mRNA expression was lower in calvarial osteoblasts from NHERF1-null mice. Under basal conditions Pi uptake in osteoblasts from wild-type mice was greater than that of knockout mice. PTH inhibited Pi uptake in proliferating osteoblasts from wild-type mice, but not in cells from knockout mice. In vitro induction of mineralization enhanced osteoblast differentiation and increased osterix and osteocalcin expression. Contrary to the results with proliferating osteoblasts, PTH increased Pi uptake and ATP secretion in differentiated osteoblasts from wild-type mice. PTH had no effect on Pi uptake or ATP release in differentiated osteoblasts from knockout mice. NHERF1 regulation of PTH-sensitive Pi uptake in proliferating osteoblasts is mediated by cAMP/PKA and PLC/PKC, while modulation of Pi uptake in differentiated osteoblasts depends only on cAMP/PKA signaling. The results suggest that NHERF1 cooperates with PTH in differentiated osteoblasts to increase matrix mineralization. We conclude that NHERF1 regulates PTH that differentially affects Na-dependent Pi transport at distinct stages of osteoblast proliferation and maturation.
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Affiliation(s)
- Bin Wang
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology & Chemical Biology, Pittsburgh, PA, USA
| | - Yanmei Yang
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology & Chemical Biology, Pittsburgh, PA, USA
| | - Li Liu
- Pittsburgh Veterans Affairs Medical Center and Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Harry C. Blair
- Pittsburgh Veterans Affairs Medical Center and Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Peter A. Friedman
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology & Chemical Biology, Pittsburgh, PA, USA
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Wang B, Means CK, Yang Y, Mamonova T, Bisello A, Altschuler DL, Scott JD, Friedman PA. Ezrin-anchored protein kinase A coordinates phosphorylation-dependent disassembly of a NHERF1 ternary complex to regulate hormone-sensitive phosphate transport. J Biol Chem 2012; 287:24148-63. [PMID: 22628548 PMCID: PMC3397842 DOI: 10.1074/jbc.m112.369405] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 05/19/2012] [Indexed: 12/14/2022] Open
Abstract
Congenital defects in the Na/H exchanger regulatory factor-1 (NHERF1) are linked to disordered phosphate homeostasis and skeletal abnormalities in humans. In the kidney, these mutations interrupt parathyroid hormone (PTH)-responsive sequestration of the renal phosphate transporter, Npt2a, with ensuing urinary phosphate wasting. We now report that NHERF1, a modular PDZ domain scaffolding protein, coordinates the assembly of an obligate ternary complex with Npt2a and the PKA-anchoring protein ezrin to facilitate PTH-responsive cAMP signaling events. Activation of ezrin-anchored PKA initiates NHERF1 phosphorylation to disassemble the ternary complex, release Npt2a, and thereby inhibit phosphate transport. Loss-of-function mutations stabilize an inactive NHERF1 conformation that we show is refractory to PKA phosphorylation and impairs assembly of the ternary complex. Compensatory mutations introduced in mutant NHERF1 re-establish the integrity of the ternary complex to permit phosphorylation of NHERF1 and rescue PTH action. These findings offer new insights into a novel macromolecular mechanism for the physiological action of a critical ternary complex, where anchored PKA coordinates the assembly and turnover of the Npt2a-NHERF1-ezrin complex.
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Affiliation(s)
- Bin Wang
- From the Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - Chris K. Means
- the Howard Hughes Medical Institute, Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington 98195
| | - Yanmei Yang
- From the Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - Tatyana Mamonova
- From the Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - Alessandro Bisello
- From the Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - Daniel L. Altschuler
- From the Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - John D. Scott
- the Howard Hughes Medical Institute, Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington 98195
| | - Peter A. Friedman
- From the Laboratory for G Protein-coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
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