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Grace AF, Olubunmi AA, Adetutu OT, Kweku RJ, Olubisi AO, Daniel OF. Prevalence and Risk Factors of Vitamin D, Calcium and Phosphate Deficiency among Apparently Healthy Children Aged 6-24 Months in a Semi-urban Community in Southwest, Nigeria. Niger Postgrad Med J 2024; 31:213-219. [PMID: 39219343 DOI: 10.4103/npmj.npmj_101_24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2024] [Accepted: 07/24/2024] [Indexed: 09/04/2024]
Abstract
BACKGROUND Adequate levels of calcium, phosphate and Vitamin D are essential for bone physiology and growth, as well as preventing some common childhood illnesses. This study aimed to determine the prevalence of the deficiencies of these nutrients and factors affecting their serum levels in Nigerian children. METHODS This was a cross-sectional study that involved 220 apparently healthy children aged 6-24 months in Ikenne Local Government Area of Ogun State, Nigeria. Serum calcium and phosphate were assayed using the calorimetric method, while Vitamin D (25-OH Vitamin D) was assayed with ELISA. RESULTS The mean (±standard deviation [SD]) serum Vitamin D level was 55.07 ± 16.53 ng/ml, while the mean (±SD) serum calcium and phosphate were 2.27 ± 0.13 mmol/l and 1.28 ± 0.18 mmol/l, respectively. Eleven (5%) of the children had hypovitaminosis D, 23 (10.5%) had hypocalcaemia and 12 (5.5%) had hypophosphataemia. Factors found to be significantly associated with hypovitaminosis D included low consumption of milk and the use of a hijab veil, while malnutrition (both undernutrition and overnutrition) was significantly associated with hypocalcaemia. CONCLUSION The prevalence levels of hypovitaminosis D and hypophosphataemia were low, while hypocalcaemia was more common. Low milk consumption and use of a hijab veil were risk factors for hypovitaminosis D, while malnutrition was a risk factor for hypocalcaemia. Malnourished children, especially overnourished ones, should be routinely screened for hypocalcaemia because of its high prevalence among them.
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Affiliation(s)
- Ajayi Fisayo Grace
- Department of Paediatrics, Babcock University Teaching Hospital, Ilishan-Remo, Nigeria
| | | | - Ogunlesi Tinuade Adetutu
- Department of Paediatrics, Babcock University Teaching Hospital, Ilishan-Remo, Nigeria
- Department of Paediatrics, Olabisi Onabanjo University Teaching Hospital, Sagamu, Ogun State, Nigeria
| | - Renner James Kweku
- Department of Paediatrics, Babcock University Teaching Hospital, Ilishan-Remo, Nigeria
| | | | - Obaya Fisayo Daniel
- Department of Paediatrics, Babcock University Teaching Hospital, Ilishan-Remo, Nigeria
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2
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Anghel L, Manole C, Nechita A, Tatu AL, Ștefănescu BI, Nechita L, Bușilă C, Zainea P, Baroiu L, Mușat CL. Calcium, Phosphorus and Magnesium Abnormalities Associated with COVID-19 Infection, and Beyond. Biomedicines 2023; 11:2362. [PMID: 37760804 PMCID: PMC10525362 DOI: 10.3390/biomedicines11092362] [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: 07/19/2023] [Revised: 08/08/2023] [Accepted: 08/18/2023] [Indexed: 09/29/2023] Open
Abstract
The coronavirus disease (COVID-19) pandemic caused by the novel coronavirus SARS-CoV-2 has had a profound impact on global health, leading to a surge in research to better understand the pathophysiology of the disease. Among the various aspects under investigation, disruptions in mineral homeostasis have emerged as a critical area of interest. This review aims to provide an overview of the current evidence linking calcium, phosphorus and magnesium abnormalities with COVID-19 infection and explores the potential implications beyond the acute phase of the disease. Beyond the acute phase of COVID-19, evidence suggests a potential impact of these mineral abnormalities on long-term health outcomes. Persistent alterations in calcium, phosphorus and magnesium levels have been linked to increased cardiovascular risk, skeletal complications and metabolic disorders, warranting continuous monitoring and management in post-COVID-19 patients.
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Affiliation(s)
- Lucreția Anghel
- Clinical Medical Department, Faculty of Medicine and Pharmacy, ‘Dunarea de Jos’ University, 800008 Galati, Romania; (L.A.); (A.N.); (A.L.T.); (L.N.); (C.B.); (L.B.)
- ‘Sf. Apostol Andrei’ Clinical Emergency County Hospital, 800578 Galati, Romania; (B.I.Ș.); (C.L.M.)
| | - Corina Manole
- Clinical Medical Department, Faculty of Medicine and Pharmacy, ‘Dunarea de Jos’ University, 800008 Galati, Romania; (L.A.); (A.N.); (A.L.T.); (L.N.); (C.B.); (L.B.)
- ‘Sf. Apostol Andrei’ Clinical Emergency County Hospital, 800578 Galati, Romania; (B.I.Ș.); (C.L.M.)
| | - Aurel Nechita
- Clinical Medical Department, Faculty of Medicine and Pharmacy, ‘Dunarea de Jos’ University, 800008 Galati, Romania; (L.A.); (A.N.); (A.L.T.); (L.N.); (C.B.); (L.B.)
- ‘Sf. Ioan’ Clinical Hospital for Children, 800487 Galati, Romania
| | - Alin Laurențiu Tatu
- Clinical Medical Department, Faculty of Medicine and Pharmacy, ‘Dunarea de Jos’ University, 800008 Galati, Romania; (L.A.); (A.N.); (A.L.T.); (L.N.); (C.B.); (L.B.)
- ‘Sf. Cuv. Parascheva’ Clinical Hospital of Infectious Diseases, 800179 Galati, Romania
- Multidisciplinary Integrated Center of Dermatological Interface Research MIC-DIR, 800010 Galati, Romania
| | - Bogdan Ioan Ștefănescu
- ‘Sf. Apostol Andrei’ Clinical Emergency County Hospital, 800578 Galati, Romania; (B.I.Ș.); (C.L.M.)
- Clinical Surgery Department, Faculty of Medicine and Pharmacy, ‘Dunarea de Jos’ University, 800008 Galati, Romania
| | - Luiza Nechita
- Clinical Medical Department, Faculty of Medicine and Pharmacy, ‘Dunarea de Jos’ University, 800008 Galati, Romania; (L.A.); (A.N.); (A.L.T.); (L.N.); (C.B.); (L.B.)
- ‘Sf. Apostol Andrei’ Clinical Emergency County Hospital, 800578 Galati, Romania; (B.I.Ș.); (C.L.M.)
| | - Camelia Bușilă
- Clinical Medical Department, Faculty of Medicine and Pharmacy, ‘Dunarea de Jos’ University, 800008 Galati, Romania; (L.A.); (A.N.); (A.L.T.); (L.N.); (C.B.); (L.B.)
- ‘Sf. Ioan’ Clinical Hospital for Children, 800487 Galati, Romania
| | - Pușica Zainea
- Clinical Emergency County Hospital Braila, 810318 Braila, Romania;
| | - Liliana Baroiu
- Clinical Medical Department, Faculty of Medicine and Pharmacy, ‘Dunarea de Jos’ University, 800008 Galati, Romania; (L.A.); (A.N.); (A.L.T.); (L.N.); (C.B.); (L.B.)
- ‘Sf. Cuv. Parascheva’ Clinical Hospital of Infectious Diseases, 800179 Galati, Romania
| | - Carmina Liana Mușat
- ‘Sf. Apostol Andrei’ Clinical Emergency County Hospital, 800578 Galati, Romania; (B.I.Ș.); (C.L.M.)
- Department of Morphological and Functional Sciences, Faculty of Medicine and Pharmacy, ‘Dunarea de Jos’ University, 800008 Galati, Romania
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Silencing of the Ca2+ Channel ORAI1 Improves the Multi-Systemic Phenotype of Tubular Aggregate Myopathy (TAM) and Stormorken Syndrome (STRMK) in Mice. Int J Mol Sci 2022; 23:ijms23136968. [PMID: 35805973 PMCID: PMC9266658 DOI: 10.3390/ijms23136968] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/17/2022] [Accepted: 06/20/2022] [Indexed: 12/04/2022] Open
Abstract
Tubular aggregate myopathy (TAM) and Stormorken syndrome (STRMK) form a clinical continuum associating progressive muscle weakness with additional multi-systemic anomalies of the bones, skin, spleen, and platelets. TAM/STRMK arises from excessive extracellular Ca2+ entry due to gain-of-function mutations in the Ca2+ sensor STIM1 or the Ca2+ channel ORAI1. Currently, no treatment is available. Here we assessed the therapeutic potential of ORAI1 downregulation to anticipate and reverse disease development in a faithful mouse model carrying the most common TAM/STRMK mutation and recapitulating the main signs of the human disorder. To this aim, we crossed Stim1R304W/+ mice with Orai1+/− mice expressing 50% of ORAI1. Systematic phenotyping of the offspring revealed that the Stim1R304W/+Orai1+/− mice were born with a normalized ratio and showed improved postnatal growth, bone architecture, and partly ameliorated muscle function and structure compared with their Stim1R304W/+ littermates. We also produced AAV particles containing Orai1-specific shRNAs, and intramuscular injections of Stim1R304W/+ mice improved the skeletal muscle contraction and relaxation properties, while muscle histology remained unchanged. Altogether, we provide the proof-of-concept that Orai1 silencing partially prevents the development of the multi-systemic TAM/STRMK phenotype in mice, and we also established an approach to target Orai1 expression in postnatal tissues.
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4
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Omosule CL, Holmes V, Jasek C, Roper SM. Pediatric ionized calcium reference intervals from archived radiometer data. Clin Biochem 2022; 104:13-18. [DOI: 10.1016/j.clinbiochem.2022.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 03/02/2022] [Accepted: 03/08/2022] [Indexed: 11/27/2022]
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Pathophysiological Effects of Overactive STIM1 on Murine Muscle Function and Structure. Cells 2021; 10:cells10071730. [PMID: 34359900 PMCID: PMC8304505 DOI: 10.3390/cells10071730] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 06/25/2021] [Accepted: 06/29/2021] [Indexed: 12/15/2022] Open
Abstract
Store-operated Ca2+ entry (SOCE) is a ubiquitous mechanism regulating extracellular Ca2+ entry to control a multitude of Ca2+-dependent signaling pathways and cellular processes. SOCE relies on the concerted activity of the reticular Ca2+ sensor STIM1 and the plasma membrane Ca2+ channel ORAI1, and dysfunctions of these key factors result in human pathologies. STIM1 and ORAI1 gain-of-function (GoF) mutations induce excessive Ca2+ influx through SOCE over-activation, and cause tubular aggregate myopathy (TAM) and Stormorken syndrome (STRMK), two overlapping disorders characterized by muscle weakness and additional multi-systemic signs affecting growth, platelets, spleen, skin, and intellectual abilities. In order to investigate the pathophysiological effect of overactive SOCE on muscle function and structure, we combined transcriptomics with morphological and functional studies on a TAM/STRMK mouse model. Muscles from Stim1R304W/+ mice displayed aberrant expression profiles of genes implicated in Ca2+ handling and excitation-contraction coupling (ECC), and in vivo investigations evidenced delayed muscle contraction and relaxation kinetics. We also identified signs of reticular stress and abnormal mitochondrial activity, and histological and respirometric analyses on muscle samples revealed enhanced myofiber degeneration associated with reduced mitochondrial respiration. Taken together, we uncovered a molecular disease signature and deciphered the pathomechanism underlying the functional and structural muscle anomalies characterizing TAM/STRMK.
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6
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Papadopoulou A, Bountouvi E, Karachaliou FE. The Molecular Basis of Calcium and Phosphorus Inherited Metabolic Disorders. Genes (Basel) 2021; 12:genes12050734. [PMID: 34068220 PMCID: PMC8153134 DOI: 10.3390/genes12050734] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 04/30/2021] [Accepted: 05/05/2021] [Indexed: 02/07/2023] Open
Abstract
Calcium (Ca) and Phosphorus (P) hold a leading part in many skeletal and extra-skeletal biological processes. Their tight normal range in serum mirrors their critical role in human well-being. The signalling “voyage” starts at Calcium Sensing Receptor (CaSR) localized on the surface of the parathyroid glands, which captures the “oscillations” of extracellular ionized Ca and transfers the signal downstream. Parathyroid hormone (PTH), Vitamin D, Fibroblast Growth Factor (FGF23) and other receptors or ion-transporters, work synergistically and establish a highly regulated signalling circuit between the bone, kidneys, and intestine to ensure the maintenance of Ca and P homeostasis. Any deviation from this well-orchestrated scheme may result in mild or severe pathologies expressed by biochemical and/or clinical features. Inherited disorders of Ca and P metabolism are rare. However, delayed diagnosis or misdiagnosis may cost patient’s quality of life or even life expectancy. Unravelling the thread of the molecular pathways involving Ca and P signaling, we can better understand the link between genetic alterations and biochemical and/or clinical phenotypes and help in diagnosis and early therapeutic intervention.
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7
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Silva-Rojas R, Laporte J, Böhm J. STIM1/ ORAI1 Loss-of-Function and Gain-of-Function Mutations Inversely Impact on SOCE and Calcium Homeostasis and Cause Multi-Systemic Mirror Diseases. Front Physiol 2020; 11:604941. [PMID: 33250786 PMCID: PMC7672041 DOI: 10.3389/fphys.2020.604941] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 10/15/2020] [Indexed: 12/19/2022] Open
Abstract
Store-operated Ca2+ entry (SOCE) is a ubiquitous and essential mechanism regulating Ca2+ homeostasis in all tissues, and controls a wide range of cellular functions including keratinocyte differentiation, osteoblastogenesis and osteoclastogenesis, T cell proliferation, platelet activation, and muscle contraction. The main SOCE actors are STIM1 and ORAI1. Depletion of the reticular Ca2+ stores induces oligomerization of the luminal Ca2+ sensor STIM1, and the oligomers activate the plasma membrane Ca2+ channel ORAI1 to trigger extracellular Ca2+ entry. Mutations in STIM1 and ORAI1 result in abnormal SOCE and lead to multi-systemic disorders. Recessive loss-of-function mutations are associated with CRAC (Ca2+ release-activated Ca2+) channelopathy, involving immunodeficiency and autoimmunity, muscular hypotonia, ectodermal dysplasia, and mydriasis. In contrast, dominant STIM1 and ORAI1 gain-of-function mutations give rise to tubular aggregate myopathy and Stormorken syndrome (TAM/STRMK), forming a clinical spectrum encompassing muscle weakness, thrombocytopenia, ichthyosis, hyposplenism, short stature, and miosis. Functional studies on patient-derived cells revealed that CRAC channelopathy mutations impair SOCE and extracellular Ca2+ influx, while TAM/STRMK mutations induce excessive Ca2+ entry through SOCE over-activation. In accordance with the opposite pathomechanisms underlying both disorders, CRAC channelopathy and TAM/STRMK patients show mirror phenotypes at the clinical and molecular levels, and the respective animal models recapitulate the skin, bones, immune system, platelet, and muscle anomalies. Here we review and compare the clinical presentations of CRAC channelopathy and TAM/STRMK patients and the histological and molecular findings obtained on human samples and murine models to highlight the mirror phenotypes in different tissues, and to point out potentially undiagnosed anomalies in patients, which may be relevant for disease management and prospective therapeutic approaches.
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Affiliation(s)
- Roberto Silva-Rojas
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Inserm U1258, CNRS UMR 7104, Université de Strasbourg, Illkirch, France
| | - Jocelyn Laporte
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Inserm U1258, CNRS UMR 7104, Université de Strasbourg, Illkirch, France
| | - Johann Böhm
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Inserm U1258, CNRS UMR 7104, Université de Strasbourg, Illkirch, France
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8
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Leung J, Crook M. Disorders of phosphate metabolism. J Clin Pathol 2019; 72:741-747. [DOI: 10.1136/jclinpath-2018-205130] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 06/13/2019] [Accepted: 07/20/2019] [Indexed: 12/26/2022]
Abstract
Phosphate in both inorganic and organic form is essential for several functions in the body. Plasma phosphate level is maintained by a complex interaction between intestinal absorption, renal tubular reabsorption, and the transcellular movement of phosphate between intracellular fluid and bone storage pools. This homeostasis is regulated by several hormones, principally the parathyroid hormone, 1,25-dihydroxyvitamin D and fibroblast growth factor 23. Abnormalities in phosphate regulation can lead to serious and fatal complications. In this review phosphate homeostasis and the aetiology, pathophysiology, clinical features, investigation and management of hypophosphataemia and hyperphosphataemia will be discussed.
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9
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Vlot MC, den Heijer M, de Jongh RT, Vervloet MG, Lems WF, de Jonge R, Obermayer-Pietsch B, Heijboer AC. Clinical utility of bone markers in various diseases. Bone 2018; 114:215-225. [PMID: 29920402 DOI: 10.1016/j.bone.2018.06.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 06/13/2018] [Accepted: 06/15/2018] [Indexed: 12/13/2022]
Abstract
Measurements of bone markers (BMs) in peripheral blood or urine are a pivotal part of bone research within modern clinical medicine. In recent years the use of BMs increased substantially as they can be useful either to diagnose bone (related) disease and to follow its natural history, but also to monitor the effects of interventions. However, the use of BMs is still complicated mainly due to (pre)analytical variability of these substances, limited accessibility of assays, variable cut-off values in different countries and laboratories and heterogeneous results with regard to clinical implications of measuring BMs in several studies. This review will provide the clinician with a practical guide, based on current evidence, in which circumstances to test which bone markers for optimal diagnostic purposes, in order to improve patient care in different areas of bone diseases including Paget's disease, primary osteoporosis, tumor induced osteomalacia, hypophosphatemic rickets, van Buchem disease, chronic kidney disease, rheumatoid arthritis, neoplasma/multiple myeloma, type 2 diabetes mellitus and primary hyperparathyroidism. The clinician should consider fasting state, recent fractures, aging, menopausal status, concomitant liver and kidney disease when ordering and interpreting BM measurements as these factors might result in misleading BM concentrations. We found that BMs are clearly useful in the current diagnosis of tumor induced osteomalacia, van Buchem disease, Paget's disease and hypophosphatemic rickets. In addition, BMs are useful to monitor disease activity in chronic kidney disease, Paget's disease and are useful to monitor treatment adherence in osteoporosis.
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Affiliation(s)
- M C Vlot
- Department of Clinical Chemistry, Endocrine Laboratory, VU University Medical Center, de Boelelaan 1117, 1081 HV Amsterdam, the Netherlands; Department of Internal Medicine, Endocrinology, VU University Medical Center, de Boelelaan 1117, 1081 HV, Amsterdam, the Netherlands
| | - M den Heijer
- Department of Internal Medicine, Endocrinology, VU University Medical Center, de Boelelaan 1117, 1081 HV, Amsterdam, the Netherlands
| | - R T de Jongh
- Department of Internal Medicine, Endocrinology, VU University Medical Center, de Boelelaan 1117, 1081 HV, Amsterdam, the Netherlands
| | - M G Vervloet
- Department Nephrology, Amsterdam Cardiovascular Sciences (ACS) VU University Medical Center, de Boelelaan 1117, 1081 HV, Amsterdam, the Netherlands
| | - W F Lems
- Department of Rheumatology, VU University Medical Center, de Boelelaan 1117, 1081 HV, Amsterdam, the Netherlands
| | - R de Jonge
- Department of Clinical Chemistry, Endocrine Laboratory, VU University Medical Center, de Boelelaan 1117, 1081 HV Amsterdam, the Netherlands
| | - B Obermayer-Pietsch
- Department of Internal Medicine, Endocrinology and Diabetology, Medical University of Graz, Graz 8036, Austria
| | - A C Heijboer
- Department of Clinical Chemistry, Endocrine Laboratory, VU University Medical Center, de Boelelaan 1117, 1081 HV Amsterdam, the Netherlands; Department of Clinical Chemistry, Laboratory of Endocrinology, Academic Medical Center, Meibergdreef 9, 1105 AZ, Amsterdam, the Netherlands.
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Abstract
Inborn errors of metabolism encompass a wide spectrum of disorders, frequently affecting bone. The most important metabolic disorders that primarily influence calcium or phosphate balance, resulting in skeletal pathology, are hypophosphatemic rickets and hypophosphatasia. Conditions involving bone marrow or affecting skeletal growth and development are mainly the lysosomal storage disorders, in particular the mucopolysaccharidoses. In these disorders skeletal abnormalities are often the presenting symptom and early recognition and intervention improves outcome in many of these diseases. Many disorders of intermediary metabolism may impact bone health as well, resulting in higher frequencies of osteopenia and osteoporosis. In these conditions factors contributing to the reduced bone mineralization can be the disorder itself, the strict dietary treatment, reduced physical activity or sunlight exposure and/or early ovarian failure. Awareness of these primary or secondary bone problems amongst physicians treating patients with inborn errors of metabolism is of importance for optimization bone health and recognition of skeletal complications.
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Affiliation(s)
- M Langeveld
- Department of Endocrinology and Metabolism, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, the Netherlands.
| | - C E M Hollak
- Department of Endocrinology and Metabolism, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, the Netherlands
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Sneddon WB, Ruiz GW, Gallo LI, Xiao K, Zhang Q, Rbaibi Y, Weisz OA, Apodaca GL, Friedman PA. Convergent Signaling Pathways Regulate Parathyroid Hormone and Fibroblast Growth Factor-23 Action on NPT2A-mediated Phosphate Transport. J Biol Chem 2016; 291:18632-42. [PMID: 27432882 PMCID: PMC5009241 DOI: 10.1074/jbc.m116.744052] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Indexed: 12/18/2022] Open
Abstract
Parathyroid hormone (PTH) and FGF23 are the primary hormones regulating acute phosphate homeostasis. Human renal proximal tubule cells (RPTECs) were used to characterize the mechanism and signaling pathways of PTH and FGF23 on phosphate transport and the role of the PDZ protein NHERF1 in mediating PTH and FGF23 effects. RPTECs express the NPT2A phosphate transporter, αKlotho, FGFR1, FGFR3, FGFR4, and the PTH receptor. FGFR1 isoforms are formed from alternate splicing of exon 3 and of exon 8 or 9 in Ir-like loop 3. Exon 3 was absent, but mRNA containing both exons 8 and 9 is present in cytoplasm. Using an FGFR1c-specific antibody together with mass spectrometry analysis, we show that RPTECs express FGFR-β1C. The data are consistent with regulated FGFR1 splicing involving a novel cytoplasmic mechanism. PTH and FGF23 inhibited phosphate transport in a concentration-dependent manner. At maximally effective concentrations, PTH and FGF23 equivalently decreased phosphate uptake and were not additive, suggesting a shared mechanism of action. Protein kinase A or C blockade prevented PTH but not FGF23 actions. Conversely, inhibiting SGK1, blocking FGFR dimerization, or knocking down Klotho expression disrupted FGF23 actions but did not interfere with PTH effects. C-terminal FGF23(180-251) competitively and selectively blocked FGF23 action without disrupting PTH effects. However, both PTH and FGF23-sensitive phosphate transport were abolished by NHERF1 shRNA knockdown. Extended treatment with PTH or FGF23 down-regulated NPT2A without affecting NHERF1. We conclude that FGFR1c and PTHR signaling pathways converge on NHERF1 to inhibit PTH- and FGF23-sensitive phosphate transport and down-regulate NPT2A.
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MESH Headings
- Cell Line, Transformed
- Fibroblast Growth Factor-23
- Fibroblast Growth Factors/genetics
- Fibroblast Growth Factors/metabolism
- Glucuronidase/biosynthesis
- Glucuronidase/genetics
- Humans
- Klotho Proteins
- Parathyroid Hormone/genetics
- Parathyroid Hormone/metabolism
- Phosphates/metabolism
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Receptor, Fibroblast Growth Factor, Type 1/genetics
- Receptor, Fibroblast Growth Factor, Type 1/metabolism
- Receptor, Fibroblast Growth Factor, Type 3/biosynthesis
- Receptor, Fibroblast Growth Factor, Type 3/genetics
- Receptor, Fibroblast Growth Factor, Type 4/biosynthesis
- Receptor, Fibroblast Growth Factor, Type 4/genetics
- Receptor, Parathyroid Hormone, Type 1/genetics
- Receptor, Parathyroid Hormone, Type 1/metabolism
- Signal Transduction/physiology
- Sodium-Hydrogen Exchangers/genetics
- Sodium-Hydrogen Exchangers/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/metabolism
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Affiliation(s)
- W Bruce Sneddon
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and
| | - Giovanni W Ruiz
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Luciana I Gallo
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Kunhong Xiao
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and
| | - Qiangmin Zhang
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and
| | - Youssef Rbaibi
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Ora A Weisz
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 Cell Biology, and
| | - Gerard L Apodaca
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 Cell Biology, and
| | - Peter A Friedman
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and the Departments of Structural Biology,
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