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Zhu Y, He Q, Aydin C, Rubera I, Tauc M, Chen M, Weinstein LS, Marshansky V, Jüppner H, Bastepe M. Ablation of the Stimulatory G Protein α-Subunit in Renal Proximal Tubules Leads to Parathyroid Hormone-Resistance With Increased Renal Cyp24a1 mRNA Abundance and Reduced Serum 1,25-Dihydroxyvitamin D. Endocrinology 2016; 157:497-507. [PMID: 26671181 PMCID: PMC4733111 DOI: 10.1210/en.2015-1639] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
PTH regulates serum calcium, phosphate, and 1,25-dihydroxyvitamin D (1,25(OH)2D) levels by acting on bone and kidney. In renal proximal tubules (PTs), PTH inhibits reabsorption of phosphate and stimulates the synthesis of 1,25(OH)2D. The PTH receptor couples to multiple G proteins. We here ablated the α-subunit of the stimulatory G protein (Gsα) in mouse PTs by using Cre recombinase driven by the promoter of type-2 sodium-glucose cotransporter (Gsα(Sglt2KO) mice). Gsα(Sglt2KO) mice were normophosphatemic but displayed, relative to controls, hypocalcemia (1.19 ±0.01 vs 1.23 ±0.01 mmol/L; P < .05), reduced serum 1,25(OH)2D (59.3 ±7.0 vs 102.5 ±12.2 pmol/L; P < .05), and elevated serum PTH (834 ±133 vs 438 ±59 pg/mL; P < .05). PTH-induced elevation in urinary cAMP excretion was blunted in Gsα(Sglt2KO) mice (2- vs 4-fold over baseline in controls; P < .05). Relative to baseline in controls, PTH-induced reduction in serum phosphate tended to be blunted in Gsα(Sglt2KO) mice (-0.39 ±0.33 vs -1.34 ±0.36 mg/dL; P = .07). Gsα(Sglt2KO) mice showed elevated renal vitamin D 24-hydroxylase and bone fibroblast growth factor-23 (FGF23) mRNA abundance (∼3.4- and ∼11-fold over controls, respectively; P < .05) and tended to have elevated serum FGF23 (829 ±76 vs 632 ±60 pg/mL in controls; P = .07). Heterozygous mice having constitutive ablation of the maternal Gsα allele (E1(m-/+)) (model of pseudohypoparathyroidism type-Ia), in which Gsα levels in PT are reduced, also exhibited elevated serum FGF23 (474 ±20 vs 374 ±27 pg/mL in controls; P < .05). Our findings indicate that Gsα is required in PTs for suppressing renal vitamin D 24-hydroxylase mRNA levels and for maintaining normal serum 1,25(OH)2D.
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Affiliation(s)
- Yan Zhu
- Endocrine Unit (Z.Y., Q.H., C.A., H.J., M.B.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Department of Endodontics (C.A.), Gülhane Military Medical Academy, 06018 Ankara, Turkey; Faculty of Medicine (I.R., M.T.), Université de Nice Sophia Antipolis, 06107 Nice, France; Metabolic Diseases Branch (M.C., L.S.W.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Program in Membrane Biology (V.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Pediatric Nephrology Unit (H.J.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Qing He
- Endocrine Unit (Z.Y., Q.H., C.A., H.J., M.B.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Department of Endodontics (C.A.), Gülhane Military Medical Academy, 06018 Ankara, Turkey; Faculty of Medicine (I.R., M.T.), Université de Nice Sophia Antipolis, 06107 Nice, France; Metabolic Diseases Branch (M.C., L.S.W.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Program in Membrane Biology (V.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Pediatric Nephrology Unit (H.J.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Cumhur Aydin
- Endocrine Unit (Z.Y., Q.H., C.A., H.J., M.B.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Department of Endodontics (C.A.), Gülhane Military Medical Academy, 06018 Ankara, Turkey; Faculty of Medicine (I.R., M.T.), Université de Nice Sophia Antipolis, 06107 Nice, France; Metabolic Diseases Branch (M.C., L.S.W.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Program in Membrane Biology (V.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Pediatric Nephrology Unit (H.J.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Isabelle Rubera
- Endocrine Unit (Z.Y., Q.H., C.A., H.J., M.B.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Department of Endodontics (C.A.), Gülhane Military Medical Academy, 06018 Ankara, Turkey; Faculty of Medicine (I.R., M.T.), Université de Nice Sophia Antipolis, 06107 Nice, France; Metabolic Diseases Branch (M.C., L.S.W.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Program in Membrane Biology (V.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Pediatric Nephrology Unit (H.J.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Michel Tauc
- Endocrine Unit (Z.Y., Q.H., C.A., H.J., M.B.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Department of Endodontics (C.A.), Gülhane Military Medical Academy, 06018 Ankara, Turkey; Faculty of Medicine (I.R., M.T.), Université de Nice Sophia Antipolis, 06107 Nice, France; Metabolic Diseases Branch (M.C., L.S.W.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Program in Membrane Biology (V.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Pediatric Nephrology Unit (H.J.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Min Chen
- Endocrine Unit (Z.Y., Q.H., C.A., H.J., M.B.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Department of Endodontics (C.A.), Gülhane Military Medical Academy, 06018 Ankara, Turkey; Faculty of Medicine (I.R., M.T.), Université de Nice Sophia Antipolis, 06107 Nice, France; Metabolic Diseases Branch (M.C., L.S.W.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Program in Membrane Biology (V.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Pediatric Nephrology Unit (H.J.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Lee S Weinstein
- Endocrine Unit (Z.Y., Q.H., C.A., H.J., M.B.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Department of Endodontics (C.A.), Gülhane Military Medical Academy, 06018 Ankara, Turkey; Faculty of Medicine (I.R., M.T.), Université de Nice Sophia Antipolis, 06107 Nice, France; Metabolic Diseases Branch (M.C., L.S.W.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Program in Membrane Biology (V.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Pediatric Nephrology Unit (H.J.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Vladimir Marshansky
- Endocrine Unit (Z.Y., Q.H., C.A., H.J., M.B.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Department of Endodontics (C.A.), Gülhane Military Medical Academy, 06018 Ankara, Turkey; Faculty of Medicine (I.R., M.T.), Université de Nice Sophia Antipolis, 06107 Nice, France; Metabolic Diseases Branch (M.C., L.S.W.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Program in Membrane Biology (V.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Pediatric Nephrology Unit (H.J.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Harald Jüppner
- Endocrine Unit (Z.Y., Q.H., C.A., H.J., M.B.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Department of Endodontics (C.A.), Gülhane Military Medical Academy, 06018 Ankara, Turkey; Faculty of Medicine (I.R., M.T.), Université de Nice Sophia Antipolis, 06107 Nice, France; Metabolic Diseases Branch (M.C., L.S.W.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Program in Membrane Biology (V.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Pediatric Nephrology Unit (H.J.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Murat Bastepe
- Endocrine Unit (Z.Y., Q.H., C.A., H.J., M.B.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Department of Endodontics (C.A.), Gülhane Military Medical Academy, 06018 Ankara, Turkey; Faculty of Medicine (I.R., M.T.), Université de Nice Sophia Antipolis, 06107 Nice, France; Metabolic Diseases Branch (M.C., L.S.W.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Program in Membrane Biology (V.M.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; Pediatric Nephrology Unit (H.J.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
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Murray RD, Holthouser K, Clark BJ, Salyer SA, Barati MT, Khundmiri SJ, Lederer ED. Parathyroid hormone (PTH) decreases sodium-phosphate cotransporter type IIa (NpT2a) mRNA stability. Am J Physiol Renal Physiol 2013; 304:F1076-85. [DOI: 10.1152/ajprenal.00632.2012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The acute inhibitory effects of parathyroid hormone (PTH) on proximal tubule Na+-K+-ATPase (Na-K) and sodium-dependent phosphate (NaPi) transport have been extensively studied, while little is known about the chronic effects of PTH. Patients with primary hyperparathyroidism, a condition characterized by chronic elevations in PTH, exhibit persistent hypophosphatemia but not significant evidence of salt wasting. We postulate that chronic PTH stimulation results in differential desensitization of PTH responses. To address this hypothesis, we compared the effects of chronic PTH stimulation on Na-Pi cotransporter (Npt2a) expression and Na-K activity and expression in Sprague Dawley rats, transgenic mice featuring parathyroid-specific cyclin D1 overexpression (PTH-D1), and proximal tubule cell culture models. We demonstrated a progressive decrease in brush-border membrane (BBM) expression of Npt2a from rats treated with PTH for 6 h or 4 days, while Na-K expression and activity in the basolateral membranes (BLM) exhibited an initial decrease followed by recovery to control levels by 4 days. Npt2a protein expression in PTH-D1 mice was decreased relative to control animals, whereas levels of Na-K, NHERF-1, and PTH receptor remained unchanged. In PTH-D1 mice, NpT2a mRNA expression was reduced by 50% relative to control mice. In opossum kidney proximal tubule cells, PTH decreased Npt2a mRNA levels. Both actinomycin D and cycloheximide treatment prevented the PTH-mediated decrease in Npt2a mRNA, suggesting that the PTH response requires transcription and translation. These findings suggest that responses to chronic PTH exposure are selectively regulated at a posttranscriptional level. The persistence of the phosphaturic response to PTH occurs through posttranscriptional mechanisms.
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Affiliation(s)
- Rebecca D. Murray
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky
| | - Kristine Holthouser
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky
- Department of Medicine/Kidney Disease Program, University of Louisville, Louisville, Kentucky; and
| | - Barbara J. Clark
- Department of Biochemistry, University of Louisville, Louisville, Kentucky
| | - Sarah A. Salyer
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky
| | - Michelle T. Barati
- Department of Medicine/Kidney Disease Program, University of Louisville, Louisville, Kentucky; and
| | - Syed J. Khundmiri
- Robley Rex Veterans Affairs Medical Center, Louisville, Kentucky
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky
- Department of Medicine/Kidney Disease Program, University of Louisville, Louisville, Kentucky; and
| | - Eleanor D. Lederer
- Robley Rex Veterans Affairs Medical Center, Louisville, Kentucky
- Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky
- Department of Medicine/Kidney Disease Program, University of Louisville, Louisville, Kentucky; and
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