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Pierre-Ferrer S, Collins B, Lukacsovich D, Wen S, Cai Y, Winterer J, Yan J, Pedersen L, Földy C, Brown SA. A phosphate transporter in VIPergic neurons of the suprachiasmatic nucleus gates locomotor activity during the light/dark transition in mice. Cell Rep 2024; 43:114220. [PMID: 38735047 DOI: 10.1016/j.celrep.2024.114220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2023] [Revised: 02/23/2024] [Accepted: 04/25/2024] [Indexed: 05/14/2024] Open
Abstract
The suprachiasmatic nucleus (SCN) encodes time of day through changes in daily firing; however, the molecular mechanisms by which the SCN times behavior are not fully understood. To identify factors that could encode day/night differences in activity, we combine patch-clamp recordings and single-cell sequencing of individual SCN neurons in mice. We identify PiT2, a phosphate transporter, as being upregulated in a population of Vip+Nms+ SCN neurons at night. Although nocturnal and typically showing a peak of activity at lights off, mice lacking PiT2 (PiT2-/-) do not reach the activity level seen in wild-type mice during the light/dark transition. PiT2 loss leads to increased SCN neuronal firing and broad changes in SCN protein phosphorylation. PiT2-/- mice display a deficit in seasonal entrainment when moving from a simulated short summer to longer winter nights. This suggests that PiT2 is responsible for timing activity and is a driver of SCN plasticity allowing seasonal entrainment.
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Affiliation(s)
- Sara Pierre-Ferrer
- Chronobiology and Sleep Research Group, Institute of Pharmacology and Toxicology, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
| | - Ben Collins
- Chronobiology and Sleep Research Group, Institute of Pharmacology and Toxicology, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland; Department of Biology, Sacred Heart University, 5151 Park Ave., Fairfield, CT 06825, USA
| | - David Lukacsovich
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Shao'Ang Wen
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Yuchen Cai
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Jochen Winterer
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Jun Yan
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Lene Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, Universitetsbyen 81, 8000 Aarhus, Denmark
| | - Csaba Földy
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
| | - Steven A Brown
- Chronobiology and Sleep Research Group, Institute of Pharmacology and Toxicology, Faculties of Medicine and Science, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
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2
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Jennings ML. Role of transporters in regulating mammalian intracellular inorganic phosphate. Front Pharmacol 2023; 14:1163442. [PMID: 37063296 PMCID: PMC10097972 DOI: 10.3389/fphar.2023.1163442] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 03/17/2023] [Indexed: 03/31/2023] Open
Abstract
This review summarizes the current understanding of the role of plasma membrane transporters in regulating intracellular inorganic phosphate ([Pi]In) in mammals. Pi influx is mediated by SLC34 and SLC20 Na+-Pi cotransporters. In non-epithelial cells other than erythrocytes, Pi influx via SLC20 transporters PiT1 and/or PiT2 is balanced by efflux through XPR1 (xenotropic and polytropic retrovirus receptor 1). Two new pathways for mammalian Pi transport regulation have been described recently: 1) in the presence of adequate Pi, cells continuously internalize and degrade PiT1. Pi starvation causes recycling of PiT1 from early endosomes to the plasma membrane and thereby increases the capacity for Pi influx; and 2) binding of inositol pyrophosphate InsP8 to the SPX domain of XPR1 increases Pi efflux. InsP8 is degraded by a phosphatase that is strongly inhibited by Pi. Therefore, an increase in [Pi]In decreases InsP8 degradation, increases InsP8 binding to SPX, and increases Pi efflux, completing a feedback loop for [Pi]In homeostasis. Published data on [Pi]In by magnetic resonance spectroscopy indicate that the steady state [Pi]In of skeletal muscle, heart, and brain is normally in the range of 1–5 mM, but it is not yet known whether PiT1 recycling or XPR1 activation by InsP8 contributes to Pi homeostasis in these organs. Data on [Pi]In in cultured cells are variable and suggest that some cells can regulate [Pi] better than others, following a change in [Pi]Ex. More measurements of [Pi]In, influx, and efflux are needed to determine how closely, and how rapidly, mammalian [Pi]In is regulated during either hyper- or hypophosphatemia.
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3
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Inden M, Kimura Y, Nishii K, Masaka T, Takase N, Tsutsui M, Ohuchi K, Kurita H, Hozumi I. Role of phosphate transporter PiT-2 in the pathogenesis of primary brain calcification. Biochem Biophys Res Commun 2023; 640:21-25. [PMID: 36495606 DOI: 10.1016/j.bbrc.2022.11.106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 11/30/2022] [Indexed: 12/07/2022]
Abstract
Primary brain calcification (PBC), also known as idiopathic basal ganglia calcification (IBGC), primary familial brain calcification (PFBC) and so on, is a rare intractable disease characterized by abnormal mineral deposits, including mostly calcium in the basal ganglia, thalamus, and cerebellum. The causative gene of familial PBC is SLC20A2, which encodes the phosphate transporter PiT-2. Despite this knowledge, the molecular mechanism underlying SLC20A2-associated PBC remains unclear. In the present study, we investigated whether haploinsufficiency or a dominant-negative mechanism reduced Pi uptake in two PiT-2 variants (T115 M and R467X). We demonstrated that the presence of T115 M or R467X had no dominant-negative effect on Pi transport activity of wild-type (WT). In addition, the subcellular localization of R467X completely differed from that of WT, indicating that there is no interaction between R467X and WT. Conversely, T115 M and WT showed almost the same localization. Therefore, we examined the interaction between T115 M and WT using the bioluminescence resonance energy transfer (BRET) method. Although WT and T115 M interact with each other, T115 M does not inhibit WT's Pi transport activity. These results suggest that the role of SLC20A2 in the pathogenesis of PBC may involve decreased intracellular Pi uptake by a haploinsufficiency mechanism rather than a dominant-negative mechanism; agents promoting PiT-2 dimerization may be promising potential therapeutic agents for PBC.
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Affiliation(s)
- Masatoshi Inden
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi Gifu City, Gifu, 501-1196, Japan.
| | - Yuna Kimura
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi Gifu City, Gifu, 501-1196, Japan
| | - Kazuya Nishii
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi Gifu City, Gifu, 501-1196, Japan
| | - Tomohiko Masaka
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi Gifu City, Gifu, 501-1196, Japan
| | - Naoko Takase
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi Gifu City, Gifu, 501-1196, Japan
| | - Mai Tsutsui
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi Gifu City, Gifu, 501-1196, Japan
| | - Kazuki Ohuchi
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi Gifu City, Gifu, 501-1196, Japan
| | - Hisaka Kurita
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi Gifu City, Gifu, 501-1196, Japan
| | - Isao Hozumi
- Laboratory of Medical Therapeutics and Molecular Therapeutics, Department Biomedical Pharmaceutics, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi Gifu City, Gifu, 501-1196, Japan
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4
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Zechner C, Henne WM, Sathe AA, Xing C, Hernandez G, Sun S, Cheong MC. Cellular abundance of sodium phosphate cotransporter SLC20A1/PiT1 and phosphate uptake are controlled post-transcriptionally by ESCRT. J Biol Chem 2022; 298:101945. [PMID: 35447110 PMCID: PMC9123275 DOI: 10.1016/j.jbc.2022.101945] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 04/09/2022] [Accepted: 04/12/2022] [Indexed: 11/30/2022] Open
Abstract
Inorganic phosphate is essential for human life. The widely expressed mammalian sodium/phosphate cotransporter SLC20A1/PiT1 mediates phosphate uptake into most cell types; however, while SLC20A1 is required for development, and elevated SLC20A1 expression is associated with vascular calcification and aggressive tumor growth, the mechanisms regulating SLC20A1 protein abundance are unknown. Here, we found that SLC20A1 protein expression is low in phosphate-replete cultured cells but is strikingly induced following phosphate starvation, whereas mRNA expression is high in phosphate-replete cells and only mildly increased by phosphate starvation. To identify regulators of SLC20A1 protein levels, we performed a genome-wide CRISPR-based loss-of-function genetic screen in phosphate-replete cells using SLC20A1 protein induction as readout. Our screen revealed that endosomal sorting complexes required for transport (ESCRT) machinery was essential for proper SLC20A1 protein downregulation in phosphate-replete cells. We show that SLC20A1 colocalizes with ESCRT and that ESCRT deficiency increases SLC20A1 protein and phosphate uptake into cells. We also found numerous additional candidate regulators of mammalian phosphate homeostasis, including genes modifying protein ubiquitination and the Krebs cycle and oxidative phosphorylation pathways. Many of these targets have not been previously implicated in this process. We present here a model in which SLC20A1 protein abundance and phosphate uptake are tonically negatively regulated post-transcriptionally in phosphate-replete cells through direct ESCRT-mediated SLC20A1 degradation. Moreover, our screening results provide a comprehensive resource for future studies to elucidate the mechanisms governing cellular phosphate homeostasis. We conclude that genome-wide CRISPR-based genetic screening is a powerful tool to discover proteins and pathways relevant to physiological processes.
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Affiliation(s)
- Christoph Zechner
- Division of Endocrinology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
| | - W Mike Henne
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Adwait A Sathe
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Chao Xing
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Department of Bioinformatics, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Department of Population and Data Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Genaro Hernandez
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Shengyi Sun
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan, USA
| | - Mi Cheong Cheong
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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5
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Chen J, Li G, Lian J, Ma N, Huang Z, Li J, Wen Z, Zhang W, Zhang Y. Slc20a1b is essential for hematopoietic stem/progenitor cell expansion in zebrafish. SCIENCE CHINA. LIFE SCIENCES 2021; 64:2186-2201. [PMID: 33751369 DOI: 10.1007/s11427-020-1878-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 01/05/2021] [Indexed: 10/21/2022]
Abstract
Hematopoietic stem and progenitor cells (HSPCs) are able to self-renew and can give rise to all blood lineages throughout their lifetime, yet the mechanisms regulating HSPC development have yet to be discovered. In this study, we characterized a hematopoiesis defective zebrafish mutant line named smu07, which was obtained from our previous forward genetic screening, and found the HSPC expansion deficiency in the mutant. Positional cloning identified that slc20a1b, which encodes a sodium phosphate cotransporter, contributed to the smu07 blood phenotype. Further analysis demonstrated that mutation of slc20a1b affects HSPC expansion through cell cycle arrest at G2/M phases in a cell-autonomous manner. Our study shows that slc20a1b is a vital regulator for HSPC proliferation in zebrafish early hematopoiesis and provides valuable insights into HSPC development.
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Affiliation(s)
- Jiakui Chen
- Department of Developmental Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Gaofei Li
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou, 510006, China
| | - Junwei Lian
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou, 510006, China
| | - Ning Ma
- Department of Developmental Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Zhibin Huang
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou, 510006, China
| | - Jianchao Li
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou, 510006, China
| | - Zilong Wen
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China
| | - Wenqing Zhang
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou, 510006, China.
| | - Yiyue Zhang
- Department of Developmental Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, China.
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou, 510006, China.
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6
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Machado A, Pouzolles M, Gailhac S, Fritz V, Craveiro M, López-Sánchez U, Kondo T, Pala F, Bosticardo M, Notarangelo LD, Petit V, Taylor N, Zimmermann VS. Phosphate Transporter Profiles in Murine and Human Thymi Identify Thymocytes at Distinct Stages of Differentiation. Front Immunol 2020; 11:1562. [PMID: 32793218 PMCID: PMC7387685 DOI: 10.3389/fimmu.2020.01562] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 06/15/2020] [Indexed: 12/22/2022] Open
Abstract
Thymocyte differentiation is dependent on the availability and transport of metabolites in the thymus niche. As expression of metabolite transporters is a rate-limiting step in nutrient utilization, cell surface transporter levels generally reflect the cell's metabolic state. The GLUT1 glucose transporter is upregulated on actively dividing thymocytes, identifying thymocytes with an increased metabolism. However, it is not clear whether transporters of essential elements such as phosphate are modulated during thymocyte differentiation. While PiT1 and PiT2 are both phosphate transporters in the SLC20 family, we show here that they exhibit distinct expression profiles on both murine and human thymocytes. PiT2 expression distinguishes thymocytes with high metabolic activity, identifying immature murine double negative (CD4−CD8−) DN3b and DN4 thymocyte blasts as well as immature single positive (ISP) CD8 thymocytes. Notably, the absence of PiT2 expression on RAG2-deficient thymocytes, blocked at the DN3a stage, strongly suggests that high PiT2 expression is restricted to thymocytes having undergone a productive TCRβ rearrangement at the DN3a/DN3b transition. Similarly, in the human thymus, PiT2 was upregulated on early post-β selection CD4+ISP and TCRαβ−CD4hiDP thymocytes co-expressing the CD71 transferrin receptor, a marker of metabolic activity. In marked contrast, expression of the PiT1 phosphate importer was detected on mature CD3+ murine and human thymocytes. Notably, PiT1 expression on CD3+DN thymocytes was identified as a biomarker of an aging thymus, increasing from 8.4 ± 1.5% to 42.4 ± 9.4% by 1 year of age (p < 0.0001). We identified these cells as TCRγδ and, most significantly, NKT, representing 77 ± 9% of PiT1+DN thymocytes by 1 year of age (p < 0.001). Thus, metabolic activity and thymic aging are associated with distinct expression profiles of the PiT1 and PiT2 phosphate transporters.
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Affiliation(s)
- Alice Machado
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health (NIH), Bethesda, MD, United States.,Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Marie Pouzolles
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health (NIH), Bethesda, MD, United States
| | - Sarah Gailhac
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Vanessa Fritz
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Marco Craveiro
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Uriel López-Sánchez
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Taisuke Kondo
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health (NIH), Bethesda, MD, United States
| | - Francesca Pala
- Laboratory of Clinical Immunology and Microbiology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, United States
| | - Marita Bosticardo
- Laboratory of Clinical Immunology and Microbiology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, United States
| | - Luigi D Notarangelo
- Laboratory of Clinical Immunology and Microbiology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, United States
| | | | - Naomi Taylor
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health (NIH), Bethesda, MD, United States.,Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Valérie S Zimmermann
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health (NIH), Bethesda, MD, United States.,Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
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7
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Belmokhtar K, Ortillon J, Jaisson S, Massy ZA, Boulagnon Rombi C, Doué M, Maurice P, Fritz G, Gillery P, Schmidt AM, Rieu P, Touré F. Receptor for advanced glycation end products: a key molecule in the genesis of chronic kidney disease vascular calcification and a potential modulator of sodium phosphate co-transporter PIT-1 expression. Nephrol Dial Transplant 2020; 34:2018-2030. [PMID: 30778553 DOI: 10.1093/ndt/gfz012] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 01/05/2019] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Chronic kidney disease (CKD) is associated with increased cardiovascular mortality, frequent vascular calcification (VC) and accumulation of uraemic toxins. Advanced glycation end products and S100 proteins interact with the receptor for advanced glycation end products (RAGE). In the present work, we aimed to investigate the role(s) of RAGE in the CKD-VC process. METHODS Apoe-/- or Apoe-/-Ager (RAGE)-/- male mice were assigned to CKD or sham-operated groups. A high-phosphate diet was given to a subgroup of Apoe-/-and Apoe-/-Ager-/- CKD mice. Primary cultures of Ager+/+ and Ager-/- vascular smooth muscle cells (VSMCs) were established and stimulated with either vehicle, inorganic phosphate (Pi) or RAGE ligands (S100A12; 20 µM). RESULTS After 12 weeks of CKD we observed a significant increase in RAGE ligand (AGE and S100 proteins) concentrations in the serum of CKD Apoe-/- mice. Ager messenger RNA (mRNA) levels were 4-fold higher in CKD vessels of Apoe-/- mice. CKD Apoe-/- but not CKD Apoe-/- or Ager-/- mice displayed a marked increase in the VC surface area. Similar trends were found in the high-phosphate diet condition. mRNA levels of Runx2 significantly increased in the Apoe-/- CKD group. In vitro, stimulation of Ager+/+VSMCs with Pi or S100A12 induced mineralization and osteoblast transformation, and this was inhibited by phosphonoformic acid (Pi co-transporters inhibitor) and Ager deletion. In vivo and in vitro RAGE was necessary for regulation of the expression of Pit-1, at least in part through production of reactive oxygen species. CONCLUSION RAGE, through the modulation of Pit-1 expression, is a key molecule in the genesis of VC.
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Affiliation(s)
- Karim Belmokhtar
- Université de Reims Champagne-Ardenne, CNRS UMR 7369 (Matrice Extracellulaire et Dynamique Cellulaire, MEDyC), Reims, France.,Laboratoire de Néphrologie, Univesrity of Reims, Faculté de Médecine, Reims, France
| | - Jeremy Ortillon
- Université de Reims Champagne-Ardenne, CNRS UMR 7369 (Matrice Extracellulaire et Dynamique Cellulaire, MEDyC), Reims, France.,Laboratoire de Néphrologie, Univesrity of Reims, Faculté de Médecine, Reims, France
| | - Stéphane Jaisson
- Université de Reims Champagne-Ardenne, CNRS UMR 7369 (Matrice Extracellulaire et Dynamique Cellulaire, MEDyC), Reims, France.,University Hospital of Reims, Maison Blanche Hospital, Laboratory of Pediatric Biology and Research, Reims, France
| | - Ziad A Massy
- Division of Nephrology, Ambroise Paré Hospital, APHP, Versailles Saint-Quentin-en-Yvelines University (Paris-Ile-de-France-Ouest University), UVSQ, Boulogne Billancourt/Paris, France.,Inserm U1018, Team5, CESP, Paris Saclay Unioversityand Versailles Saint-Quentin-en-Yvelines University (Paris-Ile-de-France-Ouest University, UVSQ), Villejuif, France
| | - Camille Boulagnon Rombi
- Université de Reims Champagne-Ardenne, CNRS UMR 7369 (Matrice Extracellulaire et Dynamique Cellulaire, MEDyC), Reims, France.,CHU Reims, Division of Anatomopathology, Reims, France
| | - Manon Doué
- Université de Reims Champagne-Ardenne, CNRS UMR 7369 (Matrice Extracellulaire et Dynamique Cellulaire, MEDyC), Reims, France
| | - Pascal Maurice
- Université de Reims Champagne-Ardenne, CNRS UMR 7369 (Matrice Extracellulaire et Dynamique Cellulaire, MEDyC), Reims, France
| | - Günter Fritz
- Institute of Neuropathology, University of Freiburg, Germany
| | - Philippe Gillery
- Université de Reims Champagne-Ardenne, CNRS UMR 7369 (Matrice Extracellulaire et Dynamique Cellulaire, MEDyC), Reims, France.,University Hospital of Reims, Maison Blanche Hospital, Laboratory of Pediatric Biology and Research, Reims, France
| | | | - Philippe Rieu
- Université de Reims Champagne-Ardenne, CNRS UMR 7369 (Matrice Extracellulaire et Dynamique Cellulaire, MEDyC), Reims, France.,Laboratoire de Néphrologie, Univesrity of Reims, Faculté de Médecine, Reims, France.,CHU Reims, Division of Nephrology, Reims, France
| | - Fatouma Touré
- Université de Reims Champagne-Ardenne, CNRS UMR 7369 (Matrice Extracellulaire et Dynamique Cellulaire, MEDyC), Reims, France.,Laboratoire de Néphrologie, Univesrity of Reims, Faculté de Médecine, Reims, France.,CHU Reims, Division of Nephrology, Reims, France
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8
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Characterization of XPR1/SLC53A1 variants located outside of the SPX domain in patients with primary familial brain calcification. Sci Rep 2019; 9:6776. [PMID: 31043717 PMCID: PMC6494797 DOI: 10.1038/s41598-019-43255-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 04/17/2019] [Indexed: 12/17/2022] Open
Abstract
Primary familial brain calcification (PFBC) is a rare neurological disease characterized by deposits of calcium phosphate in the basal ganglia and other regions of the brain. Pathogenic variants in the XPR1/SLC53A1 gene, which encodes the only known inorganic phosphate exporter, cause an autosomal dominant form of PFBC. These variants are typically located in the SPX N-terminal domain of the protein. Here, we characterize three XPR1 variants outside of SPX in three PFBC patients with an apparently sporadic presentation: c.1375C > T p.(R459C), c.1855A > G p.(N619D) and c.1886T > G p.(I629S), with the latter identified as the first XPR1/SLC53A1 de novo mutation to occur in a PFBC proband. When tested in an in vitro physiological complementation assay, the three XPR1 variants were impaired in phosphate export function, although they were normally expressed at the cell surface and could serve as functional receptors for retrovirus entry. Moreover, peripheral blood cells from the p.N619D patient could be assayed ex vivo and displayed significantly impaired phosphate export. Our results establish for the first time the clinical and molecular characteristics of XPR1 variants located outside the SPX domain and assert a direct link between these variants, deficient phosphate export, and PFBC. Moreover, we unveiled new structural features in XPR1 C-terminal domain that play a role in phosphate export and disease.
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9
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Jacquillet G, Unwin RJ. Physiological regulation of phosphate by vitamin D, parathyroid hormone (PTH) and phosphate (Pi). Pflugers Arch 2019; 471:83-98. [PMID: 30393837 PMCID: PMC6326012 DOI: 10.1007/s00424-018-2231-z] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 10/20/2018] [Accepted: 10/25/2018] [Indexed: 01/05/2023]
Abstract
Inorganic phosphate (Pi) is an abundant element in the body and is essential for a wide variety of key biological processes. It plays an essential role in cellular energy metabolism and cell signalling, e.g. adenosine and guanosine triphosphates (ATP, GTP), and in the composition of phospholipid membranes and bone, and is an integral part of DNA and RNA. It is an important buffer in blood and urine and contributes to normal acid-base balance. Given its widespread role in almost every molecular and cellular function, changes in serum Pi levels and balance can have important and untoward effects. Pi homoeostasis is maintained by a counterbalance between dietary Pi absorption by the gut, mobilisation from bone and renal excretion. Approximately 85% of total body Pi is present in bone and only 1% is present as free Pi in extracellular fluids. In humans, extracellular concentrations of inorganic Pi vary between 0.8 and 1.2 mM, and in plasma or serum Pi exists in both its monovalent and divalent forms (H2PO4- and HPO42-). In the intestine, approximately 30% of Pi absorption is vitamin D regulated and dependent. To help maintain Pi balance, reabsorption of filtered Pi along the renal proximal tubule (PT) is via the NaPi-IIa and NaPi-IIc Na+-coupled Pi cotransporters, with a smaller contribution from the PiT-2 transporters. Endocrine factors, including, vitamin D and parathyroid hormone (PTH), as well as newer factors such as fibroblast growth factor (FGF)-23 and its coreceptor α-klotho, are intimately involved in the control of Pi homeostasis. A tight regulation of Pi is critical, since hyperphosphataemia is associated with increased cardiovascular morbidity in chronic kidney disease (CKD) and hypophosphataemia with rickets and growth retardation. This short review considers the control of Pi balance by vitamin D, PTH and Pi itself, with an emphasis on the insights gained from human genetic disorders and genetically modified mouse models.
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Affiliation(s)
- Grégory Jacquillet
- Centre for Nephrology, University College London (UCL), Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK
| | - Robert J Unwin
- Centre for Nephrology, University College London (UCL), Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK.
- AstraZeneca IMED ECD CVRM R&D, Gothenburg, Sweden.
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10
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Hernando N, Wagner CA. Mechanisms and Regulation of Intestinal Phosphate Absorption. Compr Physiol 2018; 8:1065-1090. [PMID: 29978897 DOI: 10.1002/cphy.c170024] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
States of hypo- and hyperphosphatemia have deleterious consequences including rickets/osteomalacia and renal/cardiovascular disease, respectively. Therefore, the maintenance of appropriate plasma levels of phosphate is an essential requirement for health. This control is executed by the collaborative action of intestine and kidney whose capacities to (re)absorb phosphate are regulated by a number of hormonal and metabolic factors, among them parathyroid hormone, fibroblast growth factor 23, 1,25(OH)2 vitamin D3 , and dietary phosphate. The molecular mechanisms responsible for the transepithelial transport of phosphate across enterocytes are only partially understood. Indeed, whereas renal reabsorption entirely relies on well-characterized active transport mechanisms of phosphate across the renal proximal epithelia, intestinal absorption proceeds via active and passive mechanisms, with the molecular identity of the passive component still unknown. The active absorption of phosphate depends mostly on the activity and expression of the sodium-dependent phosphate cotransporter NaPi-IIb (SLC34A2), which is highly regulated by many of the factors, mentioned earlier. Physiologically, the contribution of NaPi-IIb to the maintenance of phosphate balance appears to be mostly relevant during periods of low phosphate availability. Therefore, its role in individuals living in industrialized societies with high phosphate intake is probably less relevant. Importantly, small increases in plasma phosphate, even within normal range, associate with higher risk of cardiovascular disease. Therefore, therapeutic approaches to treat hyperphosphatemia, including dietary phosphate restriction and phosphate binders, aim at reducing intestinal absorption. Here we review the current state of research in the field. © 2017 American Physiological Society. Compr Physiol 8:1065-1090, 2018.
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Affiliation(s)
- Nati Hernando
- National Center for Competence in Research NCCR Kidney.CH, Institute of Physiology, University Zurich-Irchel, Zurich, Switzerland
| | - Carsten A Wagner
- National Center for Competence in Research NCCR Kidney.CH, Institute of Physiology, University Zurich-Irchel, Zurich, Switzerland
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11
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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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12
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Bonnot C, Proust H, Pinson B, Colbalchini FPL, Lesly-Veillard A, Breuninger H, Champion C, Hetherington AJ, Kelly S, Dolan L. Functional PTB phosphate transporters are present in streptophyte algae and early diverging land plants. THE NEW PHYTOLOGIST 2017; 214:1158-1171. [PMID: 28134432 DOI: 10.1111/nph.14431] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Accepted: 12/15/2016] [Indexed: 05/12/2023]
Abstract
Two inorganic phosphate (Pi) uptake mechanisms operate in streptophytes and chlorophytes, the two lineages of green plants. PHOSPHATE TRANSPORTER B (PTB) proteins are hypothesized to be the Na+ /Pi symporters catalysing Pi uptake in chlorophytes, whereas PHOSPHATE TRANSPORTER 1 (PHT1) proteins are the H+ /Pi symporters that carry out Pi uptake in angiosperms. PHT1 proteins are present in all streptophyte lineages. However, Pi uptake in streptophyte algae and marine angiosperms requires Na+ influx, suggesting that Na+ /Pi symporters also function in some streptophytes. We tested the hypothesis that Na+ /Pi symporters exist in streptophytes. We identified PTB sequences in streptophyte genomes. Core PTB proteins are present at the plasma membrane of the liverwort Marchantia polymorpha. The expression of M. polymorpha core PTB proteins in the Saccharomyces cerevisiae pho2 mutant defective in high-affinity Pi transport rescues growth in low-Pi environments. Moreover, levels of core PTB mRNAs of M. polymorpha and the streptophyte alga Coleochaete nitellarum are higher in low-Pi than in Pi-replete conditions, consistent with a role in Pi uptake from the environment. We conclude that land plants inherited two Pi uptake mechanisms - mediated by the PTB and PHT1 proteins, respectively - from their streptophyte algal ancestor. Both systems operate in parallel in extant early diverging land plants.
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Affiliation(s)
- Clémence Bonnot
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Hélène Proust
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Benoît Pinson
- Centre National de la Recherche Scientifique (CNRS), UMR 5095 Institut de Biochimie et Génétique Cellulaire (IBGC), Bordeaux Cedex, F-33077, France
- Université de Bordeaux, Bordeaux, F-33000, France
| | | | - Alexis Lesly-Veillard
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Holger Breuninger
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Clément Champion
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | | | - Steven Kelly
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Liam Dolan
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
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13
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Candeal E, Caldas YA, Guillén N, Levi M, Sorribas V. Intestinal phosphate absorption is mediated by multiple transport systems in rats. Am J Physiol Gastrointest Liver Physiol 2017; 312:G355-G366. [PMID: 28232455 DOI: 10.1152/ajpgi.00244.2016] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 01/30/2017] [Accepted: 02/04/2017] [Indexed: 01/31/2023]
Abstract
Apical inorganic phosphate (Pi) transport in the small intestine seems to be mainly mediated by the sodium/Pi cotransporter NaPi2b. To verify this role, we have studied the combined effects of pH, phosphonoformate, and Pi deprivation on intestinal Pi transport. Rats were fed, ad libitum, three fodders containing 1.2, 0.6, or 0.1% Pi for 1, 5, or 10 days. Pi deprivation (0.1%) increased both sodium-activated and sodium-independent Pi transport in brush-border membrane vesicles from the duodenum and jejunum for all three times. Alkaline pH inhibited Pi transport, despite the increasing concentration of [Formula: see text] (NaPi2b substrate), whereas acidity increased transport when the concentration of the PiT1/PiT2 substrate, [Formula: see text], was at its highest. The effect of Pi deprivation was maximal at acid pH, but both basal and upregulated transport were inhibited (70%) with phosphonoformate, an inhibitor of NaPi2b. PiT2 and NaPi2b protein abundance increased after 24 h of Pi deprivation in the duodenum, jejunum, and ileum, whereas PiT1 required 5-10 days in the duodenum and jejunum. Therefore, whereas transporter expressions are partially correlated with Pi transport adaptation, the pH effect precludes NaPi2b, and phosphonoformic acid precludes PiT1 and PiT2 as the main transporters. Transport and transporter expression were also inconsistent when feeding was limited to 4 h daily, because the 1.2% Pi diet paradoxically increased Pi transport in the duodenum and jejunum, but NaPi2b and PiT1 expressions only increased with the 0.1% diet. These findings suggest the presence of a major transporter that carries [Formula: see text] and is inhibited by phosphonoformate.NEW & NOTEWORTHY The combined effects of dietary inorganic phosphate (Pi) content, pH, and phosphonoformate inhibition suggest that the resulting apical Pi transport in the small intestine cannot be fully explained by the presence of NaPi2b, PiT1, or PiT2. We provide evidence of the presence of a new sodium-coupled Pi transporter that uses [Formula: see text] as the preferred substrate and is inhibited by phosphonoformate, and its expression correlates with Pi transport in all assayed conditions.
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Affiliation(s)
- Eduardo Candeal
- Department of Toxicology, University of Zaragoza, Zaragoza, Spain; and
| | - Yupanqui A Caldas
- Department of Toxicology, University of Zaragoza, Zaragoza, Spain; and.,Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado Denver, Aurora, Colorado
| | - Natalia Guillén
- Department of Toxicology, University of Zaragoza, Zaragoza, Spain; and
| | - Moshe Levi
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado Denver, Aurora, Colorado
| | - Víctor Sorribas
- Department of Toxicology, University of Zaragoza, Zaragoza, Spain; and
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14
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MiR-9-5p Down-Regulates PiT2, but not PiT1 in Human Embryonic Kidney 293 Cells. J Mol Neurosci 2017; 62:28-33. [PMID: 28303467 DOI: 10.1007/s12031-017-0906-0] [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: 09/23/2016] [Accepted: 02/27/2017] [Indexed: 10/20/2022]
Abstract
PiT1 (SLC20A1) and PiT2 (SLC20A2) are members of the mammalian type-III inorganic phosphate transporters and recent studies linked SLC20A2 mutations with primary brain calcifications. MicroRNAs (miRNAs) are endogenous noncoding regulatory RNAs and MicroRNA-9 (miR-9) modulates neurogenesis but is also involved with different types of cancer. We evaluated possible interactions between miR-9 and the phosphate transporters (PiT1 and PiT2). SLC20A2, platelet-derived growth factor receptor beta (PDGFRB) and Fibrillin-2 (FBN2) showed binding sites with high affinity for mir-9, In silico. miR-9 mimic was transfected into HEK293 cells and expression was confirmed by RT-qPCR. Overexpression of miR-9 in these cells caused a significant reduction in PiT2 and FBN2. PDGFRB appeared to be decreased, but was not significantly down-regulated. PiT1 showed no significant difference relative to controls. The down-regulation of PiT2 protein by miR-9 was confirmed by western blotting. In conclusion, we showed that miR-9 can down-regulate PiT2, in HEK293 cells. [corrected].
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15
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Larsen FT, Jensen N, Autzen JK, Kongsfelt IB, Pedersen L. Primary Brain Calcification Causal PiT2 Transport-Knockout Variants can Exert Dominant Negative Effects on Wild-Type PiT2 Transport Function in Mammalian Cells. J Mol Neurosci 2016; 61:215-220. [PMID: 27943094 PMCID: PMC5321689 DOI: 10.1007/s12031-016-0868-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Accepted: 11/22/2016] [Indexed: 12/31/2022]
Abstract
Primary brain calcification (PBC) is a neurodegenerative disorder characterized by calcium-phosphate deposits in the basal ganglia and often also other areas of the brain. The prevalent clinical manifestations are cognitive impairment, neuropsychiatric symptoms, and movement disorders. In recent years, monoallelic variants in SLC20A2, which encodes the type III sodium-dependent inorganic phosphate (Pi) transporter 2 (PiT2), have been linked to the familial form of PBC in 40–50% of the families reported worldwide as well as to sporadic cases of PBC. Further insight into the disease mechanism is, however, needed. Based on co-expression studies of wild-type and variant PiT2 in Xenopus laevis oocytes, the molecular disease mechanism associated with SLC20A2 missense variants has formerly been suggested to be haploinsufficiency. We have here used mammalian cells isolated from a Slc20a2−/− mouse and co-expression of human wild-type and variant PiT2. Two of the variants studied have both been reported twice in unrelated PBC cases: PiT2D28N in two sporadic cases and PiT2E575K in a familial and a sporadic case. We find that in mammalian cells, the analyzed SLC20A2 missense variants can exert their effect in a dominant negative manner resulting in decreased wild-type PiT2 Pi transport. Thus, compared to monoallelic lack of functional PiT2 protein expression, which reasonably points towards haploinsufficiency, certain SLC20A2 missense variants may be more detrimental for cellular Pi uptake and potentially contribute to an earlier disease onset and/or a more severe phenotype as observed for Slc20a2−/− mice compared to Slc20a2+/− mice.
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Affiliation(s)
- Frederik Tibert Larsen
- Department of Molecular Biology and Genetics, Aarhus University, C. F. Møllers Allé 3, Building 1130, 8000, Aarhus, Denmark
| | - Nina Jensen
- Department of Molecular Biology and Genetics, Aarhus University, C. F. Møllers Allé 3, Building 1130, 8000, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Jacob Kwasi Autzen
- Department of Molecular Biology and Genetics, Aarhus University, C. F. Møllers Allé 3, Building 1130, 8000, Aarhus, Denmark
| | - Iben Boutrup Kongsfelt
- Department of Molecular Biology and Genetics, Aarhus University, C. F. Møllers Allé 3, Building 1130, 8000, Aarhus, Denmark
| | - Lene Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, C. F. Møllers Allé 3, Building 1130, 8000, Aarhus, Denmark. .,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
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16
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Fernandes CS, Castro R, Coroadinha AS, Roque ACA. Small synthetic ligands for the enrichment of viral particles pseudotyped with amphotropic murine leukemia virus envelope. J Chromatogr A 2016; 1438:160-70. [DOI: 10.1016/j.chroma.2016.02.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 02/03/2016] [Accepted: 02/08/2016] [Indexed: 11/24/2022]
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17
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Jensen N, Autzen JK, Pedersen L. Slc20a2 is critical for maintaining a physiologic inorganic phosphate level in cerebrospinal fluid. Neurogenetics 2015; 17:125-30. [PMID: 26660102 PMCID: PMC4794525 DOI: 10.1007/s10048-015-0469-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Accepted: 11/29/2015] [Indexed: 12/17/2022]
Abstract
Mutations in the SLC20A2-gene encoding the inorganic phosphate (Pi) transporter PiT2 can explain approximately 40 % of the familial cases of the rare neurodegenerative disorder primary familial brain calcification (Fahr’s disease). The disease characteristic, cerebrovascular-associated calcifications, is also present in Slc20a2-knockout (KO) mice. Little is known about the specific role(s) of PiT2 in the brain. Recent in vitro studies, however, suggest a role in regulation of the [Pi] in cerebrospinal fluid (CSF). We here show that Slc20a2-KO mice indeed have a high CSF [Pi] in agreement with a role of PiT2 in Pi export from the CSF. The implications in relation to disease mechanism are discussed.
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Affiliation(s)
- Nina Jensen
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Molecular Biology and Genetics, Aarhus University, C. F. Møllers Allé 3, Building 1130, 8000, Aarhus, Denmark
| | - Jacob Kwasi Autzen
- Department of Molecular Biology and Genetics, Aarhus University, C. F. Møllers Allé 3, Building 1130, 8000, Aarhus, Denmark
| | - Lene Pedersen
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark. .,Department of Molecular Biology and Genetics, Aarhus University, C. F. Møllers Allé 3, Building 1130, 8000, Aarhus, Denmark.
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18
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Villa-Bellosta R. Vascular Calcification Revisited: A New Perspective for Phosphate Transport. Curr Cardiol Rev 2015; 11:341-351. [PMID: 26242187 PMCID: PMC4774640 DOI: 10.2174/1573403x11666150805120505] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 03/10/2015] [Accepted: 03/11/2015] [Indexed: 12/30/2022] Open
Abstract
Elevated serum phosphorus has emerged as a key risk factor for pathologic calcification of
cardiovascular structures, or vascular calcification (VC). To prevent the formation of calciumphosphate
deposits (CPD), the body uses adenosine-5’-triphosphate (ATP) to synthesize inhibitors of
calcification, including proteins and inhibitors of low molecular weight. Extracellular pyrophosphate
(PPi) is a potent inhibitor of VC, which is produced during extracellular hydrolysis of ATP. Loss of
function in the enzymes and transporters that are involved in the cycle of extracellular ATP, including
Pi transporters, leads to excessive deposition of calcium-phosphate salts. Treatment of hyperphosphatemia
with Pi-binders and Injection of exogenous PPi are the effective treatments to prevent CPD
in the aortic wall. The role of sodium phosphate cotransporters in ectopic calcification is contradictory and not well defined,
but their important role in the control of intracellular Pi levels and the synthesis of ATP make them an important
target to study.
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19
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Li Q, Pratt CH, Dionne LA, Fairfield H, Karst SY, Sundberg JP, Uitto J. Spontaneous asj-2J mutant mouse as a model for generalized arterial calcification of infancy: a large deletion/insertion mutation in the Enpp1 gene. PLoS One 2014; 9:e113542. [PMID: 25479107 PMCID: PMC4257536 DOI: 10.1371/journal.pone.0113542] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 10/27/2014] [Indexed: 11/27/2022] Open
Abstract
Generalized arterial calcification of infancy (GACI), an autosomal recessive disorder caused by mutations in the ENPP1 gene, manifests with extensive mineralization of the cardiovascular system. The affected individuals in most cases die within the first year of life, and there is currently no effective treatment for this disorder. In this study, we characterized a spontaneous mutant mouse, asj-2J, as a model for GACI. These mice were identified as part of a phenotypic deviant search in a large-scale production colony of BALB/cJ mice at The Jackson Laboratory. They demonstrated a characteristic gait due to stiffening of the joints, with phenotypic similarity to a previously characterized asj (“ages with stiffened joints”) mouse, caused by a missense mutation in the Enpp1 gene. Complementation testing indicated that asj-2J and asj were allelic. PCR-based mutation detection strategy revealed in asj-2J mice a large, 40,035 bp, deletion spanning from intron 1 to the 3′-untranslated region of the Enpp1 gene, coupled with a 74 bp insertion. This was accompanied with a significant reduction in the plasma PPi concentration and reduced PPi/Pi ratio. As a consequence, extensive aberrant mineralization affecting the arterial vasculature, a number of internal organs, and the dermal sheath of vibrissae, a progressive biomarker of the ectopic mineralization process, was demonstrated by a combination of micro computed tomography, histopathology with calcium-specific stains, and direct chemical assay of calcium. Comparison of the asj and asj-2J mice demonstrated that the latter ones, particularly when placed on an acceleration diet high in phosphate and low in magnesium, had more extensive mineralization. Thus, the asj-2J mouse serves as a novel model for GACI, a currently intractable disorder.
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Affiliation(s)
- Qiaoli Li
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - C. Herbert Pratt
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Louise A. Dionne
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | | | - Son Yong Karst
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - John P. Sundberg
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Jouni Uitto
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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20
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Kongsfelt IB, Byskov K, Pedersen LE, Pedersen L. High levels of the type III inorganic phosphate transporter PiT1 (SLC20A1) can confer faster cell adhesion. Exp Cell Res 2014; 326:57-67. [PMID: 24880124 DOI: 10.1016/j.yexcr.2014.05.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Revised: 05/18/2014] [Accepted: 05/20/2014] [Indexed: 01/16/2023]
Abstract
The inorganic phosphate transporter PiT1 (SLC20A1) is ubiquitously expressed in mammalian cells. We recently showed that overexpression of human PiT1 was sufficient to increase proliferation of two strict density-inhibited cell lines, murine fibroblastic NIH3T3 and pre-osteoblastic MC3T3-E1 cells, and allowed the cultures to grow to higher cell densities. In addition, upon transformation NIH3T3 cells showed increased ability to form colonies in soft agar. The cellular regulation of PiT1 expression supports that cells utilize the PiT1 levels to control proliferation, with non-proliferating cells showing the lowest PiT1 mRNA levels. The mechanism behind the role of PiT1 in increased cell proliferation is not known. We, however, found that compared to control cells, cultures of NIH3T3 cells overexpressing PiT1 upon seeding showed increased cell number after 24h and had shifted more cells from G0/G1 to S+G2/M within 12h, suggesting that an early event may play a role. We here show that expression of human PiT1 in NIH3T3 cells led to faster cell adhesion; this effect was not cell type specific in that it was also observed when expressing human PiT1 in MC3T3-E1 cells. We also show for NIH3T3 that PiT1 overexpression led to faster cell spreading. The final total numbers of attached cells did, however, not differ between cultures of PiT1 overexpressing cells and control cells of neither cell type. We suggest that the PiT1-mediated fast adhesion potentials allow the cells to go faster out of G0/G1 and thereby contribute to their proliferative advantage within the first 24h after seeding.
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Affiliation(s)
| | - Kristina Byskov
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark; Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | | | - Lene Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark; Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; Department of Hematology, Aarhus University Hospital, Aarhus, Denmark.
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21
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Guerreiro PM, Bataille AM, Parker SL, Renfro JL. Active removal of inorganic phosphate from cerebrospinal fluid by the choroid plexus. Am J Physiol Renal Physiol 2014; 306:F1275-84. [PMID: 24740787 DOI: 10.1152/ajprenal.00458.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The P(i) concentration of mammalian cerebrospinal fluid (CSF) is about one-half that of plasma, a phenomenon also shown here in the spiny dogfish, Squalus acanthias. The objective of the present study was to characterize the possible role of the choroid plexus (CP) in determining CSF P(i) concentration. The large sheet-like fourth CP of the shark was mounted in Ussing chambers where unidirectional (33)P(i) fluxes revealed potent active transport from CSF to the blood side under short-circuited conditions. The flux ratio was 8:1 with an average transepithelial resistance of 87 ± 17.9 Ω·cm(2) and electrical potential difference of +0.9 ± 0.17 mV (CSF side positive). Active P(i) absorption from CSF was inhibited by 10 mM arsenate, 0.2 mM ouabain, Na(+)-free medium, and increasing the K(+) concentration from 5 to 100 mM. Li(+) stimulated transport twofold compared with Na(+)-free medium. Phosphonoformic acid (1 mM) had no effect on active P(i) transport. RT-PCR revealed both P(i) transporter (PiT)1 and PiT2 (SLC20 family) gene expression, but no Na(+)-P(i) cotransporter II (SLC34 family) expression, in the shark CP. PiT2 immunoreactivity was shown by immunoblot analysis and localized by immunohistochemistry in (or near) the CP apical microvillar membranes of both the shark and rat. PiT1 appeared to be localized primarily to vascular endothelial cells. Taken together, these data indicate that the CP actively removes P(i) from CSF. This process has transport properties consistent with a PiT2, Na(+)-dependent transporter that is located in the apical region of the CP epithelium.
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Affiliation(s)
- Pedro M Guerreiro
- Centre of Marine Sciences, Universidade do Algarve, Faro, Portugal; Mount Desert Island Biological Laboratory, Salisbury Cove, Maine
| | - Amy M Bataille
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut; and
| | - Sonda L Parker
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut; and
| | - J Larry Renfro
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut; and Mount Desert Island Biological Laboratory, Salisbury Cove, Maine
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Forster IC, Hernando N, Biber J, Murer H. Phosphate transporters of the SLC20 and SLC34 families. Mol Aspects Med 2013; 34:386-95. [PMID: 23506879 DOI: 10.1016/j.mam.2012.07.007] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 06/21/2012] [Indexed: 10/27/2022]
Abstract
Transport of inorganic phosphate (Pi) across the plasma membrane is essential for normal cellular function. Members of two families of SLC proteins (SLC20 and SLC34) act as Na(+)-dependent, secondary-active cotransporters to transport Pi across cell membranes. The SLC34 proteins are expressed in specific organs important for Pi homeostasis: NaPi-IIa (SLC34A1) and NaPi-IIc (SLC34A3) fulfill essential roles in Pi reabsorption in the kidney proximal tubule and NaPi-IIb (SLC34A2) mediates Pi absorption in the gut. The SLC20 proteins, PiT-1 (SLC20A1), PiT-2 (SLC20A2) are expressed ubiquitously in all tissues and although generally considered as "housekeeping" transport proteins, the discovery of tissue-specific activity, regulatory pathways and gene-related pathophysiologies, is redefining their importance. This review summarizes our current knowledge of SLC20 and SLC34 proteins in terms of their basic molecular characteristics, physiological roles, known pathophysiology and pharmacology.
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Affiliation(s)
- Ian C Forster
- Institute of Physiology and Zurich Center for Integrated Human Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
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23
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Crouthamel MH, Lau WL, Leaf EM, Chavkin NW, Wallingford MC, Peterson DF, Li X, Liu Y, Chin MT, Levi M, Giachelli CM. Sodium-dependent phosphate cotransporters and phosphate-induced calcification of vascular smooth muscle cells: redundant roles for PiT-1 and PiT-2. Arterioscler Thromb Vasc Biol 2013; 33:2625-32. [PMID: 23968976 DOI: 10.1161/atvbaha.113.302249] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Elevated serum phosphate has emerged as a major risk factor for vascular calcification. The sodium-dependent phosphate cotransporter, PiT-1, was previously shown to be required for phosphate-induced osteogenic differentiation and calcification of cultured human vascular smooth muscle cells (VSMCs), but its importance in vascular calcification in vivo and the potential role of its homologue, PiT-2, have not been determined. We investigated the in vivo requirement for PiT-1 in vascular calcification using a mouse model of chronic kidney disease and the potential compensatory role of PiT-2 using in vitro knockdown and overexpression strategies. APPROACH AND RESULTS Mice with targeted deletion of PiT-1 in VSMCs were generated (PiT-1(Δsm)). PiT-1 mRNA levels were undetectable, whereas PiT-2 mRNA levels were increased 2-fold in the vascular aortic media of PiT-1(Δsm) compared with PiT-1(flox/flox) control. When arterial medial calcification was induced in PiT-1(Δsm) and PiT-1(flox/flox) by chronic kidney disease followed by dietary phosphate loading, the degree of aortic calcification was not different between genotypes, suggesting compensation by PiT-2. Consistent with this possibility, VSMCs isolated from PiT-1(Δsm) mice had no PiT-1 mRNA expression, increased PiT-2 mRNA levels, and no difference in sodium-dependent phosphate uptake or phosphate-induced matrix calcification compared with PiT-1(flox/flox) VSMCs. Knockdown of PiT-2 decreased phosphate uptake and phosphate-induced calcification of PiT-1(Δsm) VSMCs. Furthermore, overexpression of PiT-2 restored these parameters in human PiT-1-deficient VSMCs. CONCLUSIONS PiT-2 can mediate phosphate uptake and calcification of VSMCs in the absence of PiT-1. Mechanistically, PiT-1 and PiT-2 seem to serve redundant roles in phosphate-induced calcification of VSMCs.
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Affiliation(s)
- Matthew H Crouthamel
- From the Departments of Bioengineering (M.H.C., E.M.L., N.W.C., M.C.W., D.F.P., X.L., C.M.G.), Nephrology (W.L.L.), and Cardiology (Y.L., M.T.C.), University of Washington, Seattle; and Department of Medicine, University of Colorado, Denver (M.L.)
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24
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Loss of function of Slc20a2 associated with familial idiopathic Basal Ganglia calcification in humans causes brain calcifications in mice. J Mol Neurosci 2013; 51:994-9. [PMID: 23934451 PMCID: PMC3824575 DOI: 10.1007/s12031-013-0085-6] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 07/25/2013] [Indexed: 01/30/2023]
Abstract
Familial idiopathic basal ganglia calcification (FIBGC) is a neurodegenerative disorder with neuropsychiatric and motor symptoms. Deleterious mutations in SLC20A2, encoding the type III sodium-dependent phosphate transporter 2 (PiT2), were recently linked to FIBGC in almost 50 % of the families reported worldwide. Here, we show that knockout of Slc20a2 in mice causes calcifications in the thalamus, basal ganglia, and cortex, demonstrating that reduced PiT2 expression alone can cause brain calcifications.
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25
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Bourgine A, Pilet P, Diouani S, Sourice S, Lesoeur J, Beck-Cormier S, Khoshniat S, Weiss P, Friedlander G, Guicheux J, Beck L. Mice with hypomorphic expression of the sodium-phosphate cotransporter PiT1/Slc20a1 have an unexpected normal bone mineralization. PLoS One 2013; 8:e65979. [PMID: 23785462 PMCID: PMC3681848 DOI: 10.1371/journal.pone.0065979] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 05/03/2013] [Indexed: 11/18/2022] Open
Abstract
The formation of hydroxyapatite crystals and their insertion into collagen fibrils of the matrix are essential steps for bone mineralization. As phosphate is a main structural component of apatite crystals, its uptake by skeletal cells is critical and must be controlled by specialized membrane proteins. In mammals, in vitro studies have suggested that the high-affinity sodium-phosphate cotransporter PiT1 could play this role. In vivo, PiT1 expression was detected in hypertrophic chondrocytes of murine metatarsals, but its implication in bone physiology is not yet deciphered. As the complete deletion of PiT1 results in embryonic lethality at E12.5, we took advantage of a mouse model bearing two copies of PiT1 hypomorphic alleles to study the effect of a low expression of PiT1 on bone mineralization in vivo. In this report, we show that a 85% down-regulation of PiT1 in long bones resulted in a slight (6%) but significant reduction of femur length in young mice (15- and 30-day-old). However, despite a defect in alcian blue / alizarin red S and Von Kossa staining of hypomorphic 1-day-old mice, using X-rays micro-computed tomography, energy dispersive X-ray spectroscopy and histological staining techniques we could not detect differences between hypomorphic and wild-type mice of 15- to 300-days old. Interestingly, the expression of PiT2, the paralog of PiT1, was increased 2-fold in bone of PiT1 hypomorphic mice accounting for a normal phosphate uptake in mutant cells. Whether this may contribute to the absence of bone mineralization defects remains to be further deciphered.
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Affiliation(s)
- Annabelle Bourgine
- Institut National de la Sante et de la recherche Medicale, U791, LIOAD, STEP group "Skeletal Tissue Engineering and Physiopathology”, Nantes, France
- Université de Nantes, UFR Odontologie, Nantes, France
| | - Paul Pilet
- Institut National de la Sante et de la recherche Medicale, U791, LIOAD, STEP group "Skeletal Tissue Engineering and Physiopathology”, Nantes, France
- Université de Nantes, UFR Odontologie, Nantes, France
| | - Sara Diouani
- Institut National de la Sante et de la recherche Medicale, U845, Centre de Recherche Croissance et Signalisation, Paris, France
- Université Paris Descartes, Paris, France
| | - Sophie Sourice
- Institut National de la Sante et de la recherche Medicale, U791, LIOAD, STEP group "Skeletal Tissue Engineering and Physiopathology”, Nantes, France
- Université de Nantes, UFR Odontologie, Nantes, France
| | - Julie Lesoeur
- Institut National de la Sante et de la recherche Medicale, U791, LIOAD, STEP group "Skeletal Tissue Engineering and Physiopathology”, Nantes, France
- Université de Nantes, UFR Odontologie, Nantes, France
| | - Sarah Beck-Cormier
- Institut National de la Sante et de la recherche Medicale, U791, LIOAD, STEP group "Skeletal Tissue Engineering and Physiopathology”, Nantes, France
- Université de Nantes, UFR Odontologie, Nantes, France
| | - Solmaz Khoshniat
- Institut National de la Sante et de la recherche Medicale, U791, LIOAD, STEP group "Skeletal Tissue Engineering and Physiopathology”, Nantes, France
- Université de Nantes, UFR Odontologie, Nantes, France
| | - Pierre Weiss
- Institut National de la Sante et de la recherche Medicale, U791, LIOAD, STEP group "Skeletal Tissue Engineering and Physiopathology”, Nantes, France
- Université de Nantes, UFR Odontologie, Nantes, France
| | - Gérard Friedlander
- Institut National de la Sante et de la recherche Medicale, U845, Centre de Recherche Croissance et Signalisation, Paris, France
- Université Paris Descartes, Paris, France
| | - Jérôme Guicheux
- Institut National de la Sante et de la recherche Medicale, U791, LIOAD, STEP group "Skeletal Tissue Engineering and Physiopathology”, Nantes, France
- Université de Nantes, UFR Odontologie, Nantes, France
| | - Laurent Beck
- Institut National de la Sante et de la recherche Medicale, U791, LIOAD, STEP group "Skeletal Tissue Engineering and Physiopathology”, Nantes, France
- Université de Nantes, UFR Odontologie, Nantes, France
- * E-mail:
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26
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Affiliation(s)
- Jürg Biber
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, CH-8057 Zurich, Switzerland; , ,
| | - Nati Hernando
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, CH-8057 Zurich, Switzerland; , ,
| | - Ian Forster
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, CH-8057 Zurich, Switzerland; , ,
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27
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Sengottaiyan P, Ruiz-Pavón L, Persson BL. Functional expression, purification and reconstitution of the recombinant phosphate transporter Pho89 of Saccharomyces cerevisiae. FEBS J 2013; 280:965-75. [PMID: 23216645 PMCID: PMC3633241 DOI: 10.1111/febs.12090] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 11/06/2012] [Accepted: 12/05/2012] [Indexed: 11/30/2022]
Abstract
The Saccharomyces cerevisiae high-affinity phosphate transporter Pho89 is a member of the inorganic phosphate (Pi) transporter (PiT) family, and shares significant homology with the type III Na(+)/Pi symporters, hPit1 and hPit2. Currently, detailed biochemical and biophysical analyses of Pho89 to better understand its transport mechanisms are limited, owing to the lack of purified Pho89 in an active form. In the present study, we expressed functional Pho89 in the cell membrane of Pichia pastoris, solubilized it in Triton X-100 and foscholine-12, and purified it by immobilized nickel affinity chromatography combined with size exclusion chromatography. The protein eluted as an oligomer on the gel filtration column, and SDS/PAGE followed by western blotting analysis revealed that the protein appeared as bands of approximately 63, 140 and 520 kDa, corresponding to the monomeric, dimeric and oligomeric masses of the protein, respectively. Proteoliposomes containing purified and reconstituted Pho89 showed Na(+)-dependent Pi transport activity driven by an artificially imposed electrochemical Na(+) gradient. This implies that Pho89 operates as a symporter. Moreover, its activity is sensitive to the Na(+) ionophore monensin. To our knowledge, this study represents the first report on the functional reconstitution of a Pi-coupled PiT family member.
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28
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Byskov K, Jensen N, Kongsfelt IB, Wielsøe M, Pedersen LE, Haldrup C, Pedersen L. Regulation of cell proliferation and cell density by the inorganic phosphate transporter PiT1. Cell Div 2012; 7:7. [PMID: 22394506 PMCID: PMC3325893 DOI: 10.1186/1747-1028-7-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2011] [Accepted: 03/06/2012] [Indexed: 11/10/2022] Open
Abstract
UNLABELLED ABSTACT: BACKGROUND The inorganic phosphate (Pi) transporter, PiT1 (SLC20A1), is ubiquitously expressed in mammalian cells. It has previously been shown that down-regulation of PiT1 severely impaired the proliferation of two transformed human cells lines, HepG2 and HeLa, and the tumorigenicity of HeLa cells in nude mice. Moreover, PiT1 knock-out mice do not survive past E12.5 and from E10.5, the embryos were found to be growth-retarded and showed reduced proliferation of liver cells. Isolated mouse embryonic fibroblasts with knocked out as well as reduced PiT1 expression levels also exhibited impaired proliferation. Together these results suggest that a certain level of PiT1 is important for proliferation. We have here investigated the role of PiT1 in regulation of cell proliferation using two strictly density-inhibited cells lines, the murine MC3T3-E1 and NIH3T3 cells. RESULTS We found that knock-down of PiT1 in MC3T3-E1 cells led to impaired proliferation supporting that at least a certain level of PiT1 is important for wildtype level of proliferation. We, however, also observed that MC3T3-E1 and NIH3T3 cells themselves regulate their endogenous PiT1 mRNA levels with lower levels in general correlating with decreased proliferation/increased cell density. Moreover, over-expression of human PiT1 led to increased proliferation of both MC3T3-E1 and NIH3T3 cultures and resulted in higher cell densities in cultures of these two strictly density-inhibited cell lines. In addition, when we transformed NIH3T3 cells by cultivation in fetal bovine serum, cells over-expressing human PiT1 formed more colonies in soft agar than control cells. CONCLUSIONS We conclude that not only is a certain level of PiT1 necessary for normal cell division as suggested by previously published studies, rather the cellular PiT1 level is involved in regulating cell proliferation and cell density and an increased PiT1 expression can indeed make NIH3T3 cells more sensitive to transformation. We have thus provided the first evidence for that expression of the type III Pi transporter, PiT1, above the endogenous level can drive cell proliferation and overrule cell density constraints, and the results bridge previous observations showing that a certain PiT1 level is important for regulating normal embryonic growth/development and for tumorigenicity of HeLa cells.
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Affiliation(s)
- Kristina Byskov
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark.
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29
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Forster IC, Hernando N, Biber J, Murer H. Phosphate transport kinetics and structure-function relationships of SLC34 and SLC20 proteins. CURRENT TOPICS IN MEMBRANES 2012. [PMID: 23177991 DOI: 10.1016/b978-0-12-394316-3.00010-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Transport of inorganic phosphate (P(i)) is mediated by proteins belonging to two solute carrier families (SLC20 and SLC34). Members of both families transport P(i) using the electrochemical gradient for Na(+). The role of the SLC34 members as essential players in mammalian P(i) homeostasis is well established, whereas that of SLC20 proteins is less well defined. The SLC34 family comprises the following three isoforms that preferentially cotransport divalent P(i) and are expressed in epithelial tissue: the renal NaPi-IIa and NaPi-IIc are responsible for reabsorbing P(i) in the proximal tubule, whereas NaPi-IIb is more ubiquitously expressed, including the small intestine, where it mediates dietary P(i) absorption. The SLC20 family comprises two members (PiT-1, PiT-2) that preferentially cotransport monovalent P(i) and are expressed in epithelial as well as nonepithelial tissue. The transport kinetics of members of both families have been characterized in detail using heterologous expression in Xenopus oocytes. For the electrogenic NaPi-IIa/b, and PiT-1,-2, conventional electrophysiological techniques together with radiotracer methods have been applied, as well as time-resolved fluorometric measurements that allow new insights into local conformational changes of the protein during the cotransport cycle. For the electroneutral NaPi-IIc, conventional tracer uptake and fluorometry have been used to elucidate its transport properties. The 3-D structures of these proteins remain unresolved and structure-function studies have so far concentrated on defining the topology and identifying sites of functional importance.
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Affiliation(s)
- Ian C Forster
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Winterthurerstrasse, Zurich, Switzerland.
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30
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Bøttger P, Pedersen L. Mapping of the minimal inorganic phosphate transporting unit of human PiT2 suggests a structure universal to PiT-related proteins from all kingdoms of life. BMC BIOCHEMISTRY 2011; 12:21. [PMID: 21586110 PMCID: PMC3126765 DOI: 10.1186/1471-2091-12-21] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 05/17/2011] [Indexed: 11/10/2022]
Abstract
BACKGROUND The inorganic (Pi) phosphate transporter (PiT) family comprises known and putative Na(+)- or H(+)-dependent Pi-transporting proteins with representatives from all kingdoms. The mammalian members are placed in the outer cell membranes and suggested to supply cells with Pi to maintain house-keeping functions. Alignment of protein sequences representing PiT family members from all kingdoms reveals the presence of conserved amino acids and that bacterial phosphate permeases and putative phosphate permeases from archaea lack substantial parts of the protein sequence when compared to the mammalian PiT family members. Besides being Na(+)-dependent P(i) (NaP(i)) transporters, the mammalian PiT paralogs, PiT1 and PiT2, also are receptors for gamma-retroviruses. We have here exploited the dual-function of PiT1 and PiT2 to study the structure-function relationship of PiT proteins. RESULTS We show that the human PiT2 histidine, H(502), and the human PiT1 glutamate, E(70),--both conserved in eukaryotic PiT family members--are critical for P(i) transport function. Noticeably, human PiT2 H(502) is located in the C-terminal PiT family signature sequence, and human PiT1 E(70) is located in ProDom domains characteristic for all PiT family members.A human PiT2 truncation mutant, which consists of the predicted 10 transmembrane (TM) domain backbone without a large intracellular domain (human PiT2ΔR(254)-V(483)), was found to be a fully functional P(i) transporter. Further truncation of the human PiT2 protein by additional removal of two predicted TM domains together with the large intracellular domain created a mutant that resembles a bacterial phosphate permease and an archaeal putative phosphate permease. This human PiT2 truncation mutant (human PiT2ΔL(183)-V(483)) did also support P(i) transport albeit at very low levels. CONCLUSIONS The results suggest that the overall structure of the P(i)-transporting unit of the PiT family proteins has remained unchanged during evolution. Moreover, in combination, our studies of the gene structure of the human PiT1 and PiT2 genes (SLC20A1 and SLC20A2, respectively) and alignment of protein sequences of PiT family members from all kingdoms, along with the studies of the dual functions of the human PiT paralogs show that these proteins are excellent as models for studying the evolution of a protein's structure-function relationship.
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Affiliation(s)
- Pernille Bøttger
- Department of Molecular Biology, Aarhus University, C. F. Møllers Allé 3, Aarhus C, DK-8000, Denmark
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31
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Forster I, Hernando N, Sorribas V, Werner A. Phosphate transporters in renal, gastrointestinal, and other tissues. Adv Chronic Kidney Dis 2011; 18:63-76. [PMID: 21406290 DOI: 10.1053/j.ackd.2011.01.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 01/17/2011] [Accepted: 01/18/2011] [Indexed: 11/11/2022]
Abstract
Inorganic phosphate (Pi) is essential for all living organisms. Bound to organic molecules, Pi fulfills structural, metabolic, and signaling tasks. Therefore, cell growth and maintenance depends on efficient transport of Pi across cellular membranes into the intracellular space. Uptake of Pi requires energy because the substrate is transported against its electrochemical gradient. Till recently, 2 major families of physiologically relevant Pi-specific transporters have been identified: the solute carrier families Slc34 and Slc20. Interestingly, phylogenetic links can be detected between prokaryotic and eukaryotic transporters in both families. Because less complex model organisms are often instrumental in establishing paradigms for protein function in human beings, a brief assessment of Slc34 and Slc20 phylogeny is of interest.
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32
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Beck L, Leroy C, Salaün C, Margall-Ducos G, Desdouets C, Friedlander G. Identification of a novel function of PiT1 critical for cell proliferation and independent of its phosphate transport activity. J Biol Chem 2009; 284:31363-74. [PMID: 19726692 DOI: 10.1074/jbc.m109.053132] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
PiT1 is a Na(+)-phosphate (P(i)) cotransporter located at the plasma membrane that enables P(i) entry into the cell. Its broad tissue expression pattern has led to the idea that together with the closely related family member PiT2, PiT1 is the ubiquitous supplier of P(i) to the cell. Moreover, the role of P(i) in phosphorylation reactions, ATP production, DNA structure, and synthesis has led to the view that P(i) availability could be an important determinant of cell growth. However, these issues have not been clearly addressed to date, and the role of either P(i) or PiT proteins in cell proliferation is unknown. Using RNA interference in HeLa and HepG2 cells, we show that transient or stable PiT1 depletion markedly reduces cell proliferation, delays cell cycle, and impairs mitosis and cytokinesis. In vivo, PiT1 depletion greatly reduced tumor growth when engineered HeLa cells were injected into nude mice. We provide evidence that this effect on cell proliferation is specific to PiT1 and not shared by PiT2 and is not the consequence of impaired membrane Na(+)-P(i) transport. Moreover, we show that modulation of cell proliferation by PiT1 is independent from its transport function because the proliferation of PiT1-depleted cells can be rescued by non-transporting PiT1 mutants. PiT1 depletion leads to the phosphorylation of p38 mitogen-activated protein (MAP) kinase, whereas other MAP kinases and downstream targets of mammalian target of rapamycin (mTOR) remain unaffected. This study is the first to describe the effects of a P(i) transporter in cell proliferation, tumor growth, and cell signaling.
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Affiliation(s)
- Laurent Beck
- Growth and Signalling Research Center, INSERM, U845, F-75015 Paris.
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33
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Biber J, Hernando N, Forster I, Murer H. Regulation of phosphate transport in proximal tubules. Pflugers Arch 2008; 458:39-52. [PMID: 18758808 DOI: 10.1007/s00424-008-0580-8] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Accepted: 08/13/2008] [Indexed: 12/13/2022]
Abstract
Homeostasis of inorganic phosphate (P(i)) is primarily an affair of the kidneys. Reabsorption of the bulk of filtered P(i) occurs along the renal proximal tubule and is initiated by apically localized Na(+)-dependent P(i) cotransporters. Tubular P(i) reabsorption and therefore renal excretion of P(i) is controlled by a number of hormones, including phosphatonins, and metabolic factors. In most cases, regulation of P(i) reabsorption is achieved by changing the apical abundance of Na(+)/Pi cotransporters. The regulatory mechanisms involve various signaling pathways and a number of proteins that interact with Na(+)/P(i) cotransporters.
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Affiliation(s)
- J Biber
- Institute of Physiology and Zurich Center for Integrative Human Physiology, University of Zurich, Switzerland.
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34
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Pavón LR, Lundh F, Lundin B, Mishra A, Persson BL, Spetea C. Arabidopsis ANTR1 Is a Thylakoid Na+-dependent Phosphate Transporter. J Biol Chem 2008; 283:13520-7. [DOI: 10.1074/jbc.m709371200] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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35
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Virkki LV, Biber J, Murer H, Forster IC. Phosphate transporters: a tale of two solute carrier families. Am J Physiol Renal Physiol 2007; 293:F643-54. [PMID: 17581921 DOI: 10.1152/ajprenal.00228.2007] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Phosphate is an essential component of life and must be actively transported into cells against its electrochemical gradient. In vertebrates, two unrelated families of Na+ -dependent P(i) transporters carry out this task. Remarkably, the two families transport different P(i) species: whereas type II Na+/P(i) cotransporters (SCL34) prefer divalent HPO(4)(2-), type III Na(+)/P(i) cotransporters (SLC20) transport monovalent H2PO(4)(-). The SCL34 family comprises both electrogenic and electroneutral members that are expressed in various epithelia and other polarized cells. Through regulated activity in apical membranes of the gut and kidney, they maintain body P(i) homeostasis, and in salivary and mammary glands, liver, and testes they play a role in modulating the P(i) content of luminal fluids. The two SLC20 family members PiT-1 and PiT-2 are electrogenic and ubiquitously expressed and may serve a housekeeping role for cell P(i) homeostasis; however, also more specific roles are emerging for these transporters in, for example, bone mineralization. In this review, we focus on recent advances in the characterization of the transport kinetics, structure-function relationships, and physiological implications of having two distinct Na+/P(i) cotransporter families.
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Affiliation(s)
- Leila V Virkki
- Institute of Physiology and Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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Ravera S, Virkki LV, Murer H, Forster IC. Deciphering PiT transport kinetics and substrate specificity using electrophysiology and flux measurements. Am J Physiol Cell Physiol 2007; 293:C606-20. [PMID: 17494632 DOI: 10.1152/ajpcell.00064.2007] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Members of the SLC20 family or type III Na(+) -coupled P(i) cotransporters (PiT-1, PiT-2) are ubiquitously expressed in mammalian tissue and are thought to perform a housekeeping function for intracellular P(i) homeostasis. Previous studies have shown that PiT-1 and PiT-2 mediate electrogenic P(i) cotransport when expressed in Xenopus oocytes, but only limited kinetic characterizations were made. To address this shortcoming, we performed a detailed analysis of SLC20 transport function. Three SLC20 clones (Xenopus PiT-1, human PiT-1, and human PiT-2) were expressed in Xenopus oocytes. Each clone gave robust Na(+)-dependent (32)P(i) uptake, but only Xenopus PiT-1 showed sufficient activity for complete kinetic characterization by using two-electrode voltage clamp and radionuclide uptake. Transport activity was also documented with Li(+) substituted for Na(+). The dependence of the P(i)-induced current on P(i) concentration was Michaelian, and the dependence on Na(+) concentration indicated weak cooperativity. The dependence on external pH was unique: the apparent P(i) affinity constant showed a minimum in the pH range 6.2-6.8 of approximately 0.05 mM and increased to approximately 0.2 mM at pH 5.0 and pH 8.0. Xenopus PiT-1 stoichiometry was determined by dual (22)Na-(32)P(i) uptake and suggested a 2:1 Na(+):P(i) stoichiometry. A correlation of (32)P(i) uptake and net charge movement indicated one charge translocation per P(i). Changes in oocyte surface pH were consistent with transport of monovalent P(i). On the basis of the kinetics of substrate interdependence, we propose an ordered binding scheme of Na(+):H(2)PO(4)(-):Na(+). Significantly, in contrast to type II Na(+)-P(i) cotransporters, the transport inhibitor phosphonoformic acid did not inhibit PiT-1 or PiT-2 activity.
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Affiliation(s)
- Silvia Ravera
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland
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