1
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Lin F, Tuffour A, Hao G, Peprah FA, Huang A, Zhou Y, Zhang H. Distinctive modulation of hepcidin in cancer and its therapeutic relevance. Front Oncol 2023; 13:1141603. [PMID: 36895478 PMCID: PMC9989193 DOI: 10.3389/fonc.2023.1141603] [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: 01/10/2023] [Accepted: 02/08/2023] [Indexed: 02/23/2023] Open
Abstract
Hepcidin, a short peptide synthesized primarily by hepatocytes in response to increased body iron and inflammation, is a crucial iron-regulating factor. Hepcidin regulates intestinal iron absorption and releases iron from macrophages into plasma through a negative iron feedback mechanism. The discovery of hepcidin inspired a torrent of research into iron metabolism and related problems, which have radically altered our understanding of human diseases caused by an excess of iron, an iron deficiency, or an iron disparity. It is critical to decipher how tumor cells manage hepcidin expression for their metabolic requirements because iron is necessary for cell survival, particularly for highly active cells like tumor cells. Studies show that tumor and non-tumor cells express and control hepcidin differently. These variations should be explored to produce potential novel cancer treatments. The ability to regulate hepcidin expression to deprive cancer cells of iron may be a new weapon against cancer cells.
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Affiliation(s)
- Feng Lin
- Key Laboratory of Healthy Freshwater Aquaculture, Ministry of Agriculture, Zhejiang Institute of Freshwater Fisheries, Huzhou, China
| | - Alex Tuffour
- School of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu, China.,State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China
| | - Guijie Hao
- Key Laboratory of Healthy Freshwater Aquaculture, Ministry of Agriculture, Zhejiang Institute of Freshwater Fisheries, Huzhou, China
| | | | - Aixia Huang
- Key Laboratory of Healthy Freshwater Aquaculture, Ministry of Agriculture, Zhejiang Institute of Freshwater Fisheries, Huzhou, China
| | - Yang Zhou
- School of Life Sciences, Jiangsu University, Zhenjiang, Jiangsu, China
| | - Haiqi Zhang
- Key Laboratory of Healthy Freshwater Aquaculture, Ministry of Agriculture, Zhejiang Institute of Freshwater Fisheries, Huzhou, China
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2
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Goncalves Monteiro D, Rishi G, Gorman DM, Burnet G, Aliyanto R, Rosengren KJ, Frazer DM, Subramaniam VN, Clark RJ. Engineering Peptide Inhibitors of the HFE-Transferrin Receptor 1 Complex. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27196581. [PMID: 36235117 PMCID: PMC9570809 DOI: 10.3390/molecules27196581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 09/22/2022] [Accepted: 09/28/2022] [Indexed: 11/05/2022]
Abstract
The protein HFE (homeostatic iron regulator) is a key regulator of iron metabolism, and mutations in HFE underlie the most frequent form of hereditary haemochromatosis (HH-type I). Studies have shown that HFE interacts with transferrin receptor 1 (TFR1), a homodimeric type II transmembrane glycoprotein that is responsible for the cellular uptake of iron via iron-loaded transferrin (holo-transferrin) binding. It has been hypothesised that the HFE/TFR1 interaction serves as a sensor to the level of iron-loaded transferrin in circulation by means of a competition mechanism between HFE and iron-loaded transferrin association with TFR1. To investigate this, a series of peptides based on the helical binding interface between HFE and TFR1 were generated and shown to significantly interfere with the HFE/TFR1 interaction in an in vitro proximity ligation assay. The helical conformation of one of these peptides, corresponding to the α1 and α2 helices of HFE, was stabilised by the introduction of sidechain lactam “staples”, but this did not result in an increase in the ability of the peptide to disrupt the HFE/TFR1 interaction. These peptides inhibitors of the protein–protein interaction between HFE and TFR1 are potentially useful tools for the analysis of the functional role of HFE in the regulation of hepcidin expression.
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Affiliation(s)
| | - Gautam Rishi
- Centre for Genomics and Personalised Health, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
| | - Declan M. Gorman
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Guillaume Burnet
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Randy Aliyanto
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - K. Johan Rosengren
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - David M. Frazer
- The QIMR Berghofer Medical Research Institute, 300 Herston Rd, Brisbane, QLD 4006, Australia
| | - V. Nathan Subramaniam
- Centre for Genomics and Personalised Health, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
- Correspondence: (V.N.S.); (R.J.C.)
| | - Richard J. Clark
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
- Correspondence: (V.N.S.); (R.J.C.)
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3
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Baas FS, Rishi G, Swinkels DW, Subramaniam VN. Genetic Diagnosis in Hereditary Hemochromatosis: Discovering and Understanding the Biological Relevance of Variants. Clin Chem 2021; 67:1324-1341. [PMID: 34402502 DOI: 10.1093/clinchem/hvab130] [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: 04/01/2021] [Accepted: 06/23/2021] [Indexed: 11/13/2022]
Abstract
BACKGROUND Hereditary hemochromatosis (HH) is a genetic disease, leading to iron accumulation and possible organ damage. Patients are usually homozygous for p. Cys282Tyr in the homeostatic iron regulator gene but may have mutations in other genes involved in the regulation of iron. Next-generation sequencing is increasingly being utilized for the diagnosis of patients, leading to the discovery of novel genetic variants. The clinical significance of these variants is often unknown. CONTENT Determining the pathogenicity of such variants of unknown significance is important for diagnostics and genetic counseling. Predictions can be made using in silico computational tools and population data, but additional evidence is required for a conclusive pathogenicity classification. Genetic disease models, such as in vitro models using cellular overexpression, induced pluripotent stem cells or organoids, and in vivo models using mice or zebrafish all have their own challenges and opportunities when used to model HH and other iron disorders. Recent developments in gene-editing technologies are transforming the field of genetic disease modeling. SUMMARY In summary, this review addresses methods and developments regarding the discovery and classification of genetic variants, from in silico tools to in vitro and in vivo models, and presents them in the context of HH. It also explores recent gene-editing developments and how they can be applied to the discussed models of genetic disease.
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Affiliation(s)
- Floor S Baas
- Translational Metabolic Laboratory (TML 831), Radboudumc, Nijmegen, the Netherlands.,Hepatogenomics Research Group, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD, Australia
| | - Gautam Rishi
- Hepatogenomics Research Group, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD, Australia
| | - Dorine W Swinkels
- Translational Metabolic Laboratory (TML 831), Radboudumc, Nijmegen, the Netherlands
| | - V Nathan Subramaniam
- Hepatogenomics Research Group, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD, Australia
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4
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Kowdley DS, Kowdley KV. Appropriate Clinical Genetic Testing of Hemochromatosis Type 2-4, Including Ferroportin Disease. Appl Clin Genet 2021; 14:353-361. [PMID: 34413666 PMCID: PMC8369226 DOI: 10.2147/tacg.s269622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 07/18/2021] [Indexed: 11/23/2022] Open
Abstract
Hereditary hemochromatosis (HH) is an inherited iron overload disorder due to a deficiency of hepcidin, or a failure of hepcidin to degrade ferroportin. The most common form of HH, Type 1 HH, is most commonly due to a homozygous C282Y mutation in HFE and is relatively well understood in significance and action; however, other rare forms of HH (Types 2–4) exist and are more difficult to identify and diagnose in clinical practice. In this review, we describe the clinical characteristics of HH Type 2–4 and the mutation patterns that have been described in these conditions. We also review the different methods for genetic testing available in clinical practice and a pragmatic approach to the patient with suspected non-HFE HH.
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Affiliation(s)
- Devan S Kowdley
- Liver Institute Northwest and Elson S. Floyd College of Medicine, Washington State University, Seattle, WA, USA
| | - Kris V Kowdley
- Liver Institute Northwest and Elson S. Floyd College of Medicine, Washington State University, Seattle, WA, USA
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5
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Colucci S, Marques O, Altamura S. 20 years of Hepcidin: How far we have come. Semin Hematol 2021; 58:132-144. [PMID: 34389105 DOI: 10.1053/j.seminhematol.2021.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 05/12/2021] [Accepted: 05/31/2021] [Indexed: 12/20/2022]
Abstract
Twenty years ago the discovery of hepcidin deeply changed our understanding of the regulation of systemic iron homeostasis. It is now clear that hepcidin orchestrates systemic iron levels by controlling the amount of iron exported into the bloodstream through ferroportin. Hepcidin expression is increased in situations where systemic iron levels should be reduced, such as in iron overload and infection. Conversely, hepcidin is repressed during iron deficiency, hypoxia or expanded erythropoiesis, to increase systemic iron availability and sustain erythropoiesis. In this review, we will focus on molecular mechanisms of hepcidin regulation and on the pathological consequences of their disruption.
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Affiliation(s)
- Silvia Colucci
- Department of Pediatric Hematology, Oncology and Immunology - University of Heidelberg, Heidelberg, Germany.; Molecular Medicine Partnership Unit, EMBL and University of Heidelberg, Heidelberg, Germany
| | - Oriana Marques
- Department of Pediatric Hematology, Oncology and Immunology - University of Heidelberg, Heidelberg, Germany.; Molecular Medicine Partnership Unit, EMBL and University of Heidelberg, Heidelberg, Germany
| | - Sandro Altamura
- Department of Pediatric Hematology, Oncology and Immunology - University of Heidelberg, Heidelberg, Germany.; Molecular Medicine Partnership Unit, EMBL and University of Heidelberg, Heidelberg, Germany..
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6
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Kowdley KV, Gochanour EM, Sundaram V, Shah RA, Handa P. Hepcidin Signaling in Health and Disease: Ironing Out the Details. Hepatol Commun 2021; 5:723-735. [PMID: 34027264 PMCID: PMC8122377 DOI: 10.1002/hep4.1717] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 02/22/2021] [Accepted: 02/23/2021] [Indexed: 12/19/2022] Open
Abstract
Hepcidin, a peptide hormone produced by hepatocytes, is the central regulator of systemic iron homeostasis through its interaction with ferroportin, the major cellular iron export protein. Hepcidin binding to ferroportin results in reduced iron export from macrophages and intestinal absorptive cells, leading to decreased serum iron levels. Hepcidin expression is influenced by several factors that include serum and liver iron stores, erythropoiesis, hypoxia, inflammation, and infection. Erythropoietic drive and hypoxia suppress hepcidin expression and promote red cell production. In contrast, inflammation and infection are associated with increased hepcidin production to sequester iron intracellularly as a means of depriving microorganisms of iron. Chronic inflammation may up-regulate hepcidin expression through the interleukin-6 (IL-6)-Janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) pathway. The bone morphogenetic protein (BMP)-mothers against decapentaplegic homolog (SMAD) pathway is a major positive driver of hepcidin expression in response to either increased circulating iron in the form of transferrin or iron loading in organs. Hereditary hemochromatosis (HH) consists of several inherited disorders that cause inappropriately reduced hepcidin expression in response to body iron stores, leading to increased iron absorption from a normal diet. The most common form of HH is due to a mutation in the HFE gene, which causes a failure in the hepatocyte iron-sensing mechanism, leading to reduced hepcidin expression; the clinical manifestations of HFE-HH include increased serum transferrin-iron saturation and progressive iron loading in the liver and other tissues over time among patients who express the disease phenotype. In this article, we review the physiologic mechanisms and cellular pathways by which hepcidin expression is regulated, and the different forms of HH resulting from various mutations that cause hepcidin deficiency. We also review other drivers of hepcidin expression and the associated pathophysiologic consequences.
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Affiliation(s)
- Kris V Kowdley
- Liver Institute Northwest and Elson S. Floyd College of MedicineWashington State UniversitySpokaneWAUSA.,Liver Care Network and Organ Care ResearchSwedish Medical CenterSeattleWAUSA
| | - Eric M Gochanour
- Liver Institute Northwest and Elson S. Floyd College of MedicineWashington State UniversitySpokaneWAUSA.,Liver Care Network and Organ Care ResearchSwedish Medical CenterSeattleWAUSA
| | - Vinay Sundaram
- Division of Gastroenterology and Comprehensive Transplant CenterLos AngelesCAUSA
| | - Raj A Shah
- Liver Care Network and Organ Care ResearchSwedish Medical CenterSeattleWAUSA
| | - Priya Handa
- Liver Care Network and Organ Care ResearchSwedish Medical CenterSeattleWAUSA
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7
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Evidence for dimerization of ferroportin in a human hepatic cell line using proximity ligation assays. Biosci Rep 2021; 40:222672. [PMID: 32301493 PMCID: PMC7201565 DOI: 10.1042/bsr20191499] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Revised: 04/08/2020] [Accepted: 04/16/2020] [Indexed: 12/30/2022] Open
Abstract
Mutations in the only known iron exporter ferroportin (FPN) in humans are associated with the autosomal dominantly inherited iron overload disorder ferroportin disease or type IV hereditary hemochromatosis (HH). While our knowledge of the central role of FPN in iron homeostasis has grown in the last 20 years, there exist some questions surrounding the structure and membrane topology of FPN with conflicting data on whether this receptor acts as a monomer or a multimer. To investigate and determine if FPN dimerization occurs in cells, we used novel tools including a variety of different FPN constructs expressing different tagged versions of the protein, a novel antibody that only detects cell surface FPN and proximity ligation assays. The results of the present study suggest that both the carboxy- and amino-termini of the FPN protein are intracellular. We also show that exogenously transfected FPN forms dimers; these dimers can be formed between the wild-type and mutant FPN proteins. This is the first study to examine the intracellular dimerization of FPN protein. Using proximity ligation assays, we show intracellular localization of FPN dimers and the interaction between FPN and hepcidin proteins as well. These results have important implications in the field of iron metabolism and add to our knowledge about FPN membrane topology and physiology of iron transport. This will be of importance in understanding the clinical implications of FPN mutations and of interest to future research aimed at targeting FPN expression to modulate iron homeostasis.
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8
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Dysregulated hepcidin response to dietary iron in male mice with reduced Gnpat expression. Biosci Rep 2020; 40:226001. [PMID: 32766721 PMCID: PMC7441371 DOI: 10.1042/bsr20201508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 07/13/2020] [Accepted: 08/06/2020] [Indexed: 11/17/2022] Open
Abstract
Exome sequencing has identified the glyceronephosphate O-acyltransferase (GNPAT) gene as a genetic modifier of iron overload in hereditary hemochromatosis (HH). Subjects with HFE (Homeostatic Iron Regulator) p.C282Y mutations and the GNPAT p.D519G variant had more iron loading compared with subjects without the GNPAT variant. In response to an oral iron challenge, women with GNPAT polymorphisms loaded more iron as compared with women without polymorphisms, reinforcing a role for GNPAT in iron homeostasis. The aim of the present study was to develop and characterize an animal model of disease to further our understanding of genetic modifiers, and in particular the role of GNPAT in iron homeostasis. We generated an Hfe/Gnpat mouse model reminiscent of the patients previously studied and studied these mice for up to 26 weeks. We also examined the effect of dietary iron loading on mice with reduced Gnpat expression. Gnpat heterozygosity in Hfe knockout mice does not play a role in systemic iron homeostasis; Gnpat+/− mice fed a high-iron diet, however, had lower hepatic hepcidin (HAMP) mRNA expression, whereas they have significantly higher serum iron levels and transferrin saturation compared with wildtype (WT) littermates on a similar diet. These results reinforce an independent role of GNPAT in systemic iron homeostasis, reproducing in an animal model, the observations in women with GNPAT polymorphisms subjected to an iron tolerance test.
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9
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Abstract
Since its discovery in 2001, there have been a number of important discoveries and findings that have increased our knowledge about the functioning of hepcidin. Hepcidin, the master iron regulator has been shown to be regulated by a number of physiological stimuli and their associated signaling pathways. This chapter will summarize our current understanding of how these physiological stimuli and downstream signaling molecules are involved in hepcidin modulation and ultimately contribute to the regulation of systemic or local iron homeostasis. The signaling pathways and molecules described here have been shown to primarily affect hepcidin at a transcriptional level, but these transcriptional changes correlate with changes in systemic iron levels as well, supporting the functional effects of hepcidin regulation by these signaling pathways.
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Affiliation(s)
- Gautam Rishi
- The Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD, Australia
| | - V Nathan Subramaniam
- The Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD, Australia.
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10
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Abstract
Iron, an essential nutrient, is required for many biological processes but is also toxic in excess. The lack of a mechanism to excrete excess iron makes it crucial for the body to regulate the amount of iron absorbed from the diet. This regulation is mediated by the hepatic hormone hepcidin. Hepcidin also controls iron release from macrophages that recycle iron and from hepatocytes that store iron. Hepcidin binds to the only known iron export protein, ferroportin, inducing its internalization and degradation and thus limiting the amount of iron released into the plasma. Important regulators of hepcidin, and therefore of systemic iron homeostasis, include plasma iron concentrations, body iron stores, infection and inflammation, hypoxia and erythropoiesis, and, to a lesser extent, testosterone. Dysregulation of hepcidin production contributes to the pathogenesis of many iron disorders: hepcidin deficiency causes iron overload in hereditary hemochromatosis and non-transfused β-thalassemia, whereas overproduction of hepcidin is associated with iron-restricted anemias seen in patients with chronic inflammatory diseases and inherited iron-refractory iron-deficiency anemia. The present review summarizes our current understanding of the molecular mechanisms and signaling pathways contributing to hepcidin regulation by these factors and highlights the issues that still need clarification.
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Affiliation(s)
- Marie-Paule Roth
- Institut de Recherche en Santé Digestive (IRSD), Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France.
| | - Delphine Meynard
- Institut de Recherche en Santé Digestive (IRSD), Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France
| | - Hélène Coppin
- Institut de Recherche en Santé Digestive (IRSD), Université de Toulouse, INSERM, INRA, ENVT, UPS, Toulouse, France
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11
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The hemochromatosis protein HFE signals predominantly via the BMP type I receptor ALK3 in vivo. Commun Biol 2018; 1:65. [PMID: 30271947 PMCID: PMC6123693 DOI: 10.1038/s42003-018-0071-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 04/20/2018] [Indexed: 12/24/2022] Open
Abstract
Mutations in HFE, the most common cause of hereditary hemochromatosis, lead to iron overload. The iron overload is characterized by increased iron uptake due to lower levels of the hepatic, iron regulatory hormone hepcidin. HFE was cloned 21 years ago, but the signaling pathway is still unknown. Because bone morphogenetic protein (BMP) signaling is impaired in patients with hereditary hemochromatosis, and the interaction of HFE and the BMP type I receptor ALK3 was suggested in vitro, in vivo experiments were performed. In vivo, hepatocyte-specific Alk3-deficient and control mice were injected with either AAV2/8-Hfe-Flag or PBS. HFE overexpression in control mice results in increased hepatic hepcidin levels, p-Smad1/5 levels, and iron deficiency anemia, whereas overexpression of HFE in hepatocyte-specific Alk3-deficient mice results in no change in hepcidin, p-Smad1/5 levels, or blood parameters. These results indicate that HFE signals predominantly via ALK3 to induce hepcidin in vivo. Lisa Traeger et al. show that human hereditary hemochromatosis protein (HFE) signals through ALK3 to induce hepcidin in mice in vivo. The results validate and extend previous findings from in vitro studies that suggested a link between HFE and BMP signaling.
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12
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Rishi G, Secondes ES, Nathan Subramaniam V. Hemochromatosis: Evaluation of the dietary iron model and regulation of hepcidin. Biochim Biophys Acta Mol Basis Dis 2018; 1864:2550-2556. [PMID: 29752985 DOI: 10.1016/j.bbadis.2018.05.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 04/20/2018] [Accepted: 05/07/2018] [Indexed: 12/22/2022]
Abstract
Our knowledge of iron homeostasis has increased steadily over the last two decades; much of this has been made possible through the study of animal models of iron-related disease. Analysis of transgenic mice with deletions or perturbations in genes known to be involved in systemic or local regulation of iron metabolism has been particularly informative. The effect of these genes on iron accumulation and hepcidin regulation is traditionally compared with wildtype mice fed a high iron diet, most often a 2% carbonyl iron diet. Recent studies have indicated that a very high iron diet could be detrimental to the health of the mice and could potentially affect homeostasis of other metals, for example zinc and copper. We analyzed mice fed a diet containing either 0.25%, 0.5%, 1% or 2% carbonyl iron for two weeks and compared them with mice on a control diet. Our results indicate that a 0.25% carbonyl iron diet is sufficient to induce maximal hepatic hepcidin response. Importantly these results also demonstrate that in a chronic setting of iron administration, the amount of excess hepatic iron may not further influence hepcidin regulation and that expression of hepcidin plateaus at lower hepatic iron levels. These studies provide further insights into the regulation of this important hormone.
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Affiliation(s)
- Gautam Rishi
- The Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Queensland, Australia
| | - Eriza S Secondes
- The Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Queensland, Australia
| | - V Nathan Subramaniam
- The Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Queensland, Australia.
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13
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Abstract
Haemochromatosis is defined as systemic iron overload of genetic origin, caused by a reduction in the concentration of the iron regulatory hormone hepcidin, or a reduction in hepcidin-ferroportin binding. Hepcidin regulates the activity of ferroportin, which is the only identified cellular iron exporter. The most common form of haemochromatosis is due to homozygous mutations (specifically, the C282Y mutation) in HFE, which encodes hereditary haemochromatosis protein. Non-HFE forms of haemochromatosis due to mutations in HAMP, HJV or TFR2 are much rarer. Mutations in SLC40A1 (also known as FPN1; encoding ferroportin) that prevent hepcidin-ferroportin binding also cause haemochromatosis. Cellular iron excess in HFE and non-HFE forms of haemochromatosis is caused by increased concentrations of plasma iron, which can lead to the accumulation of iron in parenchymal cells, particularly hepatocytes, pancreatic cells and cardiomyocytes. Diagnosis is noninvasive and includes clinical examination, assessment of plasma iron parameters, imaging and genetic testing. The mainstay therapy is phlebotomy, although iron chelation can be used in some patients. Hepcidin supplementation might be an innovative future approach.
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Affiliation(s)
- Pierre Brissot
- INSERM, Univ. Rennes, INRA, Institut NUMECAN (Nutrition Metabolisms and Cancer) UMR_A 1341, UMR_S 1241, F-35000 Rennes, France
| | - Antonello Pietrangelo
- Division of Internal Medicine 2 and Center for Haemochromatosis, University Hospital of Modena, Modena, Italy
| | - Paul C. Adams
- Department of Medicine, University of Western Ontario, London, Ontario, Canada
| | - Barbara de Graaff
- Menzies Institute for Medical Research, University of Tasmania, Tasmania, Australia
| | | | - Olivier Loréal
- INSERM, Univ. Rennes, INRA, Institut NUMECAN (Nutrition Metabolisms and Cancer) UMR_A 1341, UMR_S 1241, F-35000 Rennes, France
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Ambachew S, Biadgo B. Hepcidin in Iron Homeostasis: Diagnostic and Therapeutic Implications in Type 2 Diabetes Mellitus Patients. Acta Haematol 2017; 138:183-193. [PMID: 29136618 DOI: 10.1159/000481391] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 09/08/2017] [Indexed: 12/21/2022]
Abstract
The prevalence of type 2 diabetes is increasing in epidemic proportions worldwide. Evidence suggests body iron overload is frequently linked and observed in patients with type 2 diabetes. Body iron metabolism is based on iron conservation and recycling by which only a part of the daily need is replaced by duodenal absorption. The principal liver-produced peptide called hepcidin plays a fundamental role in iron metabolism. It directly binds to ferroportin, the sole iron exporter, resulting in the internalization and degradation of ferroportin. However, inappropriate production of hepcidin has been shown to play a role in the pathogenesis of type 2 diabetes mellitus and its complications, based on the regulation and expression in iron-abundant cells. Underexpression of hepcidin results in body iron overload, which triggers the production of reactive oxygen species simultaneously thought to play a major role in diabetes pathogenesis mediated both by β-cell failure and insulin resistance. Increased hepcidin expression results in increased intracellular sequestration of iron, and is associated with the complications of type 2 diabetes. Besides, hepcidin concentrations have been linked to inflammatory cytokines, matriptase 2, and chronic hepatitis C infection, which have in turn been reported to be associated with diabetes by several approaches. Either hepcidin-targeted therapy alone or as adjunctive therapy with phlebotomy, iron chelators, or dietary iron restriction may be able to alter iron parameters in diabetic patients. Therefore, measuring hepcidin may improve differential diagnosis and the monitoring of disorders of iron metabolism.
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Affiliation(s)
- Sintayehu Ambachew
- Department of Clinical Chemistry, School of Biomedical and Laboratory Sciences, College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia
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15
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Rishi G, Subramaniam VN. The liver in regulation of iron homeostasis. Am J Physiol Gastrointest Liver Physiol 2017; 313:G157-G165. [PMID: 28596277 DOI: 10.1152/ajpgi.00004.2017] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 05/31/2017] [Accepted: 05/31/2017] [Indexed: 01/31/2023]
Abstract
The liver is one of the largest and most functionally diverse organs in the human body. In addition to roles in detoxification of xenobiotics, digestion, synthesis of important plasma proteins, gluconeogenesis, lipid metabolism, and storage, the liver also plays a significant role in iron homeostasis. Apart from being the storage site for excess body iron, it also plays a vital role in regulating the amount of iron released into the blood by enterocytes and macrophages. Since iron is essential for many important physiological and molecular processes, it increases the importance of liver in the proper functioning of the body's metabolism. This hepatic iron-regulatory function can be attributed to the expression of many liver-specific or liver-enriched proteins, all of which play an important role in the regulation of iron homeostasis. This review focuses on these proteins and their known roles in the regulation of body iron metabolism.
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Affiliation(s)
- Gautam Rishi
- Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology, Brisbane, Australia
| | - V Nathan Subramaniam
- Liver Disease and Iron Disorders Research Group, Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology, Brisbane, Australia
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16
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Mehta KJ, Farnaud S, Patel VB. HFE mRNA expression is responsive to intracellular and extracellular iron loading: short communication. Mol Biol Rep 2017; 44:399-403. [PMID: 28840425 PMCID: PMC5640751 DOI: 10.1007/s11033-017-4123-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 08/19/2017] [Indexed: 11/28/2022]
Abstract
In liver hepatocytes, the HFE gene regulates cellular and systemic iron homeostasis by modulating cellular iron-uptake and producing the iron-hormone hepcidin in response to systemic iron elevation. However, the mechanism of iron-sensing in hepatocytes remain enigmatic. Therefore, to study the effect of iron on HFE and hepcidin (HAMP) expressions under distinct extracellular and intracellular iron-loading, we examined the effect of holotransferrin treatment (1, 2, 5 and 8 g/L for 6 h) on intracellular iron levels, and mRNA expressions of HFE and HAMP in wild-type HepG2 and previously characterized iron-loaded recombinant-TfR1 HepG2 cells. Gene expression was analyzed by real-time PCR and intracellular iron was measured by ferrozine assay. Data showed that in the wild-type cells, where intracellular iron content remained unchanged, HFE expression remained unaltered at low holotransferrin treatments but was upregulated upon 5 g/L (p < 0.04) and 8 g/L (p = 0.05) treatments. HAMP expression showed alternating elevations and increased upon 1 g/L (p < 0.05) and 5 g/L (p < 0.05). However, in the recombinant cells that showed higher intracellular iron levels than wild-type cells, HFE and HAMP expressions were elevated only at low 1 g/L treatment (p < 0.03) and were repressed at 2 g/L treatment (p < 0.03). Under holotransferrin-untreated conditions, the iron-loaded recombinant cells showed higher expressions of HFE (p < 0.03) and HAMP (p = 0.05) than wild-type cells. HFE mRNA was independently elevated by extracellular and intracellular iron-excess. Thus, it may be involved in sensing both, extracellular and intracellular iron. Repression of HAMP expression under simultaneous intracellular and extracellular iron-loading resembles non-hereditary iron-excess pathologies.
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Affiliation(s)
- Kosha J Mehta
- Department of Biomedical Sciences, University of Westminster, 115 New Cavendish Street, London, W1W 6UW, UK
| | - Sebastien Farnaud
- School of Life Sciences, Coventry University, 138 James Starley Building, Coventry, CV1 5FB, UK
| | - Vinood B Patel
- Department of Biomedical Sciences, University of Westminster, 115 New Cavendish Street, London, W1W 6UW, UK.
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17
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Papanikolaou G, Pantopoulos K. Systemic iron homeostasis and erythropoiesis. IUBMB Life 2017; 69:399-413. [DOI: 10.1002/iub.1629] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 03/16/2017] [Indexed: 01/01/2023]
Affiliation(s)
- George Papanikolaou
- Department of Nutrition and DieteticsSchool of Health Science and Education, Harokopion UniversityAthens Greece
| | - Kostas Pantopoulos
- Lady Davis Institute for Medical Research and Department of MedicineMcGill UniversityMontreal Quebec Canada
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18
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Dela Paz NG, Melchior B, Frangos JA. Shear stress induces Gα q/11 activation independently of G protein-coupled receptor activation in endothelial cells. Am J Physiol Cell Physiol 2017; 312:C428-C437. [PMID: 28148497 DOI: 10.1152/ajpcell.00148.2016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 01/25/2017] [Accepted: 01/25/2017] [Indexed: 12/17/2022]
Abstract
Mechanochemical signal transduction occurs when mechanical forces, such as fluid shear stress, are converted into biochemical responses within the cell. The molecular mechanisms by which endothelial cells (ECs) sense/transduce shear stress into biological signals, including the nature of the mechanosensor, are still unclear. G proteins and G protein-coupled receptors (GPCRs) have been postulated independently to mediate mechanotransduction. In this study, we used in situ proximity ligation assay (PLA) to investigate the role of a specific GPCR/Gαq/11 pair in EC shear stress-induced mechanotransduction. We demonstrated that sphingosine 1-phosphate (S1P) stimulation causes a rapid dissociation at 0.5 min of Gαq/11 from its receptor S1P3, followed by an increased association within 2 min of GPCR kinase-2 (GRK2) and β-arrestin-1/2 with S1P3 in human coronary artery ECs, which are consistent with GPCR/Gαq/11 activation and receptor desensitization/internalization. The G protein activator AlF4 resulted in increased dissociation of Gαq/11 from S1P3, but no increase in association between S1P3 and either GRK2 or β-arrestin-1/2. The G protein inhibitor guanosine 5'-(β-thio) diphosphate (GDP-β-S) and the S1P3 antagonist VPC23019 both prevented S1P-induced activation. Shear stress also caused the rapid activation within 7 s of S1P3/Gαq/11 There were no increased associations between S1P3 and GRK2 or S1P3 and β-arrestin-1/2 until 5 min. GDP-β-S, but not VPC23019, prevented dissociation of Gαq/11 from S1P3 in response to shear stress. Shear stress did not induce rapid dephosphorylation of β-arrestin-1 or rapid internalization of S1P3, indicating no GPCR activation. These findings suggest that Gαq/11 participates in the sensing/transducing of shear stress independently of GPCR activation in ECs.
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19
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Sikorska K, Bernat A, Wroblewska A. Molecular pathogenesis and clinical consequences of iron overload in liver cirrhosis. Hepatobiliary Pancreat Dis Int 2016; 15:461-479. [PMID: 27733315 DOI: 10.1016/s1499-3872(16)60135-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND The liver, as the main iron storage compartment and the place of hepcidin synthesis, is the central organ involved in maintaining iron homeostasis in the body. Excessive accumulation of iron is an important risk factor in liver disease progression to cirrhosis and hepatocellular carcinoma. Here, we review the literature on the molecular pathogenesis of iron overload and its clinical consequences in chronic liver diseases. DATA SOURCES PubMed was searched for English-language articles on molecular genesis of primary and secondary iron overload, as well as on their association with liver disease progression. We have also included literature on adjuvant therapeutic interventions aiming to alleviate detrimental effects of excessive body iron load in liver cirrhosis. RESULTS Excess of free, unbound iron induces oxidative stress, increases cell sensitivity to other detrimental factors, and can directly affect cellular signaling pathways, resulting in accelerated liver disease progression. Diagnosis of liver cirrhosis is, in turn, often associated with the identification of a pathological accumulation of iron, even in the absence of genetic background of hereditary hemochromatosis. Iron depletion and adjuvant therapy with antioxidants are shown to cause significant improvement of liver functions in patients with iron overload. Phlebotomy can have beneficial effects on liver histology in patients with excessive iron accumulation combined with compensated liver cirrhosis of different etiology. CONCLUSION Excessive accumulation of body iron in liver cirrhosis is an important predictor of liver failure and available data suggest that it can be considered as target for adjuvant therapy in this condition.
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Affiliation(s)
- Katarzyna Sikorska
- Department of Tropical Medicine and Epidemiology, Medical University of Gdansk, Powstania Styczniowego 9b, 81-519 Gdynia, Poland.
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20
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Ferro E, Di Pietro A, Visalli G, Piraino B, Salpietro C, La Rosa MA. Soluble hemojuvelin in transfused and untransfused thalassaemic subjects. Eur J Haematol 2016; 98:67-74. [PMID: 27440164 DOI: 10.1111/ejh.12786] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/16/2016] [Indexed: 12/11/2022]
Abstract
OBJECTIVE The hemojuvelin-bone morphogenetic protein axis is the principal iron-dependent mechanism of hepcidin regulation. The determination of soluble hemojuvelin (sHJV) levels could allow for a better understanding of the pathophysiological mechanisms of hepcidin regulation in thalassaemia. METHOD We have assessed sHJV in 45 transfused and 15 untransfused thalassaemic patients in comparison with 15 healthy subjects, evaluating its relationships with some parameters of iron overload, anaemia and erythropoiesis. RESULTS Untransfused thalassaemic patients had more severe anaemia and erythropoietic activity, while in transfused patients, the transfused RBCs reduced % reticulocytes and sTfR, increased serum indices of iron overload and iron stores in the liver (low MRI T2* values). sHJV levels were higher in patients than in controls and in untransfused in comparison with transfused patients. In the transfused group, we also found that sHJV values are significantly related to serum ferritin, cardiac MRI T2* and growth differentiation factor 15 and are sensitive to hepatitis C virus infection. CONCLUSION These results suggest that sHJV synthesis seems to be affected by an erythropoietic/hypoxic signal in untransfused patients that have severe anaemia, while in regularly transfused subjects, it is influenced by iron stores.
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Affiliation(s)
- Elisa Ferro
- Department of Human Pathology of Adult and Developmental Age 'Gaetano Barresi', University Hospital of Messina, Messina, Italy
| | - Angela Di Pietro
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Messina, Italy
| | - Giuseppa Visalli
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Messina, Italy
| | - Basilia Piraino
- Department of Human Pathology of Adult and Developmental Age 'Gaetano Barresi', University Hospital of Messina, Messina, Italy
| | - Carmelo Salpietro
- Department of Human Pathology of Adult and Developmental Age 'Gaetano Barresi', University Hospital of Messina, Messina, Italy
| | - Maria Angela La Rosa
- Department of Human Pathology of Adult and Developmental Age 'Gaetano Barresi', University Hospital of Messina, Messina, Italy
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21
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Mehta K, Busbridge M, Renshaw D, Evans RW, Farnaud S, Patel VB. Characterization of hepcidin response to holotransferrin in novel recombinant TfR1 HepG2 cells. Blood Cells Mol Dis 2016; 61:37-45. [PMID: 27667164 DOI: 10.1016/j.bcmd.2016.06.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/28/2016] [Accepted: 06/28/2016] [Indexed: 12/14/2022]
Abstract
Hepcidin is the key regulator of systemic iron homeostasis. The iron-sensing mechanisms and the role of intracellular iron in modulating hepatic hepcidin secretion are unclear. Therefore, we created a novel cell line, recombinant-TfR1 HepG2, expressing iron-response-element-independent TFRC mRNA to promote cellular iron-overload and examined the effect of excess holotransferrin (5g/L) on cell-surface TfR1, iron content, hepcidin secretion and mRNA expressions of TFRC, HAMP, SLC40A1, HFE and TFR2. Results showed that the recombinant cells exceeded levels of cell-surface TfR1 in wild-type cells under basal (2.8-fold; p<0.03) and holotransferrin-supplemented conditions for 24h and 48h (4.4- and 7.5-fold, respectively; p<0.01). Also, these cells showed higher intracellular iron content than wild-type cells under basal (3-fold; p<0.03) and holotransferrin-supplemented conditions (6.6-fold at 4h; p<0.01). However, hepcidin secretion was not higher than wild-type cells. Moreover, holotransferrin treatment to recombinant cells did not elevate HAMP responses compared to untreated or wild-type cells. In conclusion, increased intracellular iron content in recombinant cells did not increase hepcidin responses compared to wild-type cells, resembling hemochromatosis. Furthermore, TFR2 expression altered within 4h of treatment, while HFE expression altered later at 24h and 48h, suggesting that TFR2 may function prior to HFE in HAMP regulation.
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Affiliation(s)
- Kosha Mehta
- Department of Biomedical Sciences, University of Westminster, London, UK
| | - Mark Busbridge
- Department of Clinical Biochemistry, Charing Cross Hospital, Imperial College Healthcare NHS Trust, London, UK
| | - Derek Renshaw
- Faculty of Health & Life Sciences, Coventry University, Coventry, UK
| | - Robert W Evans
- School of Engineering and Design, Brunel University, London, UK
| | | | - Vinood B Patel
- Department of Biomedical Sciences, University of Westminster, London, UK.
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22
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Rishi G, Secondes ES, Wallace DF, Subramaniam VN. Normal systemic iron homeostasis in mice with macrophage-specific deletion of transferrin receptor 2. Am J Physiol Gastrointest Liver Physiol 2016; 310:G171-80. [PMID: 26608187 DOI: 10.1152/ajpgi.00291.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 11/23/2015] [Indexed: 01/31/2023]
Abstract
Iron is an essential element, since it is a component of many macromolecules involved in diverse physiological and cellular functions, including oxygen transport, cellular growth, and metabolism. Systemic iron homeostasis is predominantly regulated by the liver through the iron regulatory hormone hepcidin. Hepcidin expression is itself regulated by a number of proteins, including transferrin receptor 2 (TFR2). TFR2 has been shown to be expressed in the liver, bone marrow, macrophages, and peripheral blood mononuclear cells. Studies from our laboratory have shown that mice with a hepatocyte-specific deletion of Tfr2 recapitulate the hemochromatosis phenotype of the global Tfr2 knockout mice, suggesting that the hepatic expression of TFR2 is important in systemic iron homeostasis. It is unclear how TFR2 in macrophages contributes to the regulation of iron metabolism. We examined the role of TFR2 in macrophages by analysis of transgenic mice lacking Tfr2 in macrophages by crossing Tfr2(f/f) mice with LysM-Cre mice. Mice were fed an iron-rich diet or injected with lipopolysaccharide to examine the role of macrophage Tfr2 in iron- or inflammation-mediated regulation of hepcidin. Body iron homeostasis was unaffected in the knockout mice, suggesting that macrophage TFR2 is not required for the regulation of systemic iron metabolism. However, peritoneal macrophages of knockout mice had significantly lower levels of ferroportin mRNA and protein, suggesting that TFR2 may be involved in regulating ferroportin levels in macrophages. These studies further elucidate the role of TFR2 in the regulation of iron homeostasis and its role in regulation of ferroportin and thus macrophage iron homeostasis.
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Affiliation(s)
- Gautam Rishi
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia; and School of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Eriza S Secondes
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia; and
| | - Daniel F Wallace
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia; and School of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - V Nathan Subramaniam
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia; and School of Medicine, The University of Queensland, Brisbane, Queensland, Australia
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23
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Latour C, Besson-Fournier C, Meynard D, Silvestri L, Gourbeyre O, Aguilar-Martinez P, Schmidt PJ, Fleming MD, Roth MP, Coppin H. Differing impact of the deletion of hemochromatosis-associated molecules HFE and transferrin receptor-2 on the iron phenotype of mice lacking bone morphogenetic protein 6 or hemojuvelin. Hepatology 2016; 63:126-37. [PMID: 26406355 DOI: 10.1002/hep.28254] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 09/22/2015] [Indexed: 12/07/2022]
Abstract
UNLABELLED Hereditary hemochromatosis, which is characterized by inappropriately low levels of hepcidin, increased dietary iron uptake, and systemic iron accumulation, has been associated with mutations in the HFE, transferrin receptor-2 (TfR2), and hemojuvelin (HJV) genes. However, it is still not clear whether these molecules intersect in vivo with bone morphogenetic protein 6 (BMP6)/mothers against decapentaplegic (SMAD) homolog signaling, the main pathway up-regulating hepcidin expression in response to elevated hepatic iron. To answer this question, we produced double knockout mice for Bmp6 and β2-microglobulin (a surrogate for the loss of Hfe) and for Bmp6 and Tfr2, and we compared their phenotype (hepcidin expression, Bmp/Smad signaling, hepatic and extrahepatic tissue iron accumulation) with that of single Bmp6-deficient mice and that of mice deficient for Hjv, alone or in combination with Hfe or Tfr2. Whereas the phenotype of Hjv-deficient females was not affected by loss of Hfe or Tfr2, that of Bmp6-deficient females was considerably worsened, with decreased Smad5 phosphorylation, compared with single Bmp6-deficient mice, further repression of hepcidin gene expression, undetectable serum hepcidin, and massive iron accumulation not only in the liver but also in the pancreas, the heart, and the kidneys. CONCLUSION These results show that (1) BMP6 does not require HJV to transduce signal to hepcidin in response to intracellular iron, even if the loss of HJV partly reduces this signal, (2) another BMP ligand can replace BMP6 and significantly induce hepcidin expression in response to extracellular iron, and (3) BMP6 alone is as efficient at inducing hepcidin as the other BMPs in association with the HJV/HFE/TfR2 complex; they provide an explanation for the compensatory effect of BMP6 treatment on the molecular defect underlying Hfe hemochromatosis in mice.
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Affiliation(s)
- Chloé Latour
- Centre de Physiopathologie de Toulouse Purpan, Inserm U1043, CNRS U5282, Université de Toulouse III, Toulouse, France
| | - Céline Besson-Fournier
- Centre de Physiopathologie de Toulouse Purpan, Inserm U1043, CNRS U5282, Université de Toulouse III, Toulouse, France
| | - Delphine Meynard
- Centre de Physiopathologie de Toulouse Purpan, Inserm U1043, CNRS U5282, Université de Toulouse III, Toulouse, France
| | - Laura Silvestri
- San Raffaele Scientific Institute & Vita-Salute University, Milan, Italy
| | - Ophélie Gourbeyre
- Centre de Physiopathologie de Toulouse Purpan, Inserm U1043, CNRS U5282, Université de Toulouse III, Toulouse, France
| | - Patricia Aguilar-Martinez
- Centre de Physiopathologie de Toulouse Purpan, Inserm U1043, CNRS U5282, Université de Toulouse III, Toulouse, France.,Laboratory of Haematology, CHRU de Montpellier, Hôpital Saint Eloi, Montpellier, France
| | - Paul J Schmidt
- Department of Pathology, Boston Children's Hospital and Harvard Medical School, Boston, MA
| | - Mark D Fleming
- Department of Pathology, Boston Children's Hospital and Harvard Medical School, Boston, MA
| | - Marie-Paule Roth
- Centre de Physiopathologie de Toulouse Purpan, Inserm U1043, CNRS U5282, Université de Toulouse III, Toulouse, France
| | - Hélène Coppin
- Centre de Physiopathologie de Toulouse Purpan, Inserm U1043, CNRS U5282, Université de Toulouse III, Toulouse, France
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24
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Relationship of Baseline Hemoglobin Level with Serum Ferritin, Postphlebotomy Hemoglobin Changes, and Phlebotomy Requirements among HFE C282Y Homozygotes. BIOMED RESEARCH INTERNATIONAL 2015; 2015:241784. [PMID: 26380265 PMCID: PMC4563067 DOI: 10.1155/2015/241784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 08/17/2015] [Indexed: 11/17/2022]
Abstract
Objectives. We aimed to examine whether baseline hemoglobin levels in C282Y-homozygous patients are related to the degree of serum ferritin (SF) elevation and whether patients with different baseline hemoglobin have different phlebotomy requirements. Methods. A total of 196 patients (124 males and 72 females) who had undergone therapeutic phlebotomy and had SF and both pre- and posttreatment hemoglobin values were included in the study. Results. Bivariate correlation analysis suggested that baseline SF explains approximately 6 to 7% of the variation in baseline hemoglobin. The results also showed that males who had higher (≥150 g/L) baseline hemoglobin levels had a significantly greater reduction in their posttreatment hemoglobin despite requiring fewer phlebotomies to achieve iron depletion than those who had lower (<150 g/L) baseline hemoglobin, regardless of whether baseline SF was below or above 1000 µg/L. There were no significant differences between hemoglobin subgroups regarding baseline and treatment characteristics, except for transferrin saturation between male subgroups with SF above 1000 µg/L. Similar differences were observed when females with higher (≥138 g/L) baseline hemoglobin were compared with those with lower (<138 g/L) baseline hemoglobin. Conclusion. Dividing C282Y-homozygous patients into just two subgroups according to the degree of baseline SF elevation may obscure important subgroup variations.
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25
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Goh JB, Wallace DF, Hong W, Subramaniam VN. Endofin, a novel BMP-SMAD regulator of the iron-regulatory hormone, hepcidin. Sci Rep 2015; 5:13986. [PMID: 26358513 PMCID: PMC4566084 DOI: 10.1038/srep13986] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 08/12/2015] [Indexed: 11/15/2022] Open
Abstract
BMP-SMAD signalling plays a crucial role in numerous biological processes including embryonic development and iron homeostasis. Dysregulation of the iron-regulatory hormone hepcidin is associated with many clinical iron-related disorders. We hypothesised that molecules which mediate BMP-SMAD signalling play important roles in the regulation of iron homeostasis and variants in these proteins may be potential genetic modifiers of iron-related diseases. We examined the role of endofin, a SMAD anchor, and show that knockdown of endofin in liver cells inhibits basal and BMP-induced hepcidin expression along with other BMP-regulated genes, ID1 and SMAD7. We show for the first time, the in situ interaction of endofin with SMAD proteins and significantly reduced SMAD phosphorylation with endofin knockdown, suggesting that endofin modulates hepcidin through BMP-SMAD signalling. Characterisation of naturally occurring SNPs show that mutations in the conserved FYVE domain result in mislocalisation of endofin, potentially affecting downstream signalling and modulating hepcidin expression. In conclusion, we have identified a hitherto unrecognised link, endofin, between the BMP-SMAD signalling pathway, and the regulation of hepcidin expression and iron homeostasis. This study further defines the molecular network involved in iron regulation and provides potential targets for the treatment of iron-related disorders.
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Affiliation(s)
- Justin B Goh
- QIMR Berghofer Medical Research Institute, Brisbane, Australia.,Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | - Daniel F Wallace
- QIMR Berghofer Medical Research Institute, Brisbane, Australia.,Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | - Wanjin Hong
- Institute of Molecular and Cell Biology, Singapore
| | - V Nathan Subramaniam
- QIMR Berghofer Medical Research Institute, Brisbane, Australia.,Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia
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26
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27
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Silva B, Faustino P. An overview of molecular basis of iron metabolism regulation and the associated pathologies. Biochim Biophys Acta Mol Basis Dis 2015; 1852:1347-59. [PMID: 25843914 DOI: 10.1016/j.bbadis.2015.03.011] [Citation(s) in RCA: 178] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 03/05/2015] [Accepted: 03/27/2015] [Indexed: 12/18/2022]
Abstract
Iron is essential for several vital biological processes. Its deficiency or overload drives to the development of several pathologies. To maintain iron homeostasis, the organism controls the dietary iron absorption by enterocytes, its recycling by macrophages and storage in hepatocytes. These processes are mainly controlled by hepcidin, a liver-derived hormone which synthesis is regulated by iron levels, inflammation, infection, anemia and erythropoiesis. Besides the systemic regulation of iron metabolism mediated by hepcidin, cellular regulatory processes also occur. Cells are able to regulate themselves the expression of the iron metabolism-related genes through different post-transcriptional mechanisms, such as the alternative splicing, microRNAs, the IRP/IRE system and the proteolytic cleavage. Whenever those mechanisms are disturbed, due to genetic or environmental factors, iron homeostasis is disrupted and iron related pathologies may arise.
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Affiliation(s)
- Bruno Silva
- Departamento de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa, Portugal
| | - Paula Faustino
- Departamento de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa, Portugal.
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28
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Abstract
Iron, an essential nutrient, is required for many diverse biological processes. The absence of a defined pathway to excrete excess iron makes it essential for the body to regulate the amount of iron absorbed; a deficiency could lead to iron deficiency and an excess to iron overload and associated disorders such as anaemia and haemochromatosis respectively. This regulation is mediated by the iron-regulatory hormone hepcidin. Hepcidin binds to the only known iron export protein, ferroportin (FPN), inducing its internalization and degradation, thus limiting the amount of iron released into the blood. The major factors that are implicated in hepcidin regulation include iron stores, hypoxia, inflammation and erythropoiesis. The present review summarizes our present knowledge about the molecular mechanisms and signalling pathways contributing to hepcidin regulation by these factors.
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29
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Joshi R, Shvartsman M, Morán E, Lois S, Aranda J, Barqué A, de la Cruz X, Bruguera M, Vagace JM, Gervasini G, Sanz C, Sánchez M. Functional consequences of transferrin receptor-2 mutations causing hereditary hemochromatosis type 3. Mol Genet Genomic Med 2015; 3:221-32. [PMID: 26029709 PMCID: PMC4444164 DOI: 10.1002/mgg3.136] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 01/28/2015] [Accepted: 01/29/2015] [Indexed: 01/03/2023] Open
Abstract
Hereditary hemochromatosis (HH) type 3 is an autosomal recessive disorder of iron metabolism characterized by excessive iron deposition in the liver and caused by mutations in the transferrin receptor 2 (TFR2) gene. Here, we describe three new HH type 3 Spanish families with four TFR2 mutations (p.Gly792Arg, c.1606-8A>G, Gln306*, and Gln672*). The missense variation p.Gly792Arg was found in homozygosity in two adult patients of the same family, and in compound heterozygosity in an adult proband that also carries a novel intronic change (c.1606-8A>G). Two new nonsense TFR2 mutations (Gln306* and Gln672*) were detected in a pediatric case. We examine the functional consequences of two TFR2 variants (p.Gly792Arg and c.1606-8A>G) using molecular and computational methods. Cellular protein localization studies using immunofluorescence demonstrated that the plasma membrane localization of p.Gly792Arg TFR2 is impaired. Splicing studies in vitro and in vivo reveal that the c.1606-8A>G mutation leads to the creation of a new acceptor splice site and an aberrant TFR2 mRNA. The reported mutations caused HH type 3 by protein truncation, altering TFR2 membrane localization or by mRNA splicing defect, producing a nonfunctional TFR2 protein and a defective signaling transduction for hepcidin regulation. TFR2 genotyping should be considered in adult but also in pediatric cases with early-onset of iron overload.
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Affiliation(s)
- Ricky Joshi
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain
| | - Maya Shvartsman
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain
| | - Erica Morán
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain ; Diagnostics in Iron Metabolism Service (D·IRON) and Iron Metabolism: Regulation and Diseases group, Josep Carreras Leukemia Research Institute (IJC) Barcelona, Spain
| | - Sergi Lois
- Vall d'Hebron Research Institute (VHIR) Barcelona, Spain
| | - Jessica Aranda
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain ; Diagnostics in Iron Metabolism Service (D·IRON) and Iron Metabolism: Regulation and Diseases group, Josep Carreras Leukemia Research Institute (IJC) Barcelona, Spain
| | - Anna Barqué
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain ; Diagnostics in Iron Metabolism Service (D·IRON) and Iron Metabolism: Regulation and Diseases group, Josep Carreras Leukemia Research Institute (IJC) Barcelona, Spain
| | - Xavier de la Cruz
- Vall d'Hebron Research Institute (VHIR) Barcelona, Spain ; Institució Catalana de Recerca i Estudis Avançats (ICREA) Barcelona, Catalonia, Spain
| | - Miquel Bruguera
- Service of Hepatology, Clinic Hospital of Barcelona Barcelona, Spain
| | - José Manuel Vagace
- Service of Haematology, Hospital Materno-Infantil de Badajoz Badajoz, Spain
| | - Guillermo Gervasini
- Department of Surgical & Medical Therapeutics, University of Extremadura Badajoz, Spain
| | - Cristina Sanz
- Service of Haematology and Hemotherapy, Clinic Hospital of Barcelona Barcelona, Spain
| | - Mayka Sánchez
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain ; Diagnostics in Iron Metabolism Service (D·IRON) and Iron Metabolism: Regulation and Diseases group, Josep Carreras Leukemia Research Institute (IJC) Barcelona, Spain
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30
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Pagani A, Vieillevoye M, Nai A, Rausa M, Ladli M, Lacombe C, Mayeux P, Verdier F, Camaschella C, Silvestri L. Regulation of cell surface transferrin receptor-2 by iron-dependent cleavage and release of a soluble form. Haematologica 2015; 100:458-65. [PMID: 25637053 DOI: 10.3324/haematol.2014.118521] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Transferrin receptor-2 is a transmembrane protein whose expression is restricted to hepatocytes and erythroid cells. Transferrin receptor-2 has a regulatory function in iron homeostasis, since its inactivation causes systemic iron overload. Hepatic transferrin receptor-2 participates in iron sensing and is involved in hepcidin activation, although the mechanism remains unclear. Erythroid transferrin receptor-2 associates with and stabilizes erythropoietin receptors on the erythroblast surface and is essential to control erythrocyte production in iron deficiency. We identified a soluble form of transferrin receptor-2 in the media of transfected cells and showed that cultured human erythroid cells release an endogenous soluble form. Soluble transferrin receptor-2 originates from a cleavage of the cell surface protein, which is inhibited by diferric transferrin in a dose-dependent manner. Accordingly, the shedding of the transferrin receptor-2 variant G679A, mutated in the Arginine-Glycine-Aspartic acid motif and unable to bind diferric transferrin, is not modulated by the ligand. This observation links the process of transferrin receptor-2 removal from the plasma membrane to iron homeostasis. Soluble transferrin receptor-2 does not affect the binding of erythropoietin to erythropoietin receptor or the consequent signaling and partially inhibits hepcidin promoter activation only in vitro. Whether it is a component of the signals released by erythropoiesis in iron deficiency remains to be investigated. Our results indicate that membrane transferrin receptor-2, a sensor of circulating iron, is released from the cell membrane in iron deficiency.
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Affiliation(s)
- Alessia Pagani
- Vita Salute San Raffaele University, Milan, Italy Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Maud Vieillevoye
- Institut Cochin, INSERM, U1016, Université Paris Descartes, CNRS (UMR8104), Paris, France Ligue National contre le Cancer, Paris, France
| | - Antonella Nai
- Vita Salute San Raffaele University, Milan, Italy Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Marco Rausa
- Vita Salute San Raffaele University, Milan, Italy Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Meriem Ladli
- Institut Cochin, INSERM, U1016, Université Paris Descartes, CNRS (UMR8104), Paris, France Ligue National contre le Cancer, Paris, France
| | - Catherine Lacombe
- Institut Cochin, INSERM, U1016, Université Paris Descartes, CNRS (UMR8104), Paris, France Ligue National contre le Cancer, Paris, France
| | - Patrick Mayeux
- Institut Cochin, INSERM, U1016, Université Paris Descartes, CNRS (UMR8104), Paris, France Ligue National contre le Cancer, Paris, France
| | | | - Clara Camaschella
- Vita Salute San Raffaele University, Milan, Italy Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Laura Silvestri
- Vita Salute San Raffaele University, Milan, Italy Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
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31
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Kent P, Wilkinson N, Constante M, Fillebeen C, Gkouvatsos K, Wagner J, Buffler M, Becker C, Schümann K, Santos MM, Pantopoulos K. Hfe and Hjv exhibit overlapping functions for iron signaling to hepcidin. J Mol Med (Berl) 2015; 93:489-98. [DOI: 10.1007/s00109-015-1253-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 12/10/2014] [Accepted: 12/29/2014] [Indexed: 02/07/2023]
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Abstract
The review deals with genetic, regulatory and clinical aspects of iron homeostasis and hereditary haemochromatosis. Haemochromatosis was first described in the second half of the 19th century as a clinical entity characterized by excessive iron overload in the liver. Later, increased absorption of iron from the diet was identified as the pathophysiological hallmark. In the 1970s genetic evidence emerged supporting the apparent inheritable feature of the disease. And finally in 1996 a new "haemochromatosis gene" called HFE was described which was mutated in about 85% of the patients. From the year 2000 onward remarkable progress was made in revealing the complex molecular regulation of iron trafficking in the human body and its disturbance in haemochromatosis. The discovery of hepcidin and ferroportin and their interaction in regulating the release of iron from enterocytes and macrophages to plasma were important milestones. The discovery of new, rare variants of non-HFE-haemochromatosis was explained by mutations in the multicomponent signal transduction pathway controlling hepcidin transcription. Inhibited transcription induced by the altered function of mutated gene products, results in low plasma levels of hepcidin which facilitate entry of iron from enterocytes into plasma. In time this leads to progressive accumulation of iron and subsequently development of disease in the liver and other parenchymatous organs. Being the major site of excess iron storage and hepcidin synthesis the liver is a cornerstone in maintaining normal systemic iron homeostasis. Its central pathophysiological role in HFE-haemochromatosis with downgraded hepcidin synthesis, was recently shown by the finding that liver transplantation normalized the hepcidin levels in plasma and there was no sign of iron accumulation in the new liver.
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Affiliation(s)
- Rune J Ulvik
- Department of Clinical Science, University of Bergen and Laboratory of Clinical Biochemistry, Haukeland University Hospital, Bergen N-5021, Norway.
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Silva B, Ferreira J, Santos V, Baldaia C, Serejo F, Faustino P. The soluble form of HFE protein regulates hephaestin mRNA expression in the duodenum through an endocytosis-dependent mechanism. Biochim Biophys Acta Mol Basis Dis 2014; 1842:2298-305. [DOI: 10.1016/j.bbadis.2014.07.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 06/25/2014] [Accepted: 07/15/2014] [Indexed: 12/12/2022]
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Abstract
Mutations in HFE are the most common cause of hereditary hemochromatosis (HH). HFE mutations result in reduced expression of hepcidin, a hepatic hormone, which negatively regulates iron absorption from the duodenum and iron release from macrophages. However, the mechanism by which HFE regulates hepcidin expression in hepatocytes is not well understood. It is known that the bone morphogenetic protein (BMP) pathway plays a central role in controlling hepcidin expression in the liver. Here we show that HFE overexpression increased Smad1/5/8 phosphorylation and hepcidin expression, whereas inhibition of BMP signaling abolished HFE-induced hepcidin expression in Hep3B cells. HFE was found to associate with ALK3, inhibiting ALK3 ubiquitination and proteasomal degradation and increasing ALK3 protein expression and accumulation on the cell surface. The 2 HFE mutants associated with HH, HFE C282Y and HFE H63D, regulated ALK3 protein ubiquitination and trafficking differently, but both failed to increase ALK3 cell-surface expression. Deletion of Hfe in mice resulted in a decrease in hepatic ALK3 protein expression. Our results provide evidence that HFE induces hepcidin expression via the BMP pathway: HFE interacts with ALK3 to stabilize ALK3 protein and increase ALK3 expression at the cell surface.
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35
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Silvestri L, Nai A, Pagani A, Camaschella C. The extrahepatic role of TFR2 in iron homeostasis. Front Pharmacol 2014; 5:93. [PMID: 24847265 PMCID: PMC4019842 DOI: 10.3389/fphar.2014.00093] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 04/14/2014] [Indexed: 12/14/2022] Open
Abstract
Transferrin receptor 2 (TFR2), a protein homologous to the cell iron importer TFR1, is expressed in the liver and erythroid cells and is reported to bind diferric transferrin, although at lower affinity than TFR1. TFR2 gene is mutated in type 3 hemochromatosis, a disorder characterized by iron overload and inability to upregulate hepcidin in response to iron. Liver TFR2 is considered a sensor of diferric transferrin, possibly in a complex with hemochromatosis protein. In erythroid cells TFR2 is a partner of erythropoietin receptor (EPOR) and stabilizes the receptor on the cell surface. However, Tfr2 null mice as well as TFR2 hemochromatosis patients do not show defective erythropoiesis and tolerate repeated phlebotomy. The iron deficient Tfr2-Tmprss6 double knock out mice have higher red cells count and more severe microcytosis than the liver-specific Tfr2 and Tmprss6 double knock out mice. TFR2 in the bone marrow might be a sensor of iron deficiency that protects against excessive microcytosis in a way that involves EPOR, although the mechanisms remain to be worked out.
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Affiliation(s)
- Laura Silvestri
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Università Vita-Salute San Raffaele Milan, Italy
| | - Antonella Nai
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Università Vita-Salute San Raffaele Milan, Italy
| | - Alessia Pagani
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Università Vita-Salute San Raffaele Milan, Italy
| | - Clara Camaschella
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Università Vita-Salute San Raffaele Milan, Italy
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36
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Nai A, Pellegrino RM, Rausa M, Pagani A, Boero M, Silvestri L, Saglio G, Roetto A, Camaschella C. The erythroid function of transferrin receptor 2 revealed by Tmprss6 inactivation in different models of transferrin receptor 2 knockout mice. Haematologica 2014; 99:1016-21. [PMID: 24658816 DOI: 10.3324/haematol.2013.103143] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Transferrin receptor 2 (TFR2) is a transmembrane glycoprotein expressed in the liver and in the erythroid compartment, mutated in a form of hereditary hemochromatosis. Hepatic TFR2, together with HFE, activates the transcription of the iron-regulator hepcidin, while erythroid TFR2 is a member of the erythropoietin receptor complex. The TMPRSS6 gene, encoding the liver-expressed serine protease matriptase-2, is the main inhibitor of hepcidin and inactivation of TMPRSS6 leads to iron deficiency with high hepcidin levels. Here we evaluate the phenotype resulting from the genetic loss of Tmprss6 in Tfr2 total (Tfr2(-/-)) and liver-specific (Tfr2(LCKO)) knockout mice. Tmprss6(-/-)Tfr2(-/-) and Tmprss6(-/-)Tfr2(LCKO) mice have increased hepcidin levels and show iron-deficiency anemia like Tmprss6(-/-)mice. However, while Tmprss6(-/-)Tfr2(LCKO) are phenotypically identical to Tmprss6(-/-) mice, Tmprss6(-/-)Tfr2(-/-) mice have increased red blood cell count and more severe microcytosis than Tmprss6(-/-) mice. In addition hepcidin expression in Tmprss6(-/-)Tfr2(-/-) mice is higher than in the wild-type animals, but lower than in Tmprss6(-/-) mice, suggesting partial inhibition of the hepcidin activating pathway. Our results prove that hepatic TFR2 acts upstream of TMPRSS6. In addition Tfr2 deletion causes a relative erythrocytosis in iron-deficient mice, which likely attenuates the effect of over-expression of hepcidin in Tmprss6(-/-) mice. Since liver-specific deletion of Tfr2 in Tmprss6(-/-) mice does not modify the erythrocyte count, we speculate that loss of Tfr2 in the erythroid compartment accounts for the hematologic phenotype of Tmprss6(-/-)Tfr2(-/-) mice. We propose that TFR2 is a limiting factor for erythropoiesis, particularly in conditions of iron restriction.
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Affiliation(s)
- Antonella Nai
- Vita Salute University and San Raffaele Scientific Institute, Division of Genetics and Cell Biology, Milan, Italy
| | - Rosa M Pellegrino
- Department of Clinical and Biological Sciences, University of Torino, Italy
| | - Marco Rausa
- Vita Salute University and San Raffaele Scientific Institute, Division of Genetics and Cell Biology, Milan, Italy
| | - Alessia Pagani
- Vita Salute University and San Raffaele Scientific Institute, Division of Genetics and Cell Biology, Milan, Italy
| | - Martina Boero
- Department of Clinical and Biological Sciences, University of Torino, Italy
| | - Laura Silvestri
- Vita Salute University and San Raffaele Scientific Institute, Division of Genetics and Cell Biology, Milan, Italy
| | - Giuseppe Saglio
- Department of Clinical and Biological Sciences, University of Torino, Italy
| | - Antonella Roetto
- Department of Clinical and Biological Sciences, University of Torino, Italy
| | - Clara Camaschella
- Vita Salute University and San Raffaele Scientific Institute, Division of Genetics and Cell Biology, Milan, Italy
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37
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Tang J, Lu M, Tang D. Target-initiated impedimetric proximity ligation assay with DNAzyme design for in situ amplified biocatalytic precipitation. Analyst 2014; 139:2998-3001. [DOI: 10.1039/c4an00523f] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A target-initiated proximity ligation assay protocol with DNAzyme formation was for the first time designed for ultrasensitive impedimetric monitoring of heavy metal ions (silver ions were used in this case) by coupling with an enzymatic biocatalytic precipitation technique.
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Affiliation(s)
- Juan Tang
- Chongqing Key Laboratory of Environmental Materials & Remediation Technologies
- Chongqing University of Arts and Sciences
- Chongqing 402160, P.R. China
- Institute of Analytical Chemistry
- Department of Chemistry
| | - Minghua Lu
- Institute of Environmental and Analytical Science
- School of Chemistry and Chemical Engineering
- Henan University
- Kaifeng 475004, P.R. China
| | - Dianping Tang
- Chongqing Key Laboratory of Environmental Materials & Remediation Technologies
- Chongqing University of Arts and Sciences
- Chongqing 402160, P.R. China
- Institute of Analytical Chemistry
- Department of Chemistry
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