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Rostami Ravari N, Sadri F, Mahdiabadi MA, Mohammadi Y, Ourang Z, Rezaei Z. Ferroptosis and noncoding RNAs: exploring mechanisms in lung cancer treatment. Front Cell Dev Biol 2025; 13:1522873. [PMID: 40078365 PMCID: PMC11897296 DOI: 10.3389/fcell.2025.1522873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2024] [Accepted: 01/31/2025] [Indexed: 03/14/2025] Open
Abstract
Lung cancer (LC) is a highly prevalent and deadly type of cancer characterized by intricate molecular pathways that drive tumor development, metastasis, and resistance to conventional treatments. Recently, ferroptosis, a controlled mechanism of cell death instigated by iron-dependent lipid peroxidation, has gained attention for its role in LC progression and treatment. Noncoding RNAs (ncRNAs), such as microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), are emerging as key modulators of ferroptosis, significantly influencing LC biology. This review explores how ncRNAs control ferroptotic pathways and affect tumor growth, metastasis, and therapy resistance in LC. By understanding the dual functions of ncRNAs in both activating and inhibiting ferroptosis, we aim to uncover new therapeutic targets and strategies for LC. These insights provide a promising direction for the development of ncRNA-based treatments designed to induce ferroptosis, potentially improving therapeutic outcomes for patients with LC.
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Affiliation(s)
- Nadi Rostami Ravari
- Department of Animal Science Researches, Agriculture and Natural Resources Education and Research Center of Kerman, Agriculture and Natural Resources Education and Research Organization (AREEO), Kerman, Iran
| | - Farzad Sadri
- Student Research Committee, Birjand University of Medical Sciences, Birjand, Iran
- Geriatric Health Research Center, Birjand University of Medical Sciences, Birjand, Iran
| | - Mohammad Ali Mahdiabadi
- Department of Internal Medicine, School of Medicine, Birjand University of Medical Sciences, Birjand, Iran
| | - Yaser Mohammadi
- Department of Biochemistry, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Zahra Ourang
- Department of Biochemistry, School of Medicine, Arak University of Medical Sciences, Arak, Iran
| | - Zohreh Rezaei
- Geriatric Health Research Center, Birjand University of Medical Sciences, Birjand, Iran
- Department of Biology, University of Sistan and Baluchestan, Zahedan, Iran
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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: 2.0] [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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3
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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: 0.8] [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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4
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Chen X, Yu C, Kang R, Tang D. Iron Metabolism in Ferroptosis. Front Cell Dev Biol 2020; 8:590226. [PMID: 33117818 PMCID: PMC7575751 DOI: 10.3389/fcell.2020.590226] [Citation(s) in RCA: 570] [Impact Index Per Article: 114.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 09/17/2020] [Indexed: 01/12/2023] Open
Abstract
Ferroptosis is a form of regulated cell death that is characterized by iron-dependent oxidative damage and subsequent plasma membrane ruptures and the release of damage-associated molecular patterns. Due to the role of iron in mediating the production of reactive oxygen species and enzyme activity in lipid peroxidation, ferroptosis is strictly controlled by regulators involved in many aspects of iron metabolism, such as iron uptake, storage, utilization, and efflux. Translational and transcriptional regulation of iron homeostasis provide an integrated network to determine the sensitivity of ferroptosis. Impaired ferroptosis is implicated in various iron-related pathological conditions or diseases, such as cancer, neurodegenerative diseases, and ischemia-reperfusion injury. Understanding the molecular mechanisms underlying the regulation of iron metabolism during ferroptosis may provide effective strategies for the treatment of ferroptosis-associated diseases. Indeed, iron chelators effectively prevent the occurrence of ferroptosis, which may provide new approaches for the treatment of iron-related disorders. In this review, we summarize recent advances in the theoretical modeling of iron-dependent ferroptosis, and highlight the therapeutic implications of iron chelators in diseases.
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Affiliation(s)
- Xin Chen
- Guangzhou Municipal and Guangdong Provincial Key Laboratory of Protein Modification and Degradation, The Third Affiliated Hospital, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, China.,Department of Surgery, UT Southwestern Medical Center, Dallas, TX, United States
| | - Chunhua Yu
- Department of Surgery, UT Southwestern Medical Center, Dallas, TX, United States
| | - Rui Kang
- Department of Surgery, UT Southwestern Medical Center, Dallas, TX, United States
| | - Daolin Tang
- Guangzhou Municipal and Guangdong Provincial Key Laboratory of Protein Modification and Degradation, The Third Affiliated Hospital, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, China.,Department of Surgery, UT Southwestern Medical Center, Dallas, TX, United States
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5
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Billesbølle CB, Azumaya CM, Kretsch RC, Powers AS, Gonen S, Schneider S, Arvedson T, Dror RO, Cheng Y, Manglik A. Structure of hepcidin-bound ferroportin reveals iron homeostatic mechanisms. Nature 2020; 586:807-811. [PMID: 32814342 PMCID: PMC7906036 DOI: 10.1038/s41586-020-2668-z] [Citation(s) in RCA: 180] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 07/15/2020] [Indexed: 01/01/2023]
Abstract
The serum iron level in humans is tightly controlled by the action of the hormone hepcidin on the iron efflux transporter ferroportin. Hepcidin regulates iron absorption and recycling by inducing ferroportin internalization and degradation1. Aberrant ferroportin activity can lead to diseases of iron overload, like hemochromatosis, or iron limitation anemias2. Here, we determined cryogenic electron microscopy (cryo-EM) structures of ferroportin in lipid nanodiscs, both in the apo state and in complex with cobalt, an iron mimetic, and hepcidin. These structures and accompanying molecular dynamics simulations identify two metal binding sites within the N- and C-domains of ferroportin. Hepcidin binds ferroportin in an outward-open conformation and completely occludes the iron efflux pathway to inhibit transport. The carboxy-terminus of hepcidin directly contacts the divalent metal in the ferroportin C-domain. We further show that hepcidin binding to ferroportin is coupled to iron binding, with an 80-fold increase in hepcidin affinity in the presence of iron. These results suggest a model for hepcidin regulation of ferroportin, where only iron loaded ferroportin molecules are targeted for degradation. More broadly, our structural and functional insights are likely to enable more targeted manipulation of the hepcidin-ferroportin axis in disorders of iron homeostasis.
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Affiliation(s)
- Christian B Billesbølle
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, USA
| | - Caleigh M Azumaya
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Rachael C Kretsch
- Department of Computer Science, Stanford University, Stanford, CA, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, USA.,Biophysics Program, Stanford University, Stanford, CA, USA
| | - Alexander S Powers
- Department of Computer Science, Stanford University, Stanford, CA, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, USA.,Department of Chemistry, Stanford University, Stanford, CA, USA
| | - Shane Gonen
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA.,Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA, USA.,Department of Molecular Biology and Biochemistry, University of California, Irvine, Biological Sciences III, Irvine, CA, USA
| | - Simon Schneider
- Institute of Biochemistry, Goethe University Frankfurt, Max-von-Laue-Straße 9, Frankfurt am Main, Germany
| | - Tara Arvedson
- Department of Oncology Research, Amgen Inc., South San Francisco, CA, USA
| | - Ron O Dror
- Department of Computer Science, Stanford University, Stanford, CA, USA.,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.,Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, USA.,Biophysics Program, Stanford University, Stanford, CA, USA
| | - Yifan Cheng
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA. .,Howard Hughes Medical Institute, University of California San Francisco, San Francisco, CA, USA.
| | - Aashish Manglik
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, USA. .,Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA, USA.
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6
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Vlasveld LT, Janssen R, Bardou-Jacquet E, Venselaar H, Hamdi-Roze H, Drakesmith H, Swinkels DW. Twenty Years of Ferroportin Disease: A Review or An Update of Published Clinical, Biochemical, Molecular, and Functional Features. Pharmaceuticals (Basel) 2019; 12:ph12030132. [PMID: 31505869 PMCID: PMC6789780 DOI: 10.3390/ph12030132] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 08/14/2019] [Accepted: 08/20/2019] [Indexed: 12/14/2022] Open
Abstract
Iron overloading disorders linked to mutations in ferroportin have diverse phenotypes in vivo, and the effects of mutations on ferroportin in vitro range from loss of function (LOF) to gain of function (GOF) with hepcidin resistance. We reviewed 359 patients with 60 ferroportin variants. Overall, macrophage iron overload and low/normal transferrin saturation (TSAT) segregated with mutations that caused LOF, while GOF mutations were linked to high TSAT and parenchymal iron accumulation. However, the pathogenicity of individual variants is difficult to establish due to the lack of sufficiently reported data, large inter-assay variability of functional studies, and the uncertainty associated with the performance of available in silico prediction models. Since the phenotypes of hepcidin-resistant GOF variants are indistinguishable from the other types of hereditary hemochromatosis (HH), these variants may be categorized as ferroportin-associated HH, while the entity ferroportin disease may be confined to patients with LOF variants. To further improve the management of ferroportin disease, we advocate for a global registry, with standardized clinical analysis and validation of the functional tests preferably performed in human-derived enterocytic and macrophagic cell lines. Moreover, studies are warranted to unravel the definite structure of ferroportin and the indispensable residues that are essential for functionality.
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Affiliation(s)
- L Tom Vlasveld
- Department of Internal Medicine, Haaglanden MC-Bronovo, 2597AX The Hague, The Netherlands
| | - Roel Janssen
- Department of Laboratory Medicine, Translational Metabolic Laboratory, Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Edouard Bardou-Jacquet
- Liver Diseases Department, French Reference Centre for Rare Iron Overload Diseases of Genetic Origin, University Hospital Pontchaillou, 35033 Rennes, France
| | - Hanka Venselaar
- Centre for Molecular and Biomolecular Informatics, Radboud Institute for Molecular Life Sciences, Radboud, University Medical Center, P.O. Box 9191, 6500 HB Nijmegen, The Netherlands
| | - Houda Hamdi-Roze
- Molecular Genetics Department, French Reference Centre for Rare Iron Overload Diseases of Genetic Origin, University Hospital Pontchaillou, 35033 Rennes, France
| | - Hal Drakesmith
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX39DS, UK
| | - Dorine W Swinkels
- Department of Laboratory Medicine, Translational Metabolic Laboratory, Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
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Choi EK, Nguyen TT, Iwase S, Seo YA. Ferroportin disease mutations influence manganese accumulation and cytotoxicity. FASEB J 2019; 33:2228-2240. [PMID: 30247984 PMCID: PMC6338638 DOI: 10.1096/fj.201800831r] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 08/27/2018] [Indexed: 12/12/2022]
Abstract
Hemochromatosis is a frequent genetic disorder, characterized by the accumulation of excess iron across tissues. Mutations in the FPN1 gene, encoding a cell surface iron exporter [ferroportin (Fpn)], are responsible for hemochromatosis type 4, also known as ferroportin disease. Recently, Fpn has been implicated in the regulation of manganese (Mn), another essential nutrient required for numerous cellular enzymes. However, the roles of Fpn in Mn regulation remain ill-defined, and the impact of disease mutations on cellular Mn levels is unknown. Here, we provide evidence that Fpn can export Mn from cells into extracellular space. Fpn seems to play protective roles in Mn-induced cellular toxicity and oxidative stress. Finally, disease mutations interfere with the role of Fpn in controlling Mn levels as well as the stability of Fpn. These results define the function of Fpn as an exporter of both iron and Mn and highlight the potential involvement of Mn dysregulation in ferroportin disease.-Choi, E.-K., Nguyen, T.-T., Iwase, S., Seo, Y. A. Ferroportin disease mutations influence manganese accumulation and cytotoxicity.
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Affiliation(s)
- Eun-Kyung Choi
- Department of Nutritional Sciences, University of Michigan School of Public Health, Ann Arbor, Michigan, USA; and
| | - Trang-Tiffany Nguyen
- Department of Nutritional Sciences, University of Michigan School of Public Health, Ann Arbor, Michigan, USA; and
| | - Shigeki Iwase
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, USA
| | - Young Ah Seo
- Department of Nutritional Sciences, University of Michigan School of Public Health, Ann Arbor, Michigan, USA; and
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8
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Pietrangelo A. Ferroportin disease: pathogenesis, diagnosis and treatment. Haematologica 2017; 102:1972-1984. [PMID: 29101207 PMCID: PMC5709096 DOI: 10.3324/haematol.2017.170720] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 09/25/2017] [Indexed: 12/14/2022] Open
Abstract
Ferroportin Disease (FD) is an autosomal dominant hereditary iron loading disorder associated with heterozygote mutations of the ferroportin-1 (FPN) gene. It represents one of the commonest causes of genetic hyperferritinemia, regardless of ethnicity. FPN1 transfers iron from the intestine, macrophages and placenta into the bloodstream. In FD, loss-of-function mutations of FPN1 limit but do not impair iron export in enterocytes, but they do severely affect iron transfer in macrophages. This leads to progressive and preferential iron trapping in tissue macrophages, reduced iron release to serum transferrin (i.e. inappropriately low transferrin saturation) and a tendency towards anemia at menarche or after intense bloodletting. The hallmark of FD is marked iron accumulation in hepatic Kupffer cells. Numerous FD-associated mutations have been reported worldwide, with a few occurring in different populations and some more commonly reported (e.g. Val192del, A77D, and G80S). FPN1 polymorphisms also represent the gene variants most commonly responsible for hyperferritinemia in Africans. Differential diagnosis includes mainly hereditary hemochromatosis, the syndrome commonly due to either HFE or TfR2, HJV, HAMP, and, in rare instances, FPN1 itself. Here, unlike FD, hyperferritinemia associates with high transferrin saturation, iron-spared macrophages, and progressive parenchymal cell iron load. Abdominal magnetic resonance imaging (MRI), the key non-invasive diagnostic tool for the diagnosis of FD, shows the characteristic iron loading SSL triad (spleen, spine and liver). A non-aggressive phlebotomy regimen is recommended, with careful monitoring of transferrin saturation and hemoglobin due to the risk of anemia. Family screening is mandatory since siblings and offspring have a 50% chance of carrying the pathogenic mutation.
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Affiliation(s)
- Antonello Pietrangelo
- Center for Hemochromatosis, Department of Internal Medicine II, University of Modena and Reggio Emilia Policlinico, Modena, Italy
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9
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Powell LW. A career forged in iron. Hepatology 2015; 61:4-14. [PMID: 25043645 DOI: 10.1002/hep.27293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 06/27/2014] [Indexed: 12/07/2022]
Affiliation(s)
- Lawrie W Powell
- The Center for the Advancement of Clinical Research, Royal Brisbane and Women's Hospital, and The University of Queensland Center for Clinical Research, Brisbane, Queensland, Australia
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10
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Moreno-Carralero MI, Muñoz-Muñoz JA, Cuadrado-Grande N, López-Rodríguez R, José Hernández-Alfaro M, del-Castillo-Rueda A, Enríquez-de-Salamanca R, Méndez M, Morán-Jiménez MJ. A novel mutation in the SLC40A1 gene associated with reduced iron export in vitro. Am J Hematol 2014; 89:689-94. [PMID: 24644245 DOI: 10.1002/ajh.23714] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 03/14/2014] [Accepted: 03/14/2014] [Indexed: 01/09/2023]
Abstract
Ferroportin disease is an inherited disorder of iron metabolism and is caused by mutations in the ferroportin gene (SLC40A1). We present a patient with hyperferritinemia, iron overload in the liver with reticuloendothelial distribution and also in the spleen, and under treatment with erythropheresis. A molecular study of the genes involved in iron metabolism (HFE, HJV, HAMP, TFR2, SLC40A1) was undertaken. In vitro functional studies of the novel mutation found in the SLC40A1 gene was performed. The patient was heterozygous for a novel mutation, c.386T>C (p.L129P) in the SLC40A1 gene; some of his relatives were also heterozygous for this mutation. In vitro functional studies of the L129P mutation on ferroportin showed it impairs its capacity to export iron from cells but does not alter its sensitivity to hepcidin. These findings and the iron overload phenotype of the patient suggest that the novel mutation c.386T>C (p.L129P) in the SLC40A1 gene has incomplete penetrance and causes the classical form of ferroportin disease.
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McDonald CJ, Wallace DF, Crawford DHG, Subramaniam VN. Iron storage disease in Asia-Pacific populations: the importance of non-HFE mutations. J Gastroenterol Hepatol 2013; 28:1087-94. [PMID: 23577916 DOI: 10.1111/jgh.12222] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/03/2013] [Indexed: 01/24/2023]
Abstract
Hereditary hemochromatosis (HH) is a widely recognized and well-studied condition in European populations. This is largely due to the high prevalence of the C282Y mutation of HFE. Although less common than in Europe, HH cases have been reported in the Asia-Pacific region because of mutations in both HFE and non-HFE genes. Mutations in all of the currently known genes implicated in non-HFE HH (hemojuvelin, hepcidin, transferrin receptor 2, and ferroportin) have been reported in patients from the Asia-Pacific region. This review discusses the molecular basis of HH and the genes and mutations known to cause non-HFE HH with particular reference to the Asia-Pacific region. Challenges in the genetic diagnosis of non-HFE HH are also discussed and how new technologies such as next generation sequencing may be informative in the future.
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Affiliation(s)
- Cameron J McDonald
- The Membrane Transport Laboratory, The Queensland Institute of Medical Research, Brisbane, Queensland, Australia
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12
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Abstract
Ferroportin (FPN) is the sole iron export membrane protein identified in mammals that is abundantly expressed on absorptive enterocytes and macrophages, and is essential for physiological regulation of cellular iron. The expression of FPN is positively induced by cellular iron and is suppressed by liver hepcidin in response to either increased systemic iron or inflammatory stimuli. Hepcidin binds to cell surface FPN inducing FPN internalization followed by lysosomal degradation of the protein and consequently iron efflux from macrophages is blocked and there is suboptimal iron absorption by duodenal enterocytes. Dozens of FPN gene mutations have been identified in different ethnic populations and some of the mutations are associated with autosomal dominant iron overload disorder described as FPN disease or hemochromatosis type 4 that is distinct from hereditary hemochromatosis due to HFE mutations. Clinical manifestations of iron overload FPN disease can be classified into two groups according to whether there is selective macrophage iron loading or parenchymal and reticuloendothelial iron accumulation. There is evidence suggesting that altered hepcidin-FPN interaction can modulate host's response to infection. Resistance to hepcidin promotes iron egress from cells and this inhibits growth of intracellular pathogens. Conversely, iron retention due to loss of iron export activity by mutated FPN results in intracellular iron accumulation and a permissive environment for intracellular pathogens.
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Affiliation(s)
- Ishmael Kasvosve
- Department of Medical Laboratory Sciences Faculty of Health Sciences, University of Botswana Private Bag UB 00712, Gaborone, Botswana.
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13
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Del-Castillo-Rueda A, Moreno-Carralero MI, Alvarez-Sala-Walther LA, Cuadrado-Grande N, Enríquez-de-Salamanca R, Méndez M, Morán-Jiménez MJ. Two novel mutations in the SLC40A1 and HFE genes implicated in iron overload in a Spanish man. Eur J Haematol 2011; 86:260-4. [PMID: 21175851 DOI: 10.1111/j.1600-0609.2010.01565.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The most common form of hemochromatosis is caused by mutations in the HFE gene. Rare forms of the disease are caused by mutations in other genes. We present a patient with hyperferritinemia and iron overload, and facial flushing. Magnetic resonance imaging was performed to measure hepatic iron overload, and a molecular study of the genes involved in iron metabolism was undertaken. The iron overload was similar to that observed in HFE hemochromatosis, and the patient was double heterozygous for two novel mutations, c.-20G>A and c.718A>G (p.K240E), in the HFE and ferroportin (FPN1 or SLC40A1) genes, respectively. Hyperferritinemia and facial flushing improved after phlebotomy. Two of the patient's children were also studied, and the daughter was heterozygous for the mutation in the SLC40A1 gene, although she did not have hyperferritinemia. The patient presented a mild iron overload phenotype probably because of the two novel mutations in the HFE and SLC40A1 genes.
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Affiliation(s)
- Alejandro Del-Castillo-Rueda
- Unidad de Ferropatología, Departamento de Medicina Interna, Hospital General Universitario Gregorio Marañón, Facultad de Medicina, Universidad Complutense, Madrid, Spain
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14
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Ferroportin disease: a systematic meta-analysis of clinical and molecular findings. J Hepatol 2010; 53:941-9. [PMID: 20691492 PMCID: PMC2956830 DOI: 10.1016/j.jhep.2010.05.016] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 05/09/2010] [Accepted: 05/15/2010] [Indexed: 01/01/2023]
Abstract
BACKGROUND & AIMS Classical ferroportin disease is characterized by hyperferritinemia, normal transferrin saturation, and iron overload in macrophages. A non-classical form is characterized by additional hepatocellular iron deposits and a high transferrin saturation. Both forms demonstrate autosomal dominant transmission and are associated with ferroportin gene (SLC40A1) mutations. SLC40A1 encodes a cellular iron exporter expressed in macrophages, enterocytes, and hepatocytes. The aim of the analysis is to determine the penetrance of SLC40A1 mutations and to evaluate in silico tools to predict the functional impairment of ferroportin mutations as an alternative to in vitro studies. METHODS We conducted a systematic review of the literature and meta-analysis of the biochemical presentation, genetics, and pathology of ferroportin disease. RESULTS Of the 176 individuals reported with SLC40A1 mutations, 80 were classified as classical phenotype with hyperferritinemia and normal transferrin saturation. The non-classical phenotype with hyperferritinemia and elevated transferrin saturation was present in 53 patients. The remaining patients had normal serum ferritin or the data were reported incompletely. Despite an increased hepatic iron concentration in all biopsied patients, significant fibrosis or cirrhosis was present in only 11%. Hyperferritinemia was present in 86% of individuals with ferroportin mutations. Bio-informatic analysis of ferroportin mutations showed that the PolyPhen score has a sensitivity of 99% and a specificity of 67% for the discrimination between ferroportin mutations and polymorphisms. CONCLUSIONS In contrast to HFE hemochromatosis, ferroportin disease has a high penetrance, is genetically heterogeneous and is rarely associated with fibrosis. Non-classical ferroportin disease is associated with a higher risk of fibrosis and a more severe overload of hepatic iron.
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Abstract
Primary iron overload is one of the most common inherited diseases worldwide. Several genetic mutations underlie the various forms of the disease, which have similar pathophysiological profiles but distinct clinical presentations. Patients with hereditary hemochromatosis absorb too much iron from the diet, which accumulates over time within parenchymal cells. This accumulation leads to eventual organ failure as a consequence of iron-mediated formation of free radicals. The mechanism underlying this excessive absorption of iron is a sensing defect caused by the reduced formation of hepcidin, the master regulator of iron homeostasis, as a consequence of mutations in the genes encoding several membrane-bound signaling molecules present on hepatocytes. A considerable number of carriers of these specific genetic mutations, however, do not develop iron overload, indicating that additional genetic and environmental factors modify the severity and clinical penetrance of disease. In affected patients, early initiation of treatment by phlebotomy can prevent organ damage. Genetic screening of first-degree relatives can be also used to identify individuals at risk. Our expanding knowledge of the regulation of iron metabolism and the role of factors that modify the severity of the disease may lead to the design of new and improved treatments.
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16
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Wallace DF, Harris JM, Subramaniam VN. Functional analysis and theoretical modeling of ferroportin reveals clustering of mutations according to phenotype. Am J Physiol Cell Physiol 2009; 298:C75-84. [PMID: 19846751 DOI: 10.1152/ajpcell.00621.2008] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ferroportin disease is a heterogeneous iron release disorder resulting from mutations in the ferroportin gene. Ferroportin protein is a multitransmembrane domain iron transporter, responsible for iron export from cells, which, in turn, is regulated by the peptide hormone hepcidin. Mutations in the ferroportin gene may affect either regulation of the protein's transporter function or the ability of hepcidin to regulate iron efflux. We have used a combination of functional analysis of epitope-tagged ferroportin variants coupled with theoretical modeling to dissect the relationship between ferroportin mutations and their cognate phenotypes. Myc epitope-tagged human ferroportin expression constructs were transfected into Caco-2 intestinal cells and protein localization analyzed by immunofluorescence microscopy and colocalization with organelle markers. The effect of mutations on iron efflux was assessed by costaining with anti-ferritin antibodies and immunoblotting to quantitate cellular expression of ferritin and transferrin receptor 1. Wild-type ferroportin localized mainly to the cell surface and intracellular structures. All ferroportin disease-causing mutations studied had no effect on localization at the cell surface. N144H, N144T, and S338R mutant ferroportin retained the ability to transport iron. In contrast, A77D, V162Delta, and L170F mutants were iron transport defective. Surface staining experiments showed that both ends of the protein were located inside the cell. These data were used as the basis for theoretical modeling of the ferroportin molecule. The model predicted phenotypic clustering of mutations with gain-of-function variants associated with a hypothetical channel through the axis of ferroportin. Conversely, loss-of-function variants were located at the membrane/cytoplasm interface.
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Affiliation(s)
- Daniel F Wallace
- Membrane Transport Laboratory, The Queensland Institute of Medical Research, 300 Herston Rd., Herston, Brisbane, QLD 4006, Australia
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17
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Létocart E, Le Gac G, Majore S, Ka C, Radio FC, Gourlaouen I, De Bernardo C, Férec C, Grammatico P. A novel missense mutation in SLC40A1 results in resistance to hepcidin and confirms the existence of two ferroportin-associated iron overload diseases. Br J Haematol 2009; 147:379-85. [PMID: 19709084 DOI: 10.1111/j.1365-2141.2009.07834.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ferroportin-related iron overload disease differs from haemochromatosis in that it has a dominant mode of inheritance and is usually associated with macrophage iron sequestration. However, it is thought that mutations with opposite effects on protein functions, i.e. loss-of-function versus gain-of-function mutations, are responsible for variable phenotype presentations. The present study investigated the functional relevance of a novel ferroportin variant: the c.1502 A>G transition, which changes amino acid 501 from tyrosine to cysteine (p.Y501C). This novel variant was identified in a pedigree originating from Central Italy and, although an intra-familial phenotype heterogeneity was observed, it co-segregated with an iron overload picture similar to that of the HFE-related typical haemochromatosis. In cultured cells, the p.Y501C mutant protein reached the plasma membrane and retained a full iron export ability. By contrast, it was resistant to inhibition by hepcidin. These findings confirm that certain ferroportin mutations compromise the activity of hepcidin in iron homeostasis, mimicking hepcidin deficiency as described in all types of hemochromatosis.
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Affiliation(s)
- Emilie Létocart
- Inserm U613, Etablissement Français du Sang - Bretagne, Université de Bretagne Occidentale, Brest, France
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18
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Abstract
There have been major developments in the field of iron metabolism in the past decade following the identification of the HFE gene and the mutation responsible for the C282Y substitution in the HFE protein. While HFE-associated hemochromatosis occurs predominantly in people of northern European extraction, other less-common mutations can lead to the same clinical syndrome and these may occur in other populations in the Asian-Pacific region. The most common of these is the mutation that leads to changes in the ferroportin molecule, the protein responsible for the transport of iron across the basolateral membrane of the enterocyte and from macrophages. Recent research has unraveled the molecular processes of iron transport and regulation of how these are disturbed in hemochromatosis and other iron-loading disorders. At the same time, at least one new oral iron chelating agent has been developed that shows promise in the therapy of hemochromatosis as well as thalassemia and other secondary causes of iron overload. It is pertinent therefore to examine the developments in the global field of iron overload that have provided insights into the pathogenesis, disease penetrance, comorbid factors, and management.
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19
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Gan EK, Trinder D, Ayonrinde OT, Olynyk JK. Genetics of hereditary hemochromatosis: a clinical perspective. Expert Rev Endocrinol Metab 2009; 4:225-239. [PMID: 30743791 DOI: 10.1586/eem.09.9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Hereditary hemochromatosis due to homozygosity for the C282Y mutation in the HFE gene product is the most common autosomal recessive genetic disorder in populations of northern European descent, where it attains a maximum prevalence of approximately one in 200. Cross-sectional and longitudinal studies have revealed that clinically significant iron-overload disease develops in at least 28% of male and 1% of female HFE C282Y homozygotes. The relatively low clinical penetrance is largely unexplained. Current evidence suggests a limited role for digenic inheritance of mutations in iron homeostasis genes in modifying the penetrance of hemochromatosis. Male gender is a strong genetic factor, promoting expression of clinical disease. Dietary intake of alcohol and noncitrus fruit may also act as important environmental modifiers of penetrance. With genetic analyses becoming simpler to perform, new genetic modifiers of hepatic iron loading and liver fibrogenesis are likely to be forthcoming.
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Affiliation(s)
- Eng K Gan
- a School of Medicine & Pharmacology, Fremantle Hospital, PO Box 480, Fremantle 6959, WA, Australia.
| | - Debbie Trinder
- b School of Medicine & Pharmacology, Fremantle Hospital, PO Box 480, Fremantle 6959, WA, Australia.
| | - Oyekoya T Ayonrinde
- c School of Medicine & Pharmacology, Fremantle Hospital, PO Box 480, Fremantle 6959, WA, Australia.
| | - John K Olynyk
- d Professor, School of Medicine & Pharmacology, Fremantle Hospital, PO Box 480, Fremantle 6959, WA, Australia.
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20
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Abstract
The interaction between the hormone hepcidin and the iron exporter ferroportin (Fpn) regulates plasma iron concentrations. Hepcidin binds to Fpn and induces its internalization and degradation, resulting in decreased iron efflux from cells into plasma. Fpn mutations in N144, Y64N, and C326 residue cause autosomal dominant disease with parenchymal iron overload, apparently due to the resistance of mutant Fpn to hepcidin-mediated internalization. To define the mechanism of resistance, we generated human Fpn constructs bearing the pathogenic mutations. The mutants localized to the cell surface and exported iron normally, but were partially or completely resistant to hepcidin-mediated internalization and continued to export iron despite the presence of hepcidin. The primary defect with exofacial C326 substitutions was the loss of hepcidin binding, which resulted in the most severe phenotype. The thiol form of C326 was essential for interaction with hepcidin, suggesting that C326-SH homology is located in or near the binding site of hepcidin. In contrast, N144 and Y64 residues were not required for hepcidin binding, but their mutations impaired the subsequent internalization of the ligand-receptor complex. Our observations explain why the mutations in C326 Fpn residue produce a severe form of hemochromatosis with iron overload at an early age.
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21
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Abstract
Hereditary hemochromatosis is an iron overload disorder that can lead to the impairment of multiple organs and is caused by mutations in one or more different genes. Type 1 hemochromatosis is the most common form of the disease and results from mutations in the HFE gene. Juvenile hemochromatosis (JH) is the most severe form, usually caused by mutations in hemojuvelin (HJV) or hepcidin (HAMP). The autosomal dominant form of the disease, type 4, is due to mutations in the SLC40A1 gene, which encodes for ferroportin (FPN). Hereditary hemochromatosis is commonly found in populations of European origin. By contrast, hemochromatosis in Asia is rare and less well understood and can be masked by the presence of iron deficiency and secondary iron overload from thalassemia. Here, we provide a comprehensive report of hemochromatosis in a group of patients of Asian origin. We have identified novel mutations in HJV, HAMP, and SLC40A1 in countries not normally associated with hereditary hemochromatosis (Pakistan, Bangladesh, Sri Lanka, and Thailand). Our family studies show a high degree of consanguinity, highlighting the increased risk of iron overload in many countries of the developing world and in countries in which there are large immigrant populations from these regions.
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22
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Rice AE, Mendez MJ, Hokanson CA, Rees DC, Björkman PJ. Investigation of the biophysical and cell biological properties of ferroportin, a multipass integral membrane protein iron exporter. J Mol Biol 2009; 386:717-32. [PMID: 19150361 DOI: 10.1016/j.jmb.2008.12.063] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Revised: 12/03/2008] [Accepted: 12/22/2008] [Indexed: 01/01/2023]
Abstract
Ferroportin is a multipass membrane protein that serves as an iron exporter in many vertebrate cell types. Ferroportin-mediated iron export is controlled by the hormone hepcidin, which binds ferroportin, causing its internalization and degradation. Mutations in ferroportin cause a form of the iron overload hereditary disease hemochromatosis. Relatively little is known about ferroportin's properties or the mechanism by which mutations cause disease. In this study, we expressed and purified human ferroportin to characterize its biochemical/biophysical properties in solution and conducted cell biological studies in mammalian cells. We found that purified detergent-solubilized ferroportin is a well-folded monomer that binds hepcidin. In cell membranes, the N- and C-termini were both cytosolic, implying an even number of transmembrane regions, and ferroportin was mainly localized to the plasma membrane. Hepcidin addition resulted in a redistribution of ferroportin to intracellular compartments that labeled with early endosomal and lysosomal, but not Golgi, markers and that trafficked along microtubules. An analysis of 16 disease-related ferroportin mutants revealed that all were expressed and trafficked to the plasma membrane but that some were resistant to hepcidin-induced internalization. The characterizations reported here form a basis upon which models for ferroportin's role in regulating iron homeostasis in health and disease can be interpreted.
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Affiliation(s)
- Adrian E Rice
- Graduate Option in Biochemistry and Molecular Biophysics, California Institute of Technology, Pasadena, CA 91125, USA
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23
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Abstract
Following the discovery of the HFE gene in 1996 and its linkage to the iron overload disorder hereditary hemochromatosis (HH) there have been profound developments in our understanding of the pathogenesis of the biochemical and clinical manifestations of a number of iron overload disorders. This article provides an update of recent developments and key issues relating to iron homeostasis and inherited disorders of iron overload, with emphasis on HFE-related HH, and is based on the content of the American Association for the Study of Liver Diseases Single-Topic Conference entitled "Hemochromatosis: What has Happened After HFE?" which was held at the Emory Convention Center in Atlanta, September 7-9, 2007.
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Affiliation(s)
- John K Olynyk
- School of Medicine and Pharmacology, University of Western Australia, Fremantle Hospital, Fremantle, Western Australia, Australia.
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24
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Phenotypic expression of ferroportin disease in a family with the N144H mutation. ACTA ACUST UNITED AC 2008; 32:321-7. [DOI: 10.1016/j.gcb.2008.01.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 12/12/2007] [Accepted: 01/03/2008] [Indexed: 01/01/2023]
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25
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Nelson JE, Kowdley KV. Non-HFE hemochromatosis: genetics, pathogenesis, and clinical management. Curr Gastroenterol Rep 2008; 7:71-80. [PMID: 15701302 DOI: 10.1007/s11894-005-0069-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Recent advances in our understanding of iron metabolism and the epidemiology of iron overload disorders have shown that hereditary forms of hemochromatosis can result from mutations in several iron metabolism genes other than HFE, including Hamp, HJV, TFR2, and SCL40A. These "non-HFE" forms of hemochromatosis are much rarer than HFE-related hemochromatosis but exhibit a similar phenotype, and with the exception of ferroportin disease, a similar pattern of inheritance and parenchymal iron accumulation. Therefore, these diseases can be thought of as variant forms of a primary hepatic iron overload syndrome; thus, a unified approach can be used for evaluation and diagnosis. Management generally consists of periodic phlebotomies until iron is depleted.
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Affiliation(s)
- James E Nelson
- Department of Medicine, Division of Gastroenterology, University of Washington Medical Center, 1959 NE Pacific Street, Box 356424, Seattle, WA 98195, USA
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26
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Ayonrinde OT, Milward EA, Chua ACG, Trinder D, Olynyk JK. Clinical Perspectives on Hereditary Hemochromatosis. Crit Rev Clin Lab Sci 2008; 45:451-84. [DOI: 10.1080/10408360802335716] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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27
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Pelucchi S, Mariani R, Salvioni A, Bonfadini S, Riva A, Bertola F, Trombini P, Piperno A. Novel mutations of the ferroportin gene (SLC40A1): analysis of 56 consecutive patients with unexplained iron overload. Clin Genet 2007; 73:171-8. [DOI: 10.1111/j.1399-0004.2007.00950.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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28
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Speletas M, Kioumi A, Loules G, Hytiroglou P, Tsitouridis J, Christakis J, Germenis AE. Analysis of SLC40A1 gene at the mRNA level reveals rapidly the causative mutations in patients with hereditary hemochromatosis type IV. Blood Cells Mol Dis 2007; 40:353-9. [PMID: 17997113 DOI: 10.1016/j.bcmd.2007.09.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Revised: 09/11/2007] [Accepted: 09/11/2007] [Indexed: 01/01/2023]
Abstract
Mutations in the SLC40A1 gene result in a dominant genetic disorder [ferroportin disease; hereditary hemochromatosis type (HH) IV], characterized by iron overload with two different clinical manifestations, normal transferrin saturation with macrophage iron accumulation (the most prevalent type) or high transferrin saturation with hepatocyte iron accumulation (classical hemochromatosis phenotype). In previous studies, the mutational analysis of SLC40A1 gene has been performed at the genomic DNA level by PCR amplification and direct sequencing of all coding regions and flanking intron-exon boundaries (usually in 9 PCR reactions). In this study, we analyzed the SLC40A1 gene at the mRNA level, in two RT-PCR reactions, followed by direct sequencing and/or NIRCA (non-isotopic RNase cleavage assay). This protocol turned out to be rapid, sensitive and reliable, facilitating the detection of the SLC40A1 gene mutations in two patients with hyperferritinemia, normal transferrin saturation and iron accumulation predominantly in macrophages and Kupffer cells. The first one displayed the well-described alteration V162 Delta and the second a novel mutation (R178G) that was further detected in two relatives in a pedigree analysis. The proposed procedure would facilitate the wide-range molecular analysis of the SLC40A1 gene, contributing to better understanding the pathogenesis of the ferroportin disease.
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Affiliation(s)
- Matthaios Speletas
- Department of Immunology and Histocompatibility, University of Thessaly Medical School, University Hospital of Larissa, 41110 Larissa, Greece.
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29
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Abstract
Non-HFE hereditary haemochromatosis (HH) refers to a genetically heterogeneous group of iron overload disorders that are unlinked to mutations in the HFE gene. The four main types of non-HFE HH are caused by mutations in the hemojuvelin, hepcidin, transferrin receptor 2 and ferroportin genes. Juvenile haemochromatosis is an autosomal recessive disorder and can be caused by mutations in either hemojuvelin or hepcidin. An adult onset form of HH similar to HFE-HH is caused by homozygosity for mutations in transferrin receptor 2. The autosomal dominant iron overload disorder ferroportin disease is caused by mutations in the iron exporter ferroportin. The clinical characteristics and molecular basis of the various types of non-HFE haemochromatosis are reviewed. The study of these disorders and the molecules involved has been invaluable in improving our understanding of the mechanisms involved in the regulation of iron metabolism.
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Affiliation(s)
- Daniel-F Wallace
- Membrane Transport Laboratory, The Queensland Institute of Medical Research, 300 Herston Road, Herston, Brisbane, QLD 4006 Australia
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30
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Pietrangelo A, Corradini E, Ferrara F, Vegetti A, De Jong G, Luca Abbati G, Paolo Arcuri P, Martinelli S, Cerofolini E. Magnetic resonance imaging to identify classic and nonclassic forms of ferroportin disease. Blood Cells Mol Dis 2006; 37:192-196. [PMID: 17052926 DOI: 10.1016/j.bcmd.2006.08.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Revised: 08/30/2006] [Accepted: 08/30/2006] [Indexed: 12/25/2022]
Abstract
The ferroportin-related disorder is an increasingly recognized cause of hereditary iron overload. Based on the in vitro behavior of different ferroportin mutant subsets, it was suggested that different forms of the disorder might exist in humans. We used MRI to address this question in vivo in 22 patients from four different pedigrees carrying different ferroportin mutations: A77D, N144H, G80S and Val 162del. We found that, based on the iron status of spleen and bone macrophages, two different forms of the disease can be identified: a classic, common form, characterized by hepatocyte, splenic macrophage and bone marrow macrophage iron retention in patients carrying the A77D, G80S and Val 162del ferroportin variants; a rarer non-classic form, associated with liver iron overload but normal spleen and bone marrow iron content in patients with the N144H mutation. The two forms are likely caused by lack- or gain-of-protein function, respectively. Interestingly, in treated patients with the classic form, the spleen and the spine show appreciable iron accumulation even when serum ferritin is normal and liver iron content low. In conclusion, MRI is a useful non-invasive diagnostic tool to categorize and diagnose the disorder, monitor the status of iron depletion and gain insights on its natural history and management.
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Affiliation(s)
- Antonello Pietrangelo
- Center for Hemochromatosis, Department of Internal Medicine, University Hospital of Modena and Reggio Emilia, Policlinico, Via del Pozzo 71 41100 Modena, Italy.
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31
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Gonçalves A, Muzeau F, Blaybel R, Hetet G, Driss F, Delaby C, Canonne-Hergaux F, Beaumont C. Wild-type and mutant ferroportins do not form oligomers in transfected cells. Biochem J 2006; 396:265-75. [PMID: 16457665 PMCID: PMC1462719 DOI: 10.1042/bj20051682] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ferroportin [FPN; Slc40a1 (solute carrier family 40, member 1)] is a transmembrane iron export protein expressed in macrophages and duodenal enterocytes. Heterozygous mutations in the FPN gene result in an autosomal dominant form of iron overload disorder, type-4 haemochromatosis. FPN mutants either have a normal iron export activity but have lost their ability to bind hepcidin, or are defective in their iron export function. The mutant protein has been suggested to act as a dominant negative over the wt (wild-type) protein by multimer formation. Using transiently transfected human epithelial cell lines expressing mouse FPN modified by the addition of a haemagglutinin or c-Myc epitope at the C-terminus, we show that the wtFPN is found at the plasma membrane and in Rab5-containing endosomes, as are the D157G and Q182H mutants. However, the delV162 mutant is mostly intracellular in HK2 cells (human kidney-2 cells) and partially addressed at the cell surface in HEK-293 cells (human embryonic kidney 293 cells). In both cell types, it is partially associated with the endoplasmic reticulum and with Rab5-positive vesicles. However, this mutant is complex-glycosylated like the wt protein. D157G and G323V mutants have a defective iron export capacity as judged by their inability to deplete the intracellular ferritin content, whereas Q182H and delV162 have normal iron export function and probably have lost their capacity to bind hepcidin. In co-transfection experiments, the delV162 mutant does not co-localize with the wtFPN, does not prevent its normal targeting to the plasma membrane and cannot be immunoprecipitated in the same complex, arguing against the formation of FPN hetero-oligomers.
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Affiliation(s)
- Ana Sofia Gonçalves
- *INSERM, U773, 16 rue Henri Huchard, 75018 Paris, France
- †Faculté de Médecine site Bichat, Université Paris 7 Denis Diderot, Paris, France
| | - Françoise Muzeau
- *INSERM, U773, 16 rue Henri Huchard, 75018 Paris, France
- †Faculté de Médecine site Bichat, Université Paris 7 Denis Diderot, Paris, France
| | - Rand Blaybel
- *INSERM, U773, 16 rue Henri Huchard, 75018 Paris, France
- †Faculté de Médecine site Bichat, Université Paris 7 Denis Diderot, Paris, France
| | - Gilles Hetet
- ‡Assistance Publique-Hôpitaux de Paris, Hôpital Bichat, Service de Biochimie Hormonale et Génétique, 46 rue Henri Huchard, 75018 Paris, France
| | - Fathi Driss
- *INSERM, U773, 16 rue Henri Huchard, 75018 Paris, France
- ‡Assistance Publique-Hôpitaux de Paris, Hôpital Bichat, Service de Biochimie Hormonale et Génétique, 46 rue Henri Huchard, 75018 Paris, France
| | - Constance Delaby
- *INSERM, U773, 16 rue Henri Huchard, 75018 Paris, France
- †Faculté de Médecine site Bichat, Université Paris 7 Denis Diderot, Paris, France
| | - François Canonne-Hergaux
- *INSERM, U773, 16 rue Henri Huchard, 75018 Paris, France
- †Faculté de Médecine site Bichat, Université Paris 7 Denis Diderot, Paris, France
| | - Carole Beaumont
- *INSERM, U773, 16 rue Henri Huchard, 75018 Paris, France
- †Faculté de Médecine site Bichat, Université Paris 7 Denis Diderot, Paris, France
- To whom correspondence should be addressed, at INSERM U773, Centre de Recherche Biomédicale Bichat Beaujon, Université Paris 7 site Bichat, 16 rue Henri Huchard, BP416, 75018 Paris, France (email )
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32
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Abstract
Hepcidin evolves as a potent hepatocyte-derived regulator of the body's iron distribution piloting the flow of iron via, and directly binding, to the cellular iron exporter ferroportin. The hepcidin-ferroportin axis dominates the iron egress from all cellular compartments that are critical to iron homeostasis, namely placental syncytiotrophoblasts, duodenal enterocytes, hepatocytes and macrophages of the reticuloendothelial system. The gene that encodes hepcidin expression (HAMP) is subject to regulation by proinflammatory cytokines, such as IL-6 and IL-1; excessive hepcidin production explains the relative deficiency of iron during inflammatory states, eventually resulting in the anaemia of inflammation. The haemochromatosis genes HFE, TfR2 and HJV potentially facilitate the transcription of HAMP. Disruption of each of the four genes leads to a diminished hepatic release of hepcidin consistent with both a dominant role of hepcidin in hereditary haemochromatosis and an upstream regulatory role of HFE, TfR2 and HJV on HAMP expression. The engineered generation of hepcidin agonists, mimetics or antagonists could largely broaden current therapeutic strategies to redirect the flow of iron.
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Affiliation(s)
- R Deicher
- Department of Medicine III, Medical University of Vienna, Vienna, Austria
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33
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Abstract
The molecular basis of haemochromatosis has proved more complex than expected. After the 1996 identification of the main causative gene HFE and confirmation that most patients were homozygous for the founder C282Y mutation, it became clear that some families were linked to rarer conditions, first named 'non-HFE haemochromatosis'. The genetics of these less common forms was intensively studied between 2000 and 2004, leading to the recognition of haemojuvelin (HJV), hepcidin (HAMP), transferrin receptor 2 (TFR2) and ferroportin-related haemochromatosis, and opening the way for novel hypotheses such as those related to digenic modes of inheritance or the involvement of modifier genes. Molecular studies of rare haemochromatosis disorders have contributed to our understanding of iron homeostasis. In turn, recent findings from studies of knockout mice and functional studies have confirmed that HAMP plays a central role in mobilization of iron, shown that HFE, TFR2 and HJV modulate HAMP production according to the body's iron status, and demonstrated that HAMP negatively regulates cellular iron efflux by affecting the ferroportin cell surface availability. These data shed new light on the pathophysiology of all types of haemochromatosis, and offer novel opportunities to comment on phenotypic differences and distinguish mutations.
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34
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Cremonesi L, Cemonesi L, Forni GL, Soriani N, Lamagna M, Fermo I, Daraio F, Galli A, Pietra D, Malcovati L, Ferrari M, Camaschella C, Cazzola M. Genetic and clinical heterogeneity of ferroportin disease. Br J Haematol 2005; 131:663-70. [PMID: 16351644 DOI: 10.1111/j.1365-2141.2005.05815.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ferroportin is encoded by the SLC40A1 gene and mediates iron export from cells by interacting with hepcidin. SLC40A1 gene mutations are associated with an autosomal type of genetic iron overload described as haemochromatosis type 4, or HFE4 (Online Mendelian Inheritance in Man number 606069), or ferroportin disease. We report three families with this condition caused by novel SLC40A1 mutations. Denaturing high-performance liquid chromatography was employed to scan for the SLC40A1 gene. A D181V (A846T) mutation in exon 6 of the ferroportin gene was detected in the affected members of an Italian family and shown to have a de novo origin in a maternal germinal line. This mutation was associated with both parenchymal and reticuloendothelial iron overload in the liver, and with reduced urinary hepcidin excretion. A G80V (G543T) mutation in exon 3 was found in the affected members of an Italian family with autosomal hyperferritinaemia,. Finally, a G267D (G1104A) mutation was identified in exon 7 in a family of Chinese descent whose members presented with isolated hyperferritinaemia. Ferroportin disease represents a protean genetic condition in which the different SLC40A1 mutations appear to be responsible for phenotypic variability. This condition should be considered not only in families with autosomal iron overload or hyperferritinaemia, but also in cases of unexplained hyperferritinaemia.
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Affiliation(s)
- L Cremonesi
- Unit of Genomics for the Diagnosis of Human Pathologies, IRCCS H. San Raffaele, Milan, Italy
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35
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Bach V, Remacha A, Altés A, Barceló MJ, Molina MA, Baiget M. Autosomal dominant hereditary hemochromatosis associated with two novel Ferroportin 1 mutations in Spain. Blood Cells Mol Dis 2005; 36:41-5. [PMID: 16257244 DOI: 10.1016/j.bcmd.2005.09.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 09/22/2005] [Accepted: 09/22/2005] [Indexed: 01/01/2023]
Abstract
Hereditary hemochromatosis is a common disorder of iron metabolism most frequently associated with mutations in the HFE gene. Hereditary hemochromatosis may be caused by other genetic mutations including those in the SLC40A1 gene. This report describes the clinical and laboratory findings of two Spanish families with autosomal dominant iron overload associated with previously unrecognized Ferroportin 1 mutations (p.R88T and p.I180T). The phenotype of iron overload in the patients carrying these mutations could correspond to the group of clinical mutations that lose their iron export function.
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Affiliation(s)
- V Bach
- Servei de Genètica. Hospital de Sant Pau, Avda. Pare Claret 167. 08025 Barcelona, Spain
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36
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Liu XB, Yang F, Haile DJ. Functional consequences of ferroportin 1 mutations. Blood Cells Mol Dis 2005; 35:33-46. [PMID: 15935710 DOI: 10.1016/j.bcmd.2005.04.005] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Accepted: 04/11/2005] [Indexed: 12/26/2022]
Abstract
The cellular iron exporter ferroportin 1 is expressed in both the duodenum and in cells of the mononuclear phagocyte system. Expression of ferroportin 1 protein on the cell surface is regulated by the interaction of ferroportin 1 with hepcidin. Hepcidin treatment of cells results in internalization and lysosomal degradation of cell surface ferroportin 1. Recently, ferroportin 1 mutations leading to hemochromatosis (HFE4) have been identified. HFE4 differs from classical hemochromatosis in that there is a greater amount of macrophage iron sequestration. The data presented here demonstrate that HFE4 mutations are heterogeneous in their effects on protein function. Some mutations result in loss of function with partial protein sequestration in the ER. Others are indistinguishable from native ferroportin 1 and have a similar ability to deplete transfected cells of iron as evidenced by activation of the iron-response proteins and cellular ferritin depletion. Significantly, all mutants appear to be unresponsive to hepcidin and do not demonstrate the expected internalization on exposure to hepcidin. The clinical phenotypes observed in patients may be secondary to cell-type-specific defects in hepcidin-mediated inhibition of ferroportin 1 expression.
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Affiliation(s)
- Xiao-Bing Liu
- Audie Murphy Veterans Administration Hospital, South Texas Veterans Health Care System, San Antonio, TX 78229, USA
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37
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Huang FW, Pinkus JL, Pinkus GS, Fleming MD, Andrews NC. A mouse model of juvenile hemochromatosis. J Clin Invest 2005; 115:2187-91. [PMID: 16075059 PMCID: PMC1180543 DOI: 10.1172/jci25049] [Citation(s) in RCA: 275] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Accepted: 05/10/2005] [Indexed: 12/15/2022] Open
Abstract
Hereditary hemochromatosis is an iron-overload disorder resulting from mutations in proteins presumed to be involved in the maintenance of iron homeostasis. Mutations in hemojuvelin (HJV) cause severe, early-onset juvenile hemochromatosis. The normal function of HJV is unknown. Juvenile hemochromatosis patients have decreased urinary levels of hepcidin, a peptide hormone that binds to the cellular iron exporter ferroportin, causing its internalization and degradation. We have disrupted the murine Hjv gene and shown that Hjv-/- mice have markedly increased iron deposition in liver, pancreas, and heart but decreased iron levels in tissue macrophages. Hepcidin mRNA expression was decreased in Hjv-/- mice. Accordingly, ferroportin expression detected by immunohistochemistry was markedly increased in both intestinal epithelial cells and macrophages. We propose that excess, unregulated ferroportin activity in these cell types leads to the increased intestinal iron absorption and plasma iron levels characteristic of the juvenile hemochromatosis phenotype.
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Affiliation(s)
- Franklin W Huang
- Children's Hospital Boston, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115-5737, USA
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38
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Sham RL, Phatak PD, West C, Lee P, Andrews C, Beutler E. Autosomal dominant hereditary hemochromatosis associated with a novel ferroportin mutation and unique clinical features. Blood Cells Mol Dis 2005; 34:157-61. [PMID: 15727899 DOI: 10.1016/j.bcmd.2004.12.002] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Indexed: 12/13/2022]
Abstract
Hereditary hemochromatosis is a common disorder of iron metabolism most frequently associated with mutations in the HFE gene. Hereditary hemochromatosis may be caused by other less common genetic mutations including those in the ferroportin gene. Whereas hereditary hemochromatosis associated with HFE mutations is an autosomal recessive disorder, essentially all cases of hereditary hemochromatosis associated with ferroportin mutations follow an autosomal dominant pattern of inheritance, and most cases are notable for the lack of an elevated transferrin saturation and presence of iron deposition in Kupffer cells. This report describes the clinical and laboratory features of a family with hereditary hemochromatosis associated with a previously unrecognized ferroportin mutation (Cys326Ser). Three generations of the family are described. The disease in this family is notable for young age at onset, elevated transferrin saturation values, and hepatocyte iron deposition. The distinct molecular and clinical features reflect the heterogeneous nature of this disease.
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Affiliation(s)
- Ronald L Sham
- Hematology/Oncology Division, Rochester General Hospital, Mary M Gooley Hemophilia Center, 1425 Portland Avenue, Rochester, NY 14621, USA.
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39
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Koyama C, Wakusawa S, Hayashi H, Ueno T, Suzuki R, Yano M, Saito H, Okazaki T. A Japanese family with ferroportin disease caused by a novel mutation of SLC40A1 gene: hyperferritinemia associated with a relatively low transferrin saturation of iron. Intern Med 2005; 44:990-3. [PMID: 16258219 DOI: 10.2169/internalmedicine.44.990] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ferroportin disease, autosomal-dominant reticuloendothelial iron overload, may be more prevalent than hemochromatosis in Japan. Hyperferritinemia of 822 ng/ml with 24.8% transferrin saturation of iron was incidentally noted in a 43-year-old man. His iron overload was selective in Kupffer cells of the liver. Subsequently, his father was found to have asymptomatic hyperferritinemia of 2,283 ng/ml with 62.1% saturation. These affected subjects were heterozygous for 1467A>C (R489S) in SLC40A1, and without other mutations of the hemochromatosis genes. Here, we report a Japanese family with ferroportin disease, characterized by hyperferritinemia with relatively low transferrin saturations of iron.
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Affiliation(s)
- Chizu Koyama
- Department of Medicine, Faculty of Pharmaceutical Sciences of Hokuriku University, Kanazawa, Japan
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40
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Morris TJ, Litvinova MM, Ralston D, Mattman A, Holmes D, Lockitch G. A novel ferroportin mutation in a Canadian family with autosomal dominant hemochromatosis. Blood Cells Mol Dis 2005; 35:309-14. [PMID: 16111902 DOI: 10.1016/j.bcmd.2005.07.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Accepted: 07/18/2005] [Indexed: 12/19/2022]
Abstract
We report a new mutation, Asn185Asp, in exon 6 of the ferroportin gene (FPN1) in 15 members of three successive generations of a Canadian family of Scandinavian origin with autosomal dominant hemochromatosis. Hyperferritinemia with low transferrin saturation was noted in younger family members, seven of whom were aged 20 years or less at the time of diagnosis. In those individuals first diagnosed with hemochromatosis in later life, marked hyperferritinemia was accompanied by high transferrin saturation. In contrast to the phenotype of high ferritin with low saturation first reported for ferroportin disease, this family demonstrates a phenotype of iron indices that varies with age.
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Affiliation(s)
- Tara J Morris
- Department of Pathology and Laboratory Medicine, Children's and Women's Health Centre of British Columbia, 4480 Oak Street, Vancouver, Canada BC V6H3V4
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41
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Abstract
Mutations in the hepcidin gene HAMP and the hemojuvelin gene HJV have recently been shown to result in juvenile haemochromatosis (JH). Hepcidin is an antimicrobial peptide that plays a key role in regulating intestinal iron absorption. Hepcidin levels are reduced in patients with haemochromatosis due to mutations in the HFE and HJV genes. Digenic inheritance of mutations in HFE and HAMP can result in either JH or hereditary haemochromatosis (HH) depending upon the severity of the mutation in HAMP. Here we review these findings and discuss how understanding the different types of haemochromatosis and our increasing knowledge of iron metabolism may help to elucidate the host's response to infection.
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42
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Zoller H, McFarlane I, Theurl I, Stadlmann S, Nemeth E, Oxley D, Ganz T, Halsall DJ, Cox TM, Vogel W. Primary iron overload with inappropriate hepcidin expression in V162del ferroportin disease. Hepatology 2005; 42:466-72. [PMID: 15986403 DOI: 10.1002/hep.20775] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Ferroportin disease (hemochromatosis type 4) is a recently recognized disorder of human iron metabolism, characterized by iron deposition in macrophages, including Kupffer cells. Mutations in the gene encoding ferroportin 1, a cellular iron exporter, are responsible for this iron storage disease, inherited as an autosomal dominant trait. We present clinical, histopathological, and radiological findings in a family with the most common ferroportin mutation, V162del. In the index case, the disorder is characterized by abundant deposition of hemosiderin in all tissues investigated (mesenteric lymph node, liver, gastric and duodenal mucosa, and also in squamous cell carcinoma of the lung). The radiological findings indicated the presence of excess iron in bone marrow and spleen. Despite a significant burden of iron, no features of chronic liver disease were found in affected members of the family, including individuals aged up to 80 years. Hyperferritinemia greater than 1,000 microg/L was a penetrant biochemical finding before the second decade in life and was associated with significantly increased serum concentrations of pro-hepcidin that correlated positively with urinary hepcidin concentrations. In conclusion, the systemic iron burden in ferroportin disease is not a sufficient cause for chronic liver disease. In patients with most, but not all, ferroportin mutations, retention of iron in macrophages of the liver and other organs may protect against damage to parenchymal cells. Finally, macrophage iron storage in ferroportin disease is associated with elevated serum pro-hepcidin levels.
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Affiliation(s)
- Heinz Zoller
- Clinical Division of Gastroenterology and Hepatology, Innsbruck Medical University, Innsbruck, Austria.
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43
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Camaschella C. Understanding iron homeostasis through genetic analysis of hemochromatosis and related disorders. Blood 2005; 106:3710-7. [PMID: 16030190 DOI: 10.1182/blood-2005-05-1857] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Genetic analysis of hemochromatosis has led to the discovery of a number of genes whose mutations disrupt iron homeostasis and lead to iron overload. The introduction of molecular tests into clinical practice has provided a tool for early diagnosis of these conditions. It has become clear that hemochromatosis includes a spectrum of disorders that range from simple biochemical abnormalities to chronic asymptomatic tissue damage in midlife to serious life-threatening diseases in young subjects. Molecular studies have identified the systemic loop that controls iron homeostasis and is centered on the hepcidin-ferroportin interaction. The complexity of this regulatory pathway accounts for the genetic heterogeneity of hemochromatosis and related disorders and raises the possibility that genes encoding components of the pathway may be modifiers of the main genotype. Molecular diagnosis has improved the classification of the genetic conditions leading to iron overload and identified novel entities, characterized by both iron loading and variable degrees of anemia. Despite the progress in the diagnosis, classification, and mechanisms of iron overload disorders, the treatment of affected patients continues to rely on regular phlebotomy. Understanding the molecular circuitry of iron control may lead to the identification of potential therapeutic targets for novel treatment strategies to be used in association with or as an alternative to phlebotomy.
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Affiliation(s)
- Clara Camaschella
- Università Vita-Salute and Istituto di Ricovero e Cura a Carratere Scientifico Ospedale San Raffaele, Via Olgettina, 60, 20132 Milano, Italy.
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44
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De Domenico I, Ward DM, Nemeth E, Vaughn MB, Musci G, Ganz T, Kaplan J. The molecular basis of ferroportin-linked hemochromatosis. Proc Natl Acad Sci U S A 2005; 102:8955-60. [PMID: 15956209 PMCID: PMC1157058 DOI: 10.1073/pnas.0503804102] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Indexed: 12/19/2022] Open
Abstract
Mutations in the iron exporter ferroportin (Fpn) (IREG1, SLC40A1, and MTP1) result in hemochromatosis type IV, a disorder with a dominant genetic pattern of inheritance and heterogeneous clinical presentation. Most patients develop iron loading of Kupffer cells with relatively low saturation of plasma transferrin, but others present with high transferrin saturation and iron-loaded hepatocytes. We show that known human mutations introduced into mouse Fpn-GFP generate proteins that either are defective in cell surface localization or have a decreased ability to be internalized and degraded in response to hepcidin. Studies using co-immunoprecipitation of epitope-tagged Fpn and size-exclusion chromatography demonstrated that Fpn is multimeric. Both WT and mutant Fpn participate in the multimer, and mutant Fpn can affect the localization of WT Fpn, its stability, and its response to hepcidin. The behavior of mutant Fpn in cell culture and the ability of mutant Fpn to act as a dominant negative explain the dominant inheritance of the disease as well as the different patient phenotypes.
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Affiliation(s)
- Ivana De Domenico
- Dipartimento di Scienze Microbiologiche Genetiche e Molecolari, Università di Messina, 98166 Messina, Italy
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45
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Abstract
Elucidation of the molecular pathways of iron transport through cells and its control is leading to an understanding of genetic iron loading conditions. The general phenotype of haemochromatosis is iron accumulation in liver parenchymal cells, a raised serum transferrin saturation and ferritin concentration. Four types have been identified: type 1 is the common form and is an autosomal recessive disorder of low penetrance strongly associated with mutations in the HFE gene on chromosome 6(p21.3); type 2 (juvenile haemochromatosis) is autosomal recessive, of high penetrance with causative mutations identified in the HFE2 gene on chromosome 1 (q21) and the HAMP gene on chromosome 19 (q13); type 3 is also autosomal recessive with mutations in the TfR2 gene on chromosome 3 (7q22); type 4 is an autosomal dominant condition with heterozygous mutations in the ferroportin 1 gene. In type 4, iron accumulates in both parenchymal and reticuloendothelial cells and the transferrin saturation may be normal. There are also inherited neurodegenerative conditions associated with iron accumulation. The current research challenges include understanding the central role of the HAMP gene (hepcidin) in controlling iron absorption and the reasons for the variable penetrance in HFE type 1.
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Affiliation(s)
- Mark Worwood
- Department of Haematology, University of Wales College of Medicine, Cardiff CF14 4XN, Wales, UK.
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46
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Fraenkel PG, Traver D, Donovan A, Zahrieh D, Zon LI. Ferroportin1 is required for normal iron cycling in zebrafish. J Clin Invest 2005; 115:1532-41. [PMID: 15902304 PMCID: PMC1089797 DOI: 10.1172/jci23780] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2004] [Accepted: 03/29/2005] [Indexed: 12/21/2022] Open
Abstract
Missense mutations in ferroportin1 (fpn1), an intestinal and macrophage iron exporter, have been identified between transmembrane helices 3 and 4 in the zebrafish anemia mutant weissherbst (weh(Tp85c-/-)) and in patients with type 4 hemochromatosis. To explore the effects of fpn1 mutation on blood development and iron homeostasis in the adult zebrafish, weh(Tp85c-/-) zebrafish were rescued by injection with iron dextran and studied in comparison with injected and uninjected WT zebrafish and heterozygotes. Although iron deposition was observed in all iron-injected fish, only weh(Tp85c-/-) zebrafish exhibited iron accumulation in the intestinal epithelium compatible with a block in iron export. Iron injections initially reversed the anemia. However, 8 months after iron injections were discontinued, weh(Tp85c-/-) zebrafish developed hypochromic anemia and impaired erythroid maturation despite the persistence of iron-loaded macrophages and elevated hepatic nonheme iron stores. Quantitative real-time RT-PCR revealed a significant decrease in mean hepatic transcript levels of the secreted iron-regulator hepcidin and increased intestinal expression of fpn1 in anemic weh(Tp85c-/-) adults. Injection of iron dextran into WT or mutant zebrafish embryos, however, resulted in significant increases in hepcidin expression 18 hours after injection, demonstrating that hepcidin expression in zebrafish is iron responsive and independent of fpn1's function as an iron exporter.
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Affiliation(s)
- Paula G Fraenkel
- Division of Hematology/Oncology, Children's Hospital, Karp Research Laboratories, Boston, Massachusetts 02115, USA
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47
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48
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Cadet E, Perez AS, Capron D, Rochette J. Bases moléculaires des hémochromatoses génétiques. Rev Med Interne 2005; 26:393-402. [PMID: 15893030 DOI: 10.1016/j.revmed.2004.09.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Accepted: 09/16/2004] [Indexed: 10/26/2022]
Abstract
PURPOSE Recent discoveries in molecular mechanisms of iron metabolism have changed the classical view of hereditary iron overload conditions. We present natural mutations in newly discovered genes and related phenotypes observed in patients with different form of haemochromatosis. CURRENT KNOWLEDGE AND KEY POINTS Most haemochromatosis patients are homozygous for the C282Y mutation in the HFE gene. Ferroportin, TFR2, hemojuvelin and hepcidin mutations also cause iron overload. Recent data support the hypothesis that haemochromatosis should no longer be considered a monogenic disease but rather an oligogenic disorder. Several results suggest that haemochromatosis could result from digenic inheritance of mutations in HFE and HAMP. FUTURE PROSPECTS AND PROJECTS Other modifier genes probably influence penetrance in C282Y homozygous patients. Such genes could enhance or reduce the phenotypic expression in various iron overload conditions.
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Affiliation(s)
- E Cadet
- Service de génétique moléculaire médicale et UPRES EA 2629, CHU d'Amiens, université de Picardie-Jules-Verne, 3, rue des Louvels, 80036 Amiens cedex, France.
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49
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Drakesmith H, Schimanski LM, Ormerod E, Merryweather-Clarke AT, Viprakasit V, Edwards JP, Sweetland E, Bastin JM, Cowley D, Chinthammitr Y, Robson KJH, Townsend ARM. Resistance to hepcidin is conferred by hemochromatosis-associated mutations of ferroportin. Blood 2005; 106:1092-7. [PMID: 15831700 DOI: 10.1182/blood-2005-02-0561] [Citation(s) in RCA: 186] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Ferroportin (FPN) mediates iron export from cells; FPN mutations are associated with the iron overloading disorder hemochromatosis. Previously, we found that the A77D, V162del, and G490D mutations inhibited FPN activity, but that other disease-associated FPN variants retained full iron export capability. The peptide hormone hepcidin inhibits FPN as part of a homeostatic negative feedback loop. We measured surface expression and function of wild-type FPN and fully active FPN mutants in the presence of hepcidin. We found that the Y64N and C326Y mutants of FPN are completely resistant to hepcidin inhibition and that N144D and N144H are partially resistant. Hemochromatosis-associated FPN mutations, therefore, either reduce iron export ability or produce an FPN variant that is insensitive to hepcidin. The former mutation type is associated with Kupffer-cell iron deposition and normal transferrin saturation in vivo, whereas patients with the latter category of FPN mutation have high transferrin saturation and tend to deposit iron throughout the liver parenchyma. FPN-linked hemochromatosis may have a variable pathogenesis depending on the causative FPN mutant.
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Affiliation(s)
- Hal Drakesmith
- Weatherall Institute of Molecular Medicine, Oxford. OX3 9DS, United Kingdom.
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50
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Schimanski LM, Drakesmith H, Merryweather-Clarke AT, Viprakasit V, Edwards JP, Sweetland E, Bastin JM, Cowley D, Chinthammitr Y, Robson KJH, Townsend ARM. In vitro functional analysis of human ferroportin (FPN) and hemochromatosis-associated FPN mutations. Blood 2005; 105:4096-102. [PMID: 15692071 DOI: 10.1182/blood-2004-11-4502] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Type IV hemochromatosis is associated with dominant mutations in the SLC40A1 gene encoding ferroportin (FPN). Known as the "ferroportin disease," this condition is typically characterized by high serum ferritin, reduced transferrin saturation, and macrophage iron loading. Previously FPN expression in vitro has been shown to cause iron deficiency in human cell lines and mediate iron export from Xenopus oocytes. We confirm these findings by showing that expression of human FPN in a human cell line results in an iron deficiency because of a 3-fold increased export of iron. We show that FPN mutations A77D, V162delta, and G490D that are associated with a typical pattern of disease in vivo cause a loss of iron export function in vitro but do not physically or functionally impede wild-type FPN. These mutants may, therefore, lead to disease by haploinsufficiency. By contrast the variants Y64N, N144D, N144H, Q248H, and C326Y, which can be associated with greater transferrin saturation and more prominent iron deposition in liver parenchyma in vivo, retained iron export function in vitro. Because FPN is a target for negative feedback in iron homeostasis, we postulate that the latter group of mutants may resist inhibition, resulting in a permanently "turned on" iron exporter.
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Affiliation(s)
- Lisa M Schimanski
- Molecular Immunology Group, Weatherall Institute of Molecular Medicine, Headley Way, Oxford, OX3 9DS, United Kingdom.
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