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Hernández G, Ferrer-Cortès X, Venturi V, Musri M, Pilquil MF, Torres PMM, Rodríguez IH, Mínguez MÀR, Kelleher NJ, Pelucchi S, Piperno A, Alberca EP, Ricós GG, Giró EC, Pérez-Montero S, Tornador C, Villà-Freixa J, Sánchez M. New Mutations in HFE2 and TFR2 Genes Causing Non HFE-Related Hereditary Hemochromatosis. Genes (Basel) 2021; 12:1980. [PMID: 34946929 PMCID: PMC8702017 DOI: 10.3390/genes12121980] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 12/07/2021] [Accepted: 12/08/2021] [Indexed: 01/04/2023] Open
Abstract
Hereditary hemochromatosis (HH) is an iron metabolism disease clinically characterized by excessive iron deposition in parenchymal organs such as liver, heart, pancreas, and joints. It is caused by mutations in at least five different genes. HFE hemochromatosis is the most common type of hemochromatosis, while non-HFE related hemochromatosis are rare cases. Here, we describe six new patients of non-HFE related HH from five different families. Two families (Family 1 and 2) have novel nonsense mutations in the HFE2 gene have novel nonsense mutations (p.Arg63Ter and Asp36ThrfsTer96). Three families have mutations in the TFR2 gene, one case has one previously unreported mutation (Family A-p.Asp680Tyr) and two cases have known pathogenic mutations (Family B and D-p.Trp781Ter and p.Gln672Ter respectively). Clinical, biochemical, and genetic data are discussed in all these cases. These rare cases of non-HFE related hereditary hemochromatosis highlight the importance of an earlier molecular diagnosis in a specialized center to prevent serious clinical complications.
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Affiliation(s)
- Gonzalo Hernández
- Iron Metabolism: Regulation and Diseases Group, Department of Basic Sciences, Universitat Internacional de Catalunya (UIC), 08195 Sant Cugat del Vallès, Spain; (G.H.); (X.F.-C.); (V.V.)
- BloodGenetics S.L., Diagnostics in Inherited Blood Diseases, 08950 Esplugues de Llobregat, Spain; (M.M.); (S.P.-M.); (C.T.)
| | - Xenia Ferrer-Cortès
- Iron Metabolism: Regulation and Diseases Group, Department of Basic Sciences, Universitat Internacional de Catalunya (UIC), 08195 Sant Cugat del Vallès, Spain; (G.H.); (X.F.-C.); (V.V.)
- BloodGenetics S.L., Diagnostics in Inherited Blood Diseases, 08950 Esplugues de Llobregat, Spain; (M.M.); (S.P.-M.); (C.T.)
| | - Veronica Venturi
- Iron Metabolism: Regulation and Diseases Group, Department of Basic Sciences, Universitat Internacional de Catalunya (UIC), 08195 Sant Cugat del Vallès, Spain; (G.H.); (X.F.-C.); (V.V.)
| | - Melina Musri
- BloodGenetics S.L., Diagnostics in Inherited Blood Diseases, 08950 Esplugues de Llobregat, Spain; (M.M.); (S.P.-M.); (C.T.)
| | - Martin Floor Pilquil
- Department of Basic Sciences, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Spain; (M.F.P.); (P.M.M.T.); (J.V.-F.)
- Department of Biosciences, Faculty of Sciences and Technology, Universitat de Vic—Universitat Central de Catalunya, 08500 Vic, Spain
| | - Pau Marc Muñoz Torres
- Department of Basic Sciences, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Spain; (M.F.P.); (P.M.M.T.); (J.V.-F.)
| | | | - Maria Àngels Ruiz Mínguez
- Department of Laboratory Medicine/Fundació Hospital de l’Esperit Sant, 08923 Santa Coloma de Gramenet, Spain;
| | | | - Sara Pelucchi
- Department of Medicine and Surgery, University of Milano-Bicocca, 20126 Monza, Italy; (S.P.); (A.P.)
| | - Alberto Piperno
- Department of Medicine and Surgery, University of Milano-Bicocca, 20126 Monza, Italy; (S.P.); (A.P.)
- Medical Genetics—ASST-Monza, S. Gerardo Hospital, 20900 Monza, Italy
- Centre for Rare Diseases—Disorders of Iron Metabolism—ASST-Monza, San Gerardo Hospital, 20900 Monza, Italy
| | - Esther Plensa Alberca
- Hematologia i Hemoteràpia, Consorci Sanitari del Maresme, Institut Català d’Oncologia, 08304 Mataró, Spain; (E.P.A.); (G.G.R.); (E.C.G.)
| | - Georgina Gener Ricós
- Hematologia i Hemoteràpia, Consorci Sanitari del Maresme, Institut Català d’Oncologia, 08304 Mataró, Spain; (E.P.A.); (G.G.R.); (E.C.G.)
| | - Eloi Cañamero Giró
- Hematologia i Hemoteràpia, Consorci Sanitari del Maresme, Institut Català d’Oncologia, 08304 Mataró, Spain; (E.P.A.); (G.G.R.); (E.C.G.)
| | - Santiago Pérez-Montero
- BloodGenetics S.L., Diagnostics in Inherited Blood Diseases, 08950 Esplugues de Llobregat, Spain; (M.M.); (S.P.-M.); (C.T.)
| | - Cristian Tornador
- BloodGenetics S.L., Diagnostics in Inherited Blood Diseases, 08950 Esplugues de Llobregat, Spain; (M.M.); (S.P.-M.); (C.T.)
| | - Jordi Villà-Freixa
- Department of Basic Sciences, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Spain; (M.F.P.); (P.M.M.T.); (J.V.-F.)
- Department of Biosciences, Faculty of Sciences and Technology, Universitat de Vic—Universitat Central de Catalunya, 08500 Vic, Spain
| | - Mayka Sánchez
- Iron Metabolism: Regulation and Diseases Group, Department of Basic Sciences, Universitat Internacional de Catalunya (UIC), 08195 Sant Cugat del Vallès, Spain; (G.H.); (X.F.-C.); (V.V.)
- BloodGenetics S.L., Diagnostics in Inherited Blood Diseases, 08950 Esplugues de Llobregat, Spain; (M.M.); (S.P.-M.); (C.T.)
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2
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Kowdley KV, Gochanour EM, Sundaram V, Shah RA, Handa P. Hepcidin Signaling in Health and Disease: Ironing Out the Details. Hepatol Commun 2021; 5:723-735. [PMID: 34027264 PMCID: PMC8122377 DOI: 10.1002/hep4.1717] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 02/22/2021] [Accepted: 02/23/2021] [Indexed: 12/19/2022] Open
Abstract
Hepcidin, a peptide hormone produced by hepatocytes, is the central regulator of systemic iron homeostasis through its interaction with ferroportin, the major cellular iron export protein. Hepcidin binding to ferroportin results in reduced iron export from macrophages and intestinal absorptive cells, leading to decreased serum iron levels. Hepcidin expression is influenced by several factors that include serum and liver iron stores, erythropoiesis, hypoxia, inflammation, and infection. Erythropoietic drive and hypoxia suppress hepcidin expression and promote red cell production. In contrast, inflammation and infection are associated with increased hepcidin production to sequester iron intracellularly as a means of depriving microorganisms of iron. Chronic inflammation may up-regulate hepcidin expression through the interleukin-6 (IL-6)-Janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) pathway. The bone morphogenetic protein (BMP)-mothers against decapentaplegic homolog (SMAD) pathway is a major positive driver of hepcidin expression in response to either increased circulating iron in the form of transferrin or iron loading in organs. Hereditary hemochromatosis (HH) consists of several inherited disorders that cause inappropriately reduced hepcidin expression in response to body iron stores, leading to increased iron absorption from a normal diet. The most common form of HH is due to a mutation in the HFE gene, which causes a failure in the hepatocyte iron-sensing mechanism, leading to reduced hepcidin expression; the clinical manifestations of HFE-HH include increased serum transferrin-iron saturation and progressive iron loading in the liver and other tissues over time among patients who express the disease phenotype. In this article, we review the physiologic mechanisms and cellular pathways by which hepcidin expression is regulated, and the different forms of HH resulting from various mutations that cause hepcidin deficiency. We also review other drivers of hepcidin expression and the associated pathophysiologic consequences.
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Affiliation(s)
- Kris V. Kowdley
- Liver Institute Northwest and Elson S. Floyd College of MedicineWashington State UniversitySpokaneWAUSA
- Liver Care Network and Organ Care ResearchSwedish Medical CenterSeattleWAUSA
| | - Eric M. Gochanour
- Liver Institute Northwest and Elson S. Floyd College of MedicineWashington State UniversitySpokaneWAUSA
- Liver Care Network and Organ Care ResearchSwedish Medical CenterSeattleWAUSA
| | - Vinay Sundaram
- Division of Gastroenterology and Comprehensive Transplant CenterLos AngelesCAUSA
| | - Raj A. Shah
- Liver Care Network and Organ Care ResearchSwedish Medical CenterSeattleWAUSA
| | - Priya Handa
- Liver Care Network and Organ Care ResearchSwedish Medical CenterSeattleWAUSA
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3
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Abd El-Hack ME, Samak DH, Noreldin AE, El-Naggar K, Abdo M. Probiotics and plant-derived compounds as eco-friendly agents to inhibit microbial toxins in poultry feed: a comprehensive review. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2018; 25:31971-31986. [PMID: 30229484 DOI: 10.1007/s11356-018-3197-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 09/11/2018] [Indexed: 06/08/2023]
Abstract
Some of pathogenic bacteria and fungi have the ability to produce fetal toxins which may be the direct causes of cytotoxicity or cellular dysfunction in the colonization site. Biological and non-biological environmental factors, challenge and microbes influence the effect of toxins on these pathogens. Modern research mentions that many natural materials can reduce the production of toxins in pathogenic microbes. However, researches that explain the mechanical theories of their effects are meager. This review aimed to discuss the ameliorative potential role of plant-derived compounds and probiotics to reduce the toxin production of food-borne microbes either in poultry bodies or poultry feedstuff. Moreover, studies that highlight their own toxicological mechanisms have been discussed. Adding natural additives to feed has a clear positive effect on the enzymatic and microbiological appearance of the small intestine without any adverse effect on the liver. Studies in this respect were proposed to clarify the effects of these natural additives for feed. In conclusion, it could be suggested that the incorporation of probiotics, herbal extracts, and herbs in the poultry diets has some beneficial effects on productive performance, without a positive impact on economic efficiency. In addition, the use of these natural additives in feed has a useful impact on the microbiological appearance of the small intestine and do not have any adverse impacts on intestinal absorption or liver activity as evidenced by histological examination.
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Affiliation(s)
- Mohamed E Abd El-Hack
- Department of Poultry, Faculty of Agriculture, Zagazig University, Zagazig, 44511, Egypt.
| | - Dalia H Samak
- Department of Veterinary Forensic Medicine and Toxicology, Faculty of Veterinary Medicine, Damanhour University, Damanhour, Egypt
| | - Ahmed E Noreldin
- Department of Histology and Cytology, Faculty of Veterinary Medicine, Damanhour University, Damanhour, Egypt
| | - Karima El-Naggar
- Department of Nutrition and Veterinary Clinical Nutrition, Faculty of Veterinary Medicine, Alexandria University, Alexandria, Egypt
| | - Mohamed Abdo
- Department of Anatomy and Embryology, Faculty of Veterinary Medicine, University of Sadat City, Sadat, Egypt
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4
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McDonald CJ, Ostini L, Wallace DF, Lyons A, Crawford DHG, Subramaniam VN. Next-generation sequencing: Application of a novel platform to analyze atypical iron disorders. J Hepatol 2015; 63:1288-93. [PMID: 26151776 DOI: 10.1016/j.jhep.2015.06.027] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Revised: 06/25/2015] [Accepted: 06/29/2015] [Indexed: 12/31/2022]
Abstract
The development of targeted next-generation sequencing (NGS) applications now promises to be a clinically viable option for the diagnosis of rare disorders. This approach is proving to have significant utility where standardized testing has failed to identify the underlying molecular basis of disease. We have developed a unique targeted NGS panel for the systematic sequence-based analysis of atypical iron disorders. We report the analysis of 39 genes associated with iron regulation in eight cases of atypical iron dysregulation, in which five cases we identified the definitive causative mutation, and a possible causative mutation in a sixth. We further provide a molecular and cellular characterization study of one of these mutations (TFR2, p.I529N) in a familial case as proof of principle. Cellular analysis of the mutant protein indicates that this amino acid substitution affects the localization of the protein, which results in its retention in the endoplasmic reticulum and thus failure to function at the cell surface. Our unique NGS panel presents a rapid and cost-efficient approach to identify the underlying genetic cause in cases of atypical iron homeostasis disorders.
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Affiliation(s)
- Cameron J McDonald
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Australia
| | - Lesa Ostini
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Australia
| | - Daniel F Wallace
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Australia; Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | | | - Darrell H G Crawford
- Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | - V Nathan Subramaniam
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Australia; Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, Australia.
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McDonald CJ, Ostini L, Bennett N, Subramaniam N, Hooper J, Velasco G, Wallace DF, Subramaniam VN. Functional analysis of matriptase-2 mutations and domains: insights into the molecular basis of iron-refractory iron deficiency anemia. Am J Physiol Cell Physiol 2015; 308:C539-47. [DOI: 10.1152/ajpcell.00264.2014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 01/09/2015] [Indexed: 12/17/2022]
Abstract
Mutations in the TMPRSS6 gene are associated with severe iron-refractory iron deficiency anemia resulting from an overexpression of hepcidin, the key regulator of iron homeostasis. The matriptase (MT)-2 protein (encoded by the TMPRSS6 gene) regulates hepcidin expression by cleaving hemojuvelin [HJV/hemochromatosis type 2 (HFE2)], a bone morphogenetic protein (BMP) coreceptor in the hepcidin regulatory pathway. We investigated the functional consequences of five clinically associated TMPRSS6 variants and the role of MT-2 protein domains by generating epitope-tagged mutant and domain-swapped MT-2-MT-1 (encoded by the ST14 gene) chimeric constructs and expressing them in HepG2/C3A cells. We developed a novel cell culture immunofluorescence assay to assess the effect of MT-2 on cell surface HJV expression levels, compatible with HJV cleavage. The TMPRSS6 variants Y141C, I212T, G442R, and C510S were retained intracellularly and were unable to inhibit BMP6 induction of hepcidin. The R271Q variant, although it has been associated with iron-refractory iron deficiency anemia, appears to remain functional. Analysis of the chimeric constructs showed that replacement of sperm protein, enterokinase, and agrin (SEA), low-density-lipoprotein receptor class A (LDLRA), and protease (PROT) domains from MT-2 with those from MT-1 resulted in limited cell surface localization, while the complement C1r/C1s, Uegf, Bmp1 (CUB) domain chimera retained localization at the cell surface. The SEA domain chimera was able to reduce cell surface HJV expression, while the CUB, LDLRA, and PROT domain chimeras were not. These studies suggest that the SEA and LDLRA domains of MT-2 are important for trafficking to the cell surface and that the CUB, LDLRA, and PROT domains are required for cleavage of HJV.
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Affiliation(s)
- Cameron J. McDonald
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - Lesa Ostini
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - Nigel Bennett
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - Nanthakumar Subramaniam
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - John Hooper
- Mater Research Institute-University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia
| | - Gloria Velasco
- Departamento de Bioquímica y Biología Molecular, Instituto Universitario de Oncología, Universidad de Oviedo, Oviedo, Spain; and
| | - Daniel F. Wallace
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
| | - V. Nathan Subramaniam
- Membrane Transport Laboratory, QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia
- Faculty of Medicine and Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
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Joshi R, Shvartsman M, Morán E, Lois S, Aranda J, Barqué A, de la Cruz X, Bruguera M, Vagace JM, Gervasini G, Sanz C, Sánchez M. Functional consequences of transferrin receptor-2 mutations causing hereditary hemochromatosis type 3. Mol Genet Genomic Med 2015; 3:221-32. [PMID: 26029709 PMCID: PMC4444164 DOI: 10.1002/mgg3.136] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 01/28/2015] [Accepted: 01/29/2015] [Indexed: 01/03/2023] Open
Abstract
Hereditary hemochromatosis (HH) type 3 is an autosomal recessive disorder of iron metabolism characterized by excessive iron deposition in the liver and caused by mutations in the transferrin receptor 2 (TFR2) gene. Here, we describe three new HH type 3 Spanish families with four TFR2 mutations (p.Gly792Arg, c.1606-8A>G, Gln306*, and Gln672*). The missense variation p.Gly792Arg was found in homozygosity in two adult patients of the same family, and in compound heterozygosity in an adult proband that also carries a novel intronic change (c.1606-8A>G). Two new nonsense TFR2 mutations (Gln306* and Gln672*) were detected in a pediatric case. We examine the functional consequences of two TFR2 variants (p.Gly792Arg and c.1606-8A>G) using molecular and computational methods. Cellular protein localization studies using immunofluorescence demonstrated that the plasma membrane localization of p.Gly792Arg TFR2 is impaired. Splicing studies in vitro and in vivo reveal that the c.1606-8A>G mutation leads to the creation of a new acceptor splice site and an aberrant TFR2 mRNA. The reported mutations caused HH type 3 by protein truncation, altering TFR2 membrane localization or by mRNA splicing defect, producing a nonfunctional TFR2 protein and a defective signaling transduction for hepcidin regulation. TFR2 genotyping should be considered in adult but also in pediatric cases with early-onset of iron overload.
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Affiliation(s)
- Ricky Joshi
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain
| | - Maya Shvartsman
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain
| | - Erica Morán
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain ; Diagnostics in Iron Metabolism Service (D·IRON) and Iron Metabolism: Regulation and Diseases group, Josep Carreras Leukemia Research Institute (IJC) Barcelona, Spain
| | - Sergi Lois
- Vall d'Hebron Research Institute (VHIR) Barcelona, Spain
| | - Jessica Aranda
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain ; Diagnostics in Iron Metabolism Service (D·IRON) and Iron Metabolism: Regulation and Diseases group, Josep Carreras Leukemia Research Institute (IJC) Barcelona, Spain
| | - Anna Barqué
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain ; Diagnostics in Iron Metabolism Service (D·IRON) and Iron Metabolism: Regulation and Diseases group, Josep Carreras Leukemia Research Institute (IJC) Barcelona, Spain
| | - Xavier de la Cruz
- Vall d'Hebron Research Institute (VHIR) Barcelona, Spain ; Institució Catalana de Recerca i Estudis Avançats (ICREA) Barcelona, Catalonia, Spain
| | - Miquel Bruguera
- Service of Hepatology, Clinic Hospital of Barcelona Barcelona, Spain
| | - José Manuel Vagace
- Service of Haematology, Hospital Materno-Infantil de Badajoz Badajoz, Spain
| | - Guillermo Gervasini
- Department of Surgical & Medical Therapeutics, University of Extremadura Badajoz, Spain
| | - Cristina Sanz
- Service of Haematology and Hemotherapy, Clinic Hospital of Barcelona Barcelona, Spain
| | - Mayka Sánchez
- Cancer and Iron Group and Advanced Genetic Diagnostic Unit of Rare Iron Disorders (UDGAEMH), Institut of Predictive and Personalized Medicine of Cancer (IMPPC) Barcelona, Spain ; Diagnostics in Iron Metabolism Service (D·IRON) and Iron Metabolism: Regulation and Diseases group, Josep Carreras Leukemia Research Institute (IJC) Barcelona, Spain
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7
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Worthen CA, Enns CA. The role of hepatic transferrin receptor 2 in the regulation of iron homeostasis in the body. Front Pharmacol 2014; 5:34. [PMID: 24639653 PMCID: PMC3944196 DOI: 10.3389/fphar.2014.00034] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 02/18/2014] [Indexed: 12/22/2022] Open
Abstract
Fine-tuning of body iron is required to prevent diseases such as iron-overload and anemia. The putative iron sensor, transferrin receptor 2 (TfR2), is expressed in the liver and mutations in this protein result in the iron-overload disease Type III hereditary hemochromatosis (HH). With the loss of functional TfR2, the liver produces about 2-fold less of the peptide hormone hepcidin, which is responsible for negatively regulating iron uptake from the diet. This reduction in hepcidin expression leads to the slow accumulation of iron in the liver, heart, joints, and pancreas and subsequent cirrhosis, heart disease, arthritis, and diabetes. TfR2 can bind iron-loaded transferrin (Tf) in the bloodstream, and hepatocytes treated with Tf respond with a 2-fold increase in hepcidin expression through stimulation of the bone morphogenetic protein (BMP)-signaling pathway. Loss of functional TfR2 or its binding partner, the original HH protein, results in a loss of this transferrin-sensitivity. While much is known about the trafficking and regulation of TfR2, the mechanism of its transferrin-sensitivity through the BMP-signaling pathway is still not known.
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Affiliation(s)
- Christal A Worthen
- Department of Cell and Developmental Biology, Oregon Health and Science University Portland, OR, USA
| | - Caroline A Enns
- Department of Cell and Developmental Biology, Oregon Health and Science University Portland, OR, USA
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Rishi G, Crampton EM, Wallace DF, Subramaniam VN. In situ proximity ligation assays indicate that hemochromatosis proteins Hfe and transferrin receptor 2 (Tfr2) do not interact. PLoS One 2013; 8:e77267. [PMID: 24155934 PMCID: PMC3796466 DOI: 10.1371/journal.pone.0077267] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2013] [Accepted: 09/02/2013] [Indexed: 01/05/2023] Open
Abstract
The hemochromatosis associated proteins HFE and Transferrin Receptor 2 (TFR2) have been shown to be important for the proper regulation of hepcidin. A number of in vitro studies using transient overexpression systems have suggested that an interaction between HFE and TFR2 is required for the regulation of hepcidin. This model of iron sensing which centers upon the requirement for an interaction between HFE and TFR2 has recently been questioned with in vivo studies in mice from our laboratory and others which suggest that Hfe and Tfr2 can regulate hepcidin independently of each other. To re-examine the postulated interaction between Hfe and Tfr2 we developed a novel expression system in which both proteins are stably co-expressed and used the proximity ligation assay to examine the interactions between Hfe, Tfr1 and Tfr2 at a cellular level. We were able to detect the previously described interaction between Hfe and Tfr1, and heterodimers between Tfr1 and Tfr2; however no interaction between Hfe and Tfr2 was observed in our system. The results from this study indicate that Hfe and Tfr2 do not interact with each other when they are stably expressed at similar levels. Furthermore, these results support in vivo studies which suggest that Hfe and Tfr2 can independently regulate hepcidin.
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Affiliation(s)
- Gautam Rishi
- The Membrane Transport Laboratory, the Queensland Institute of Medical Research, Queensland, Australia
- Liver Research Centre, School of Medicine, University of Queensland, Brisbane, Queensland, Australia
| | - Emily M. Crampton
- The Membrane Transport Laboratory, the Queensland Institute of Medical Research, Queensland, Australia
| | - Daniel F. Wallace
- The Membrane Transport Laboratory, the Queensland Institute of Medical Research, Queensland, Australia
| | - V. Nathan Subramaniam
- The Membrane Transport Laboratory, the Queensland Institute of Medical Research, Queensland, Australia
- Liver Research Centre, School of Medicine, University of Queensland, Brisbane, Queensland, Australia
- * E-mail:
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9
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Zhao N, Enns CA. N-linked glycosylation is required for transferrin-induced stabilization of transferrin receptor 2, but not for transferrin binding or trafficking to the cell surface. Biochemistry 2013; 52:3310-9. [PMID: 23556518 PMCID: PMC3656769 DOI: 10.1021/bi4000063] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Transferrin receptor 2 (TfR2) is
a member of the transferrin receptor-like
family of proteins. Mutations in TfR2 can lead to a rare form of the
iron overload disease, hereditary hemochromatosis. TfR2 is proposed
to sense body iron levels and increase the level of expression of
the iron regulatory hormone, hepcidin. Human TfR2 (hTfR2) contains
four potential Asn-linked (N-linked) glycosylation sites on its ectodomain.
The importance of glycosylation in TfR2 function has not been elucidated.
In this study, by employing site-directed mutagenesis to remove glycosylation
sites of hTfR2 individually or in combination, we found that hTfR2
was glycosylated at Asn 240, 339, and 754, while the consensus sequence
for N-linked glycosylation at Asn 540 was not utilized. Cell surface
protein biotinylation and biotin-labeled Tf indicated that in the
absence of N-linked oligosaccharides, hTfR2 still moved to the plasma
membrane and bound its ligand, holo-Tf. However, without N-linked
glycosylation, hTfR2 did not form the intersubunit disulfide bonds
as efficiently as the wild type (WT). Moreover, the unglycosylated
form of hTfR2 could not be stabilized by holo-Tf. We further provide
evidence that the unglycosylated hTfR2 behaved in manner different
from that of the WT in response to holo-Tf treatment. Thus, the putative
iron-sensing function of TfR2 could not be achieved in the absence
of N-linked oligosaccharides. On the basis of our analyses, we conclude
that unlike TfR1, N-linked glycosylation is dispensable for the cell
surface expression and holo-Tf binding, but it is required for efficient
intersubunit disulfide bond formation and holo-Tf-induced stabilization
of TfR2.
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Affiliation(s)
- Ningning Zhao
- Department of Cell and Developmental Biology, Oregon Health & Science University , Portland, Oregon 97239, United States
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10
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Comparison of 3 Tfr2-deficient murine models suggests distinct functions for Tfr2-α and Tfr2-β isoforms in different tissues. Blood 2010; 115:3382-9. [DOI: 10.1182/blood-2009-09-240960] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Abstract
Transferrin receptor 2 (TFR2) is a transmembrane protein that is mutated in hemochromatosis type 3. The TFR2 gene is transcribed in 2 main isoforms: the full-length (α) and a shorter form (β). α-Tfr2 is the sensor of diferric transferrin, implicated in the modulation of hepcidin, the main regulator of iron homeostasis. The function of the putative β-Tfr2 protein is unknown. We have developed a new mouse model (KI) lacking β-Tfr2 compared with Tfr2 knockout mice (KO). Adult Tfr2 KO mice show liver iron overload and inadequate hepcidin levels relative to body iron stores, even though they increase Bmp6 production. KI mice have normal transferrin saturation, liver iron concentration, hepcidin and Bmp6 levels but show a transient anemia at young age and severe spleen iron accumulation in adult animals. Fpn1 is strikingly decreased in the spleen of these animals. These findings and the expression of β-Tfr2 in wild-type mice spleen suggest a role for β-Tfr2 in Fpn1 transcriptional control. Selective inactivation of liver α-Tfr2 in KI mice (LCKO-KI) returned the phenotype to liver iron overload. Our results strengthen the function of hepatic α-Tfr2 in hepcidin activation, suggest a role for extrahepatic Tfr2 and indicate that β-Tfr2 may specifically control spleen iron efflux.
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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: 4.3] [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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Hower V, Mendes P, Torti FM, Laubenbacher R, Akman S, Shulaev V, Torti SV. A general map of iron metabolism and tissue-specific subnetworks. MOLECULAR BIOSYSTEMS 2009; 5:422-43. [PMID: 19381358 PMCID: PMC2680238 DOI: 10.1039/b816714c] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Iron is required for survival of mammalian cells. Recently, understanding of iron metabolism and trafficking has increased dramatically, revealing a complex, interacting network largely unknown just a few years ago. This provides an excellent model for systems biology development and analysis. The first step in such an analysis is the construction of a structural network of iron metabolism, which we present here. This network was created using CellDesigner version 3.5.2 and includes reactions occurring in mammalian cells of numerous tissue types. The iron metabolic network contains 151 chemical species and 107 reactions and transport steps. Starting from this general model, we construct iron networks for specific tissues and cells that are fundamental to maintaining body iron homeostasis. We include subnetworks for cells of the intestine and liver, tissues important in iron uptake and storage, respectively, as well as the reticulocyte and macrophage, key cells in iron utilization and recycling. The addition of kinetic information to our structural network will permit the simulation of iron metabolism in different tissues as well as in health and disease.
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Affiliation(s)
- Valerie Hower
- Department of Cancer Biology, Wake Forest University School of Medicine, Medical Center Blvd, Winston Salem, NC 27157, USA
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13
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Pelucchi S, Mariani R, Trombini P, Coletti S, Pozzi M, Paolini V, Barisani D, Piperno A. Expression of hepcidin and other iron-related genes in type 3 hemochromatosis due to a novel mutation in transferrin receptor-2. Haematologica 2009; 94:276-9. [PMID: 19144662 DOI: 10.3324/haematol.13576] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Transferrin receptor-2 (TFR2) regulates hepatic hepcidin secretion and when mutated causes type-3 hemochromatosis. No functional study is available in humans. We studied a 47 year-old woman with hemochromatosis. TFR2 DNA and its hepatic transcript were directly sequenced. Hepatic expression of hepcidin and other iron-related genes were measured by qRT-PCR. Urinary hepcidin was measured at baseline and after an oral iron challenge (ferrous sulfate, 65 mg) by SELDI-TOF-MS. A novel homozygous TFR2 mutation was identified in the splicing donor site of intron 4 (c.614+4 A>G) causing exon 4 skipping. Hepcidin and hemojuvelin expression were markedly reduced. Urinary hepcidin was lower than normal and further decreased after iron challenge. This is the first description of iron-related gene expression profiles in a TFR2 mutated patient. The decreased hepatic and urinary expression of hepcidin and lack of acute response to iron challenge confirms the primary role of TFR2 in iron homeostasis.
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Affiliation(s)
- Sara Pelucchi
- Consortium for Human Molecular Genetics, Monza, Milan
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Ruddell RG, Knight B, Tirnitz-Parker JEE, Akhurst B, Summerville L, Subramaniam VN, Olynyk JK, Ramm GA. Lymphotoxin-beta receptor signaling regulates hepatic stellate cell function and wound healing in a murine model of chronic liver injury. Hepatology 2009; 49:227-39. [PMID: 19111021 DOI: 10.1002/hep.22597] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
UNLABELLED Lymphotoxin-beta (LTbeta) is a proinflammatory cytokine and a member of the tumor necrosis factor (TNF) superfamily known for its role in mediating lymph node development and homeostasis. Our recent studies suggest a role for LTbeta in mediating the pathogenesis of human chronic liver disease. We hypothesize that LTbeta co-ordinates the wound healing response in liver injury via direct effects on hepatic stellate cells. This study used the choline-deficient, ethionine-supplemented (CDE) dietary model of chronic liver injury, which induces inflammation, liver progenitor cell proliferation, and portal fibrosis, to assess (1) the cellular expression of LTbeta, and (2) the role of LTbeta receptor (LTbetaR) in mediating wound healing, in LTbetaR(-/-) versus wild-type mice. In addition, primary isolates of hepatic stellate cells were treated with LTbetaR-ligands LTbeta and LTbeta-related inducible ligand competing for glycoprotein D binding to herpesvirus entry mediator on T cells (LIGHT), and mediators of hepatic stellate cell function and fibrogenesis were assessed. LTbeta was localized to progenitor cells immediately adjacent to activated hepatic stellate cells in the periportal region of the liver in wild-type mice fed the CDE diet. LTbetaR(-/-) mice fed the CDE diet showed significantly reduced fibrosis and a dysregulated immune response. LTbetaR was demonstrated on isolated hepatic stellate cells, which when stimulated by LTbeta and LIGHT, activated the nuclear factor kappa B (NF-kappaB) signaling pathway. Neither LTbeta nor LIGHT had any effect on alpha-smooth muscle actin, tissue inhibitor of metalloproteinase 1, transforming growth factor beta, or procollagen alpha(1)(I) expression; however, leukocyte recruitment-associated factors intercellular adhesion molecule 1 and regulated upon activation T cells expressed and secreted (RANTES) were markedly up-regulated. RANTES caused the chemotaxis of a liver progenitor cell line expressing CCR5. CONCLUSION This study suggests that LTbetaR on hepatic stellate cells may be involved in paracrine signaling with nearby LTbeta-expressing liver progenitor cells mediating recruitment of progenitor cells, hepatic stellate cells, and leukocytes required for wound healing and regeneration during chronic liver injury.
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Affiliation(s)
- Richard G Ruddell
- Hepatic Fibrosis Group, The University of Queensland, Brisbane, Australia
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Kambe T, Weaver BP, Andrews GK. The genetics of essential metal homeostasis during development. Genesis 2008; 46:214-28. [PMID: 18395838 DOI: 10.1002/dvg.20382] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The essential metals copper, zinc, and iron play key roles in embryonic, fetal, and postnatal development in higher eukaryotes. Recent advances in our understanding of the molecules involved in the intricate control of the homeostasis of these metals and the availability of natural mutations and targeted mutations in many of the genes involved have allowed for elucidation of the diverse roles of these metals during development. Evidence suggests that the ability of the embryo to control the homeostasis of these metals becomes essential at the blastocyst stage and during early morphogenesis. However, these metals play unique roles throughout development and exert pleiotropic, metal-specific, and often cell-specific effects on morphogenesis, growth, and differentiation. Herein, we briefly review the major players known to be involved in the homeostasis of each of these essential metals and their known roles in development.
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Affiliation(s)
- Taiho Kambe
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas 66160-7421, USA
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