1
|
Uguen K, Le Tertre M, Tchernitchko D, Elbahnsi A, Maestri S, Gourlaouen I, Férec C, Ka C, Callebaut I, Le Gac G. The dual loss and gain of function of the FPN1 iron exporter results in the ferroportin disease phenotype. HGG ADVANCES 2024; 5:100335. [PMID: 39039793 PMCID: PMC11343060 DOI: 10.1016/j.xhgg.2024.100335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Revised: 07/16/2024] [Accepted: 07/16/2024] [Indexed: 07/24/2024] Open
Abstract
Heterozygous mutations in SLC40A1, encoding a multi-pass membrane protein of the major facilitator superfamily known as ferroportin 1 (FPN1), are responsible for two distinct hereditary iron-overload diseases: ferroportin disease, which is associated with reduced FPN1 activity (i.e., decrease in cellular iron export), and SLC40A1-related hemochromatosis, which is associated with abnormally high FPN1 activity (i.e., resistance to hepcidin). Here, we report three SLC40A1 missense variants with opposite functional consequences. In cultured cells, the p.Arg40Gln and p.Ser47Phe substitutions partially reduced the ability of FPN1 to export iron and also partially reduced its sensitivity to hepcidin. The p.Ala350Val substitution had more profound effects, resulting in low FPN1 iron egress and weak FPN1/hepcidin interaction. Structural analyses helped to differentiate the first two substitutions, which are predicted to cause local instabilities, and the third, which is thought to prevent critical rigid-body movements that are essential to the iron transport cycle. The phenotypic traits observed in a total of 12 affected individuals are highly suggestive of ferroportin disease. Our findings dismantle the classical dualism of FPN1 loss versus gain of function, highlight some specific and unexpected functions of FPN1 transmembrane helices in the molecular mechanism of iron export and its regulation by hepcidin, and extend the spectrum of rare genetic variants that may cause ferroportin disease.
Collapse
Affiliation(s)
- Kevin Uguen
- University Brest, Inserm, EFS, UMR 1078, GGB, 29200 Brest, France; CHU de Brest, 29200 Brest, France
| | - Marlène Le Tertre
- University Brest, Inserm, EFS, UMR 1078, GGB, 29200 Brest, France; CHU de Brest, 29200 Brest, France
| | - Dimitri Tchernitchko
- CHU Paris Nord-Val de Seine - Hôpital Xavier Bichat-Claude Bernard, 75018 Paris, France; Centre de Recherche sur l'Inflammation, Inserm U1149, 75018 Paris, France
| | - Ahmad Elbahnsi
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, IRD, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France
| | - Sandrine Maestri
- University Brest, Inserm, EFS, UMR 1078, GGB, 29200 Brest, France
| | | | - Claude Férec
- University Brest, Inserm, EFS, UMR 1078, GGB, 29200 Brest, France; CHU de Brest, 29200 Brest, France; Association Gaétan Saleün, 29200 Brest, France
| | - Chandran Ka
- University Brest, Inserm, EFS, UMR 1078, GGB, 29200 Brest, France; CHU de Brest, 29200 Brest, France; Laboratory of Excellence GR-Ex, 75015 Paris, France
| | - Isabelle Callebaut
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, IRD, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France
| | - Gérald Le Gac
- University Brest, Inserm, EFS, UMR 1078, GGB, 29200 Brest, France; CHU de Brest, 29200 Brest, France; Laboratory of Excellence GR-Ex, 75015 Paris, France.
| |
Collapse
|
2
|
Debbiche R, Elbahnsi A, Uguen K, Ka C, Callebaut I, Le Gac G. Insights into the role of glycerophospholipids on the iron export function of SLC40A1 and the molecular mechanisms of ferroportin disease. FASEB J 2024; 38:e23725. [PMID: 38959016 DOI: 10.1096/fj.202400337r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 05/13/2024] [Accepted: 05/23/2024] [Indexed: 07/04/2024]
Abstract
SLC40A1 is the sole iron export protein reported in mammals. In humans, its dysfunction is responsible for ferroportin disease, an inborn error of iron metabolism transmitted as an autosomal dominant trait and observed in different ethnic groups. As a member of the major facilitator superfamily, SLC40A1 requires a series of conformational changes to enable iron translocation across the plasma membrane. The influence of lipids on protein stability and its conformational changes has been little investigated to date. Here, we combine molecular dynamics simulations of SLC40A1 embedded in membrane bilayers with experimental alanine scanning mutagenesis to analyze the specific role of glycerophospholipids. We identify four basic residues (Lys90, Arg365, Lys366, and Arg371) that are located at the membrane-cytosol interface and consistently interact with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) molecules. These residues surround a network of salt bridges and hydrogens bonds that play a critical role in stabilizing SLC40A1 in its basal outward-facing conformation. More deeply embedded in the plasma membrane, we identify Arg179 as a charged amino acid residue also tightly interacting with lipid polar heads. This results in a local deformation of the lipid bilayer. Interestingly, Arg179 is adjacent to Arg178, which forms a functionally important salt-bridge with Asp473 and is a recurrently associated with ferroportin disease when mutated to glutamine. We demonstrate that the two p.Arg178Gln and p.Arg179Thr missense variants have similar functional behaviors. These observations provide insights into the role of phospholipids in the formation/disruption of the SLC40A1 inner gate, and give a better understanding of the diversity of molecular mechanisms of ferroportin disease.
Collapse
Affiliation(s)
- Rim Debbiche
- University of Brest, Inserm, EFS, UMR 1078, GGB, Brest, France
| | - Ahmad Elbahnsi
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, IRD, Paris, France
| | - Kévin Uguen
- University of Brest, Inserm, EFS, UMR 1078, GGB, Brest, France
- CHU de Brest, Service de Génétique Médicale et Biologie de la Reproduction, Brest, France
| | - Chandran Ka
- University of Brest, Inserm, EFS, UMR 1078, GGB, Brest, France
- CHU de Brest, Service de Génétique Médicale et Biologie de la Reproduction, Brest, France
| | - Isabelle Callebaut
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, IRD, Paris, France
| | - Gérald Le Gac
- University of Brest, Inserm, EFS, UMR 1078, GGB, Brest, France
- CHU de Brest, Service de Génétique Médicale et Biologie de la Reproduction, Brest, France
- Laboratory of Excellence GR-Ex, Paris, France
| |
Collapse
|
3
|
Li Y, Duan F, Yang S. SLC40A1-related hemochromatosis associated with a p.Y333H mutation in mainland China: a pedigree report and literature review. BMC Med Genomics 2024; 17:161. [PMID: 38886778 PMCID: PMC11181628 DOI: 10.1186/s12920-024-01929-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Accepted: 06/10/2024] [Indexed: 06/20/2024] Open
Abstract
BACKGROUND Haemochromatosis is a genetic disease characterized by the excessive deposition of iron in various tissues and organs, eventually results in organ damage including cirrhosis, diabetes, cardiomyopathy, etc. SLC40A1-related haemochromatosis is associated with gain-of-function mutations in the SLC40A1 gene, which encodes ferroportin. While sporadic reports of this condition exist in mainland China, the understanding of the phenotype and genetic pattern associated with the SLC40A1 p.Y333H mutation remains incomplete. CASE PRESENTATION We report a pedigree with heterozygous p.Y333H mutation in Chinese Han population. The proband is a 64-year-old man complaining of persistent abnormality of liver enzyme levels for 1 year, with a history of knee joint pain, diabetes and skin pigmentation. He displayed markedly elevated serum ferritin level and transferrin saturation. Magnetic resonance imaging showed iron deposition in the liver, spleen, and pancreas, along with cirrhosis and splenomegaly. Whole exome sequencing identified a heterozygous allelic variant c.997T > C (p.Y333H). Genetic screening of family members identified four first-degree relatives and three second-degree relatives having the same mutation. Additional cases with this mutation from two published studies were included. Among the probands and screened relatives, all eight males aged over 30 y had ferritin level > 1000 µg/L, transferrin saturation > 90%. Four patients with organ damage in the present study received therapeutic phlebotomy, alleviating clinical symptoms and improving in transferrin saturation and serum ferritin. CONCLUSIONS This study reports the largest pedigree with heterozygous SLC40A1 p.Y333H mutation in the Chinese population to date. In Chinese families, males over 30 years old with hemochromatosis due to SLC40A1 p.Y333H mutation exhibit severe iron overload phenotypes.
Collapse
Affiliation(s)
- Yue Li
- Division 3, Department of Hepatology, Beijing Ditan Hospital, Capital Medical University, Beijing, 100015, China
| | - Fangfang Duan
- Division 3, Department of Hepatology, Beijing Ditan Hospital, Capital Medical University, Beijing, 100015, China
| | - Song Yang
- Division 3, Department of Hepatology, Beijing Ditan Hospital, Capital Medical University, Beijing, 100015, China.
- Division 2, Department of Hepatology, The Fourth People's Hospital of Qinghai Province, Qinghai, 810000, China.
- Center of Hepatology, Beijing Ditan Hospital, Capital Medical University, 8 Jingshun East Street, Beijing, 100015, China.
| |
Collapse
|
4
|
Pasquadibisceglie A, Bonaccorsi di Patti MC, Musci G, Polticelli F. Membrane Transporters Involved in Iron Trafficking: Physiological and Pathological Aspects. Biomolecules 2023; 13:1172. [PMID: 37627237 PMCID: PMC10452680 DOI: 10.3390/biom13081172] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 07/25/2023] [Accepted: 07/26/2023] [Indexed: 08/27/2023] Open
Abstract
Iron is an essential transition metal for its involvement in several crucial biological functions, the most notable being oxygen storage and transport. Due to its high reactivity and potential toxicity, intracellular and extracellular iron levels must be tightly regulated. This is achieved through transport systems that mediate cellular uptake and efflux both at the level of the plasma membrane and on the membranes of lysosomes, endosomes and mitochondria. Among these transport systems, the key players are ferroportin, the only known transporter mediating iron efflux from cells; DMT1, ZIP8 and ZIP14, which on the contrary, mediate iron influx into the cytoplasm, acting on the plasma membrane and on the membranes of lysosomes and endosomes; and mitoferrin, involved in iron transport into the mitochondria for heme synthesis and Fe-S cluster assembly. The focus of this review is to provide an updated view of the physiological role of these membrane proteins and of the pathologies that arise from defects of these transport systems.
Collapse
Affiliation(s)
| | | | - Giovanni Musci
- Department of Biosciences and Territory, University of Molise, 86090 Pesche, Italy;
| | - Fabio Polticelli
- Department of Sciences, University Roma Tre, 00146 Rome, Italy;
- National Institute of Nuclear Physics, Roma Tre Section, 00146 Rome, Italy
| |
Collapse
|
5
|
Amadei M, Niro A, Fullone MR, Miele R, Polticelli F, Musci G, Bonaccorsi di Patti MC. Genetic Incorporation of Dansylalanine in Human Ferroportin to Probe the Alternating Access Mechanism of Iron Transport. Int J Mol Sci 2023; 24:11919. [PMID: 37569293 PMCID: PMC10418311 DOI: 10.3390/ijms241511919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/17/2023] [Accepted: 07/24/2023] [Indexed: 08/13/2023] Open
Abstract
Ferroportin (Fpn), a member of the major facilitator superfamily (MFS) of transporters, is the only known iron exporter found in mammals and plays a crucial role in regulating cellular and systemic iron levels. MFSs take on different conformational states during the transport cycle: inward open, occluded, and outward open. However, the precise molecular mechanism of iron translocation by Fpn remains unclear, with conflicting data proposing different models. In this work, amber codon suppression was employed to introduce dansylalanine (DA), an environment-sensitive fluorescent amino acid, into specific positions of human Fpn (V46, Y54, V161, Y331) predicted to undergo major conformational changes during metal translocation. The results obtained indicate that different mutants exhibit distinct fluorescence spectra depending on the position of the fluorophore within the Fpn structure, suggesting that different local environments can be probed. Cobalt titration experiments revealed fluorescence quenching and blue-shifts of λmax in Y54DA, V161DA, and Y331DA, while V46DA exhibited increased fluorescence and blue-shift of λmax. These observations suggest metal-induced conformational transitions, interpreted in terms of shifts from an outward-open to an occluded conformation. Our study highlights the potential of genetically incorporating DA into Fpn, enabling the investigation of conformational changes using fluorescence spectroscopy. This approach holds great promise for the study of the alternating access mechanism of Fpn and advancing our understanding of the molecular basis of iron transport.
Collapse
Affiliation(s)
- Matteo Amadei
- Department of Biochemical Sciences ‘A. Rossi Fanelli’, Sapienza University of Rome, 00185 Rome, Italy; (M.A.); (M.R.F.); (R.M.)
| | - Antonella Niro
- Department of Biosciences and Territory, University of Molise, 86090 Pesche, Italy; (A.N.); (G.M.)
| | - Maria Rosaria Fullone
- Department of Biochemical Sciences ‘A. Rossi Fanelli’, Sapienza University of Rome, 00185 Rome, Italy; (M.A.); (M.R.F.); (R.M.)
| | - Rossella Miele
- Department of Biochemical Sciences ‘A. Rossi Fanelli’, Sapienza University of Rome, 00185 Rome, Italy; (M.A.); (M.R.F.); (R.M.)
| | | | - Giovanni Musci
- Department of Biosciences and Territory, University of Molise, 86090 Pesche, Italy; (A.N.); (G.M.)
| | | |
Collapse
|
6
|
Zhao Q, Ge Z, Fu S, Wan S, Shi J, Wu Y, Zhang Y. DNA methylation plays an important role in iron-overloaded Tibetans. Gene 2022; 97:55-66. [PMID: 35644542 DOI: 10.1266/ggs.21-00006] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The prevalence of iron overload in Tibetans in Tibet is higher than that in Han. DNA methylation (DNAm) is closely related to iron metabolism and iron level. Nevertheless, the epigenetic status of Tibetans with iron overload is unknown, and we therefore aimed to explore whether the phenomenon observed in the Tibetan population is regulated by epigenetics. The results showed that 2.26% of cytosine was methylated in the whole genome, and that the rate of CG cytosine methylation was higher in individuals in the iron overload (TH) group than in those in the iron normal (TL) group. We analyzed differentially methylated genes (DMGs) in whole-genome bisulfite sequencing data from the TH and TL groups of high-altitude Tibetans. Protein-protein interaction and pathway analyses of candidate DMGs related to iron uptake and transport showed that epigenetic changes in 10 candidate genes (ACO1, CYBRD1, FLVCR1, HFE, HMOX2, IREB2, NEDD8, SLC11A2, SLC40A1 and TFRC) are likely to relate to iron overload. This work reveals, for the first time, changes of DNAm in Tibetan people with iron overload, which suggest that DNAm is a mechanism underlying differences in iron content between individuals in the high-altitude Tibetan population. Our findings should contribute to the study of iron metabolism and the overall health status of Tibetans.
Collapse
Affiliation(s)
- Qin Zhao
- Hospital of Chengdu Office of People's Government of Tibetan Autonomous Region (Hospital C.T.)
| | - Zhijing Ge
- School of Basic Medical Sciences, Tibet University
| | - Suhong Fu
- Laboratory of Natural Medicine, West China Hospital, West China Medical School, Sichuan University
| | - Sha Wan
- Hospital of Chengdu Office of People's Government of Tibetan Autonomous Region (Hospital C.T.)
| | - Jing Shi
- Hospital of Chengdu Office of People's Government of Tibetan Autonomous Region (Hospital C.T.)
| | - Yunhong Wu
- Hospital of Chengdu Office of People's Government of Tibetan Autonomous Region (Hospital C.T.)
| | - Yongqun Zhang
- Hospital of Chengdu Office of People's Government of Tibetan Autonomous Region (Hospital C.T.)
| |
Collapse
|
7
|
Insights into the Role of the Discontinuous TM7 Helix of Human Ferroportin through the Prism of the Asp325 Residue. Int J Mol Sci 2021; 22:ijms22126412. [PMID: 34203920 PMCID: PMC8232785 DOI: 10.3390/ijms22126412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 06/09/2021] [Accepted: 06/11/2021] [Indexed: 11/16/2022] Open
Abstract
The negatively charged Asp325 residue has proved to be essential for iron export by human (HsFPN1) and primate Philippine tarsier (TsFpn) ferroportin, but its exact role during the iron transport cycle is still to be elucidated. It has been posited as being functionally equivalent to the metal ion-coordinating residue His261 in the C-lobe of the bacterial homolog BbFpn, but the two residues arise in different sequence motifs of the discontinuous TM7 transmembrane helix. Furthermore, BbFpn is not subject to extracellular regulation, contrary to its mammalian orthologues which are downregulated by hepcidin. To get further insight into the molecular mechanisms related to iron export in mammals in which Asp325 is involved, we investigated the behavior of the Asp325Ala, Asp325His, and Asp325Asn mutants in transiently transfected HEK293T cells, and performed a comparative structural analysis. Our biochemical studies clearly distinguished between the Asp325Ala and Asp325His mutants, which result in a dramatic decrease in plasma membrane expression of FPN1, and the Asp325Asn mutant, which alters iron egress without affecting protein localization. Analysis of the 3D structures of HsFPN1 and TsFpn in the outward-facing (OF) state indicated that Asp325 does not interact directly with metal ions but is involved in the modulation of Cys326 metal-binding capacity. Moreover, models of the architecture of mammalian proteins in the inward-facing (IF) state suggested that Asp325 may form an inter-lobe salt-bridge with Arg40 (TM1) when not interacting with Cys326. These findings allow to suggest that Asp325 may be important for fine-tuning iron recognition in the C-lobe, as well as for local structural changes during the IF-to-OF transition at the extracellular gate level. Inability to form a salt-bridge between TM1 and TM7b during iron translocation could lead to protein instability, as shown by the Asp325Ala and Asp325His mutants.
Collapse
|
8
|
Liu B, Song Z, Fan Y, Zhang G, Cao P, Li D, Liu X, Chang Y, Tan K. Downregulation of FPN1 acts as a prognostic biomarker associated with immune infiltration in lung cancer. Aging (Albany NY) 2021; 13:8737-8761. [PMID: 33714956 PMCID: PMC8034901 DOI: 10.18632/aging.202685] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 02/01/2021] [Indexed: 12/24/2022]
Abstract
Lung cancer morbidity and mortality remain the leading causes of tumor-associated death worldwide. The discovery of early diagnostic and prognostic markers of lung cancer could significantly improve the survival rate and decrease the mortality rate. FPN1 is the only known mammalian iron exporter. However, the molecular and biological functions of FPN1 in lung cancer remain unclear. Here, FPN1 mRNA expression in lung cancer was estimated using the TCGA, Oncomine, TIMER, and UALCAN databases. The prognostic role of FPN1 was evaluated using Kaplan-Meier plotter and PrognoScan. Associations between FPN1 and immune infiltration in lung cancer were evaluated by the TIMER and CIBERSORT algorithms. FPN1 mRNA and protein expressions were significantly downregulated in lung cancer. Low FPN1 expression was strongly related to worse prognosis in patients with lung cancer. GO and KEGG analyses and GSEA suggested that FPN1 was remarkably related to iron homeostasis and immunity. Importantly, FPN1 was remarkably associated with the infiltrating abundance of multiple immune cells. Moreover, FPN1 displayed a strong correlation with various immune marker sets. We investigated the clinical application value of FPN1 and provided a basis for the sensitive diagnosis, prognostication and targeted therapy of lung cancer.
Collapse
Affiliation(s)
- Bing Liu
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, Hebei, China
| | - Zhiyuan Song
- Department of Neurosurgery, HanDan Central Hospital, Handan 056001, Hebei, China
| | - Yumei Fan
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, Hebei, China
| | - Guangyu Zhang
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, Hebei, China
| | - Pengxiu Cao
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, Hebei, China
| | - Danyu Li
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, Hebei, China
| | - Xiaopeng Liu
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, Hebei, China.,Department of Neurosurgery, The Second Hospital of Hebei Medical University, Shijiazhuang 050000, Hebei, China
| | - Yanzhong Chang
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, Hebei, China
| | - Ke Tan
- Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, Hebei, China
| |
Collapse
|
9
|
Le Tertre M, Ka C, Raud L, Berlivet I, Gourlaouen I, Richard G, Uguen K, Chen JM, Férec C, Fichou Y, Le Gac G. Splicing analysis of SLC40A1 missense variations and contribution to hemochromatosis type 4 phenotypes. Blood Cells Mol Dis 2020; 87:102527. [PMID: 33341511 DOI: 10.1016/j.bcmd.2020.102527] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/24/2020] [Accepted: 11/24/2020] [Indexed: 02/09/2023]
Abstract
Hemochromatosis type 4, or ferroportin disease, is considered as the second leading cause of primary iron overload after HFE-related hemochromatosis. The disease, which is predominantly associated with missense variations in the SLC40A1 gene, is characterized by wide clinical heterogeneity. We tested the possibility that some of the reported missense mutations, despite their positions within exons, cause splicing defects. Fifty-eight genetic variants were selected from the literature based on two criteria: a precise description of the nucleotide change and individual evidence of iron overload. The selected variants were investigated by different in silico prediction tools and prioritized for midigene splicing assays. Of the 15 variations tested in vitro, only two were associated with splicing changes. We confirm that the c.1402G>A transition (p.Gly468Ser) disrupts the exon 7 donor site, leading to the use of an exonic cryptic splicing site and the generation of a truncated reading frame. We observed, for the first time, that the p.Gly468Ser substitution has no effect on the ferroportin iron export function. We demonstrate alternative splicing of exon 5 in different cell lines and show that the c.430A>G (p.Asn144Asp) variant promotes exon 5 inclusion. This could be part of a gain-of-function mechanism. We conclude that splicing mutations rarely contribute to hemochromatosis type 4 phenotypes. An in-depth investigation of exon 5 auxiliary splicing sequences may help to elucidate the mechanism by which splicing regulatory proteins regulate the production of the full length SLC40A1 transcript and to clarify its physiological importance.
Collapse
Affiliation(s)
- Marlène Le Tertre
- Univ Brest, Inserm, EFS, UMR1078, GGB, F-29200, France; CHRU de Brest, Service de Génétique Médicale et Biologie de la Reproduction, Laboratoire de Génétique Moléculaire et Histocompatibilité, F-29200, France
| | - Chandran Ka
- Univ Brest, Inserm, EFS, UMR1078, GGB, F-29200, France; CHRU de Brest, Service de Génétique Médicale et Biologie de la Reproduction, Laboratoire de Génétique Moléculaire et Histocompatibilité, F-29200, France; Laboratory of Excellence GR-Ex, F-75015, France
| | - Loann Raud
- Univ Brest, Inserm, EFS, UMR1078, GGB, F-29200, France; Association Gaétan Saleün, F-29200, France
| | | | - Isabelle Gourlaouen
- Univ Brest, Inserm, EFS, UMR1078, GGB, F-29200, France; Laboratory of Excellence GR-Ex, F-75015, France
| | | | - Kévin Uguen
- Univ Brest, Inserm, EFS, UMR1078, GGB, F-29200, France; CHRU de Brest, Service de Génétique Médicale et Biologie de la Reproduction, Laboratoire de Génétique Moléculaire et Histocompatibilité, F-29200, France
| | - Jian-Min Chen
- Univ Brest, Inserm, EFS, UMR1078, GGB, F-29200, France
| | - Claude Férec
- Univ Brest, Inserm, EFS, UMR1078, GGB, F-29200, France; CHRU de Brest, Service de Génétique Médicale et Biologie de la Reproduction, Laboratoire de Génétique Moléculaire et Histocompatibilité, F-29200, France; Association Gaétan Saleün, F-29200, France
| | - Yann Fichou
- Univ Brest, Inserm, EFS, UMR1078, GGB, F-29200, France; Laboratory of Excellence GR-Ex, F-75015, France
| | - Gérald Le Gac
- Univ Brest, Inserm, EFS, UMR1078, GGB, F-29200, France; CHRU de Brest, Service de Génétique Médicale et Biologie de la Reproduction, Laboratoire de Génétique Moléculaire et Histocompatibilité, F-29200, France; Laboratory of Excellence GR-Ex, F-75015, France.
| |
Collapse
|
10
|
Helgudottir SS, Routhe LJ, Burkhart A, Jønsson K, Pedersen IS, Lichota J, Moos T. Epigenetic Regulation of Ferroportin in Primary Cultures of the Rat Blood-Brain Barrier. Mol Neurobiol 2020; 57:3526-3539. [PMID: 32542592 DOI: 10.1007/s12035-020-01953-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Accepted: 05/22/2020] [Indexed: 02/06/2023]
Abstract
Ferroportin plays an essential role for iron transport through the blood-brain barrier (BBB), which is formed by brain capillary endothelial cells (BCECs). To maintain the integrity of the BBB, the BCECs gain support from pericytes and astrocytes, which together with neurons form the neurovascular unit (NVU). The objectives of the present study were to investigate ferroportin expression in primary cells of the NVU and to determine if ferroportin mRNA (Fpn) expression is epigenetically regulated. Primary rat BCECs, pericytes, astrocytes, and neurons all expressed ferroportin mRNA at varying levels, with BCECs exhibiting the highest expression of Fpn, peaking when co-cultured but examined separately from astrocytes. Conversely, Fpn expression was lowest in isolated astrocytes, which correlated with high DNA methylation in their Slc40a1 promoter. To provide further evidence for epigenetic regulation, mono-cultured BCECs, pericytes, and astrocytes were treated with the histone deacetylase inhibitors valproic acid (VPA) and sodium butyrate (SB), which significantly increased Fpn and ferroportin protein in BCECs and pericytes. Furthermore, 59Fe export from BCECs was elevated after treatment with VPA. In conclusion, we present first time evidence stating that Fpn expression is epigenetically regulated in BCECs, which may have implications for pharmacological induction of iron transport through the BBB.
Collapse
Affiliation(s)
- Steinunn Sara Helgudottir
- Neurobiology Research and Drug Delivery (NRD) Department of Health Science and Technology, Aalborg University, Fr. Bajers Vej 3B, 9220, Aalborg, Denmark
| | - Lisa J Routhe
- Neurobiology Research and Drug Delivery (NRD) Department of Health Science and Technology, Aalborg University, Fr. Bajers Vej 3B, 9220, Aalborg, Denmark
| | - Annette Burkhart
- Neurobiology Research and Drug Delivery (NRD) Department of Health Science and Technology, Aalborg University, Fr. Bajers Vej 3B, 9220, Aalborg, Denmark
| | - Katrine Jønsson
- Department of Health Technology, Center for Nanomedicine and Theranostics, Technical University of Denmark, Copenhagen, Denmark
| | - Inge S Pedersen
- Department of Clinical Medicine, Aalborg University Hospital, Aalborg, Denmark.,Department of Molecular Diagnostics, Aalborg University Hospital, Aalborg, Denmark
| | - Jacek Lichota
- Laboratory of Molecular Pharmacology, Department of Health Science and Technology, Aalborg University, Fr. Bajers Vej 7E, 9220, Aalborg, Denmark.
| | - Torben Moos
- Neurobiology Research and Drug Delivery (NRD) Department of Health Science and Technology, Aalborg University, Fr. Bajers Vej 3B, 9220, Aalborg, Denmark.
| |
Collapse
|
11
|
Guellec J, Elbahnsi A, Le Tertre M, Uguen K, Gourlaouen I, Férec C, Ka C, Callebaut I, Le Gac G. Molecular model of the ferroportin intracellular gate and implications for the human iron transport cycle and hemochromatosis type 4A. FASEB J 2019; 33:14625-14635. [PMID: 31690120 DOI: 10.1096/fj.201901857r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ferroportin 1 (FPN1) is a major facilitator superfamily transporter that is essential for proper maintenance of human iron homeostasis at the systemic and cellular level. FPN1 dysfunction leads to the progressive accumulation of iron in reticuloendothelial cells, causing hemochromatosis type 4A (or ferroportin disease), an autosomal dominant disorder that displays large phenotypic heterogeneity. Although crystal structures have unveiled the outward- and inward-facing conformations of the bacterial homolog Bdellovibrio bacteriovorus Fpn (or Bd2019) and calcium has recently been identified as an essential cofactor, our molecular understanding of the iron transport mechanism remains incomplete. Here, we used a combination of molecular modeling, molecular dynamics simulations, and Ala site-directed mutagenesis, followed by complementary in vitro functional analyses, to explore the structural architecture of the human FPN1 intracellular gate. We reveal an interdomain network that involves 5 key amino acids and is likely very important for stability of the iron exporter facing the extracellular milieu. We also identify inter- and intradomain interactions that rely on the 2 Asp84 and Asn174 critical residues and do not exist in the bacterial homolog. These interactions are thought to play an important role in the modulation of conformational changes during the transport cycle. We interpret these results in the context of hemochromatosis type 4A, reinforcing the idea that different categories of loss-of-function mutations exist. Our findings provide an unprecedented view of the human FPN1 outward-facing structure and the particular function of the so-called "gating residues" in the mechanism of iron export.-Guellec, J., Elbahnsi, A., Le Tertre, M., Uguen, K., Gourlaouen, I., Férec, C., Ka, C., Callebaut, I., Le Gac, G. Molecular model of the ferroportin intracellular gate and implications for the human iron transport cycle and hemochromatosis type 4A.
Collapse
Affiliation(s)
- Julie Guellec
- INSERM Unité Mixte de Recherche (UMR) 1078, Etablissement Français du Sang-Bretagne, Institut Brestois Santé-Agro-Matière, Université Bretagne Loire-Université de Brest, Brest, France.,Association Gaetan Saleun, Brest, France
| | - Ahmad Elbahnsi
- Muséum National d'Histoire Naturelle, UMR Centre National de la Recherche Scientifique (CNRS) 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Sorbonne Université, Paris, France
| | - Marlène Le Tertre
- INSERM Unité Mixte de Recherche (UMR) 1078, Etablissement Français du Sang-Bretagne, Institut Brestois Santé-Agro-Matière, Université Bretagne Loire-Université de Brest, Brest, France.,Service de Génétique Médicale, Centre Hospitalier Régional et Universitaire (CHRU) de Brest, Hôpital Morvan, Brest, France; and
| | - Kévin Uguen
- INSERM Unité Mixte de Recherche (UMR) 1078, Etablissement Français du Sang-Bretagne, Institut Brestois Santé-Agro-Matière, Université Bretagne Loire-Université de Brest, Brest, France.,Service de Génétique Médicale, Centre Hospitalier Régional et Universitaire (CHRU) de Brest, Hôpital Morvan, Brest, France; and
| | - Isabelle Gourlaouen
- INSERM Unité Mixte de Recherche (UMR) 1078, Etablissement Français du Sang-Bretagne, Institut Brestois Santé-Agro-Matière, Université Bretagne Loire-Université de Brest, Brest, France
| | - Claude Férec
- INSERM Unité Mixte de Recherche (UMR) 1078, Etablissement Français du Sang-Bretagne, Institut Brestois Santé-Agro-Matière, Université Bretagne Loire-Université de Brest, Brest, France.,Association Gaetan Saleun, Brest, France.,Service de Génétique Médicale, Centre Hospitalier Régional et Universitaire (CHRU) de Brest, Hôpital Morvan, Brest, France; and
| | - Chandran Ka
- INSERM Unité Mixte de Recherche (UMR) 1078, Etablissement Français du Sang-Bretagne, Institut Brestois Santé-Agro-Matière, Université Bretagne Loire-Université de Brest, Brest, France.,Service de Génétique Médicale, Centre Hospitalier Régional et Universitaire (CHRU) de Brest, Hôpital Morvan, Brest, France; and.,Laboratory of Excellence Laboratory of Excellence (GR-Ex), Paris, France
| | - Isabelle Callebaut
- Muséum National d'Histoire Naturelle, UMR Centre National de la Recherche Scientifique (CNRS) 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Sorbonne Université, Paris, France
| | - Gérald Le Gac
- INSERM Unité Mixte de Recherche (UMR) 1078, Etablissement Français du Sang-Bretagne, Institut Brestois Santé-Agro-Matière, Université Bretagne Loire-Université de Brest, Brest, France.,Service de Génétique Médicale, Centre Hospitalier Régional et Universitaire (CHRU) de Brest, Hôpital Morvan, Brest, France; and.,Laboratory of Excellence Laboratory of Excellence (GR-Ex), Paris, France
| |
Collapse
|
12
|
Vlasveld LT, Swinkels DW. Loss-of-function ferroportin disease: novel mechanistic insights and unanswered questions. Haematologica 2019; 103:1753-1755. [PMID: 30381414 DOI: 10.3324/haematol.2018.203315] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- L Tom Vlasveld
- Department of Internal Medicine, Haaglanden Medical Center, Location Bronovo, The Hague
| | - Dorine W Swinkels
- Translational Metabolic Laboratory, Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, the Netherlands
| |
Collapse
|
13
|
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: 4.8] [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.
Collapse
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.
| |
Collapse
|
14
|
Ferroportin downregulation promotes cell proliferation by modulating the Nrf2-miR-17-5p axis in multiple myeloma. Cell Death Dis 2019; 10:624. [PMID: 31423010 PMCID: PMC6698482 DOI: 10.1038/s41419-019-1854-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 07/19/2019] [Accepted: 07/26/2019] [Indexed: 12/20/2022]
Abstract
Recent findings demonstrate that aberrant downregulation of the iron-exporter protein, ferroportin (FPN1), is associated with poor prognosis and osteoclast differentiation in multiple myeloma (MM). Here, we show that FPN1 was downregulated in MM and that clustered regularly interspaced short palindromic repeat (CRISPR)-mediated FPN1 knockout promoted MM cell growth and survival. Using a microRNA target-scan algorithm, we identified miR-17-5p as an FPN1 regulator that promoted cell proliferation and cell cycle progression, and inhibited apoptosis—both in vitro and in vivo. miR-17-5p inhibited retarded tumor growth in a MM xenograft model. Moreover, restoring FPN1 expression at least partially abrogated the biological effects of miR-17-5p in MM cells. The cellular iron concentration regulated the expression of the iron-regulatory protein (IRP) via the 5′-untranslated region of IRP messenger RNA and modulated the post-transcriptional stability of FPN1. Bioinformatics analysis with subsequent chromatin immunoprecipitation-polymerase chain reaction and luciferase activity experiments revealed that the transcription factor Nrf2 drove FPN1 transcription through promoter binding and suppressed miR-17-5p (which also increased FPN1 expression). Nrf2-mediated FPN1 downregulation promoted intracellular iron accumulation and reactive oxygen species. Our study links FPN1 transcriptional and post-transcriptional regulation with MM cell growth and survival, and validates the prognostic value of FPN1 and its utility as a novel therapeutic target in MM.
Collapse
|
15
|
Hydrogen Gas Alleviates Chronic Intermittent Hypoxia-Induced Renal Injury through Reducing Iron Overload. Molecules 2019; 24:molecules24061184. [PMID: 30917568 PMCID: PMC6471060 DOI: 10.3390/molecules24061184] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 03/23/2019] [Accepted: 03/25/2019] [Indexed: 12/20/2022] Open
Abstract
Iron-induced oxidative stress has been found to be a central player in the pathogenesis of kidney injury. Recent studies have indicated H2 can be used as a novel antioxidant to protect cells. The present study was designed to investigate the protective effects of H2 against chronic intermittent hypoxia (CIH)-induced renal injury and its correlation mechanism involved in iron metabolism. We found that CIH-induced renal iron overloaded along with increased apoptosis and oxidative stress. Iron accumulates mainly occurred in the proximal tubule epithelial cells of rats as showed by Perl’s stain. Moreover, we found that CIH could promote renal transferrin receptor and divalent metal transporter-1 expression, inhibit ceruloplasmin expression. Renal injury, apoptosis and oxidative stress induced by CIH were strikingly attenuated in H2 treated rats. In conclusion, hydrogen may attenuate CIH-induced renal injury at least partially via inhibiting renal iron overload.
Collapse
|
16
|
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: 4.2] [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.
Collapse
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
| |
Collapse
|
17
|
Helgudottir SS, Lichota J, Burkhart A, Moos T. Hepcidin Mediates Transcriptional Changes in Ferroportin mRNA in Differentiated Neuronal-Like PC12 Cells Subjected to Iron Challenge. Mol Neurobiol 2018; 56:2362-2374. [DOI: 10.1007/s12035-018-1241-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 07/11/2018] [Indexed: 01/01/2023]
|
18
|
Ka C, Guellec J, Pepermans X, Kannengiesser C, Ged C, Wuyts W, Cassiman D, de Ledinghen V, Varet B, de Kerguenec C, Oudin C, Gourlaouen I, Lefebvre T, Férec C, Callebaut I, Le Gac G. The SLC40A1 R178Q mutation is a recurrent cause of hemochromatosis and is associated with a novel pathogenic mechanism. Haematologica 2018; 103:1796-1805. [PMID: 30002125 PMCID: PMC6278975 DOI: 10.3324/haematol.2018.189845] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 07/06/2018] [Indexed: 12/29/2022] Open
Abstract
Hemochromatosis type 4 is one of the most common causes of primary iron overload, after HFE-related hemochromatosis. It is an autosomal dominant disorder, primarily due to missense mutations in SLC40A1. This gene encodes ferroportin 1 (FPN1), which is the sole iron export protein reported in mammals. Not all heterozygous missense mutations in SLC40A1 are disease-causing. Due to phenocopies and an increased demand for genetic testing, rare SLC40A1 variations are fortuitously observed in patients with a secondary cause of hyperferritinemia. Structure/function analysis is the most effective way of establishing causality when clinical and segregation data are lacking. It can also provide important insights into the mechanism of iron egress and FPN1 regulation by hepcidin. The present study aimed to determine the pathogenicity of the previously reported p.Arg178Gln variant. We present the biological, clinical, histological and radiological findings of 22 patients from six independent families of French, Belgian or Iraqi decent. Despite phenotypic variability, all patients with p.Arg178Gln had elevated serum ferritin concentrations and normal to low transferrin saturation levels. In vitro experiments demonstrated that the p.Arg178Gln mutant reduces the ability of FPN1 to export iron without causing protein mislocalization. Based on a comparative model of the 3D structure of human FPN1 in an outward facing conformation, we argue that p.Arg178 is part of an interaction network modulating the conformational changes required for iron transport. We conclude that p.Arg178Gln represents a new category of loss-of-function mutations and that the study of “gating residues” is necessary in order to fully understand the action mechanism of FPN1.
Collapse
Affiliation(s)
- Chandran Ka
- UMR1078, INSERM, Université Bretagne Loire - Université de Bretagne Occidentale, Etablissement Français du Sang - Bretagne, Institut Brestois Santé-Agro-Matière, Brest, France.,Laboratoire de Génétique Moléculaire et Histocompatibilité, CHRU de Brest, Hôpital Morvan, France.,Laboratory of Excellence GR-Ex, Paris, France
| | - Julie Guellec
- UMR1078, INSERM, Université Bretagne Loire - Université de Bretagne Occidentale, Etablissement Français du Sang - Bretagne, Institut Brestois Santé-Agro-Matière, Brest, France.,Laboratory of Excellence GR-Ex, Paris, France.,Association Gaetan Saleun, Brest, France
| | - Xavier Pepermans
- Center for Human Genetics, University Hospital of St-Luc, Brussels, Belgium
| | - Caroline Kannengiesser
- Laboratory of Excellence GR-Ex, Paris, France.,UMR1149, INSERM, Centre de Recherche sur l'Inflammation, Université Paris Diderot, AP-HP, Hôpital Bichat, Département de Génétique, France.,On behalf of the French National Network for the Molecular Diagnosis of Inherited Iron Overload Disorders (J. Rochette, E. Cadet, C. Kannengiesser, H. Puy, C. Ged, H. de Verneuil, G. Le Gac, C. Férec, S. Pissard, V. Gérolami), Brest, France
| | - Cécile Ged
- On behalf of the French National Network for the Molecular Diagnosis of Inherited Iron Overload Disorders (J. Rochette, E. Cadet, C. Kannengiesser, H. Puy, C. Ged, H. de Verneuil, G. Le Gac, C. Férec, S. Pissard, V. Gérolami), Brest, France.,INSERM U1035, BMGIC, CHU de Bordeaux, Laboratoire de Biochimie et Biologie Moléculaire, France
| | - Wim Wuyts
- Department of Medical Genetics, University and University Hospital of Antwerp, Edegem, Belgium
| | - David Cassiman
- Department of Gastroenterology-Hepatology and Metabolic Center, University Hospital of Leuven, Belgium
| | - Victor de Ledinghen
- Department of Gastroenterology and Digestive Oncology, University Hospital of Bordeaux, France
| | - Bruno Varet
- Université Paris Descartes et AP-HP, Hôpital Necker, Service d'Hématologie, France
| | | | - Claire Oudin
- UMR1149, INSERM, Centre de Recherche sur l'Inflammation, Université Paris Diderot, AP-HP, Hôpital Bichat, Département de Génétique, France
| | - Isabelle Gourlaouen
- UMR1078, INSERM, Université Bretagne Loire - Université de Bretagne Occidentale, Etablissement Français du Sang - Bretagne, Institut Brestois Santé-Agro-Matière, Brest, France.,Laboratory of Excellence GR-Ex, Paris, France
| | - Thibaud Lefebvre
- UMR1149, INSERM, Centre de Recherche sur l'Inflammation, Université Paris Diderot, AP-HP, Hôpital Bichat, Département de Génétique, France
| | - Claude Férec
- UMR1078, INSERM, Université Bretagne Loire - Université de Bretagne Occidentale, Etablissement Français du Sang - Bretagne, Institut Brestois Santé-Agro-Matière, Brest, France.,Laboratoire de Génétique Moléculaire et Histocompatibilité, CHRU de Brest, Hôpital Morvan, France.,On behalf of the French National Network for the Molecular Diagnosis of Inherited Iron Overload Disorders (J. Rochette, E. Cadet, C. Kannengiesser, H. Puy, C. Ged, H. de Verneuil, G. Le Gac, C. Férec, S. Pissard, V. Gérolami), Brest, France
| | - Isabelle Callebaut
- UMR7590, CNRS, Sorbonne Universités, Université Pierre et Marie Curie-Paris, France
| | - Gérald Le Gac
- UMR1078, INSERM, Université Bretagne Loire - Université de Bretagne Occidentale, Etablissement Français du Sang - Bretagne, Institut Brestois Santé-Agro-Matière, Brest, France .,Laboratoire de Génétique Moléculaire et Histocompatibilité, CHRU de Brest, Hôpital Morvan, France.,Laboratory of Excellence GR-Ex, Paris, France.,On behalf of the French National Network for the Molecular Diagnosis of Inherited Iron Overload Disorders (J. Rochette, E. Cadet, C. Kannengiesser, H. Puy, C. Ged, H. de Verneuil, G. Le Gac, C. Férec, S. Pissard, V. Gérolami), Brest, France
| |
Collapse
|
19
|
Abstract
Haemochromatosis is defined as systemic iron overload of genetic origin, caused by a reduction in the concentration of the iron regulatory hormone hepcidin, or a reduction in hepcidin-ferroportin binding. Hepcidin regulates the activity of ferroportin, which is the only identified cellular iron exporter. The most common form of haemochromatosis is due to homozygous mutations (specifically, the C282Y mutation) in HFE, which encodes hereditary haemochromatosis protein. Non-HFE forms of haemochromatosis due to mutations in HAMP, HJV or TFR2 are much rarer. Mutations in SLC40A1 (also known as FPN1; encoding ferroportin) that prevent hepcidin-ferroportin binding also cause haemochromatosis. Cellular iron excess in HFE and non-HFE forms of haemochromatosis is caused by increased concentrations of plasma iron, which can lead to the accumulation of iron in parenchymal cells, particularly hepatocytes, pancreatic cells and cardiomyocytes. Diagnosis is noninvasive and includes clinical examination, assessment of plasma iron parameters, imaging and genetic testing. The mainstay therapy is phlebotomy, although iron chelation can be used in some patients. Hepcidin supplementation might be an innovative future approach.
Collapse
Affiliation(s)
- Pierre Brissot
- INSERM, Univ. Rennes, INRA, Institut NUMECAN (Nutrition Metabolisms and Cancer) UMR_A 1341, UMR_S 1241, F-35000 Rennes, France
| | - Antonello Pietrangelo
- Division of Internal Medicine 2 and Center for Haemochromatosis, University Hospital of Modena, Modena, Italy
| | - Paul C. Adams
- Department of Medicine, University of Western Ontario, London, Ontario, Canada
| | - Barbara de Graaff
- Menzies Institute for Medical Research, University of Tasmania, Tasmania, Australia
| | | | - Olivier Loréal
- INSERM, Univ. Rennes, INRA, Institut NUMECAN (Nutrition Metabolisms and Cancer) UMR_A 1341, UMR_S 1241, F-35000 Rennes, France
| |
Collapse
|
20
|
Bonaccorsi di Patti MC, Cutone A, Polticelli F, Rosa L, Lepanto MS, Valenti P, Musci G. The ferroportin-ceruloplasmin system and the mammalian iron homeostasis machine: regulatory pathways and the role of lactoferrin. Biometals 2018; 31:399-414. [PMID: 29453656 DOI: 10.1007/s10534-018-0087-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 02/14/2018] [Indexed: 02/08/2023]
Abstract
In the last 20 years, several new genes and proteins involved in iron metabolism in eukaryotes, particularly related to pathological states both in animal models and in humans have been identified, and we are now starting to unveil at the molecular level the mechanisms of iron absorption, the regulation of iron transport and the homeostatic balancing processes. In this review, we will briefly outline the general scheme of iron metabolism in humans and then focus our attention on the cellular iron export system formed by the permease ferroportin and the ferroxidase ceruloplasmin. We will finally summarize data on the role of the iron binding protein lactoferrin on the regulation of the ferroportin/ceruloplasmin couple and of other proteins involved in iron homeostasis in inflamed human macrophages.
Collapse
Affiliation(s)
| | - Antimo Cutone
- Department of Biosciences and Territory, University of Molise, C.da Fonte Lappone, 86090, Pesche, IS, Italy
| | - Fabio Polticelli
- Department of Sciences, University Roma Tre, Rome, Italy.,National Institute of Nuclear Physics, Roma Tre Section, Rome, Italy
| | - Luigi Rosa
- Department of Public Health and Infectious Diseases, Sapienza University, Rome, Italy
| | | | - Piera Valenti
- Department of Public Health and Infectious Diseases, Sapienza University, Rome, Italy
| | - Giovanni Musci
- Department of Biosciences and Territory, University of Molise, C.da Fonte Lappone, 86090, Pesche, IS, Italy.
| |
Collapse
|
21
|
Tortosa V, Bonaccorsi di Patti MC, Brandi V, Musci G, Polticelli F. An improved structural model of the human iron exporter ferroportin. Insight into the role of pathogenic mutations in hereditary hemochromatosis type 4. BIO-ALGORITHMS AND MED-SYSTEMS 2017. [DOI: 10.1515/bams-2017-0029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
AbstractFerroportin (Fpn) is a membrane protein representing the major cellular iron exporter, essential for metal translocation from cells into plasma. Despite its pivotal role in human iron homeostasis, many questions on Fpn structure and biology remain unanswered. In this work, we present two novel and more reliable structural models of human Fpn (hFpn; inward-facing and outward-facing conformations) obtained using as templates the recently solved crystal structures of a bacterial homologue of hFpn,
Collapse
|
22
|
Structure-function analysis of ferroportin defines the binding site and an alternative mechanism of action of hepcidin. Blood 2017; 131:899-910. [PMID: 29237594 DOI: 10.1182/blood-2017-05-786590] [Citation(s) in RCA: 210] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 11/30/2017] [Indexed: 02/07/2023] Open
Abstract
Nonclassical ferroportin disease (FD) is a form of hereditary hemochromatosis caused by mutations in the iron transporter ferroportin (Fpn), resulting in parenchymal iron overload. Fpn is regulated by the hormone hepcidin, which induces Fpn endocytosis and cellular iron retention. We characterized 11 clinically relevant and 5 nonclinical Fpn mutations using stably transfected, inducible isogenic cell lines. All clinical mutants were functionally resistant to hepcidin as a consequence of either impaired hepcidin binding or impaired hepcidin-dependent ubiquitination despite intact hepcidin binding. Mapping the residues onto 2 computational models of the human Fpn structure indicated that (1) mutations that caused ubiquitination-resistance were positioned at helix-helix interfaces, likely preventing the hepcidin-induced conformational change, (2) hepcidin binding occurred within the central cavity of Fpn, (3) hepcidin interacted with up to 4 helices, and (4) hepcidin binding should occlude Fpn and interfere with iron export independently of endocytosis. We experimentally confirmed hepcidin-mediated occlusion of Fpn in the absence of endocytosis in multiple cellular systems: HEK293 cells expressing an endocytosis-defective Fpn mutant (K8R), Xenopus oocytes expressing wild-type or K8R Fpn, and mature human red blood cells. We conclude that nonclassical FD is caused by Fpn mutations that decrease hepcidin binding or hinder conformational changes required for ubiquitination and endocytosis of Fpn. The newly documented ability of hepcidin and its agonists to occlude iron transport may facilitate the development of broadly effective treatments for hereditary iron overload disorders.
Collapse
|
23
|
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: 87] [Impact Index Per Article: 12.4] [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.
Collapse
Affiliation(s)
- Antonello Pietrangelo
- Center for Hemochromatosis, Department of Internal Medicine II, University of Modena and Reggio Emilia Policlinico, Modena, Italy
| |
Collapse
|
24
|
Hamp1 but not Hamp2 regulates ferroportin in fish with two functionally distinct hepcidin types. Sci Rep 2017; 7:14793. [PMID: 29093559 PMCID: PMC5665920 DOI: 10.1038/s41598-017-14933-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 10/18/2017] [Indexed: 01/01/2023] Open
Abstract
Hepcidin is a small cysteine rich peptide that regulates the sole known cellular iron exporter, ferroportin, effectively controlling iron metabolism. Contrary to humans, where a single hepcidin exists, many fish have two functionally distinct hepcidin types, despite having a single ferroportin gene. This raises the question of whether ferroportin is similarly regulated by the iron regulator Hamp1 and the antimicrobial Hamp2. In sea bass (Dicentrarchus labrax), iron overload prompted a downregulation of ferroportin, associated with an upregulation of hamp1, whereas an opposite response was observed during anemia, with no changes in hamp2 in either situation. During infection, ferroportin expression decreased, indicating iron withholding to avoid microbial proliferation. In vivo administration of Hamp1 but not Hamp2 synthetic peptides caused significant reduction in ferroportin expression, indicating that in teleost fish with two hepcidin types, ferroportin activity is mediated through the iron-regulator Hamp1, and not through the dedicated antimicrobial Hamp2. Additionally, in vitro treatment of mouse macrophages with fish Hamp1 but not Hamp2 caused a decrease in ferroportin levels. These results raise questions on the evolution of hepcidin and ferroportin functional partnership and open new possibilities for the pharmaceutical use of selected fish Hamp2 hepcidins during infections, with no impact on iron homeostasis.
Collapse
|
25
|
Wallace DF, McDonald CJ, Ostini L, Iser D, Tuckfield A, Subramaniam VN. The dynamics of hepcidin-ferroportin internalization and consequences of a novel ferroportin disease mutation. Am J Hematol 2017; 92:1052-1061. [PMID: 28681497 DOI: 10.1002/ajh.24844] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 06/29/2017] [Accepted: 06/30/2017] [Indexed: 12/31/2022]
Abstract
The hepcidin-ferroportin axis underlies the pathophysiology of many iron-associated disorders and is a key target for the development of therapeutics for treating iron-associated disorders. The aims of this study were to investigate the dynamics of hepcidin-mediated ferroportin internalization and the consequences of a novel disease-causing mutation on ferroportin function. Specific reagents for ferroportin are limited; we developed and characterized antibodies against the largest extracellular loop of ferroportin and developed a novel cell-based assay for studying hepcidin-ferroportin function. We show that hepcidin-mediated ferroportin internalization is a rapid process and could be induced using low concentrations of hepcidin. Targeted next-generation sequencing utilizing an iron metabolism gene panel developed in our group identified a novel ferroportin p.D84E variant in a patient with iron overload. Wild-type and mutant ferroportin constructs were generated, transfected into HEK293 cells and analysed using an all-in-one flow-cytometry-based assay to study the effects on hepcidin-mediated internalization and iron transport. Consistent with the classical phenotype of ferroportin disease, the p.D84E mutation results in an inability to transport iron and hepcidin insensitivity. These results validate a recently proposed 3D-structural model of ferroportin and highlight the significance of this variant in the structure and function of ferroportin. Our novel ferroportin antibody and assay will be valuable tools for investigating the regulation of hepcidin/ferroportin function and the development of novel approaches for the therapeutic modulation of iron homeostasis.
Collapse
Affiliation(s)
- Daniel F. Wallace
- Institute of Health and Biomedical Innovation and School of Biomedical Sciences. Queensland University of Technology (QUT); Brisbane Queensland Australia
- Membrane Transport Laboratory; QIMR Berghofer Medical Research Institute; Brisbane Queensland Australia
| | - Cameron J. McDonald
- Membrane Transport Laboratory; QIMR Berghofer Medical Research Institute; Brisbane Queensland Australia
| | - Lesa Ostini
- Membrane Transport Laboratory; QIMR Berghofer Medical Research Institute; Brisbane Queensland Australia
| | - David Iser
- Department of Gastroenterology; St Vincent's Hospital; Fitzroy Victoria Australia
| | | | - V. Nathan Subramaniam
- Institute of Health and Biomedical Innovation and School of Biomedical Sciences. Queensland University of Technology (QUT); Brisbane Queensland Australia
- Membrane Transport Laboratory; QIMR Berghofer Medical Research Institute; Brisbane Queensland Australia
| |
Collapse
|
26
|
Le Tertre M, Ka C, Guellec J, Gourlaouen I, Férec C, Callebaut I, Le Gac G. Deciphering the molecular basis of ferroportin resistance to hepcidin: Structure/function analysis of rare SLC40A1 missense mutations found in suspected hemochromatosis type 4 patients. Transfus Clin Biol 2017; 24:462-467. [PMID: 28826751 DOI: 10.1016/j.tracli.2017.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 07/20/2017] [Indexed: 01/25/2023]
Abstract
Genetic medicine applied to the study of hemochromatosis has identified the systemic loop controlling iron homeostasis, centered on hepcidin-ferroportin interaction. Current challenges are to dissect the molecular pathways underlying liver hepcidin synthesis in response to circulatory iron, HFE, TFR2, HJV, TMPRSS6 and BMP6 functions, and to define the major structural elements of hepcidin-ferroportin interaction. We built a first 3D model of human ferroportin structure, using the crystal structure of EmrD, a bacterial drug efflux transporter of the Major Facilitator Superfamily, as template. The model enabled study of disease-associated mutations, and guided mutagenesis experiments to determine the role of conserved residues in protein stability and iron transport. Results revealed novel amino acids that are critical for the iron export function and the hepcidin-mediated inhibition mechanism: for example, tryptophan 42, localized in the extracellular end of the ferroportin pore and involved in both biological functions. Here, we propose a strategy that is not limited to structure analysis, but integrates information from different sources, including human disease-associated mutations and functional in vitro assays. The first major hypothesis of this PhD thesis is that ferroportin resistance to hepcidin relies on different molecular mechanisms that are critical for ferroportin endocytosis, and include at least three fundamental steps: (i) hepcidin binding to ferroportin, (ii) structural reorganization of the N- and C-ter ferroportin lobes, and (iii) ferroportin ubiquitination.
Collapse
Affiliation(s)
- M Le Tertre
- Inserm UMR1078, faculté de médecine et des sciences de la santé, université Bretagne Loire-université de Bretagne Occidentale, IBSAM, IBRBS, 22, rue Camille-Desmoulins, 29200 Brest, France; Laboratory of Excellence GR-Ex, institut Imagine, 24, boulevard du Montparnasse, 75015, Paris, France; Laboratoire de génétique moléculaire et histocompatibilité, hôpital Morvan, CHRU de Brest, 2, avenue Foch, 29200 Brest, France.
| | - C Ka
- Inserm UMR1078, faculté de médecine et des sciences de la santé, université Bretagne Loire-université de Bretagne Occidentale, IBSAM, IBRBS, 22, rue Camille-Desmoulins, 29200 Brest, France; Laboratory of Excellence GR-Ex, institut Imagine, 24, boulevard du Montparnasse, 75015, Paris, France; Laboratoire de génétique moléculaire et histocompatibilité, hôpital Morvan, CHRU de Brest, 2, avenue Foch, 29200 Brest, France
| | - J Guellec
- Inserm UMR1078, faculté de médecine et des sciences de la santé, université Bretagne Loire-université de Bretagne Occidentale, IBSAM, IBRBS, 22, rue Camille-Desmoulins, 29200 Brest, France; Laboratory of Excellence GR-Ex, institut Imagine, 24, boulevard du Montparnasse, 75015, Paris, France; Association Gaetan-Saleun, 29, rue Félix-Le-Dantec, 29200 Brest, France
| | - I Gourlaouen
- Inserm UMR1078, faculté de médecine et des sciences de la santé, université Bretagne Loire-université de Bretagne Occidentale, IBSAM, IBRBS, 22, rue Camille-Desmoulins, 29200 Brest, France; Laboratory of Excellence GR-Ex, institut Imagine, 24, boulevard du Montparnasse, 75015, Paris, France; Établissement français du sang, Bretagne, site de Brest, 46 rue Félix-Le-Dantec, 29200 Brest, France
| | - C Férec
- Inserm UMR1078, faculté de médecine et des sciences de la santé, université Bretagne Loire-université de Bretagne Occidentale, IBSAM, IBRBS, 22, rue Camille-Desmoulins, 29200 Brest, France; Laboratoire de génétique moléculaire et histocompatibilité, hôpital Morvan, CHRU de Brest, 2, avenue Foch, 29200 Brest, France; Établissement français du sang, Bretagne, site de Brest, 46 rue Félix-Le-Dantec, 29200 Brest, France
| | - I Callebaut
- Muséum d'histoire naturelle, IRD UMR 206, case 115, IMPMC, Sorbonne universités-UMR CNRS 7590, UPMC université Paris 06, 4, place Jussieu, 75252 Paris cedex 05, France
| | - G Le Gac
- Inserm UMR1078, faculté de médecine et des sciences de la santé, université Bretagne Loire-université de Bretagne Occidentale, IBSAM, IBRBS, 22, rue Camille-Desmoulins, 29200 Brest, France; Laboratory of Excellence GR-Ex, institut Imagine, 24, boulevard du Montparnasse, 75015, Paris, France; Laboratoire de génétique moléculaire et histocompatibilité, hôpital Morvan, CHRU de Brest, 2, avenue Foch, 29200 Brest, France; Établissement français du sang, Bretagne, site de Brest, 46 rue Félix-Le-Dantec, 29200 Brest, France
| |
Collapse
|
27
|
Wu J, Bao L, Zhang Z, Yi X. Nrf2 induces cisplatin resistance via suppressing the iron export related gene SLC40A1 in ovarian cancer cells. Oncotarget 2017; 8:93502-93515. [PMID: 29212168 PMCID: PMC5706814 DOI: 10.18632/oncotarget.19548] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 03/21/2017] [Indexed: 11/25/2022] Open
Abstract
Induction of Nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) has been demonstrated to be involved in cisplatin resistance in ovarian cancer. Solute carrier family 40 member 1 (SLC40A1) is an iron exporter, which possesses many putative Nrf2 binding sites. Here we hypothesize that it may be a possible downstream gene of Nrf2. Elevated level of Nrf2 and reduced level of SLC40A1 were found in cisplatin–resistant ovarian cancer cells as compared with cisplatin-sensitive ovarian cancer cells. Exogenous knockdown of Nrf2 leaded to increased expression of SLC40A1. While overexpression of Nrf2 resulted in decreased expression of SLC40A1. Chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assay revealed that Nrf2 inhibited the transcription of SLC40A1. Overexpression of SLC40A1 was able to reverse cisplatin resistance induced by Nrf2, while knockdown of SLC40A1 restored cisplatin resistance and increased iron concentration. Desferal, an iron chelator, was found to overcome cisplatin resistance through iron deprivation. Its function was boosted when combined with brusatol, an Nrf2 inhibitor. Taken together, this study first demonstrated that Nrf2 could transcriptionally suppress the expression of SLC40A1. Iron overload induced by SLC40A1 resulted in cisplatin resistance in ovarian cancer. Targeting iron metabolism may be a new therapeutic strategy to reverse drug resistance in ovarian cancer treatment.
Collapse
Affiliation(s)
- Jianfa Wu
- Department of Gynecology, Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China.,Department of Obstetrics and Gynecology of Shanghai Medical School, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, Shanghai, China
| | - Lingjie Bao
- Department of Gynecology, Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China.,Department of Obstetrics and Gynecology of Shanghai Medical School, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, Shanghai, China
| | - Zhenbo Zhang
- Department of Obstetrics and Gynecology, Shanghai First People's Hospital, Shanghai Jiaotong University, Shanghai, China
| | - Xiaofang Yi
- Department of Gynecology, Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China.,Department of Obstetrics and Gynecology of Shanghai Medical School, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, Shanghai, China
| |
Collapse
|
28
|
Crielaard BJ, Lammers T, Rivella S. Targeting iron metabolism in drug discovery and delivery. Nat Rev Drug Discov 2017; 16:400-423. [PMID: 28154410 PMCID: PMC5455971 DOI: 10.1038/nrd.2016.248] [Citation(s) in RCA: 235] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Iron fulfils a central role in many essential biochemical processes in human physiology; thus, proper processing of iron is crucial. Although iron metabolism is subject to relatively strict physiological control, numerous disorders, such as cancer and neurodegenerative diseases, have recently been linked to deregulated iron homeostasis. Consequently, iron metabolism constitutes a promising and largely unexploited therapeutic target for the development of new pharmacological treatments for these diseases. Several iron metabolism-targeted therapies are already under clinical evaluation for haematological disorders, and these and newly developed therapeutic agents are likely to have substantial benefit in the clinical management of iron metabolism-associated diseases, for which few efficacious treatments are currently available.
Collapse
Affiliation(s)
- Bart J. Crielaard
- Department of Polymer Chemistry and Bioengineering, Zernike Institute for Advanced Materials, Faculty of Mathematics and Natural Sciences, University of Groningen, Groningen, The Netherlands
- W.J. Kolff Institute for Biomedical Engineering and Materials Science, University Medical Center Groningen, Groningen, The Netherlands
| | - Twan Lammers
- Department of Nanomedicine and Theranostics, Institute for Experimental Molecular Imaging, University Clinic and Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Aachen, Germany
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands
- Department of Targeted Therapeutics, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
| | - Stefano Rivella
- Children’s Hospital of Philadelphia, Abramson Research Center, Philadelphia, PA, United States of America
| |
Collapse
|
29
|
Sabelli M, Montosi G, Garuti C, Caleffi A, Oliveto S, Biffo S, Pietrangelo A. Human macrophage ferroportin biology and the basis for the ferroportin disease. Hepatology 2017; 65:1512-1525. [PMID: 28027576 PMCID: PMC5413859 DOI: 10.1002/hep.29007] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 12/15/2016] [Indexed: 01/01/2023]
Abstract
Ferroportin (FPN1) is the sole iron exporter in mammals, but its cell-specific function and regulation are still elusive. This study examined FPN1 expression in human macrophages, the cells that are primarily responsible on a daily basis for plasma iron turnover and are central in the pathogenesis of ferroportin disease (FD), the disease attributed to lack-of-function FPN1 mutations. We characterized FPN1 protein expression and traffic by confocal microscopy, western blotting, gel filtration, and immunoprecipitation studies in macrophages from control blood donors (donor) and patients with either FPN1 p.A77D, p.G80S, and p.Val162del lack-of-function or p.A69T gain-of-function mutations. We found that in normal macrophages, FPN1 cycles in the early endocytic compartment does not multimerize and is promptly degraded by hepcidin (Hepc), its physiological inhibitor, within 3-6 hours. In FD macrophages, endogenous FPN1 showed a similar localization, except for greater accumulation in lysosomes. However, in contrast with previous studies using overexpressed mutant protein in cell lines, FPN1 could still reach the cell surface and be normally internalized and degraded upon exposure to Hepc. However, when FD macrophages were exposed to large amounts of heme iron, in contrast to donor and p.A69T macrophages, FPN1 could no longer reach the cell surface, leading to intracellular iron retention. CONCLUSION FPN1 cycles as a monomer within the endocytic/plasma membrane compartment and responds to its physiological inhibitor, Hepc, in both control and FD cells. However, in FD, FPN1 fails to reach the cell surface when cells undergo high iron turnover. Our findings provide a basis for the FD characterized by a preserved iron transfer in the enterocytes (i.e., cells with low iron turnover) and iron retention in cells exposed to high iron flux, such as liver and spleen macrophages. (Hepatology 2017;65:1512-1525).
Collapse
Affiliation(s)
- Manuela Sabelli
- Division of Internal Medicine 2 and Center for HemochromatosisUniversity Hospital of ModenaModenaItaly
| | - Giuliana Montosi
- Division of Internal Medicine 2 and Center for HemochromatosisUniversity Hospital of ModenaModenaItaly
| | - Cinzia Garuti
- Division of Internal Medicine 2 and Center for HemochromatosisUniversity Hospital of ModenaModenaItaly
| | - Angela Caleffi
- Division of Internal Medicine 2 and Center for HemochromatosisUniversity Hospital of ModenaModenaItaly
| | | | - Stefano Biffo
- INGM, ‘Romeo ed Enrica Invernizzi’MilanoItaly
- Department of BiosciencesUniversity of MilanMilanItaly
| | - Antonello Pietrangelo
- Division of Internal Medicine 2 and Center for HemochromatosisUniversity Hospital of ModenaModenaItaly
| |
Collapse
|
30
|
Sheokand N, Malhotra H, Chauhan AS, Kumar M, Chaudhary S, Patidar A, Boradia VM, Raje CI, Raje M. Reverse overshot water-wheel retroendocytosis of apotransferrin extrudes cellular iron. J Cell Sci 2016; 129:843-53. [PMID: 26743084 DOI: 10.1242/jcs.180356] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 12/29/2015] [Indexed: 01/17/2023] Open
Abstract
Iron (Fe), a vital micronutrient for all organisms, must be managed judiciously because both deficiency or excess can trigger severe pathology. Although cellular Fe import is well understood, its export is thought to be limited to transmembrane extrusion through ferroportin (also known as Slc40a1), the only known mammalian Fe exporter. Utilizing primary cells and cell lines (including those with no discernible expression of ferroportin on their surface), we demonstrate that upon Fe loading, the multifunctional enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which is recruited to the cell surface, 'treadmills' apotransferrin in and out of the cell. Kinetic analysis utilizing labeled ligand, GAPDH-knockdown cells, (55)Fe-labeled cells and pharmacological inhibitors of endocytosis confirmed GAPDH-dependent apotransferrin internalization as a prerequisite for cellular Fe export. These studies define an unusual rapid recycling process of retroendocytosis for cellular Fe extrusion, a process mirroring receptor mediated internalization that has never before been considered for maintenance of cellular cationic homeostasis. Modulation of this unusual pathway could provide insights for management of Fe overload disorders.
Collapse
Affiliation(s)
- Navdeep Sheokand
- Institute of Microbial Technology, CSIR, Sector 39A, Chandigarh 160036, India
| | - Himanshu Malhotra
- Institute of Microbial Technology, CSIR, Sector 39A, Chandigarh 160036, India
| | - Anoop Singh Chauhan
- Institute of Microbial Technology, CSIR, Sector 39A, Chandigarh 160036, India
| | - Manoj Kumar
- Institute of Microbial Technology, CSIR, Sector 39A, Chandigarh 160036, India
| | - Surbhi Chaudhary
- Institute of Microbial Technology, CSIR, Sector 39A, Chandigarh 160036, India
| | - Anil Patidar
- Institute of Microbial Technology, CSIR, Sector 39A, Chandigarh 160036, India
| | - Vishant Mahendra Boradia
- National Institute of Pharmaceutical Education & Research, Phase X, Sector 67, SAS Nagar, Punjab 160062, India
| | - Chaaya Iyengar Raje
- National Institute of Pharmaceutical Education & Research, Phase X, Sector 67, SAS Nagar, Punjab 160062, India
| | - Manoj Raje
- Institute of Microbial Technology, CSIR, Sector 39A, Chandigarh 160036, India
| |
Collapse
|
31
|
Bonaccorsi di Patti MC, Polticelli F, Tortosa V, Furbetta PA, Musci G. A bacterial homologue of the human iron exporter ferroportin. FEBS Lett 2015; 589:3829-35. [PMID: 26608034 DOI: 10.1016/j.febslet.2015.11.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 11/13/2015] [Accepted: 11/16/2015] [Indexed: 10/22/2022]
Abstract
A bacterial homologue of the human iron exporter ferroportin found in the predatory Gram-negative bacterium Bdellovibrio bacteriovorus has been investigated. Molecular modelling, expression in recombinant form and iron binding and transport assays demonstrate that B. bacteriovorus ferroportin (bdFpn) is indeed an orthologue of human ferroportin. Key residues corresponding to those essential for iron binding and transport in human ferroportin are conserved in the bacterial homologue and are predicted to be correctly clustered in the central cavity of the protein. Mutation of these residues grossly affects the iron binding and transport ability of bdFpn.
Collapse
Affiliation(s)
| | - Fabio Polticelli
- Department of Sciences, Roma Tre University, Rome, Italy; National Institute of Nuclear Physics, Roma Tre Section, Rome, Italy.
| | | | | | - Giovanni Musci
- Department of Biosciences and Territory, University of Molise, Pesche, Italy.
| |
Collapse
|
32
|
Taniguchi R, Kato HE, Font J, Deshpande CN, Wada M, Ito K, Ishitani R, Jormakka M, Nureki O. Outward- and inward-facing structures of a putative bacterial transition-metal transporter with homology to ferroportin. Nat Commun 2015; 6:8545. [PMID: 26461048 PMCID: PMC4633820 DOI: 10.1038/ncomms9545] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 09/03/2015] [Indexed: 12/21/2022] Open
Abstract
In vertebrates, the iron exporter ferroportin releases Fe2+ from cells into plasma, thereby maintaining iron homeostasis. The transport activity of ferroportin is suppressed by the peptide hormone hepcidin, which exhibits upregulated expression in chronic inflammation, causing iron-restrictive anaemia. However, due to the lack of structural information about ferroportin, the mechanisms of its iron transport and hepcidin-mediated regulation remain largely elusive. Here we report the crystal structures of a putative bacterial homologue of ferroportin, BbFPN, in both the outward- and inward-facing states. Despite undetectable sequence similarity, BbFPN adopts the major facilitator superfamily fold. A comparison of the two structures reveals that BbFPN undergoes an intra-domain conformational rearrangement during the transport cycle. We identify a substrate metal-binding site, based on structural and mutational analyses. Furthermore, the BbFPN structures suggest that a predicted hepcidin-binding site of ferroportin is located within its central cavity. Thus, BbFPN may be a valuable structural model for iron homeostasis regulation by ferroportin. Iron export from vertebrate cells is mediated by ferroportin, which is suppressed by the peptide hormone hepcidin. Taniguchi et al. present crystal structures of a putative bacterial ferroportin homologue in both outward- and inward-facing states, providing insight into its transport mechanism.
Collapse
Affiliation(s)
- Reiya Taniguchi
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.,Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Hideaki E Kato
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.,Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Josep Font
- Structural Biology Program, Centenary Institute, Locked Bag 6, Sydney, New South Wales 2042, Australia.,Faculty of Medicine, Central Clinical School, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Chandrika N Deshpande
- Structural Biology Program, Centenary Institute, Locked Bag 6, Sydney, New South Wales 2042, Australia.,Faculty of Medicine, Central Clinical School, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Miki Wada
- Technical office, The Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
| | - Koichi Ito
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
| | - Ryuichiro Ishitani
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.,Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Mika Jormakka
- Structural Biology Program, Centenary Institute, Locked Bag 6, Sydney, New South Wales 2042, Australia.,Faculty of Medicine, Central Clinical School, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.,Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| |
Collapse
|
33
|
Protein moonlighting in iron metabolism: glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Biochem Soc Trans 2015; 42:1796-801. [PMID: 25399609 DOI: 10.1042/bst20140220] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Iron is essential for the survival of both prokaryotic and eukaryotic organisms. It functions as a cofactor for several vital enzymes and iron deprivation is fatal to cells. However, at the same time, excess amounts of iron are also toxic to cells due to the formation of free radicals via the Fenton reaction. As a consequence of its double-edged behaviour, the uptake and regulation of iron involves an intricate balance of acquisition, trafficking, recycling and shuffling between various tissues and organs. This is accomplished by differential regulation of genes involving numerous proteins and enzymes. Several of the proteins identified in these processes, such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH), aconitase and lactoferrin (Lf), possess multiple functions within the cell. Such proteins are referred to as moonlighting or multifunctional proteins, whereby proteins initially thought to possess a single well-established function have subsequently been discovered to exhibit alternative functions. In many cases, these multiple functions are conserved across species.
Collapse
|
34
|
Chen SR, Yang LQ, Chong YT, Jie YS, Wu YK, Yang J, Lin GL, Li XH. Novel gain of function mutation in the SLC40A1 gene associated with hereditary haemochromatosis type 4. Intern Med J 2015; 45:672-6. [PMID: 26059880 DOI: 10.1111/imj.12764] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 02/28/2015] [Indexed: 02/05/2023]
Abstract
Here we report the case of a 69-year-old Chinese Han woman who presented with liver cirrhosis, diabetes mellitus, skin hyperpigmentation, hyperferritinaemia and high transferrin saturation. Subsequent genetic analyses identified a novel heterozygous mutation (p.Cys326Phe) in the SLC40A1 gene. This is the first report regarding a SLC40A1 mutation in the Chinese Han population and provides novel clinical evidence for the importance of p.Cys326 in SLC40A1 gene function.
Collapse
Affiliation(s)
- S-R Chen
- Department of Infectious Diseases, The Third Affiliated Hospital of Sun-Yat-Sen University, GuangZhou, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, GuangZhou, China
| | - L-Q Yang
- Department of Infectious Diseases, The First People's Hospital of YueYang, YueYang, China
| | - Y-T Chong
- Department of Infectious Diseases, The Third Affiliated Hospital of Sun-Yat-Sen University, GuangZhou, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, GuangZhou, China
| | - Y-S Jie
- Department of Infectious Diseases, The Third Affiliated Hospital of Sun-Yat-Sen University, GuangZhou, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, GuangZhou, China
| | - Y-K Wu
- Department of Infectious Diseases, The Third Affiliated Hospital of Sun-Yat-Sen University, GuangZhou, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, GuangZhou, China
| | - J Yang
- Department of Infectious Diseases, The First People's Hospital of YueYang, YueYang, China
| | - G-L Lin
- Department of Infectious Diseases, The Third Affiliated Hospital of Sun-Yat-Sen University, GuangZhou, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, GuangZhou, China
| | - X-H Li
- Department of Infectious Diseases, The Third Affiliated Hospital of Sun-Yat-Sen University, GuangZhou, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, GuangZhou, China
| |
Collapse
|
35
|
Structural comparison, substrate specificity, and inhibitor binding of AGPase small subunit from monocot and dicot: present insight and future potential. BIOMED RESEARCH INTERNATIONAL 2014; 2014:583606. [PMID: 25276800 PMCID: PMC4167649 DOI: 10.1155/2014/583606] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 04/08/2014] [Accepted: 04/21/2014] [Indexed: 11/18/2022]
Abstract
ADP-glucose pyrophosphorylase (AGPase) is the first rate limiting enzyme of starch biosynthesis pathway and has been exploited as the target for greater starch yield in several plants. The structure-function analysis and substrate binding specificity of AGPase have provided enormous potential for understanding the role of specific amino acid or motifs responsible for allosteric regulation and catalytic mechanisms, which facilitate the engineering of AGPases. We report the three-dimensional structure, substrate, and inhibitor binding specificity of AGPase small subunit from different monocot and dicot crop plants. Both monocot and dicot subunits were found to exploit similar interactions with the substrate and inhibitor molecule as in the case of their closest homologue potato tuber AGPase small subunit. Comparative sequence and structural analysis followed by molecular docking and electrostatic surface potential analysis reveal that rearrangements of secondary structure elements, substrate, and inhibitor binding residues are strongly conserved and follow common folding pattern and orientation within monocot and dicot displaying a similar mode of allosteric regulation and catalytic mechanism. The results from this study along with site-directed mutagenesis complemented by molecular dynamics simulation will shed more light on increasing the starch content of crop plants to ensure the food security worldwide.
Collapse
|
36
|
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: 1.0] [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.
Collapse
|
37
|
Bonaccorsi di Patti MC, Polticelli F, Cece G, Cutone A, Felici F, Persichini T, Musci G. A structural model of human ferroportin and of its iron binding site. FEBS J 2014; 281:2851-60. [PMID: 24767627 DOI: 10.1111/febs.12825] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 03/17/2014] [Accepted: 04/24/2014] [Indexed: 11/29/2022]
Abstract
A structural model of human ferroportin has been built using two Escherichia coli proteins belonging to the major facilitator superfamily of transporters. A potential iron binding site was identified in the inward-open conformation of the model, and its relevance was tested through measurement of iron export of HEK293T cells expressing wild-type or mutated ferroportin. Aspartates 39 and 181 were found to be essential for the transport ability of the protein. Noteworthy, the D181V mutation is naturally found in type 4 hemochromatosis with reticuloendothelial system iron retention phenotype. The outward-open conformation of ferroportin was also predicted, and showed that significant conformational changes must occur in the inward- to outward-open transition of ferroportin. In particular, putative iron ligands move several ångströms away from each other, leading to the logical conclusion that the iron binding site is not occupied by the metal in the outward-open conformation of ferroportin.
Collapse
|
38
|
Callebaut I, Joubrel R, Pissard S, Kannengiesser C, Gérolami V, Ged C, Cadet E, Cartault F, Ka C, Gourlaouen I, Gourhant L, Oudin C, Goossens M, Grandchamp B, De Verneuil H, Rochette J, Férec C, Le Gac G. Comprehensive functional annotation of 18 missense mutations found in suspected hemochromatosis type 4 patients. Hum Mol Genet 2014; 23:4479-90. [PMID: 24714983 DOI: 10.1093/hmg/ddu160] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Hemochromatosis type 4 is a rare form of primary iron overload transmitted as an autosomal dominant trait caused by mutations in the gene encoding the iron transport protein ferroportin 1 (SLC40A1). SLC40A1 mutations fall into two functional categories (loss- versus gain-of-function) underlying two distinct clinical entities (hemochromatosis type 4A versus type 4B). However, the vast majority of SLC40A1 mutations are rare missense variations, with only a few showing strong evidence of causality. The present study reports the results of an integrated approach collecting genetic and phenotypic data from 44 suspected hemochromatosis type 4 patients, with comprehensive structural and functional annotations. Causality was demonstrated for 10 missense variants, showing a clear dichotomy between the two hemochromatosis type 4 subtypes. Two subgroups of loss-of-function mutations were distinguished: one impairing cell-surface expression and one altering only iron egress. Additionally, a new gain-of-function mutation was identified, and the degradation of ferroportin on hepcidin binding was shown to probably depend on the integrity of a large extracellular loop outside of the hepcidin-binding domain. Eight further missense variations, on the other hand, were shown to have no discernible effects at either protein or RNA level; these were found in apparently isolated patients and were associated with a less severe phenotype. The present findings illustrate the importance of combining in silico and biochemical approaches to fully distinguish pathogenic SLC40A1 mutations from benign variants. This has profound implications for patient management.
Collapse
Affiliation(s)
- Isabelle Callebaut
- IMPMC, Sorbonne Universités - UMR CNRS 7590, UPMC Univ Paris 06, Muséum d'Histoire Naturelle, IRD UMR 206, Paris, France
| | - Rozenn Joubrel
- Laboratoire de Génétique Moléculaire et d'Histocompatibilité, Inserm U1078, Université de Brest, SFR SnInBioS, CHRU de Brest, Etablissement Français du Sang - Bretagne, Brest, France
| | - Serge Pissard
- Laboratoire de Génétique, UPEC (Université Paris Est Creteil), GHU Henri Mondor, Créteil, France
| | - Caroline Kannengiesser
- Hôpital Bichat, Département de Génétique, Inserm U1149 - Center for Research on Inflammation, Université Paris Diderot, AP-HP, Paris, France
| | | | - Cécile Ged
- Inserm U1035, Biothérapies des Maladies Génétiques et Cancers, Université de Bordeaux, CHU de Bordeaux, Pôle de Biologie et Pathologie, Bordeaux, France
| | - Estelle Cadet
- Laboratoire de Génétique Moléculaire, UPJV EA4666, CHU d'Amiens, Amiens, France
| | | | - Chandran Ka
- Laboratoire de Génétique Moléculaire et d'Histocompatibilité, Inserm U1078, Université de Brest, SFR SnInBioS, CHRU de Brest, Etablissement Français du Sang - Bretagne, Brest, France
| | - Isabelle Gourlaouen
- Laboratoire de Génétique Moléculaire et d'Histocompatibilité, Inserm U1078, Université de Brest, SFR SnInBioS, CHRU de Brest, Etablissement Français du Sang - Bretagne, Brest, France
| | | | - Claire Oudin
- Hôpital Bichat, Département de Génétique, Inserm U1149 - Center for Research on Inflammation, Université Paris Diderot, AP-HP, Paris, France
| | - Michel Goossens
- Laboratoire de Génétique, UPEC (Université Paris Est Creteil), GHU Henri Mondor, Créteil, France
| | - Bernard Grandchamp
- Hôpital Bichat, Département de Génétique, Inserm U1149 - Center for Research on Inflammation, Université Paris Diderot, AP-HP, Paris, France
| | - Hubert De Verneuil
- Inserm U1035, Biothérapies des Maladies Génétiques et Cancers, Université de Bordeaux, CHU de Bordeaux, Pôle de Biologie et Pathologie, Bordeaux, France
| | - Jacques Rochette
- Laboratoire de Génétique Moléculaire, UPJV EA4666, CHU d'Amiens, Amiens, France
| | - Claude Férec
- Laboratoire de Génétique Moléculaire et d'Histocompatibilité, Inserm U1078, Université de Brest, SFR SnInBioS, CHRU de Brest, Etablissement Français du Sang - Bretagne, Brest, France
| | - Gérald Le Gac
- Laboratoire de Génétique Moléculaire et d'Histocompatibilité, Inserm U1078, Université de Brest, SFR SnInBioS, CHRU de Brest, Etablissement Français du Sang - Bretagne, Brest, France CHRU de Brest, Inserm CIC0502, Brest, France
| |
Collapse
|
39
|
Frazer DM, Anderson GJ. The regulation of iron transport. Biofactors 2014; 40:206-14. [PMID: 24132807 DOI: 10.1002/biof.1148] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 09/02/2013] [Accepted: 09/06/2013] [Indexed: 01/01/2023]
Abstract
Iron is an essential nutrient, but its concentration and distribution in the body must be tightly controlled due to its inherent toxicity and insolubility in aqueous solution. Living systems have successfully overcome these potential limitations by evolving a range of iron binding proteins and transport systems that effectively maintain iron in a nontoxic and soluble form for much, if not all, of its time within the body. In the circulation, iron is transported to target organs bound to the serum iron binding protein transferrin. Individual cells modulate their uptake of transferrin-bound iron depending on their iron requirements, using both transferrin receptor 1-dependent and independent pathways. Once inside the cell, iron can be chaperoned to sites of need or, if in excess, stored within ferritin. Iron is released from cells by the iron export protein ferroportin1, which requires the ferroxidase activity of ceruloplasmin or hephestin to load iron safely onto transferrin. The regulation of iron export is controlled predominantly at the systemic level by the master regulator of iron homeostasis hepcidin. Hepcidin, in turn, responds to changes in body iron demand, making use of a range of regulatory mechanisms that center on the bone morphogenetic protein signaling pathway. This review provides an overview of recent advances in the field of iron metabolism and outlines the key components of the iron transport and regulation systems.
Collapse
Affiliation(s)
- David M Frazer
- Iron Metabolism Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Qld, Australia
| | | |
Collapse
|
40
|
Sheokand N, Malhotra H, Kumar S, Tillu VA, Chauhan AS, Raje CI, Raje M. Moonlighting cell surface GAPDH recruits Apo Transferrin to effect iron egress from mammalian cells. J Cell Sci 2014; 127:4279-91. [DOI: 10.1242/jcs.154005] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Iron homeostasis is a tightly regulated process with precise control of its influx and egress from cells. Though mechanisms of its import into cells via iron carrier molecules are well characterized, iron export remains poorly understood. The current paradigm envisages unique functions associated with specialized macromolecules for its cellular import (transferrin receptors) or export (ferroportin) Earlier studies have revealed that, iron depleted cells recruit Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a moonlighting protein to their surface for internalization of the iron carrier holo transferrin (holo Tf). Here we report that under the contrary condition of intracellular iron excess, cells switch the isoform of GAPDH on their surface which now recruits iron free apo transferrin in close association with ferroportin to facilitate efflux of iron. Increased surface GAPDH expression synchronized with increased apo Tf binding and enhanced iron export from cells, a capability lost in GAPDH knockdown cells. These findings were confirmed in vivo utilizing a rodent model of iron overload. Besides identifying for the first time an apo transferrin receptor, our work uncovers two-way switching of multifunctional molecules for managing cellular micronutrient requirements.
Collapse
|