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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.
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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
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Corti P, Ferrari GM, Faraguna MC, Capitoli G, Longo F, Corradini E, Casini T, Boscarol G, Pinto VM, Ghilardi R, Russo G, Colombatti R, Mariani R, Piperno A. Haemochromatosis in children: A national retrospective cohort promoted by the A.I.E.O.P. (Associazione Italiana Emato-Oncologia Pediatrica) study group. Br J Haematol 2024; 204:306-314. [PMID: 37990447 DOI: 10.1111/bjh.19208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 10/25/2023] [Accepted: 11/06/2023] [Indexed: 11/23/2023]
Abstract
Haemochromatosis (HC) encompasses a range of genetic disorders. HFE-HC is by far the most common in adults, while non-HFE types are rare due to mutations of HJV, HAMP, TFR2 and gain-of-function mutations of SLC40A1. HC is often unknown to paediatricians as it is usually asymptomatic in childhood. We report clinical and biochemical data from 24 paediatric cases of HC (10 cases of HFE-, 5 TFR2-, 9 HJV-HC), with a median follow-up of 9.6 years. Unlike in the adult population, non-HFE-HC constitutes 58% (14/24) of the population in our series. Transferrin saturation was significantly higher in TFR2- and HJV-HC compared to HFE-HC, and serum ferritin and LIC were higher in HJV-HC compared to TFR2- and HFE-HC. Most HFE-HC subjects had relatively low ferritin and LIC at the time of diagnosis, so therapy could be postponed for most of them after the age of 18. Our results confirm that HJV-HC is a severe form already in childhood, emphasizing the importance of early diagnosis and treatment to avoid the development of organ damage and reduce morbidity and mortality. Although phlebotomies were tolerated by most patients, oral iron chelators could be a valid option in early-onset HC.
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Affiliation(s)
- Paola Corti
- Pediatria, Fondazione IRCCS San Gerardo dei Tintori, Monza, Italy
| | | | - Martha Caterina Faraguna
- Pediatria, Fondazione IRCCS San Gerardo dei Tintori, Monza, Italy
- Residency in Pediatrics, University of Milano Bicocca, Milan, Italy
| | - Giulia Capitoli
- Bicocca Bioinformatics Biostatistics and Bioimaging B4 Center, Department of Medicine and Surgery, University of Milan-Bicocca, Monza, Italy
| | - Filomena Longo
- Thalassemia Reference Centre, Orbassano, Italy
- Regional HUB Centre for Thalassaemia and Haemoglobinopathies, Department of Medicine, AOU S. Anna, Ferrara, Italy
| | - Elena Corradini
- Internal Medicine Unit and Centre for Hemochromatosis and Hereditary Liver Diseases, ERN-EuroBloodNet and ERN-RARE-LIVER, Azienda Ospedaliero-Universitaria di Modena-Policlinico, Modena, Italy
| | - Tommaso Casini
- Pediatric Hematology/Oncology Department, Meyer's Children University Hospital, Firenze, Italy
| | | | - Valeria Maria Pinto
- Centro della Microcitemia e delle Anemie Congenite, Ospedale Galliera, Genova, Italy
| | - Roberta Ghilardi
- Department of Pediatrics, Ospedale Maggiore Policlinico, IRCCS, Milano, Italy
| | - Giovanna Russo
- Pediatric Hematology and Oncology Unit, Azienda Policlinico "Rodolico-San Marco", University of Catania, Catania, Italy
| | - Raffaella Colombatti
- Pediatric Hematology Oncology and Bone Marrow Transplantation Unit, Department of Woman's and Child's Health, University of Padova, Padova, Italy
| | - Raffaella Mariani
- SSD Rare Diseases-European Reference Network for Rare Hematological Diseases-EuroBloodNet-Fondazione IRCCS San Gerardo dei Tintori, Monza, Italy
| | - Alberto Piperno
- SSD Rare Diseases-European Reference Network for Rare Hematological Diseases-EuroBloodNet-Fondazione IRCCS San Gerardo dei Tintori, Monza, Italy
- Centro Ricerca Tettamanti, Monza, Italy
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Ruivard M, Lobbes H. [Diagnosis and treatment of iron overload]. Rev Med Interne 2023; 44:656-661. [PMID: 37507250 DOI: 10.1016/j.revmed.2023.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 07/03/2023] [Indexed: 07/30/2023]
Abstract
Etiological investigation of hyperferritinemia includes a full clinical examination, with the measurement of waist circumference, and simple biological tests including transferrin saturation. The classification between hyperferritinemia without iron overload (inflammation, excessive alcohol intake, cytolysis, L-ferritin mutation) or with iron overload is then relatively easy. Dysmetabolic iron overload syndrome is the most common iron overload disease and is defined by an unexplained serum ferritin level elevation associated with various metabolic syndrome criteria and mild hepatic iron content increase assessed by magnetic resonance imaging. Bloodlettings are often poorly tolerated without clear benefit. Type 1 genetic hemochromatosis (homozygous C282Y mutation on the HFE gene) leads to iron accumulation through an increase of dietary iron absorption due to hypohepcidinemia. More than 95% of hemochromatosis are type 1 hemochromatosis but the phenotypic expression is highly variable. Elastography is recommended to identify advanced hepatic fibrosis when serum ferritin exceeds 1000μg/L. Life expectancy is normal when bloodlettings are started early. Ferroportin gene mutation is an autosomal dominant disease with generally moderate iron overload. Chelators are used in iron overload associated with anaemia (myelodysplastic syndromes or transfusion-dependent thalassemia). Chelation is initiated when hepatic iron content exceeds 120μmol/g. Deferasirox is often used as first-line therapy, but deferiprone may be of interest despite haematological toxicity (neutropenia). Deferoxamine (parenteral route) is the treatment of choice for severe iron overload or emergency conditions.
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Affiliation(s)
- M Ruivard
- Service médecine Interne, CHU de Clermont-Ferrand, CHU d'Estaing, 63003 Clermont-Ferrand, France; UMR 6602 UCA/CNRS/SIGMA, thérapies guidées par l'image (TGI), université Clermont Auvergne, 63000 Clermont-Ferrand, France.
| | - H Lobbes
- Service médecine Interne, CHU de Clermont-Ferrand, CHU d'Estaing, 63003 Clermont-Ferrand, France; UMR 6602 UCA/CNRS/SIGMA, thérapies guidées par l'image (TGI), université Clermont Auvergne, 63000 Clermont-Ferrand, France.
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