Structure-function analysis of ferroportin defines the binding site and an alternative mechanism of action of hepcidin
| Autor: | Bo Qiao, Mika Jormakka, T Alex Ruwe, Sharraya Aschemeyer, Kyle R. Vieth, Tomas Ganz, Bryan Mackenzie, Deborah Stefanova, Albert C. Sek, Stefano Rivella, Erika V. Valore, Carla Casu, Elizabeta Nemeth, Grace Jung |
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| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
Protein Conformation Ferroportin Drug Resistance Plasma protein binding medicine.disease_cause Biochemistry Mice Xenopus laevis 0302 clinical medicine hemic and lymphatic diseases Cation Transport Proteins Cells Cultured Mutation biology Chemistry Hematology Endocytosis Cell biology Hereditary hemochromatosis BLOOD Commentary Protein Binding inorganic chemicals congenital hereditary and neonatal diseases and abnormalities Iron Immunology Structure-Activity Relationship 03 medical and health sciences Red Cells Iron and Erythropoiesis Hepcidins Protein Domains Hepcidin medicine Animals Humans Computer Simulation Binding site Binding Sites HEK 293 cells Ubiquitination nutritional and metabolic diseases Cell Biology Mice Inbred C57BL HEK293 Cells 030104 developmental biology Mutagenesis Site-Directed Oocytes biology.protein 030215 immunology |
| Zdroj: | Blood. 131:899-910 |
| ISSN: | 1528-0020 0006-4971 |
| DOI: | 10.1182/blood-2017-05-786590 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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