title: The molecular basis of ferroportin-linked hemochromatosis.
abstract: Mutations in the iron exporter ferroportin (Fpn) (IREG1, SLC40A1, and MTP1) result in hemochromatosis type IV, a disorder with a dominant genetic pattern of inheritance and heterogeneous clinical presentation. Most patients develop iron loading of Kupffer cells with relatively low saturation of plasma transferrin, but others present with high transferrin saturation and iron-loaded hepatocytes. We show that known human mutations introduced into mouse Fpn-GFP generate proteins that either are defective in cell surface localization or have a decreased ability to be internalized and degraded in response to hepcidin. Studies using co-immunoprecipitation of epitope-tagged Fpn and size-exclusion chromatography demonstrated that Fpn is multimeric. Both WT and mutant Fpn participate in the multimer, and mutant Fpn can affect the localization of WT Fpn, its stability, and its response to hepcidin. The behavior of mutant Fpn in cell culture and the ability of mutant Fpn to act as a dominant negative explain the dominant inheritance of the disease as well as the different patient phenotypes.
authors.affiliation: Dipartimento di Scienze Microbiologiche Genetiche e Molecolari, Università di Messina, 98166 Messina, Italy.
authors.forename: Ivana
authors.initials: I
authors.lastname: De Domenico
authors.forename: Diane McVey
authors.initials: DM
authors.lastname: Ward
authors.forename: Elizabeta
authors.initials: E
authors.lastname: Nemeth
authors.forename: Michael B
authors.initials: MB
authors.lastname: Vaughn
authors.forename: Giovanni
authors.initials: G
authors.lastname: Musci
authors.forename: Tomas
authors.initials: T
authors.lastname: Ganz
authors.forename: Jerry
authors.initials: J
authors.lastname: Kaplan
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000378:metabolism; D001665:Binding Sites; D027682:Cation Transport Proteins / Q000235:genetics*; D006367:HeLa Cells; D006432:Hemochromatosis / Q000235:genetics*; D064451:Hepcidins; D006801:Humans; D007501:Iron / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D015183:Restriction Mapping; D014168:Transferrin / Q000378:metabolism; D000098742:Ferroportin
chemical_list: D023181:Antimicrobial Cationic Peptides; D027682:Cation Transport Proteins; C578702:HAMP protein, human; C579599:Hamp protein, mouse; D064451:Hepcidins; D014168:Transferrin; D000098742:Ferroportin; D007501:Iron