The molecular mechanism of hepcidin-mediated ferroportin down-regulation.
Ferroportin (Fpn) is the only known iron exporter in vertebrates. Hepcidin, a peptide secreted by the liver in response to iron or inflammation, binds to Fpn, inducing its internalization and degradation. We show that after binding of hepcidin, Fpn is tyrosine phosphorylated at the plasma membrane. Mutants of human Fpn that do not get internalized or that are internalized slowly show either absent or impaired phosphorylation. We identify adjacent tyrosines as the phosphorylation sites and show that mutation of both tyrosines prevents hepcidin-mediated Fpn internalization. Once internalized, Fpn is dephosphorylated and subsequently ubiquitinated. An inability to ubiquitinate Fpn does not prevent hepcidin-induced internalization, but it inhibits the degradation of Fpn. Ubiquitinated Fpn is trafficked through the multivesicular body pathway en route to degradation in the late endosome/lysosome. Depletion of proteins involved in multivesicular body trafficking (Endosome Sorting Complex Required for Transport proteins), by small-interfering RNA, reduces the trafficking of Fpn-green fluorescent to the lysosome.
De Domenico
Ivana
I
Department of Pathology, School of Medicine, University of Utah, Salt Lake City, UT 84132, USA.
Ward
Diane McVey
DM
Langelier
Charles
C
Vaughn
Michael B
MB
Nemeth
Elizabeta
E
Sundquist
Wesley I
WI
Ganz
Tomas
T
Musci
Giovanni
G
Kaplan
Jerry
J
D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D027682:Cation Transport Proteins / Q000235:genetics*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects*; D004705:Endocytosis / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000378:metabolism; D064451:Hepcidins; D006801:Humans; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D022161:Transport Vesicles / Q000187:drug effects / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D000098742:Ferroportin
D023181:Antimicrobial Cationic Peptides; D027682:Cation Transport Proteins; C578702:HAMP protein, human; C579599:Hamp protein, mouse; D064451:Hepcidins; D047428:Protein Kinase Inhibitors; D011993:Recombinant Fusion Proteins; D025801:Ubiquitin; D000098742:Ferroportin; D049452:Green Fluorescent Proteins