Molecular mechanism of hepcidin-mediated ferroportin internalization requires ferroportin lysines, not tyrosines or JAK-STAT.
Ferroportin is the primary means of cellular iron efflux and a key component of iron metabolism. Hepcidin regulates Fpn activity by inducing its internalization and degradation. The mechanism of internalization is reported to require JAK2 activation, phosphorylation of Fpn tyrosine residues 302 and 303, and initiation of transcription through STAT3 phosphorylation. These findings suggest Fpn may be a target for therapeutic intervention through JAK2 modulation. To evaluate the proposed mechanism, Fpn internalization was assessed using several techniques combined with reagents that specifically recognized cell-surface Fpn. In vitro results demonstrated that Hepc-induced Fpn internalization did not require JAK2 or phosphorylation of Fpn residues 302 and 303, nor did it induce JAK-STAT signaling. In vivo, inhibition of JAK2 had no effect on Hepc-induced hypoferremia. However, internalization was delayed by mutation of two Fpn lysine residues that may be targets of ubiquitination.
Department of Oncology, Amgen Inc., Thousand Oaks, CA 91320, USA.
Sandra L
SL
Ross
Lynn
L
Tran
Aaron
A
Winters
Ki-Jeong
KJ
Lee
Cherylene
C
Plewa
Ian
I
Foltz
Chadwick
C
King
Les P
LP
Miranda
Jennifer
J
Allen
Holger
H
Beckman
Keegan S
KS
Cooke
Gordon
G
Moody
Barbra J
BJ
Sasu
Elizabeta
E
Nemeth
Tomas
T
Ganz
Graham
G
Molineux
Tara L
TL
Arvedson
D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D023181:Antimicrobial Cationic Peptides; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D064451:Hepcidins; D006801:Humans; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D050791:STAT Transcription Factors / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism*; D054875:Ubiquitination; D000098742:Ferroportin
D023181:Antimicrobial Cationic Peptides; D027682:Cation Transport Proteins; C578702:HAMP protein, human; D064451:Hepcidins; D008565:Membrane Proteins; D050791:STAT Transcription Factors; D000098742:Ferroportin; D014443:Tyrosine; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D008239:Lysine