Pro-hepcidin is unable to degrade the iron exporter ferroportin unless maturated by a furin-dependent process.
OBJECTIVE
The iron-regulatory peptide hepcidin is synthesized in the liver as an 84-aa pre-pro-hormone maturated by proteolysis through a consensus furin cleavage site to generate the bioactive 25-aa peptide secreted in the circulation. This peptide regulates iron export from enterocytes and macrophages by binding the membrane iron exporter, ferroportin, leading to its degradation. Whether pro-hepcidin could be secreted and reflect hepcidin levels remains an open question. However, the activity of the pro-peptide on ferroportin degradation has never been addressed.


METHODS
To answer this question, we produced recombinant pro-hepcidin, both the wild-type form and a furin cleavage site mutant, and tested their activity on ferroportin levels in macrophagic J774 cells. Furin activity was also modulated using furin inhibitor or siRNA-mediated furin mRNA knockdown.


RESULTS
We found that pro-hepcidin could fully induce ferroportin degradation, but only when processed by furin to generate the mature hepcidin-25 form. Pro-hepcidin activity was abolished in the presence of furin inhibitor and diminished after siRNA-mediated knockdown of furin mRNA. Furthermore, the mutated version of pro-hepcidin was completely inefficient at degrading ferroportin in macrophages.


CONCLUSIONS
Our results demonstrate that pro-hepcidin lacks biological activity, unless fully maturated by a furin-dependent process to yield the bioactive 25-aa peptide.
Gagliardo
Bruno
B
Université Paris Descartes, CNRS (UMR 8601), Paris, France.
Kubat
Nicole
N
Faye
Audrey
A
Jaouen
Maryse
M
Durel
Béatrice
B
Deschemin
Jean-Christophe
JC
Canonne-Hergaux
François
F
Sari
Marie-Agnès
MA
Vaulont
Sophie
S
D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000502:physiology*; D027682:Cation Transport Proteins / Q000378:metabolism*; D002460:Cell Line; D045683:Furin / Q000502:physiology*; D064451:Hepcidins; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D011498:Protein Precursors / Q000502:physiology*; D000098742:Ferroportin
D023181:Antimicrobial Cationic Peptides; D027682:Cation Transport Proteins; C579599:Hamp protein, mouse; D064451:Hepcidins; D011498:Protein Precursors; D000098742:Ferroportin; D045683:Furin