BACKGROUND/AIMS: 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.