BACKGROUND AND AIMS: Hepcidin is an iron homoeostasis regulator peptide. 
Loss-of-function mutations cause juvenile haemochromatosis while its 
over-expression results in anaemia. However, the mechanism and function of 
preprohepcidin conversion to mature hepcidins (25, 22 and 20 amino acid 
C-terminal peptides) are not well known. After removal of the signal peptide, 
the first proteolytic cleavage occurs within the basic motif RRRRR(59)DT, 
suggesting the involvement of proprotein convertase (PC) family members in this 
process.
METHODS AND RESULTS: Using cell transfection experiments, the processing of 
preprohepcidin in the human hepatocyte line Huh-7 was found to be inhibited by 
the Furin inhibitors serpin alpha1-antitrypsin (alpha1-PDX) and prosegment 
preproFurin (ppFurin). Site-directed mutagenesis analysis confirmed the 
RRRRR(59)DT preprohepcidin cleavage site. In parallel, the lack of 
preprohepcidin processing found in the PC activity-deficient cell line LoVo was 
restored by the expression of Furin, paired basic amino acid cleaving enzyme 4 
(PACE4), PC5 or PC7. This finding is consistent with the in vitro digestions of 
a synthetic peptide mimicking the cleavage site of preprohepcidin. In addition, 
during mouse embryonic development the major expression of hepcidin found in the 
liver coincided with that of Furin. While hepcidin induces the degradation of 
the iron transporter ferroportin, its RRRRR(59) to SSSSS(59) mutant is not 
active.
CONCLUSIONS: These results demonstrate the key role of the convertases Furin, 
PACE4, PC5 and/or PC7 in the generation and secretion of active hepcidin and 
suggest that the control of hepcidin processing as a potential 
therapeutic/diagnostic strategy in hepcidin-related disorders such as 
haemochromatosis, inflammatory diseases, anaemia and cancer.