Pro-hepcidin is unable to degrade the iron exporter ferroportin unless maturated by a furin-dependent process☆☆☆
Received 8 August 2008; received in revised form 11 September 2008; accepted 15 September 2008. published online 03 December 2008.
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.
4CNRS, Institut de Chimie des Substances Naturelles, Gif-Sur-Yvette, France
5Département de Génétique, Développement et Pathologie Moléculaire, Institut Cochin, Faculté de Médecine Cochin-Port Royal, 24, rue du Fg St Jacques, 75014 Paris, France
☆ The authors who have taken part in the research of this paper declared that they do not have a relationship with the manufacturers of the materials involved either in the past or present and they did not receive funding from the manufacturers to carry out their research.
☆☆ Financial support: This work was supported by ANR, Institut National de la Santé et de la Recherche Médicale and CNRS.
ABSTRACT