A new mouse liver-specific gene, encoding a protein homologous to human antimicrobial peptide hepcidin, is overexpressed during iron overload

Considering that the development of hepatic lesions related to iron overloa d diseases might be a result of abnormally expressed hepatic genes, we sear ched for new genes up-regulated under the condition of iron excess. By supp ressive subtractive hybridization performed between livers from carbonyl ir on-overloaded and control mice, we isolated a 225-base pair cDNA. By Northe rn blot analysis, the corresponding mRNA was confirmed to be overexpressed in livers of experimentally (carbonyl iron and iron-dextran-treated mice) a nd spontaneously (beta (2)-microglobulin knockout mice) iron-overloaded mic e. In addition, beta (2)-microglobulin knockout mice fed with a low iron co ntent diet exhibited a decrease of hepatic mRNA expression. The murine full -length cDNA was Isolated and was found to encode an 83-amino acid protein presenting a strong homology in its C-terminal region to the human antimicr obial peptide hepcidin, In addition, we cloned the corresponding rat and hu man orthologue cDNAs, Both mouse and human genes named HEPC are constituted of 3 exons and 2 introns and are located on chromosome 7 and 19, respectiv ely, in close proximity to USF2 gene. In mouse and human, HEPC mRNA was pre dominantly expressed in the liver. During both in vivo and in vitro studies , HEPC mRNA expression was enhanced in mouse hepatocytes under the effect o f lipopolysaccharide. Finally, to analyze the intracellular localization of the predicted protein, we used the green fluorescent protein chimera expre ssion vectors. The murine green fluorescent protein-prohepcidin protein was exclusively localized in the nucleus. When the putative nuclear localizati on signal was deleted, the resulting protein was addressed to the cytoplasm . Taken together, our data strongly suggest that the product of the new liv er-specific gene HEPC might play a specific role during iron overload and e xhibit additional functions distinct from its antimicrobial activity.