Hemojuvelin: The Hepcidin Story Continues

Abstract

Hemojuvelin (HJV) is a membrane protein that is responsible for the iron overload condition known as juvenile hemochromatosis. HJV, highly expressed in the liver, skeletal muscle and heart, seems to play a role in iron absorption and release from cells and has anti-inflammatory properties. HJV is a bone morphogenetic protein (BMP) co-receptor and signals via the SMAD (human homolog of Drosophila mad – mother against decapentaplegic) pathway to regulate hepcidin expression. HJV acts as a BMP co-receptor. Moreover, HJV plays an essential role in the regulation of hepcidin expression, specifically in the iron-sensing pathway, although through unknown mechanisms. Dietary iron sensing and inflammatory pathways converge in the regulation of the key regulator hepcidin, but how these two pathways intersect remains unclear. Inflammation, through downregulation of hepatic HJV, might induce temporary elimination of iron sensing. Despite enormous scientific achievements in explaining the pathogenetic mechanisms of iron metabolism, many questions still remain unanswered: What is the functional role of HJV in iron metabolism? How it is related to hepcidin expression in different settings? How do iron-sensing and inflammatory pathways cooperate in hepcidin gene expression?