Figure 2.

Main features of iron transport and metabolism in the placenta [26,37,48,62,63]. This figure describes placental iron import from maternal holo-transferrin, which is the main origin of iron, and intravascular hemolysis. Briefly, iron can be internalized in the heme form, as hemoglobin or heme, complexed with either haptoglobin or hemopexin, respectively, through their receptors CD163 and CD91. Heme iron is degraded by HO and the resulting free iron can be either stored or exported. Internalization by clathrin-mediated endocytosis of the complex of transferrin and its receptor leads, after the formation of an acidic endosome, to the export of reduced iron into the cytoplasm, where it can be stored or exported. FLVCR1: feline leukemia virus subgroup C receptor-related protein 2, FLVCR2: feline leukemia virus subgroup C receptor-related protein 2, HO-1: heme-oxygenase 1, Fe: iron, Hb: hemoglobin, TF: transferrin, TFR1: transferrin receptor 1, DMT1: divalent metal transporter 1, poly(rC) binding protein (PCBP) 1 and 2, VM: villosity membrane, FPN: ferroportin.