Figure 2.

Schematic depiction of iron trafficking across the plasma membrane into the cell. Transferrin-(Tf-) bound iron is transported into the cell via transferrin receptor 1 (TfR1) or 2 (TfR2). The complex is endocytosed, and a decrease in luminal pH causes the release of iron from the complex. Tf that is completely free of iron (apotransferrin, ApoTf) and the TfR are then recycled back to the cell membrane. The labile pool of iron within the cell exits the endosome via divalent metal transporter 1 (DMT1) and is stored as ferritin. ApoTf: apotransferrin.