Transferrin receptor

Transferrin receptor (TfR) is a carrier protein for transferrin. It is needed for the import of iron into the cell and is regulated in response to intracellular iron concentration. It imports iron by internalizing the transferrin-iron complex through receptor-mediated endocytosis.

Regulation
Low iron concentrations promote increased levels of transferrin receptor, to increase iron intake into the cell. Thus, transferrin receptor maintains cellular iron homeostasis.

TfR production in the cell is regulated according to iron levels by iron response/regulatory element binding protein (IRE-BP), also referred to as Iron Regulatory Protein (IRP). This protein binds to the hairpin like structure (IRE) that is in the 3' UTR of the TfR receptor. Once binding occurs, degradation of mRNA of IRE is inhibited.