Abstract
The transferrin receptor (TfR) is one of the key proteins involved in cellular iron uptake. TfR-mediated endocytosis of transferrin-bound iron is the major pathway for iron acquisition by most cells in the body. Over the past three decades, the studies on TfR have made significant progress, and also, our knowledge on cell iron uptake has greatly been improved. Here we focus on recent advances in the studies on TfR and a brief discussion of the structures and functions of four different types of TfR, namely TfR1 (transferrin receptor 1), TfR2 (transferrin receptor 2), TfR3 (glyceraldehyde-3-phosphate dehydrogenase) and TfR4 (cubilin). These proteins work in different cells or organs and at different times, ensuring that cells and tissues get the iron they need. Their normal expression and function are fundamental to the body's iron homeostasis.