PURPOSE OF REVIEW: The type 1 transferrin receptor (TfR1) is well known as a key 
player in erythroid differentiation through its role in iron uptake. Recently, 
it has been demonstrated that TfR1 could also have signaling functions in 
erythroid cells. Moreover, the second transferrin receptor, TfR2, whose 
signaling functions in hepatic cells are well established, was recently shown to 
be a partner of the erythropoietin receptor (EpoR) and thereby likely to play a 
role in erythroid differentiation.
RECENT FINDINGS: This review reports recent findings regarding the specificities 
of the regulation of TfR1 expression and iron uptake in erythroblasts. The newly 
discovered noncanonical actions of TfR1 and TfR2 in erythroid cells are also 
discussed.
SUMMARY: Erythrocytes contain more than 60% of the iron of the body and each 
day, differentiating erythroid cells uptake around 20 mg of iron for heme 
synthesis. Accordingly, TfR1 is one of the most abundant membrane proteins of 
the erythroblasts and it is not surprising that specific regulations regarding 
both its expression and its mechanism of action operate in erythroblasts. The 
signaling functions of both TfR1 and TfR2 in erythroid cells were unexpected and 
these recent findings open a new field of research regarding the last steps of 
erythroid differentiation and their regulation.