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Description

Transferrin receptor protein 1 (UniProt: P02786, also known as TR, TfR, TfR1, Trfr, T9, p90, CD71) is encoded by the TFRC gene (Gene ID: 7037) in human. Tfr is a disulfide-bonded homodimeric type II transmembrane glycoprotein that is involved in iron uptake. TfR is more abundantly expressed in rapidly dividing cells. Higher expression levels of TfR are seen in the placental trophoblast and hemoglobin-synthesizing reticulocytes, but expression is lost in mature erythrocytes. Cellular uptake of iron occurs via receptor-mediated endocytosis of ligand-occupied transferrin receptor into specialized endosomes. Endosomal acidification leads to iron release. Both TfR and TfR2 bind diferric transferrin better than apo-transferrin at neutral pH. However, TFR2 displays about 25-fold lower affinity for transferrin compared to TfR. TfR levels are regulated by cellular iron levels through binding of the iron regulatory proteins, IRP1 and IRP2, to iron-responsive elements in the 3'-UTR. Up-regulated upon mitogenic stimulation. TfR can be N- and O-glycosylated, phosphorylated and palmitoylated, however, the serum form is only glycosylated. TfR can be proteolytically cleaved on Arg100 to produce the soluble serum form (sTfR). Mutations in TFRC gene result in immunodeficiency 46, an autosomal recessive disorder that is characterized by early-onset chronic diarrhea, recurrent infections, hypo- or agammaglobulinemia, intermittent neutropenia, and thrombocytopenia.