Comparison of the Interactions of Transferrin Receptor and Transferrin Receptor 2 with Transferrin and the Hereditary Hemochromatosis Protein HFE

• Published in: The Journal of biological chemistry 2000-12, Vol.275 (49), p.38135-38138
• Main Authors: West, Jr, A P, Bennett, M J, Sellers, V M, Andrews, N C, Enns, C A, Bjorkman, P J
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino Acid Substitution; Animals; Binding Sites; Cell Line; Dimerization; Hemochromatosis - genetics; Hemochromatosis Protein; Histocompatibility Antigens Class I - chemistry; Histocompatibility Antigens Class I - metabolism; HLA Antigens - chemistry; HLA Antigens - metabolism; Humans; Kinetics; Membrane Proteins; Models, Molecular; Molecular Sequence Data; Protein Conformation; Receptors, Transferrin - chemistry; Receptors, Transferrin - metabolism; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Transferrin - chemistry; Transferrin - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.C000664200

The transferrin receptor (TfR) interacts with two proteins important for iron metabolism, transferrin (Tf) and HFE, the protein mutated in hereditary hemochromatosis. A second receptor for Tf, TfR2, was recently identified and found to be functional for iron uptake in transfected cells (Kawabata, H., Germain, R. S., Vuong, P. T., Nakamaki, T., Said, J. W., and Koeffler, H. P. (2000) J. Biol. Chem. 275, 16618–16625). TfR2 has a pattern of expression and regulation that is distinct from TfR, and mutations in TfR2 have been recognized as the cause of a non-HFE linked form of hemochromatosis (Camaschella, C., Roetto, A., Cali, A., De Gobbi, M., Garozzo, G., Carella, M., Majorano, N., Totaro, A., and Gasparini, P. (2000) Nat. Genet. 25, 14–15). To investigate the relationship between TfR, TfR2, Tf, and HFE, we performed a series of binding experiments using soluble forms of these proteins. We find no detectable binding between TfR2 and HFE by co-immunoprecipitation or using a surface plasmon resonance-based assay. The affinity of TfR2 for iron-loaded Tf was determined to be 27 n m , 25-fold lower than the affinity of TfR for Tf. These results imply that HFE regulates Tf-mediated iron uptake only from the classical TfR and that TfR2 does not compete for HFE binding in cells expressing both forms of TfR.