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|Quelle: Visser 2005|
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|The expression level of the TfR depends on the level of iron supply and rate of cell proliferation. The iron concentration determines TfR synthesis and expression via an iron-responsive element (IRE) in the mRNA of the TfR (Kuhn, L. C. et al, 1991, Casey, J. L. et al, 1989). This IRE is also found in the mRNA of ferritin, a protein that can store iron (Kuhn, L. C. et al, 1991). In cases of low iron concentrations, a so called IRE binding protein stabilises the mRNA of the TfR, which can therefore be translated. The mRNA of ferritin is in low-iron situations less stable and is therefore translated to a lesser extent. Recently, a second TfR (TfR-2) has been identified (Trinder, D. and Baker, E. et al, 2003), which does not contain an IRE in its mRNA. TfR-2 is differentially distributed from TfR and has a 25-fold lower affinity for Tf.
The TfR is expressed mainly on hepatocytes, erythrocytes, intestinal cells, monocytes, as well as on endothelial cells of the BBB [...] (Morgan, E. [H. et al, 1996, Ponka, P. and Lok, C. N. et al, 1999).]
|The TfR is expressed mainly on hepatocytes, erythrocytes, intestinal cells, monocytes, as well as on endothelial cells of the BBB (34, 35).
Recently, a second TfR (TfR-2) has been identified (39), which does not contain an IRE in its mRNA. TfR-2 is differentially distributed from TfR and has a 25-fold lower affinity for Tf.
34. Morgan, E. H. (1996) Iron metabolism and transport. In Hepatology. A textbook of liver disease, Vol. 1 (D. Zakin and T. D. Boyer, eds.), Saunders, Philadelphia, pp. 526-554
35. Ponka, P. and Lok, C. N. (1999) The transferrin receptor: role in health and disease. Int J Biochem Cell Biol 31 (10): 1111-1137
37. Kuhn, L. C. (1991) mRNA-protein interactions regulate critical pathways in cellular iron metabolism. Br J Haematol 79 (1): 1-5
38. Casey, J. L., Koeller, D. M., Ramin, V. C., Klausner, R. D. and Harford, J. B. (1989) Iron regulation of transferrin receptor mRNA levels requires iron- responsive elements and a rapid turnover determinant in the 3' untranslated region of the mRNA. Embo J 8 (12): 3693-3699
39. Trinder, D. and Baker, E. (2003) Transferrin receptor 2: a new molecule in iron metabolism. Int J Biochem Cell Biol 35 (3): 292-296
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