Transferrin receptor 1 (TfR1) and putative stimulator of Fe transport (SFT) expression in iron deficiency and overload: an overview.

Transferrin Receptor 1 (TfR1) and putative Stimulator of Fe Transport (SFT) represent two different proteins involved in iron metabolism in mammalian cells. The expression of TfR1 in the duodenum of subjects with normal body iron stores has been mainly localized in the basolateral portion of the cytoplasm of crypt cells, supporting the idea that this molecule may be involved in the sensing of body iron stores. In iron deficiency anemia TfR1 expression demonstrated an inverse relationship with body iron stores as assessed by immunohistochemistry with anti-TfR1 antibodies. In iron overload, TfR1 expression in the duodenum differed according to the presence or absence of the C282Y mutation in the HFE gene, being increased in HFE-related hemochromatosis and similar to controls in non-HFE-related iron overload. SFT is characterized by its ability to increase iron transport both through the transferrin dependent and independent uptake, and could thus affect iron absorption in the intestine. Immunohistochemistry using anti-SFT antibodies which recognize a putative stimulator of Fe transport of approximately 80 KDa revealed a localization of this protein in the apical part of the cytoplasm of enterocytes localized at the tip of the villi. The expression of the protein recognized by these antibodies was increased in iron deficiency, as well as in patients carrying the C282Y HFE mutation. Thus, the increased expression of both proteins only in patients with HFE-related hemochromatosis suggests that other factors should be involved in determining non-HFE-related iron overload.