Enhanced NTPDase and 5′-nucleotidase activities in diabetes mellitus and iron-overload model
OBJECTIVES While body iron status may influence platelets, little information is available about platelet expression of proteins regulating iron homeostasis. HFE, the protein defective in hereditary hemochromatosis, and transferrin receptor 2 (TfR2) are two novel protein candidates that could be involved in mechanisms of iron transport across the platelet plasma membrane. METHODS The expression and localization of HFE, TfR1 and TfR2 proteins in human platelets were examined using Western blotting and immunocytochemistry. RESULTS Human platelets expressed HFE and TfR2, whereas no signal for TfR1 was found. The positive reactions for HFE and TfR2 were mainly confined to the platelet plasma membrane. CONCLUSIONS Expression of HFE and TfR2 proteins in human platelets may indicate that the mutations in the corresponding genes could influence platelet count, size and/or activation. The presence of TfR2 and absence of TfR1 suggests that HFE may serve a different function in platelets compared with the other HFE-positive cell types, e.g. enterocytes, macrophages and syncytiotrophoblasts.