Haemochromatosis protein is expressed on the terminal web of enterocytes in proximal small intestine of the rat

The haemochromatosis protein (HFE) is an important regulator of body iron stores. In the liver, HFE is required for appropriate expression of hepcidin, a humoral mediator of iron absorption. HFE is also present in enterocytes, though its function in the intestine is unknown; it is not intrinsically required for iron absorption, but can augment iron absorption when over-expressed-independent of hepcidin regulation by the liver. In this study, an antibody was raised against rat HFE and validated by enzyme-linked immunosorbent assay, Western blot and quenching of antibody function by the immunising peptide. The sub-cellular location of HFE in enterocytes of iron-deficient and control rats was determined by double-labelling experiments with markers for the microvillus membrane, terminal web, early endosomes, lysosomes and the transferrin receptor. Parallel studies were performed for the primary iron absorption protein, divalent metal transporter 1 (DMT1). HFE co-localised exclusively with the terminal web of intestinal enterocytes. HFE expression was increased in iron deficiency, consistent with a second regulatory role for HFE in iron absorption, independent of hepcidin from the liver. DMT1 was localised primarily on the microvillus membrane, but did partially co-localise with HFE raising the possibility that the two proteins may interact to regulate iron absorption.