Fig 1.
HFE increases ferritin and reduces TfR1 expression by the reticuloendothelial cell line THP-1. (A and B) Expression of HFE by THP-1 and U937 cells. (A) THP-1 endogenously express low levels of HFE (green, 10G4 antibody). (B) HFE is not detected on U937 cells with this antibody. TfR1 expression at log phase is shown in red. (C–H) Effect of HFE on ferritin and TfR1 expression in THP-1 cells. Full-length HFE was expressed by infection with recombinant vaccinia virus (C and D), or cells were exposed for 16 h to soluble HFE at 300 nM (20 μg/ml) (G and H). Both forms of HFE increased ferritin expression (C and G, green histograms) and decreased TfR1 (D and H, green histograms) compared with untreated THP-1 cells (filled gray histograms). Controls: expression of mouse H2-Kb by vaccinia infection (E and F, green line) does not alter ferritin or TfR1 levels in THP-1 cells. (I and J) In contrast, a 16-h incubation of U937 cells with 300 nM soluble HFE (or infection of U937 cells with HFE-vacc, not shown) reduces ferritin expression (I, green) and raises TfR1 (J, green) compared with untreated U937 cells (filled gray). (G–J) In both THP-1 and U937, iron loading with 250 μg/ml FAC (blue) raises ferritin and reduces TfR1, whereas chelation of iron with 50 μM DFO (red) reduces ferritin and raises TfR1. (K Inset) HeLa-HFE cells grown in the absence of tetracycline express full-length HFE (red), whereas cells grown with tetracycline are HFE negative (blue). (K and L) HeLa-HFE cells positive for full-length HFE (green histograms) express less ferritin (K) and more TfR1 (L) than HFE-negative HeLa-HFE cells (filled gray). Filled purple histograms represent staining with isotype control antibodies.