Cell-specific KO of Fpn in erythroid cells decreased serum iron but increased tissue iron contents. (A) Protein abundance in mouse RBC membrane measured by mass spectrometry. The abundance of band 3, one of the most abundant RBC membrane proteins, was taken as 100%, and other proteins were normalized to band 3 according to their exponentially modified protein abundance index (emPAI). N/A, not applicable. (B) FPN, TfR1, actin, and band 3 levels in total cell lysates of purified splenic macrophages (Mac), peripheral RBCs, and bone marrow erythroblasts (n = 3). Ponceau S staining is shown as a loading control. Actin-S, short exposure; actin-L, long exposure. Serum iron (C), total iron binding capacity (TIBC) (D), transferrin (Tf) saturation levels (E), and serum ferritin (F) of WT and erythroblast-specific Fpn KO mice (Fpn KO). Nonheme iron (NHI) and ferritin levels in spleens (G), liver (H), kidneys (I), and splenic macrophages (J) of WT and Fpn KO mice. Data are presented as mean ± 95% confidence interval (CI).