Western blotting

Immunoblotting was carried out as previously described (27). The membrane was blocked and probed with antibodies to ferritin heavy chain (Cell Signaling Technology, Danvers, MA, USA), FPN (Alpha Diagnostics, San Antonio, TX, USA), sodium-potassium ATPase (Novus Biologicals, Littleton, CO, USA) or β-actin (Sigma-Aldrich, St Louis, MO, USA). The blots were developed with fluorescently-tagged anti-rabbit or anti-mouse secondary antibodies as appropriate and the signals were visualized with an Odyssey infra-red fluorescence imaging system (Li-Cor Biosciences, Lincoln, NE, USA).