Depletion of PCBP1 impairs ferritin iron loading in Huh7 cells. Huh7 cells transfected with PCBP1 or control siRNAs were labeled with 55FeCl3 for the indicated times. Ferritin was detected by autoradiography (A), or immunoblotting (B). (C) Relative quantitation of ferritin protein, iron, and iron/protein ratio (n=5). *P<0.0002. (D) Degradation of IRP2 in cells lacking PCBP1. HEK293 cells expressing IRP2 were transfected with PCBP1 and control siRNAs. IRP2, PCBP1, and actin were detected by immunoblotting. (E) Increased labile iron pool in cells lacking PCBP1. PCBP1 was depleted in Huh7 cells, and the relative amounts of the chelatable intracellular iron pool measured (n=6). *P=0.003.