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  • Each member of the poly-r(C)-binding protein 1 (PCBP) family exhibits iron chaperone activity toward ferritin.

Each member of the poly-r(C)-binding protein 1 (PCBP) family exhibits iron chaperone activity toward ferritin.

The Journal of biological chemistry (2013-05-04)
Sebastien Leidgens, Kimberly Z Bullough, Haifeng Shi, Fengmin Li, Minoo Shakoury-Elizeh, Toshiki Yabe, Poorna Subramanian, Emory Hsu, Navin Natarajan, Anjali Nandal, Timothy L Stemmler, Caroline C Philpott
ABSTRACT

The mechanisms through which iron-dependent enzymes receive their metal cofactors are largely unknown. Poly r(C)-binding protein 1 (PCBP1) is an iron chaperone for ferritin; both PCBP1 and its paralog PCBP2 are required for iron delivery to the prolyl hydroxylase that regulates HIF1. Here we show that PCBP2 is also an iron chaperone for ferritin. Co-expression of PCBP2 and human ferritins in yeast activated the iron deficiency response and increased iron deposition into ferritin. Depletion of PCBP2 in Huh7 cells diminished iron incorporation into ferritin. Both PCBP1 and PCBP2 were co-immunoprecipitated with ferritin in HEK293 cells, and expression of both PCBPs was required for ferritin complex formation in cells. PCBP1 and -2 exhibited high affinity binding to ferritin in vitro. Mammalian genomes encode 4 PCBPs, including the minimally expressed PCBPs 3 and 4. Expression of PCBP3 and -4 in yeast activated the iron deficiency response, but only PCBP3 exhibited strong interactions with ferritin. Expression of PCBP1 and ferritin in an iron-sensitive, ccc1 yeast strain intensified the toxic effects of iron, whereas expression of PCBP4 protected the cells from iron toxicity. Thus, PCBP1 and -2 form a complex for iron delivery to ferritin, and all PCBPs may share iron chaperone activity.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Ferritin from equine spleen, Type I, saline solution
Sigma-Aldrich
Ferritin from human spleen, Type V, 10 μg/mL in 0.15 M NaCl, 10 mM Tris, pH 8.0, containing 0.1% sodium azide
Sigma-Aldrich
Ferritin from human liver, Type IV, 10 μg/mL