Iron Uptake Mediated by Binding of H-Ferritin to the TIM-2 Receptor in Mouse Cells

Department of Biology, North Carolina Agricultural and Technical State University, Greensboro, North Carolina, United States of America.
PLoS ONE (Impact Factor: 3.23). 08/2011; 6(8):e23800. DOI: 10.1371/journal.pone.0023800
Source: PubMed

ABSTRACT Ferritin binds specifically and saturably to a variety of cell types, and recently several ferritin receptors have been cloned. TIM-2 is a specific receptor for H ferritin (HFt) in the mouse. TIM-2 is a member of the T cell immunoglobulin and mucin domain containing (TIM) protein family and plays an important role in immunity. The expression of TIM-2 outside of the immune system indicates that this receptor may have broader roles. We tested whether ferritin binding to TIM-2 can serve as an iron delivery mechanism. TIM-2 was transfected into normal (TCMK-1) mouse kidney cells, where it was appropriately expressed on the cell surface. HFt was labeled with (55)Fe and (55)Fe-HFt was incubated with TIM-2 positive cells or controls. (55)Fe-HFt uptake was observed only in TIM-2 positive cells. HFt uptake was also seen in A20 B cells, which express endogenous TIM-2. TIM-2 levels were not increased by iron chelation. Uptake of (55)Fe-HFt was specific and temperature-dependent. HFt taken up by TIM-2 positive cells transited through the endosome and eventually entered a lysosomal compartment, distinguishing the HFt pathway from that of transferrin, the classical vehicle for cellular iron delivery. Iron delivered following binding of HFt to TIM-2 entered the cytosol and became metabolically available, resulting in increased levels of endogenous intracellular ferritin. We conclude that TIM-2 can function as an iron uptake pathway.

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Available from: Wei Wang, Aug 27, 2015
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    • "The uptake of H-ferritin results in an increase in the labile pool of iron within oligodendrocytes, which in turn causes a decrease in IRP/IRE binding and presumably decreased transferrin receptor expression, while the expression of the Hferritin receptor in rodents is thought to be independent of IRE/IRP control (Hulet et al. 2000). The receptor for H-ferritin on rat oligodendrocytes is T cell immunoglobulin and mucin domain-containing protein-2 (Tim-2) (Todorich et al. 2008), and indeed, no standard IRE was found for Tim-2 (Han et al. 2011). However, Tim-2 is not expressed in humans (Kuchroo et al. 2003). "
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