title: Ferroportin and exocytoplasmic ferroxidase activity are required for brain microvascular endothelial cell iron efflux.
abstract: The mechanism(s) of iron flux across the brain microvasculature endothelial cells (BMVEC) of the blood-brain barrier remains unknown. Although both hephaestin (Hp) and the ferrous iron permease ferroportin (Fpn) have been identified in BMVEC, their roles in iron efflux have not been examined. Using a human BMVEC line (hBMVEC), we have demonstrated that these proteins are required for iron efflux from these cells. Expression of both Hp and Fpn protein was confirmed in hBMVEC by immunoblot and indirect immunofluorescence; we show that hBMVEC express soluble ceruloplasmin (Cp) transcript as well. Depletion of endogenous Hp and Cp via copper chelation leads to the reduction of hBMVEC Fpn protein levels as well as a complete inhibition of (59)Fe efflux. Both hBMVEC Fpn protein and (59)Fe efflux activity are restored upon incubation with 6.6 nm soluble plasma Cp. These results are independent of the source of cell iron, whether delivered as transferrin- or non-transferrin-bound (59)Fe. Our results demonstrate that iron efflux from hBMVEC Fpn requires the action of an exocytoplasmic ferroxidase, which can be either endogenous Hp or extracellular Cp.
authors: Department of Biochemistry, University at Buffalo, School of Medicine and Biomedical Sciences, Buffalo, New York 14214, USA.
authors: Ryan C
authors: RC
authors: McCarthy
authors: Daniel J
authors: DJ
authors: Kosman
mesh_terms: D001921:Brain / Q000098:blood supply; D018938:Caco-2 Cells; D027682:Cation Transport Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002570:Ceruloplasmin / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D003300:Copper / Q000378:metabolism; D017077:Culture Media, Conditioned; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology*; D056945:Hep G2 Cells; D006801:Humans; D007501:Iron / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D055806:Microvessels / Q000166:cytology*; D010618:Phenanthrolines / Q000494:pharmacology; D011485:Protein Binding; D021381:Protein Transport; D000098742:Ferroportin
chemical_list: D027682:Cation Transport Proteins; D002614:Chelating Agents; D017077:Culture Media, Conditioned; C492164:HEPH protein, human; D008565:Membrane Proteins; D010618:Phenanthrolines; D000098742:Ferroportin; C028559:bathocuproine sulfonate; D003300:Copper; D007501:Iron; D002570:Ceruloplasmin
keywords: Blood Brain Barrier; Brain Metabolism; Cell Biology; Ceruloplasmin; Ferroportin; Ferroxidase; Hephaestin; Iron Metabolism; Neurochemistry; Transport Metals
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