title: Ferroxidase hephaestin's cell-autonomous role in the retinal pigment epithelium.
abstract: Hephaestin (Heph) is a ferroxidase protein that converts ferrous to ferric iron to facilitate cellular iron export by ferroportin. Many tissues express either Heph or its homologue, ceruloplasmin (Cp), but the retina expresses both. In mice, a combined systemic mutation of Heph and systemic knockout of Cp (Cp(-/-), Heph(sla/sla)) causes retinal iron accumulation and retinal degeneration, with features of human age-related macular degeneration; however, the role of Heph and Cp in the individual retinal cells is unclear. Herein, we used conditional knockout mice to study Heph's role in retinal pigment epithelial (RPE) and photoreceptor cells. Loss of both Heph and Cp from RPE cells alone results in RPE cell iron accumulation and degeneration. We found, however, that RPE iron accumulation in these conditional knockout mice is not as great as in systemic knockout mice. Photoreceptor-specific Heph knockout indicates that the additional iron in the RPE cells does not result from loss of ferroxidases in the photoreceptors, and Cp and Heph play minor roles in photoreceptors. Instead, loss of ferroxidases in other retinal cells causes retinal iron accumulation and transfer of iron to the RPE cells. Cp and Heph are necessary for iron export from the retina but are not essential for iron import into the retina. Thus, our studies, revise how we think about iron import and export from the retina.
authors.affiliation: F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Natalie
authors.initials: N
authors.lastname: Wolkow
authors.forename: Delu
authors.initials: D
authors.lastname: Song
authors.forename: Ying
authors.initials: Y
authors.lastname: Song
authors.forename: Sally
authors.initials: S
authors.lastname: Chu
authors.forename: Majda
authors.initials: M
authors.lastname: Hadziahmetovic
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Lee
authors.forename: Jared
authors.initials: J
authors.lastname: Iacovelli
authors.forename: Steven
authors.initials: S
authors.lastname: Grieco
authors.forename: Joshua L
authors.initials: JL
authors.lastname: Dunaief
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002570:Ceruloplasmin / Q000378:metabolism; D004195:Disease Models, Animal; D007501:Iron / Q000378:metabolism; D008268:Macular Degeneration / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism / Q000473:pathology; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics; D055351:Retinal Neurons / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000378:metabolism* / Q000473:pathology
chemical_list: C117324:Heph protein, mouse; D008565:Membrane Proteins; C095148:Sla protein, mouse; D007501:Iron; D002570:Ceruloplasmin; D016392:Proto-Oncogene Proteins pp60(c-src)