Functional analysis and theoretical modeling of ferroportin reveals clustering of mutations according to phenotype

Wallace, Daniel F., Harris, Jonathan M. and Subramaniam, V. Nathan (2010) Functional analysis and theoretical modeling of ferroportin reveals clustering of mutations according to phenotype. American Journal of Physiology: Cell Physiology, 298 1: C75-C84. doi:10.1152/ajpcell.00621.2008

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Author Wallace, Daniel F.
Harris, Jonathan M.
Subramaniam, V. Nathan
Title Functional analysis and theoretical modeling of ferroportin reveals clustering of mutations according to phenotype
Journal name American Journal of Physiology: Cell Physiology   Check publisher's open access policy
ISSN 0363-6143
Publication date 2010-01-01
Sub-type Article (original research)
DOI 10.1152/ajpcell.00621.2008
Volume 298
Issue 1
Start page C75
End page C84
Total pages 10
Place of publication Bethesda, MD, U.S.A.
Publisher American Physiological Society
Collection year 2011
Language eng
Formatted abstract
Ferroportin disease is a heterogeneous iron release disorder resulting from mutations in the ferroportin gene. Ferroportin protein is a multitransmembrane domain iron transporter, responsible for iron export from cells, which, in turn, is regulated by the peptide hormone hepcidin. Mutations in the ferroportin gene may affect either regulation of the protein's transporter function or the ability of hepcidin to regulate iron efflux. We have used a combination of functional analysis of epitope-tagged ferroportin variants coupled with theoretical modeling to dissect the relationship between ferroportin mutations and their cognate phenotypes. Myc epitope-tagged human ferroportin expression constructs were transfected into Caco-2 intestinal cells and protein localization analyzed by immunofluorescence microscopy and colocalization with organelle markers. The effect of mutations on iron efflux was assessed by costaining with anti-ferritin antibodies and immunoblotting to quantitate cellular expression of ferritin and transferrin receptor 1. Wild-type ferroportin localized mainly to the cell surface and intracellular structures. All ferroportin disease-causing mutations studied had no effect on localization at the cell surface. N144H, N144T, and S338R mutant ferroportin retained the ability to transport iron. In contrast, A77D, V162Δ, and L170F mutants were iron transport defective. Surface staining experiments showed that both ends of the protein were located inside the cell. These data were used as the basis for theoretical modeling of the ferroportin molecule. The model predicted phenotypic clustering of mutations with gain-of-function variants associated with a hypothetical channel through the axis of ferroportin. Conversely, loss-of-function variants were located at the membrane/cytoplasm interface.

Copyright © 2010 the American Physiological Society
Keyword Iron
Hemochromatosis
Ferritin
Hepcidin
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2011 Collection
School of Medicine Publications
 
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Created: Thu, 25 Nov 2010, 20:32:04 EST