Ferroportin (Fpn, IREG1, MTP1) is the only identified transmembrane iron exporter in vertebrates. Our preliminary data indicate that hepcidin inhibits cellular iron export by inducing the internalization and degradation of Fpn. The goals of this proposal are to understand the mechanism of Fpn-mediated iron export and the mechanism of hepcidin-mediated Fpn internalization. The entry of iron into plasma is highly regulated and is affected by iron stores, inflammation and hypoxia. Chronic inflammation results in decreased plasma iron and an iron-limited anemia, referred to as the Anemia of Chronic Disease. Increased iron stores or inflammation result in high levels of hepcidin, a peptide secreted by liver that regulates iron metabolism. We hypothesize that this interaction is a major controlling factor in mammalian iron homeostasis. We will determine if metal export by Fpn is specific for iron through the use of metal sensitive fluorescent dyes. We will define the structure of Fpn and determine the number of transmembrane domains and the location of intracellular and extracellular domains. Biochemical and genetic approaches will be used to determine how hepcidin binds to Fpn and how Fpn is internalized. Human hepcidin will be modified to generate radiolabeled and photoaffinity ligands, which will then be used to characterize the hepcidin/Fpn interaction. By selectively changing amino acid residues in human and fish hepcidins, we will define residues critical for Fpn binding. Residues in Fpn that are required for internalization and metal transport will be identified through genetic screens and biochemical examination of hepcidin treated Fpn. RNAi silencing will be used to determine if Fpn is the only mammalian iron exporter or if are there are other iron export systems. These studies will probe the mechanism that underlines the regulation of iron export by hepcidin and will define the roles of hepcidin and Fpn in iron physiology. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK070947-03
Application #
7219530
Study Section
Erythrocyte and Leukocyte Biology Study Section (ELB)
Program Officer
Wright, Daniel G
Project Start
2005-05-15
Project End
2010-04-30
Budget Start
2007-05-01
Budget End
2008-04-30
Support Year
3
Fiscal Year
2007
Total Cost
$382,309
Indirect Cost
Name
University of Utah
Department
Pathology
Type
Schools of Medicine
DUNS #
009095365
City
Salt Lake City
State
UT
Country
United States
Zip Code
84112
Ben-Othman, Rym; Flannery, Andrew R; Miguel, Danilo C et al. (2014) Leishmania-mediated inhibition of iron export promotes parasite replication in macrophages. PLoS Pathog 10:e1003901
(2012) Retraction notice to: The role of ubiquitination in hepcidin-independent and hepcidin-dependent degradation of ferroportin. Cell Metab 15:927
Ward, Diane M; Kaplan, Jerry (2012) Ferroportin-mediated iron transport: expression and regulation. Biochim Biophys Acta 1823:1426-33
Kaplan, Jerry; Ward, Diane M; De Domenico, Ivana (2011) The molecular basis of iron overload disorders and iron-linked anemias. Int J Hematol 93:14-20
De Domenico, Ivana; Ward, Diane McVey; Kaplan, Jerry (2011) Hepcidin and ferroportin: the new players in iron metabolism. Semin Liver Dis 31:272-9
De Domenico, Ivana; Lo, Eric; Yang, Baoli et al. (2011) The role of ubiquitination in hepcidin-independent and hepcidin-dependent degradation of ferroportin. Cell Metab 14:635-46
Troadec, Marie-Berengere; Ward, Diane McVey; Lo, Eric et al. (2010) Induction of FPN1 transcription by MTF-1 reveals a role for ferroportin in transition metal efflux. Blood 116:4657-64
De Domenico, Ivana; Zhang, Tian Y; Koening, Curry L et al. (2010) Hepcidin mediates transcriptional changes that modulate acute cytokine-induced inflammatory responses in mice. J Clin Invest 120:2395-405
De Domenico, Ivana; Lo, Eric; Ward, Diane M et al. (2010) Human mutation D157G in ferroportin leads to hepcidin-independent binding of Jak2 and ferroportin down-regulation. Blood 115:2956-9
De Domenico, Ivana; Ward, Diane McVey; Kaplan, Jerry (2009) Serum ferritin regulates blood vessel formation: a role beyond iron storage. Proc Natl Acad Sci U S A 106:1683-4

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