application) Failure to maintain appropriate iron levels in man is characteristic of hereditary hemochromatosis and acquired iron overload or deficiency disorders. The overall goals of this application are to determine the molecular mechanisms of intestinal iron absorption, the structure-function relationships and the regulation of the proteins involved, and the key physiological and pathophysiological implications of their normal function or dysfunction. The proteins involved include the brush-border iron transporter DCT1, the brush-border ferrireductase, and a putative basolateral iron efflux system comprising Ireg and hephaestin. We propose to test the following hypotheses: That the binding and translocation of metal-ion (Fe2+) and the thermodynamically-coupled driving ion (H+) can be described by a kinetic model comprising a series of ligand-induced conformational changes; that striking changes in the properties of DCT1 result from a naturally-occurring mutation (G185R) associated with microcytic anemia in the mk mouse and the Belgrade rat; that atypical conductances that result from this mutation (expressed in oocytes) will reveal novel aspects of the molecular mechanisms of DCT1; that Ireg and hephaestin function together to form the basolateral iron export mechanism in enterocytes; that the sensing mechanism for serum iron is disrupted in hereditary hemochromatosis patients with the HFE C282Y mutation and in certain children with iron-deficiency anemia leading to excessive (hemochromatosis) or insufficient (anemia) intestinal iron absorption; that this abnormal iron absorption may be due to abnormal regulation of DCT1, ferrireductase, Ireg and/or hephaestin; that DCT1 is regulated at the message stability level by the IRE/IRP system and possibly also at the transcriptional level; and that DCT1 in the intestine is expressed in the brush border membrane of intestinal enterocytes whereas in non-intestinal tissues, DCT1 is localized in endosomes where it allows transferrin receptor mediated iron uptake. The results of this work will lead to a greater understanding of how iron, and other transition metal-ions, are absorbed, and will create the basic knowledge required for the design of therapeutic strategies for treating metal-ion overload and deficiency disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK057782-05
Application #
6752515
Study Section
Special Emphasis Panel (ZDK1-GRB-1 (J2))
Program Officer
May, Michael K
Project Start
2000-06-01
Project End
2005-05-31
Budget Start
2004-06-01
Budget End
2005-05-31
Support Year
5
Fiscal Year
2004
Total Cost
$254,101
Indirect Cost
Name
Brigham and Women's Hospital
Department
Type
DUNS #
030811269
City
Boston
State
MA
Country
United States
Zip Code
02115
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Mackenzie, Bryan; Ujwal, M L; Chang, Min-Hwang et al. (2006) Divalent metal-ion transporter DMT1 mediates both H+ -coupled Fe2+ transport and uncoupled fluxes. Pflugers Arch 451:544-58
Rolfs, Andreas; Bonkovsky, Herbert L; Kohlroser, James G et al. (2002) Intestinal expression of genes involved in iron absorption in humans. Am J Physiol Gastrointest Liver Physiol 282:G598-607
Gunshin, H; Allerson, C R; Polycarpou-Schwarz, M et al. (2001) Iron-dependent regulation of the divalent metal ion transporter. FEBS Lett 509:309-16