Hereditary hemochromatosis (HH) is the most common inherited disorder in people of Northern European origin. Iron overload results in damage specific organs leading to cirrhosis of the liver, liver cancer, diabetes, cardiomyopathy, and arthritis. The liver is a major iron-sensing organ in the body. Transferrin is the major iron transport protein in the blood. Mutations in transferrin receptor 2 (TfR2), which is predominantly expressed in hepatocytes and erythrocyte precursors result in HH. Tfr2 forms a complex with HFE, another protein involved in iron homeostasis. Experiments described in this proposal will test the model that the TfR2-HFE complex provides a sensing mechanism to detect iron-loaded Tf and thereby regulates the transcription of hepcidin, a peptide hormone that negatively regulates the efflux of iron out of intestinal cells and macrophages. Alternatively, the TfR2-HFE complex could establish basal levels of hepcidin transcription. Other proteins involved in the complex and in signaling mechanisms will be identified. The long-term goal of this research is to understand how mutations in key proteins disturb the iron balance in the body to reveal the mechanisms by which the body regulates iron-homeostasis.

Public Health Relevance

The uptake of iron into the body is tightly controlled. Too little iron causes anemia and compromised brain development. Complications of too much iron include liver cirrhosis, liver cancer, heart arrythmias, and arthritis. This project seeks to understand how the body senses and regulates iron-uptake.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Molecular and Cellular Hematology (MCH)
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Bishop, Terry Rogers
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Oregon Health and Science University
Anatomy/Cell Biology
Schools of Medicine
United States
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Zhao, Ningning; Zhang, An-Sheng; Worthen, Christal et al. (2014) An iron-regulated and glycosylation-dependent proteasomal degradation pathway for the plasma membrane metal transporter ZIP14. Proc Natl Acad Sci U S A 111:9175-80
Zhao, Ningning; Zhang, An-Sheng; Enns, Caroline A (2013) Iron regulation by hepcidin. J Clin Invest 123:2337-43
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Gao, Junwei; Chen, Juxing; De Domenico, Ivana et al. (2010) Hepatocyte-targeted HFE and TFR2 control hepcidin expression in mice. Blood 115:3374-81
Chloupkova, Maja; Zhang, An-Sheng; Enns, Caroline A (2010) Stoichiometries of transferrin receptors 1 and 2 in human liver. Blood Cells Mol Dis 44:28-33
Maxson, Julia E; Chen, Juxing; Enns, Caroline A et al. (2010) Matriptase-2- and proprotein convertase-cleaved forms of hemojuvelin have different roles in the down-regulation of hepcidin expression. J Biol Chem 285:39021-8
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Chen, Juxing; Wang, Jinzhi; Meyers, Kathrin R et al. (2009) Transferrin-directed internalization and cycling of transferrin receptor 2. Traffic 10:1488-501

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