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Title: Molecular pathophysiology of intestinal iron transport in hereditary haemochromatosis
Author: Griffiths, W. J. H.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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Hereditary haemochromatosis is characterized by unregulated intestinal iron absorption but the molecular mechanism by which this occurs is not understood. Most patients are homozygous for a disabling mutation, C282Y, in the HFE gene. Lately, mutations in a newly-identified second transferrin receptor gene (TfR2) have been associated with haemochromatosis. The physiological function of the HFE protein is unknown although it appears to mediate cellular transferrin-iron uptake in vitro. The divalent metal transporter (DMT1) is implicated in the mucosal uptake of ferrous iron but whether this process is regulated by HFE is not clear. To examine interactions between HFE and iron-transport proteins, rabbit and avian antibodies specific for HFE, DMT1 and TfR2 were generated. Confocal microscopy in human intestinal Caco-2 cells showed that endogenous HFE and DMT1 localise to separate vesicular compartments and that HFE interacts directly with both TfR1 and TfR2 in early endosomes. Within human duodenal mucosa TfR2 protein expression was restricted to the undifferentiated crypts where colocalisation with HFE occurred. The functional effects of HFE deficiency were investigated in an authentic genetic mouse model of hereditary haemochromatosis. The Vmax for unidirectional ferrous iron uptake was greater in HFE-knockout mice than in matched wild-type controls (29.8 ± 4.6 compared with 13.0 ± 1.0 pmol/mg/min, p<0.01). Immunoreactive DMT1 protein was increased two-fold in duodenal mucosal extracts from HFE-knockout mice compared with wild-type, and pre-treatment of HFE-knockout mucosa with antibody to DMT1 abolished the increase in Vmax. Uptake of iron presented as Fe3+ was enhanced, at low/physiological concentrations, in HFE-knockout mice (p<0.05) and studies using the Fe2+ -chelator ferrozine showed that mucosal ferric reductase activity reduced Fe3+ to Fe2+ for uptake.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available