Defective trafficking and localization of mutated transferrin receptor 2: implications for type 3 hereditary hemochromatosis

Wallace, Daniel F.; Summerville, Lesa; Crampton, Emily M.; Subramaniam, V. Nathan

doi:10.1152/ajpcell.00492.2007

Cited by 21 publications

(26 citation statements)

References 38 publications

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“…In contrast, adult KI mice have normal transferrin saturation and LIC and develop liver iron overload only with aging. Although it has been previously shown that, in overexpressing cells, the mutated Tfr2-M167K ␣ protein is predominantly retained in the endoplasmic reticulum and does not reach the plasma membrane, 25 the phenotype of KI mice indicates that in vivo this variant is functional. Furthermore, KI mice show transient macrocytic anemia during weaning but surprisingly accumulate iron in spleen macrophages.…”

Section: Discussionmentioning

confidence: 97%

Comparison of 3 Tfr2-deficient murine models suggests distinct functions for Tfr2-α and Tfr2-β isoforms in different tissues

Roetto¹,

Cunto²,

Pellegrino³

et al. 2010

Blood

109

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Section: Discussionmentioning

confidence: 97%

Comparison of 3 Tfr2-deficient murine models suggests distinct functions for Tfr2-α and Tfr2-β isoforms in different tissues

Roetto¹,

Cunto²,

Pellegrino³

et al. 2010

Blood

109

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“…These two vectors were engineered to contain either amino-or carboxyl-terminal double-myc (DMyc) tags, and their construction is described in Ref. 36.…”

Section: Methodsmentioning

confidence: 99%

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

Wallace

Harris

Subramaniam

2010

American Journal of Physiology-Cell Physiology

Self Cite

104

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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, V162Delta, 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.

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“…16 The absence of surface expression of mutant TFR2 would hamper the interaction with diferric transferrin and the activation of the signaling pathway resulting in hepcidin induction. This likely occurs also in the present case in which the lack of exon 4 extensively disrupts the extracellular domain of the full transmembrane protein.…”

confidence: 99%

Expression of hepcidin and other iron-related genes in type 3 hemochromatosis due to a novel mutation in transferrin receptor-2

Pelucchi¹,

Mariani²,

Trombini³

et al. 2009

Haematologica

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Citation: Pelucchi S, Mariani R, Trombini P, Coletti S, Pozzi M, Paolini V, Barisani D, Piperno A. Expression of hepcidin and other iron-related genes in type 3 hemochromatosis due to a novel mutation in transferrin receptor-2. Haematologica 2009; 94:276-279. doi: 10.3324/haematol.13576 ©2009 Ferrata Storti Foundation. This is an open-access paper. ABSTRACT Expression of hepcidin and other iron-related genes in type 3 hemochromatosis due to a novel mutation in transferrin receptor-2 © F e r r a t a S t o r t i F o u n d a t i o nTfR2 mutation and expression study haematologica | 2009; 94(2) | 277 | Liver biopsy was processed for histology and mRNA analysis. Assessment of hepatic fibrosis and iron overload, mRNA extraction and cDNA synthesis were performed as previously described in detail.11 cDNA was stored at -80°C until its use. cDNA was amplified by PCR (Online Supplementary Table S1), directly sequenced and compared with reference sequence (GenBank Accession N°NM_003227.2).mRNA expression levels of BMP2, BMP4, CP, DMT1, HAMP, HFE, HJV, SLC40A1, TFR1, TFR2 (the commercial probe was designed in exon boundary 3-4, Part Number Hs00162690_m1) and HPRT1, chosen as housekeeping gene, were evaluated by quantitative Real-Time PCR (qRT-PCR) as previously described.11 The proband's results were compared to those observed in 10 patients HFE-HH (C282Y homozygotes) and 8 controls with nonalcoholic-fatty-liver (NAFLD) without hepatic iron overload, absent fibrosis and inflammation. Full clinical data of HFE-HH patients and NAFLD subjects are reported in Barisani et al. 11Urinary hepcidin was measured by SELDI-TOF-MS according to Bozzini et al. 12 A challenge test by 65 mg oral iron as ferrous sulfate (iron, 65 mg, CVS Pharmacy) was conducted to assess hepatic response to iron, as previously reported. 13Written informed consent for genetic study, liver biopsy and iron challenge were obtained according to the Institution's guidelines. The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki as reflected in a priori approval by the Ethical Committee of San Gerardo Hospital. Results and Discussion Case descriptionA 47 year-old woman came to our attention in January 2007. In 1998, serum ferritin and transferrin saturation were 2207 µg/L and 88% respectively. HFE (C282Y and H63D), TFR2 (E60X, M172K, Y250X, AVAQ594-597 del) and Ferroportin1 (N144H, V162 del) mutations were absent. Hepatitis B and C viral infections, hematologic and inflammatory diseases were excluded. No further analysis and treatment were performed. At our evaluation, serum ferritin was 2674 µg/L, transferrin saturation 88%, hemoglobin 14.6 g/dL and mean corpuscular volume 89 fl. Both parents originated from the same village in Southern Italy but there was neither family history of consanguinity or hemocromatosis; her 2 offspring and 2 siblings have normal serum iron indices. She had regular menstrual blood losses, no history of alcohol intake, blood transfusions or parenteral iron administration. Metabolic syndrome, char...

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Defective trafficking and localization of mutated transferrin receptor 2: implications for type 3 hereditary hemochromatosis

Abstract: Wallace DF, Summerville L, Crampton EM, Subramaniam VN. Defective trafficking and localization of mutated transferrin receptor 2: implications for type 3 hereditary hemochromatosis.

Cited by 21 publications

References 38 publications

Comparison of 3 Tfr2-deficient murine models suggests distinct functions for Tfr2-α and Tfr2-β isoforms in different tissues

Comparison of 3 Tfr2-deficient murine models suggests distinct functions for Tfr2-α and Tfr2-β isoforms in different tissues

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

Expression of hepcidin and other iron-related genes in type 3 hemochromatosis due to a novel mutation in transferrin receptor-2

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