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Hamdi-Rozé H, Ben Ali Z, Ropert M, Detivaud L, Aggoune S, Simon D, Pelletier G, Deugnier Y, David V, Bardou-Jacquet E. Variable expressivity of HJV related hemochromatosis: "Juvenile" hemochromatosis? Blood Cells Mol Dis 2018; 74:30-33. [PMID: 30389309 DOI: 10.1016/j.bcmd.2018.10.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 10/19/2018] [Accepted: 10/19/2018] [Indexed: 12/18/2022]
Abstract
Juvenile hemochromatosis is a rare autosomal recessive disease due to variants in the Hemojuvelin (HJV) gene. Although biological features mimic HFE hemochromatosis, clinical presentation is worst with massive iron overload diagnosed during childhood. Our study describes clinical features and results of genetic testing for a group of patients initially referred for a hepcidino-deficiency syndrome and for whom HJV hemochromatosis was finally diagnosed. 662 patients with iron overload and high serum transferrin saturation were tested, and five genes (HFE, HJV, HAMP, TFR2, SLC40A1) were sequenced. Among our cohort, ten unrelated patients were diagnosed with HJV hemochromatosis. Genetic testing revealed five previously published and five undescribed variants: p.Arg41Pro, p.His180Arg, p.Lys299Glu, p.Cys361Arg and p.Ala384Val. Surprisingly, this study revealed a late age of onset in some patients, contrasting with the commonly accepted definition of "juvenile" hemochromatosis. Five of our patients were 30 years old or older, including two very late discoveries. Biological features and severity of iron overload were similar in younger and older patients. Our study brings new insight on HJV hemochromatosis showing that mild phenotype and late onset are possible. Genetic testing for HJV variants should thus be performed for all patients displaying a non-p.Cys282Tyr homozygous HFE hemochromatosis with hepcidin deficiency phenotype.
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Affiliation(s)
- Houda Hamdi-Rozé
- Univ Rennes, CHU Rennes, INSERM, French Reference Center for Hemochromatosis and Iron Metabolism Disease, F-35000 Rennes, France; Univ Rennes, CHU Rennes, CNRS, IGDR, UMR 6290, Molecular Genetics Department, F-35000 Rennes, France.
| | - Zeineb Ben Ali
- Univ Rennes, CHU Rennes, INSERM, French Reference Center for Hemochromatosis and Iron Metabolism Disease, F-35000 Rennes, France; Univ Rennes, CHU Rennes, INSERM, Liver Disease Department, F-35000 Rennes, France
| | - Martine Ropert
- Univ Rennes, CHU Rennes, INSERM, French Reference Center for Hemochromatosis and Iron Metabolism Disease, F-35000 Rennes, France; Univ Rennes, CHU Rennes, INSERM, Biochemistry Department, F-35000 Rennes, France
| | - Lénaïck Detivaud
- Univ Rennes, CHU Rennes, INSERM, French Reference Center for Hemochromatosis and Iron Metabolism Disease, F-35000 Rennes, France
| | - Samira Aggoune
- EPH Belfort, Pediatric Department, El Harrach, Alger 16000, Algeria
| | - Dominique Simon
- Hopital Universitaire Robert-Debré, Endocrinology and Pediatric Diabetology, Paris 75019, France
| | - Gilles Pelletier
- Hopital Bicêtre, Hepatogastroenterology, Le Kremlin-Bicêtre 94275, France
| | - Yves Deugnier
- Univ Rennes, CHU Rennes, INSERM, French Reference Center for Hemochromatosis and Iron Metabolism Disease, F-35000 Rennes, France; Univ Rennes, CHU Rennes, INSERM, Liver Disease Department, F-35000 Rennes, France
| | - Véronique David
- Univ Rennes, CHU Rennes, CNRS, IGDR, UMR 6290, Molecular Genetics Department, F-35000 Rennes, France
| | - Edouard Bardou-Jacquet
- Univ Rennes, CHU Rennes, INSERM, French Reference Center for Hemochromatosis and Iron Metabolism Disease, F-35000 Rennes, France; Univ Rennes, CHU Rennes, INSERM, Liver Disease Department, F-35000 Rennes, France
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Lampi KJ, Murray MR, Peterson MP, Eng BS, Yue E, Clark AR, Barbar E, David LL. Differences in solution dynamics between lens β-crystallin homodimers and heterodimers probed by hydrogen-deuterium exchange and deamidation. Biochim Biophys Acta Gen Subj 2015; 1860:304-14. [PMID: 26145577 DOI: 10.1016/j.bbagen.2015.06.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 06/12/2015] [Accepted: 06/18/2015] [Indexed: 11/28/2022]
Abstract
BACKGROUND Lens transparency is due to the ordered arrangement of the major structural proteins, called crystallins. βB2 crystallin in the lens of the eye readily forms dimers with other β-crystallin subunits, but the resulting heterodimer structures are not known and were investigated in this study. METHODS Structures of βA3 and βB2 crystallin homodimers and the βA3/βB2 crystallin heterodimers were probed by measuring changes in solvent accessibility using hydrogen-deuterium exchange with mass spectrometry. We further mimicked deamidation in βB2 and probed the effect on the βA3/βB2 heterodimer. Results were confirmed with chemical crosslinking and NMR. RESULTS Both βA3 and βB2 had significantly decreased deuterium levels in the heterodimer compared to their respective homodimers, suggesting that they had less solvent accessibility and were more compact in the heterodimer. The compact structure of βB2 was supported by the identification of chemical crosslinks between lysines in βB2 within the heterodimer that were inconsistent with βB2's extended homodimeric structure. The compact structure of βA3 was supported by an overall decrease in mobility of βA3 in the heterodimer detected by NMR. In βB2, peptides 70-84 and 121-134 were exposed in the homodimer, but buried in the heterodimer with ≥50% decreases in deuterium levels. Homologous peptides in βA3, 97-109 and 134-149, had 25-50% decreases in deuterium levels in the heterodimer. These peptides are probable sites of interaction between βB2 and βA3 and are located at the predicted interface between subunits with bent linkers. Deamidation at Q184 in βB2 at this predicted interface led to a less compact βB2 in the heterodimer. The more compact structure of the βA3/βB2 heterodimer was also more heat stable than either of the homodimers. CONCLUSIONS The major structural proteins in the lens, the β-crystallins, are not static, but dynamic in solution, with differences in accessibility between the homo-and hetero-dimers. This structural flexibility, particularly of βB2, may facilitate formation of different size higher-ordered structures found in the transparent lens. GENERAL SIGNIFICANCE Understanding complex hetero-oligomer interactions between β-crystallins in normal lens and how these interactions change during aging is fundamental to understanding the cause of cataracts. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Affiliation(s)
- Kirsten J Lampi
- Integrative Biosciences, Oregon Health & Science University, Portland, OR 97239-3098, United States.
| | - Matthew R Murray
- Integrative Biosciences, Oregon Health & Science University, Portland, OR 97239-3098, United States
| | - Matthew P Peterson
- Integrative Biosciences, Oregon Health & Science University, Portland, OR 97239-3098, United States
| | - Bryce S Eng
- Integrative Biosciences, Oregon Health & Science University, Portland, OR 97239-3098, United States
| | - Eileen Yue
- Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, OR 97239-3098, United States
| | - Alice R Clark
- Birkbeck College, University of London, United Kingdom
| | - Elisar Barbar
- Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, United States
| | - Larry L David
- Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, OR 97239-3098, United States
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Rausa M, Ghitti M, Pagani A, Nai A, Campanella A, Musco G, Camaschella C, Silvestri L. Identification of TMPRSS6 cleavage sites of hemojuvelin. J Cell Mol Med 2015; 19:879-88. [PMID: 25704252 PMCID: PMC4395201 DOI: 10.1111/jcmm.12462] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Accepted: 09/19/2014] [Indexed: 12/11/2022] Open
Abstract
Hemojuvelin (HJV), the coreceptor of the BMP-SMAD pathway that up-regulates hepcidin transcription, is a repulsive guidance molecule (RGMc) which undergoes a complex intracellular processing. Following autoproteolysis, it is exported to the cell surface both as a full-length and a heterodimeric protein. In vitro membrane HJV (m-HJV) is cleaved by the transmembrane serine protease TMPRSS6 to attenuate signalling and to inhibit hepcidin expression. In this study, we investigated the number and position of HJV cleavage sites by mutagenizing arginine residues (R), potential TMPRSS6 targets, to alanine (A). We analysed translation and membrane expression of HJV R mutants and the pattern of fragments they release in the culture media in the presence of TMPRSS6. Abnormal fragments were observed for mutants at arginine 121, 176, 218, 288 and 326. Considering that all variants, except HJVR121A, lack autoproteolytic activity and some (HJVR176A and HJVR288A) are expressed at reduced levels on cell surface, we identified the fragments originating from either full-length or heterodimeric proteins and defined the residues 121 and 326 as the TMPRSS6 cleavage sites in both isoforms. Using the N-terminal FLAG-tagged HJV, we showed that residue 121 is critical also in the rearrangement of the N-terminal heterodimeric HJV. Exploiting the recently reported RGMb crystallographic structure, we generated a model of HJV that was used as input structure for all-atoms molecular dynamics simulation in explicit solvent. As assessed by in silico studies, we concluded that some arginines in the von Willebrand domain appear TMPRSS6 insensitive, likely because of partial protein structure destabilization.
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Affiliation(s)
- Marco Rausa
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milan, Italy; Vita Salute University, Milan, Italy
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Liver Fatty Acid Binding Protein And Hemojuvelin - Potential Biomarkers For Liver Function in Rat Model. CURRENT HEALTH SCIENCES JOURNAL 2015; 41:115-120. [PMID: 30364790 PMCID: PMC6201200 DOI: 10.12865/chsj.41.02.05] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Accepted: 03/01/2015] [Indexed: 11/30/2022]
Abstract
PURPOSE The purpose of the present study was to investigate whether the co-administration of aripiprazole and fluoxetine could produce impaired liver function in Wistar rats by means of liver fatty acid binding protein (L-FABP) and hemojuvelin (HJV) serum levels. Furthermore, the experiment intended to assess the salivary levels of L-FABP and HJV and to determine whether they correlate with the serum levels of the two markers. MATERIALS AND METHODS Adult male Wistar rats were randomly assigned to four groups: control (saline 10ml/kg), aripiprazole (4.05 mg/kg), fluoxetine (10 mg/kg) and aripiprazole + fluoxetine (4.05 mg/kg + 10 mg/kg). The drugs were administered by gavage, daily at the same hour, along a 6 week period. L-FABP and HJV levels were determined in serum, from intraventricular blood, and in saliva. Also from intraventricular blood, serum levels for aspartate aminotransferase (ASAT) and alanine amino transferase (ALAT) were assessed. RESULTS Positive and statistically significant correlations between serum and salivary levels of L-FABP and HJV were found. Aripiprazole + fluoxetine group experienced increased serum L-FABP levels than aripiprazole and fluoxetine groups, and salivary L-FABP as compared to aripiprazole group; but it registered decreased levels for serum and salivary HJV, for ASAT and ALAT than aripiprazole and fluoxetine groups, and for salivary L-FABP compared to fluoxetine group. CONCLUSIONS The data indicate that: aripiprazole coprescribed with fluoxetine do not cause additional alterations in liver function; L-FABP and HJV levels can be helpful as biomarkers for impaired function of hepatocytes; and that their salivary determination can replace serum determination.
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