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Paz D, Pinales BE, Castellanos BS, Perez I, Gil CB, Madrigal LJ, Reyes-Nava NG, Castro VL, Sloan JL, Quintana AM. Abnormal chondrocyte development in a zebrafish model of cblC syndrome restored by an MMACHC cobalamin binding mutant. Differentiation 2023; 131:74-81. [PMID: 37167860 DOI: 10.1016/j.diff.2023.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 04/10/2023] [Accepted: 04/24/2023] [Indexed: 05/13/2023]
Abstract
Variants in the MMACHC gene cause combined methylmalonic acidemia and homocystinuria cblC type, the most common inborn error of intracellular cobalamin (vitamin B12) metabolism. cblC is associated with neurodevelopmental, hematological, ocular, and biochemical abnormalities. In a subset of patients, mild craniofacial dysmorphia has also been described. Mouse models of Mmachc deletion are embryonic lethal but cause severe craniofacial phenotypes such as facial clefts. MMACHC encodes an enzyme required for cobalamin processing and variants in this gene result in the accumulation of two metabolites: methylmalonic acid (MMA) and homocysteine (HC). Interestingly, other inborn errors of cobalamin metabolism, such as cblX syndrome, are associated with mild facial phenotypes. However, the presence and severity of MMA and HC accumulation in cblX syndrome is not consistent with the presence or absence of facial phenotypes. Thus, the mechanisms by which mutations in MMACHC cause craniofacial defects are yet to be completely elucidated. Here we have characterized the craniofacial phenotypes in a zebrafish model of cblC (hg13) and performed restoration experiments with either a wildtype or a cobalamin binding deficient MMACHC protein. Homozygous mutants did not display gross morphological defects in facial development but did have abnormal chondrocyte nuclear organization and an increase in the average number of neighboring cell contacts, both phenotypes were fully penetrant. Abnormal chondrocyte nuclear organization was not associated with defects in the localization of neural crest specific markers, sox10 (RFP transgene) or barx1. Both nuclear angles and the number of neighboring cell contacts were fully restored by wildtype MMACHC and a cobalamin binding deficient variant of the MMACHC protein. Collectively, these data suggest that mutation of MMACHC causes mild to moderate craniofacial phenotypes that are independent of cobalamin binding.
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Affiliation(s)
- David Paz
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Briana E Pinales
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Barbara S Castellanos
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Isaiah Perez
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Claudia B Gil
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Lourdes Jimenez Madrigal
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Nayeli G Reyes-Nava
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Victoria L Castro
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Jennifer L Sloan
- Metabolic Medicine Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Anita M Quintana
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX, 79968, USA.
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2
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Paz D, Pinales BE, Castellanos BS, Perez I, Gil CB, Madrigal LJ, Reyes-Nava NG, Castro VL, Sloan JL, Quintana AM. Abnormal chondrocyte intercalation in a zebrafish model of cblC syndrome restored by an MMACHC cobalamin binding mutant. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.20.524982. [PMID: 36711998 PMCID: PMC9882310 DOI: 10.1101/2023.01.20.524982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Variants in the MMACHC gene cause combined methylmalonic acidemia and homocystinuria cblC type, the most common inborn error of intracellular cobalamin (vitamin B12) metabolism. cblC is associated with neurodevelopmental, hematological, ocular, and biochemical abnormalities. In a subset of patients, mild craniofacial dysmorphia has also been described. Mouse models of Mmachc deletion are embryonic lethal but cause severe craniofacial phenotypes such as facial clefts. MMACHC encodes an enzyme required for cobalamin processing and variants in this gene result in the accumulation of two metabolites: methylmalonic acid (MMA) and homocysteine (HC). Interestingly, other inborn errors of cobalamin metabolism, such as cblX syndrome, are associated with mild facial phenotypes. However, the presence and severity of MMA and HC accumulation in cblX syndrome is not consistent with the presence or absence of facial phenotypes. Thus, the mechanisms by which mutation of MMACHC cause craniofacial defects have not been completely elucidated. Here we have characterized the craniofacial phenotypes in a zebrafish model of cblC ( hg13 ) and performed restoration experiments with either wildtype or a cobalamin binding deficient MMACHC protein. Homozygous mutants did not display gross morphological defects in facial development, but did have abnormal chondrocyte intercalation, which was fully penetrant. Abnormal chondrocyte intercalation was not associated with defects in the expression/localization of neural crest specific markers, sox10 or barx1 . Most importantly, chondrocyte organization was fully restored by wildtype MMACHC and a cobalamin binding deficient variant of MMACHC protein. Collectively, these data suggest that mutation of MMACHC causes mild to moderate craniofacial phenotypes that are independent of cobalamin binding.
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Affiliation(s)
- David Paz
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX 79968 USA
| | - Briana E Pinales
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX 79968 USA
| | - Barbara S Castellanos
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX 79968 USA
| | - Isaiah Perez
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX 79968 USA
| | - Claudia B Gil
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX 79968 USA
| | - Lourdes Jimenez Madrigal
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX 79968 USA
| | - Nayeli G Reyes-Nava
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX 79968 USA
| | - Victoria L Castro
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX 79968 USA
| | - Jennifer L Sloan
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX 79968 USA
| | - Anita M Quintana
- Department of Biological Sciences, Border Biomedical Research Center, The University of Texas at El Paso, El Paso, TX 79968 USA
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3
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Temova Rakuša Ž, Roškar R, Hickey N, Geremia S. Vitamin B 12 in Foods, Food Supplements, and Medicines-A Review of Its Role and Properties with a Focus on Its Stability. MOLECULES (BASEL, SWITZERLAND) 2022; 28:molecules28010240. [PMID: 36615431 PMCID: PMC9822362 DOI: 10.3390/molecules28010240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 12/21/2022] [Accepted: 12/22/2022] [Indexed: 12/29/2022]
Abstract
Vitamin B12, also known as the anti-pernicious anemia factor, is an essential micronutrient totally dependent on dietary sources that is commonly integrated with food supplements. Four vitamin B12 forms-cyanocobalamin, hydroxocobalamin, 5'-deoxyadenosylcobalamin, and methylcobalamin-are currently used for supplementation and, here, we provide an overview of their biochemical role, bioavailability, and efficacy in different dosage forms. Since the effective quantity of vitamin B12 depends on the stability of the different forms, we further provide a review of their main reactivity and stability under exposure to various environmental factors (e.g., temperature, pH, light) and the presence of some typical interacting compounds (oxidants, reductants, and other water-soluble vitamins). Further, we explore how the manufacturing process and storage affect B12 stability in foods, food supplements, and medicines and provide a summary of the data published to date on the content-related quality of vitamin B12 products on the market. We also provide an overview of the approaches toward their stabilization, including minimization of the destabilizing factors, addition of proper stabilizers, or application of some (innovative) technological processes that could be implemented and contribute to the production of high-quality vitamin B12 products.
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Affiliation(s)
| | - Robert Roškar
- Faculty of Pharmacy, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Neal Hickey
- Department of Chemical and Pharmaceutical Sciences, Centre of Excellence in Biocrystallography, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
| | - Silvano Geremia
- Department of Chemical and Pharmaceutical Sciences, Centre of Excellence in Biocrystallography, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
- Correspondence:
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4
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Esser AJ, Mukherjee S, Dereven‘kov IA, Makarov SV, Jacobsen DW, Spiekerkoetter U, Hannibal L. Versatile Enzymology and Heterogeneous Phenotypes in Cobalamin Complementation Type C Disease. iScience 2022; 25:104981. [PMID: 36105582 PMCID: PMC9464900 DOI: 10.1016/j.isci.2022.104981] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Nutritional deficiency and genetic errors that impair the transport, absorption, and utilization of vitamin B12 (B12) lead to hematological and neurological manifestations. The cblC disease (cobalamin complementation type C) is an autosomal recessive disorder caused by mutations and epi-mutations in the MMACHC gene and the most common inborn error of B12 metabolism. Pathogenic mutations in MMACHC disrupt enzymatic processing of B12, an indispensable step before micronutrient utilization by the two B12-dependent enzymes methionine synthase (MS) and methylmalonyl-CoA mutase (MUT). As a result, patients with cblC disease exhibit plasma elevation of homocysteine (Hcy, substrate of MS) and methylmalonic acid (MMA, degradation product of methylmalonyl-CoA, substrate of MUT). The cblC disorder manifests early in childhood or in late adulthood with heterogeneous multi-organ involvement. This review covers current knowledge on the cblC disease, structure–function relationships of the MMACHC protein, the genotypic and phenotypic spectra in humans, experimental disease models, and promising therapies.
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Wiedemann A, Oussalah A, Lamireau N, Théron M, Julien M, Mergnac JP, Augay B, Deniaud P, Alix T, Frayssinoux M, Feillet F, Guéant JL. Clinical, phenotypic and genetic landscape of case reports with genetically proven inherited disorders of vitamin B 12 metabolism: A meta-analysis. Cell Rep Med 2022; 3:100670. [PMID: 35764087 PMCID: PMC9381384 DOI: 10.1016/j.xcrm.2022.100670] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 11/22/2021] [Accepted: 06/02/2022] [Indexed: 10/31/2022]
Abstract
Inherited disorders of B12 metabolism produce a broad spectrum of manifestations, with limited knowledge of the influence of age and the function of related genes. We report a meta-analysis on 824 patients with a genetically proven diagnosis of an inherited disorder of vitamin B12 metabolism. Gene clusters and age categories are associated with patients' manifestations. The "cytoplasmic transport" cluster is associated with neurological and ophthalmological manifestations, the "mitochondrion" cluster with hypotonia, acute metabolic decompensation, and death, and the "B12 availability" and "remethylation" clusters with anemia and cytopenia. Hypotonia, EEG abnormalities, nystagmus, and strabismus are predominant in the younger patients, while neurological manifestations, such as walking difficulties, peripheral neuropathy, pyramidal syndrome, cerebral atrophy, psychiatric disorders, and thromboembolic manifestations, are predominant in the older patients. These results should prompt systematic checking of markers of vitamin B12 status, including homocysteine and methylmalonic acid, when usual causes of these manifestations are discarded in adult patients.
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Affiliation(s)
- Arnaud Wiedemann
- Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, University of Lorraine, INSERM UMR_S 1256, 54000 Nancy, France; Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France; Reference Center for Inborn Errors of Metabolism (ORPHA67872), University Hospital of Nancy, 54000 Nancy, France
| | - Abderrahim Oussalah
- Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, University of Lorraine, INSERM UMR_S 1256, 54000 Nancy, France; Reference Center for Inborn Errors of Metabolism (ORPHA67872), University Hospital of Nancy, 54000 Nancy, France; Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, 54000 Nancy, France
| | - Nathalie Lamireau
- Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France
| | - Maurane Théron
- Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France
| | - Melissa Julien
- Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, 54000 Nancy, France
| | | | - Baptiste Augay
- Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France
| | - Pauline Deniaud
- Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France
| | - Tom Alix
- Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, 54000 Nancy, France
| | - Marine Frayssinoux
- Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, 54000 Nancy, France
| | - François Feillet
- Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, University of Lorraine, INSERM UMR_S 1256, 54000 Nancy, France; Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France; Reference Center for Inborn Errors of Metabolism (ORPHA67872), University Hospital of Nancy, 54000 Nancy, France
| | - Jean-Louis Guéant
- Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, University of Lorraine, INSERM UMR_S 1256, 54000 Nancy, France; Reference Center for Inborn Errors of Metabolism (ORPHA67872), University Hospital of Nancy, 54000 Nancy, France; Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, 54000 Nancy, France.
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6
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Passantino R, Mangione MR, Ortore MG, Costa MA, Provenzano A, Amenitsch H, Sabbatella R, Alfano C, Martorana V, Vilasi S. Investigation on a MMACHC mutant from cblC disease: The c.394C>T variant. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2022; 1870:140793. [PMID: 35618206 DOI: 10.1016/j.bbapap.2022.140793] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 05/17/2022] [Accepted: 05/19/2022] [Indexed: 06/15/2023]
Abstract
The cblC disease is an inborn disorder of the vitamin B12 (cobalamin, Cbl) metabolism characterized by methylmalonic aciduria and homocystinuria. The clinical consequences of this disease are devastating and, even when early treated with current therapies, the affected children manifest symptoms involving vision, growth, and learning. The illness is caused by mutations in the gene codifying for MMACHC, a 282aa protein that transports and transforms the different Cbl forms. Here we present data on the structural properties of the truncated protein p.R132X resulting from the c.394C > T mutation that, along with c.271dupA and c.331C > T, is among the most common mutations in cblC. Although missing part of the Cbl binding domain, p.R132X is associated to late-onset symptoms and, therefore, it is supposed to retain residual function. However, to our knowledge structural-functional studies on c.394C > T mutant aimed at verifying this hypothesis are still lacking. By using a biophysical approach including Circular Dichroism, fluorescence, Small Angle X-ray Scattering, and Molecular Dynamics, we show that the mutant protein MMACHC-R132X retains secondary structure elements and remains compact in solution, partly preserving its binding affinity for Cbl. Insights on the fragile stability of MMACHC-R132X-Cbl are provided.
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Affiliation(s)
- Rosa Passantino
- Biophysics Institute, National Research Council, Palermo 90143, Italy
| | | | - Maria Grazia Ortore
- Dept. Life and Environmental Sciences, Marche Polytechnic University, Ancona 60131, Italy
| | | | | | | | | | | | | | - Silvia Vilasi
- Biophysics Institute, National Research Council, Palermo 90143, Italy.
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7
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Zhu J, Wan S, Zhao X, Zhu B, Lv Y, Jiang H. Acute Lymphoblastic Leukemia in Combined Methylmalonic Acidemia and Homocysteinemia (cblC Type): A Case Report and Literature Review. Front Genet 2022; 13:856552. [PMID: 35495149 PMCID: PMC9048794 DOI: 10.3389/fgene.2022.856552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 03/21/2022] [Indexed: 11/25/2022] Open
Abstract
Background: Methylmalonic acidemia (MMA) can display many clinical manifestations, among which acute lymphoblastic leukemia (ALL) has not been reported, and congenital heart disease (CHD) is also rare. Case presentation: We report an MMA case with ALL and CHD in a 5.5-year-old girl. With developmental delay and local brain atrophy in MRI, she was diagnosed with cerebral palsy at 9 months old. Rehabilitation was performed since then. This time she was admitted to hospital because of weakness and widespread bleeding spots. ALL-L2 (pre-B-cell) was confirmed by bone marrow morphology and immunophenotyping. Echocardiography showed patent foramen ovale. The girl was treated with VDLD and CAML chemotherapy, during which she developed seizures, edema and renal insufficiency. Decrease of muscle strength was also found in physical examination. Screening for inherited metabolic disorders showed significantly elevated levels of methylmalonate-2, acetylcarnitine (C2), propionylcarnitine (C3), C3/C2 and homocysteine. Gene analysis revealed a compound heterozygous mutaion in MMACHC (NM_015,560): c.80A > G (p.Gln27Arg) and c.609G > A (p.Trp203*). CblC type MMA was diagnosed. Intramuscular injection of cyanocobalamin and intravenous L-carnitine treatment were applied. The edema vanished gradually, and chemotherapy of small dosage of vindesine was given intermittently when condition permitted. 2 months later, muscle strength of both lower limbs were significantly improved to nearly grade 5. The levels of methylmalonic acid and homocysteine were improved. Conclusion: Metabolic disease screening and gene analysis are very necessary for diseases with complex clinical symptoms. ALL can be a rare manifestation for MMA. Synopsis: We report a case of methylmalonic acidemia with acute lymphoblastic leukemia and congenital heart disease, which uncovered the importance of genetic testing and metabolic diseases screening in patients with multiple systemic organ involvement.
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Affiliation(s)
- Jun Zhu
- Department of Pediatrics, The First Hospital of China Medical University, Shenyang, China
| | - Shuisen Wan
- Department of Pediatrics, The First Hospital of China Medical University, Shenyang, China
| | - Xueqi Zhao
- Department of Pediatrics, The First Hospital of China Medical University, Shenyang, China
| | - Binlu Zhu
- Department of Pediatrics, West China Second University Hospital, Chengdu, China
| | - Yuan Lv
- Department of Gynecology and Obstetrics, Shengjing Hospital of China Medical University, Shenyang, China
| | - Hongkun Jiang
- Department of Pediatrics, The First Hospital of China Medical University, Shenyang, China
- *Correspondence: Hongkun Jiang,
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Structural Study of the Complex of cblC Methylmalonic Aciduria and Homocystinuria-Related Protein MMACHC with Cyanocobalamin. CRYSTALS 2022. [DOI: 10.3390/cryst12040468] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
MMACHC is an essential protein for the body to metabolise vitamin B12, and its deficiency will cause cblC-type methylmalonic aciduria and homocystinuria. MMACHC can interact with cyanocobalamin (a type of vitamin B12) cofactor and plays an important role in targeting cyanocobalamin to the enzyme of interest. In this paper, the GST-tag fusion-tagged MMACHC protein was successfully expressed by Escherichia coli (E. coli) low-temperature induction, and the high-purity MMACHC protein was successfully purified by affinity chromatography and gel filtration. Further, the crystal structure of MMACHC and cyanocobalamin complex was obtained with a resolution of 1.93 Å using X-ray diffraction. By analysing the complex structure of MMACHC and cyanocobalamin, we revealed the reasons for the diversity of MMACHC substrates and explained the reasons for the differences in disease conditions caused by different MMACHC site mutations. The acquisition of the complex structure of MMACHC and cyanocobalamin will play a significant role in promoting research on the metabolic pathway of vitamin B12.
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Hannibal L, Jacobsen DW. Intracellular processing of vitamin B 12 by MMACHC (CblC). VITAMINS AND HORMONES 2022; 119:275-298. [PMID: 35337623 DOI: 10.1016/bs.vh.2022.02.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Vitamin B12 (cobalamin, Cbl, B12) is a water-soluble micronutrient synthesized exclusively by a group of microorganisms. Human beings are unable to make B12 and thus obtain the vitamin via intake of animal products, fermented plant-based foods or supplements. Vitamin B12 obtained from the diet comprises three major chemical forms, namely hydroxocobalamin (HOCbl), methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl). The most common form of B12 present in supplements is cyanocobalamin (CNCbl). Yet, these chemical forms cannot be utilized directly as they come, but instead, they undergo chemical processing by the MMACHC protein, also known as CblC. Processing of dietary B12 by CblC involves removal of the upper-axial ligand (beta-ligand) yielding the one-electron reduced intermediate cob(II)alamin. Newly formed cob(II)alamin undergoes trafficking and delivery to the two B12-dependent enzymes, cytosolic methionine synthase (MS) and mitochondrial methylmalonyl-CoA mutase (MUT). The catalytic cycles of MS and MUT incorporate cob(II)alamin as a precursor to regenerate the coenzyme forms MeCbl and AdoCbl, respectively. Mutations and epimutations in the MMACHC gene result in cblC disease, the most common inborn error of B12 metabolism, which manifests with combined homocystinuria and methylmalonic aciduria. Elevation of metabolites homocysteine and methylmalonic acid occurs because the lack of an active CblC blocks formation of the indispensable precursor cob(II)alamin that is necessary to activate MS and MUT. Thus, in patients with cblC disease, vitamin B12 is absorbed and present in circulation in normal to high concentrations, yet, cells are unable to make use of it. Mutations in seemingly unrelated genes that modify MMACHC gene expression also result in clinical phenotypes that resemble cblC disease. We review current knowledge on structural and functional aspects of intracellular processing of vitamin B12 by the versatile protein CblC, its partners and possible regulators.
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Affiliation(s)
- Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany.
| | - Donald W Jacobsen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
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10
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Xu B, Zhang L, Chen Q, Wang Y, Peng Y, Tang H. Case Report: A Case of Late-Onset Combined Methylmalonic Acidemia and Hyperhomocysteinemia Induced by a Vegetarian Diet. Front Pediatr 2022; 10:896177. [PMID: 35903162 PMCID: PMC9315243 DOI: 10.3389/fped.2022.896177] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 06/21/2022] [Indexed: 11/13/2022] Open
Abstract
Methylmalonic acidemia is a rare autosomal recessive metabolic disease. However, because of the atypical clinical symptoms, the type of late-onset methylmalonic academia is often misdiagnosed. Especially when the blood vitamin B12 and folic acid levels are normal, it is not easy to think of this disease. Herein we report a 9-year-old girl who developed normally on a relatively balanced diet before 7 years of age. However, she presented with fatigue and attention deficit when she followed a vegetarian diet. Laboratory examination showed moderate macrocytic anemia, high levels of homocysteine, high level of propionylcarnitine/acetylcarnitine, urinary methylmalonic acid and methyl citrate. Gene mutation analysis showed c.609G > A and c.80A > G compound heterozygous mutations in the MMACHC gene, supported late-onset combined methylmalonic academia with homocysteinemia. Then treatment performed with add meat to the diet, vitamin B12, folic acid betaine and L-carnitine supplement. One week later, the child's clinical symptoms and the laboratory examinations were significantly improved.
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Affiliation(s)
- Bei Xu
- Department of Pediatrics, Baoding No. 1 Central Hospital, Baoding, China
| | - Lihong Zhang
- Department of Pediatrics, Baoding No. 1 Central Hospital, Baoding, China
| | - Qiang Chen
- Department of Emergency, Baoding No. 1 Central Hospital, Baoding, China
| | - Yajuan Wang
- Department of Pediatrics, Baoding No. 1 Central Hospital, Baoding, China
| | - Yahong Peng
- Department of Pediatrics, Baoding No. 1 Central Hospital, Baoding, China
| | - Hui Tang
- Department of Pediatrics, Baoding No. 1 Central Hospital, Baoding, China
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Waheed N, Fayyaz Z, Imran A. Spectrum of clinical manifestation of methylmalonic acidemia and homocystinuria in a family of six siblings: novel combination of transcobalamin receptor defect (CD320) and cblC deficiency (MMACHC). EGYPTIAN JOURNAL OF MEDICAL HUMAN GENETICS 2021. [DOI: 10.1186/s43042-021-00197-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
Methylmalonic acidemia with homocystinuria is caused by a rare inborn error of vitamin B12 (cobalamin) metabolism. There are four complementation classes of cobalamin defects cblC, cblD, cblF, and cblJ that are responsible for combined methylmalonic acidemia and homocystinuria.
Case presentation
We report a case of a Pakistani family composed of six children diagnosed with methylmalonic acidemia and homocystinuria (MMA + HCU). Mutation analysis of siblings revealed a variable combination of c.394C>T mutation in the MMACHC gene and c.262_264del in CD320 gene. All siblings had variable age of onset, initial symptomatology, the severity of disease, and response to treatment. The maximum age of presentation was 6.5 years and the minimum age was at birth. The spectrum of symptoms ranged from a subtle learning disability to global developmental delay within the same family. None of them had a seizure disorder, megaloblastic anemia, visual disturbance, and vascular events.CD320 defect itself is very rare, and only 12 cases have been reported so far. We report six cases, four of them had homozygous MMACHC variant c.394C>T and the other two had heterozygous MMACHC mutations in c.394C>T and c.262_264del in CD 320 genes. To date, neither such case has been reported in the literature or this compound heterozygous mutation.
Conclusion
Our case report emphasizes that the diagnosis of inherited metabolic disorder in a child obviates the need to screen all siblings for the same disorder.
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12
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Konings H, Jacquemyn Y. Cobalamin deficiency in pregnancy. Clin Case Rep 2021; 9:e04282. [PMID: 34194790 PMCID: PMC8222745 DOI: 10.1002/ccr3.4282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 03/17/2021] [Accepted: 04/18/2021] [Indexed: 11/09/2022] Open
Abstract
Hydroxycobolamine supplementation in hereditary cobolamine deficiency and serial biochemical follow-up allow uncomplicated pregnancy outcome.
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Affiliation(s)
- Heleen Konings
- Global Health InstituteDepartment of Obstetrics and GynaecologyAntwerp University Hospital UZAAntwerp University UAAntwerpBelgium
| | - Yves Jacquemyn
- Global Health InstituteDepartment of Obstetrics and GynaecologyAntwerp University Hospital UZAAntwerp University UAAntwerpBelgium
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Yuan H, Deng S, Gao W, Li H, Yuan M. Identification of MMACHC and PROKR2 mutations causing coexistent cobalamin C disease and Kallmann syndrome in a young woman. Metab Brain Dis 2021; 36:447-452. [PMID: 33411215 DOI: 10.1007/s11011-020-00654-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 12/01/2020] [Indexed: 10/22/2022]
Abstract
Cobalamin C (cblC) disease and Kallmann syndrome (KS) are rare hereditary diseases. To date, no report has described the coexistence of those two genetic disorders in the same patient, or an association between them. We report the case of a 23-year-old woman with cblC defect and KS. She first presented mild memory problems in puberty, which worsened in adulthood to progressive memory loss accompanied by slow and unsteady walking, slow response, inattention, cognitive impairment, insomnia, no sense of smell, and the lack of spontaneous puberty. Laboratory tests revealed gonadotropin deficiency, a low estrogen level, and remarkably elevated serum homocysteine and serum and urine organic acid levels. Whole-exome sequencing detected compound heterozygous variants in MMACHC [c.398_399del (p.Gln133Argfs*4) and c.482G > A (p.Arg161Gln)] and heterozygous variants in PROKR2 [c.337T > C (p.Tyr113His)]. Thus, clinical and genetic examinations confirmed the cblC disease and KS diagnoses. This report on coexisting cblC disease and KS caused by different pathogenic genes in a single patient enriches the clinical research on these two rare genetic diseases.
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Affiliation(s)
- Haijun Yuan
- Department of Emergence, the Second Hospital, University of South China, Hengyang, Hunan, China
- Department of Emergence, Foresea Life Insurance Guangxi Hospital, Nanning, Guangxi, China
| | - Sipeng Deng
- Institute of Neurology, the Second Hospital, University of South China, Hengyang, Hunan, China
| | - Wei Gao
- Institute of Neurology, the Second Hospital, University of South China, Hengyang, Hunan, China
| | - Huaxin Li
- Institute of Neurology, the Second Hospital, University of South China, Hengyang, Hunan, China
| | - Mei Yuan
- Institute of Neurology, the Second Hospital, University of South China, Hengyang, Hunan, China.
- Department of Neurology, The Second Hospital, University of South China, 35 Jiefang Road, Huaxin Development District, Hengyang, Hunan, 421001, People's Republic of China.
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Wingert V, Mukherjee S, Esser AJ, Behringer S, Tanimowo S, Klenzendorf M, Derevenkov IA, Makarov SV, Jacobsen DW, Spiekerkoetter U, Hannibal L. Thiolatocobalamins repair the activity of pathogenic variants of the human cobalamin processing enzyme CblC. Biochimie 2020; 183:108-125. [PMID: 33190793 DOI: 10.1016/j.biochi.2020.10.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 10/08/2020] [Accepted: 10/19/2020] [Indexed: 01/08/2023]
Abstract
Thiolatocobalamins are a class of cobalamins comprised of naturally occurring and synthetic ligands. Glutathionylcobalamin (GSCbl) occurs naturally in mammalian cells, and also as an intermediate in the glutathione-dependent dealkylation of methylcobalamin (MeCbl) to form cob(I)alamin by pure recombinant CblC from C. elegans. Glutathione-driven deglutathionylation of GSCbl was demonstrated both in mammalian as well as in C. elegans CblC. Dethiolation is orders of magnitude faster than dealkylation of Co-C bonded cobalamins, which motivated us to investigate two synthetic thiolatocobalamins as substrates to repair the enzymatic activity of pathogenic CblC variants in humans. We report the synthesis and kinetic characterization of cysteaminylcobalamin (CyaCbl) and 2-mercaptopropionylglycinocobalamin (MpgCbl). Both CyaCbl and MpgCbl were obtained in high purity (90-95%) and yield (78-85%). UV-visible spectral properties agreed with those reported for other thiolatocobalamins with absorbance maxima observed at 372 nm and 532 nm. Both CyaCbl and MpgCbl bound to wild type human recombinant CblC inducing spectral blue-shifts characteristic of the respective base-on to base-off transitions. Addition of excess glutathione (GSH) resulted in rapid elimination of the β-ligand to give aquacobalamin (H2OCbl) as the reaction product under aerobic conditions. Further, CyaCbl and MpgCbl underwent spontaneous dethiolation thereby repairing the loss of activity of pathogenic variants of human CblC, namely R161G and R161Q. We posit that thiolatocobalamins could be exploited therapeutically for the treatment of inborn errors of metabolism that impair processing of dietary and supplemental cobalamin forms. While these disorders are targets for newborn screening in some countries, there is currently no effective treatment available to patients.
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Affiliation(s)
- Victoria Wingert
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center - University of Freiburg, 79106, Freiburg, Germany
| | - Srijan Mukherjee
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center - University of Freiburg, 79106, Freiburg, Germany
| | - Anna J Esser
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center - University of Freiburg, 79106, Freiburg, Germany
| | - Sidney Behringer
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center - University of Freiburg, 79106, Freiburg, Germany
| | - Segun Tanimowo
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center - University of Freiburg, 79106, Freiburg, Germany
| | - Melissa Klenzendorf
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center - University of Freiburg, 79106, Freiburg, Germany; Faculty of Biology, University of Freiburg Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany
| | - Ilia A Derevenkov
- Department of Food Chemistry, Ivanovo State University of Chemistry and Technology, Ivanovo, Russian Federation
| | - Sergei V Makarov
- Department of Food Chemistry, Ivanovo State University of Chemistry and Technology, Ivanovo, Russian Federation
| | - Donald W Jacobsen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, USA
| | - Ute Spiekerkoetter
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center - University of Freiburg, 79106, Freiburg, Germany
| | - Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center - University of Freiburg, 79106, Freiburg, Germany.
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15
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Mascarenhas R, Li Z, Gherasim C, Ruetz M, Banerjee R. The human B 12 trafficking protein CblC processes nitrocobalamin. J Biol Chem 2020; 295:9630-9640. [PMID: 32457044 DOI: 10.1074/jbc.ra120.014094] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 05/22/2020] [Indexed: 01/12/2023] Open
Abstract
In humans, cobalamin or vitamin B12 is delivered to two target enzymes via a complex intracellular trafficking pathway comprising transporters and chaperones. CblC (or MMACHC) is a processing chaperone that catalyzes an early step in this trafficking pathway. CblC removes the upper axial ligand of cobalamin derivatives, forming an intermediate in the pathway that is subsequently converted to the active cofactor derivatives. Mutations in the cblC gene lead to methylmalonic aciduria and homocystinuria. Here, we report that nitrosylcobalamin (NOCbl), which was developed as an antiproliferative reagent, and is purported to cause cell death by virtue of releasing nitric oxide, is highly unstable in air and is rapidly oxidized to nitrocobalamin (NO2Cbl). We demonstrate that CblC catalyzes the GSH-dependent denitration of NO2Cbl forming 5-coordinate cob(II)alamin, which had one of two fates. It could be oxidized to aquo-cob(III)alamin or enter a futile thiol oxidase cycle forming GSH disulfide. Arg-161 in the active site of CblC suppressed the NO2Cbl-dependent thiol oxidase activity, whereas the disease-associated R161G variant stabilized cob(II)alamin and promoted futile cycling. We also report that CblC exhibits nitrite reductase activity, converting cob(I)alamin and nitrite to NOCbl. Finally, the denitration activity of CblC supported cell proliferation in the presence of NO2Cbl, which can serve as a cobalamin source. The newly described nitrite reductase and denitration activities of CblC extend its catalytic versatility, adding to its known decyanation and dealkylation activities. In summary, upon exposure to air, NOCbl is rapidly converted to NO2Cbl, which is a substrate for the B12 trafficking enzyme CblC.
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Affiliation(s)
- Romila Mascarenhas
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Zhu Li
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Carmen Gherasim
- Department of Pathology, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Markus Ruetz
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan, USA
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Wang SJ, Yan CZ, Wen B, Zhao YY. Clinical feature and outcome of late-onset cobalamin C disease patients with neuropsychiatric presentations: a Chinese case series. Neuropsychiatr Dis Treat 2019; 15:549-555. [PMID: 30863077 PMCID: PMC6391119 DOI: 10.2147/ndt.s196924] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
OBJECTIVE The Cobalamin C (cblC) disease is an inborn error of cobalamin metabolism. Late-onset cblC disease was diagnosed in patients having overt symptoms after 4 years of age. The late-onset cblC disease patients were rare and easily misdiagnosed. This study analyzed the clinical presentations, gene mutations, and treatments of Chinese patients with late-onset cblC disease. METHODS The clinical data of 26 Han Chinese patients diagnosed with late-onset cblC disease were retrospectively analyzed. All patients underwent serum homocysteine level exam, urine concentrations of organic acids measurement, neuroimaging scans, gene analysis, and treatments evaluations. RESULTS The mean age at disease onset and diagnosis was 17.8±7.0 years. The most frequent neuropsychiatric disturbances were lower limb weakness (50%), psychiatric disturbances (46.2%), and gait instability (42.3%). The mean methylmalonic acid level in urine was 107.4±56.6 μmol/L, and mean serum total homocysteine was 105.4±41.0 μmol/L. The most common abnormal radioimaging changes were observed in the spinal cord (88%) and brain (32%). Scoliosis was detected in 85.7% of patients. The methylmalonic aciduria and homocystinuria type C protein gene analysis showed that c.482G>A (57.7%) and c.609G>A (34.6%) mutations were the most frequent genotypes. After treatments with hydroxycobalamin, betaine, folic acid, L-carnitine, and compound vitamin B, the clinical features and biochemical parameters of patients with late-onset cblC disease were found to be alleviated. CONCLUSION In our late-onset cblC disease cases, lower limb weakness, psychiatric disturbances, and gait instability were the most frequent manifestations. Patients responded well to the drug treatments with hydrocobalamin and betaine. When juvenile or adult patients with hyperhomocysteinemia present with neurological symptoms, cblC disease needs to be considered.
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Affiliation(s)
- Sheng-Jun Wang
- Department of Neurology, Qilu Hospital, Shandong University, Jinan, China,
| | - Chuan-Zhu Yan
- Department of Neurology, Qilu Hospital, Shandong University, Jinan, China,
| | - Bing Wen
- Department of Neurology, Qilu Hospital, Shandong University, Jinan, China,
| | - Yu-Ying Zhao
- Department of Neurology, Qilu Hospital, Shandong University, Jinan, China,
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McDonald MK, Fritz JA, Jia D, Scheuchner D, Snyder FF, Stanislaus A, Curle J, Li L, Stabler SP, Allen RH, Mains PE, Gravel RA. Identification of ABC transporters acting in vitamin B 12 metabolism in Caenorhabditis elegans. Mol Genet Metab 2017; 122:160-171. [PMID: 29153845 DOI: 10.1016/j.ymgme.2017.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 11/10/2017] [Accepted: 11/10/2017] [Indexed: 01/19/2023]
Abstract
Vitamin B12 (cobalamin, Cbl) is a micronutrient essential to human health. Cbl is not utilized as is but must go through complex subcellular and metabolic processing to generate two cofactor forms: methyl-Cbl for methionine synthase, a cytosolic enzyme; and adenosyl-Cbl for methylmalonyl-CoA mutase, a mitochondrial enzyme. Some 10-12 human genes have been identified responsible for the intracellular conversion of Cbl to cofactor forms, including genes that code for ATP-binding cassette (ABC) transporters acting at the lysosomal and plasma membranes. However, the gene for mitochondrial uptake is not known. We hypothesized that ABC transporters should be candidates for other uptake and efflux functions, including mitochondrial transport, and set out to screen ABC transporter mutants for blocks in Cbl utilization using the nematode roundworm Caenorhabditis elegans. Thirty-seven mutant ABC transporters were screened for the excretion of methylmalonic acid (MMA), which should result from loss of Cbl transport into the mitochondria. One mutant, wht-6, showed elevated MMA excretion and reduced [14C]-propionate incorporation, pointing to a functional block in methylmalonyl-CoA mutase. In contrast, the wht-6 mutant appeared to have a normal cytosolic pathway based on analysis of cystathionine excretion, suggesting that cytosolic methionine synthase was functioning properly. Further, the MMA excretion in wht-6 could be partially reversed by including vitamin B12 in the assay medium. The human ortholog of wht-6 is a member of the G family of ABC transporters. We propose wht-6 as a candidate for the transport of Cbl into mitochondria and suggest that a member of the corresponding ABCG family of ABC transporters has this role in humans. Our ABC transporter screen also revealed that mrp-1 and mrp-2 mutants excreted lower MMA than wild type, suggesting they were concentrating intracellular Cbl, consistent with the cellular efflux defect proposed for the mammalian MRP1 ABC transporter.
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Affiliation(s)
- Megan K McDonald
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, T2N 4N1, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, T2N 4N1, Canada
| | - Julie-Anne Fritz
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, T2N 4N1, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, T2N 4N1, Canada
| | - Dongxin Jia
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, T2N 4N1, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, T2N 4N1, Canada
| | - Deborah Scheuchner
- Department of Medical Genetics, University of Calgary, Calgary, T2N 4N1, Canada
| | - Floyd F Snyder
- Department of Medical Genetics, University of Calgary, Calgary, T2N 4N1, Canada
| | - Avalyn Stanislaus
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada
| | - Jared Curle
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada
| | - Liang Li
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada
| | - Sally P Stabler
- Division of Hematology, University of Colorado Denver, Aurora, CO, USA
| | - Robert H Allen
- Division of Hematology, University of Colorado Denver, Aurora, CO, USA
| | - Paul E Mains
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, T2N 4N1, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, T2N 4N1, Canada
| | - Roy A Gravel
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, T2N 4N1, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, T2N 4N1, Canada.
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Late Onset Cobalamin Disorder and Hemolytic Uremic Syndrome: A Rare Cause of Nephrotic Syndrome. Case Rep Pediatr 2017; 2017:2794060. [PMID: 28835862 PMCID: PMC5557262 DOI: 10.1155/2017/2794060] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 05/14/2017] [Indexed: 11/22/2022] Open
Abstract
Hemolytic uremic syndrome (HUS) is an unrare and severe thrombotic microangiopathy (TMA) caused by several pathogenetic mechanisms among which Shiga toxin-producing Escherichia coli infections and complement dysregulation are the most common. However, very rarely and particularly in neonates and infants, disorders of cobalamin metabolism (CblC) can present with or be complicated by TMA. Herein we describe a case of atypical HUS (aHUS) related to CblC disease which first presented in a previously healthy boy at age of 13.6 years. The clinical picture was initially dominated by nephrotic range proteinuria and severe hypertension followed by renal failure. The specific treatment with high dose of hydroxycobalamin rapidly obtained the remission of TMA and the complete recovery of renal function. We conclude that plasma homocysteine and methionine determinations together with urine organic acid analysis should be included in the diagnostic work-up of any patient with TMA and/or nephrotic syndrome regardless of age.
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Hannibal L, Siebert M, Basgalupp S, Vario F, Spiekerkoetter U, Blom HJ. Hampered Vitamin B12 Metabolism in Gaucher Disease? JOURNAL OF INBORN ERRORS OF METABOLISM AND SCREENING 2017. [DOI: 10.1177/2326409817692359] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department of Pediatrics, Medical Center, University of Freiburg, Freiburg, Germany
| | - Marina Siebert
- Hospital de Clínicas de Porto Alegre—HCPA, Medical Genetics Service, Porto Alegre, Rio Grande do Sul, Brazil
| | - Suélen Basgalupp
- Hospital de Clínicas de Porto Alegre—HCPA, Medical Genetics Service, Porto Alegre, Rio Grande do Sul, Brazil
| | - Filippo Vario
- Hospital de Clínicas de Porto Alegre—HCPA, Medical Genetics Service, Porto Alegre, Rio Grande do Sul, Brazil
| | - Ute Spiekerkoetter
- Laboratory of Clinical Biochemistry and Metabolism, Department of Pediatrics, Medical Center, University of Freiburg, Freiburg, Germany
| | - Henk J. Blom
- Laboratory of Clinical Biochemistry and Metabolism, Department of Pediatrics, Medical Center, University of Freiburg, Freiburg, Germany
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Efficacy of early treatment in patients with cobalamin C disease identified by newborn screening: a 16-year experience. Genet Med 2017; 19:926-935. [PMID: 28151490 DOI: 10.1038/gim.2016.214] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 11/15/2016] [Indexed: 02/07/2023] Open
Abstract
PURPOSE Despite implementation of newborn screening (NBS), outcomes in cobalamin C disease (cblC) remain poor. Therapy with hydroxycobalamin and betaine is widely used, but dietary recommendations vary among metabolic centers. We present a longitudinal analysis of the relationship between metabolic control, diet, and outcomes in a cohort of cblC patients. METHODS We completed a retrospective analysis of 12 patients with cblC referred for abnormal NBS results and followed in our center between 1999 and 2015. RESULTS Of the patients, 87.5% had intellectual disability and 75% had retinopathy; 16.7% had one episode of mild acidosis. However, no patients manifested major metabolic decompensation. Developmental outcomes correlated more closely with initial metabolic abnormalities than with long-term metabolic control. Increased intake of medical foods resulted in better control but also perturbations in the ratios of essential amino acids and lower z-scores for head circumference. We found no relationship between diet and cognitive outcomes. CONCLUSIONS Although dietary therapy for cblC patients improves metabolic control, few patients experience metabolic decompensation regardless of diet. Increased incomplete protein intake is not correlated with improvements in outcomes. Overall, outcomes are poor despite early initiation of therapy and regardless of the dietary strategy used.Genet Med advance online publication 02 February 2017.
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Richard E, Brasil S, Leal F, Navarrete R, Vega A, Ecay MJ, Desviat LR, Pérez-Cerda C, Ugarte M, Merinero B, Pérez B. Isolated and Combined Remethylation Disorders. JOURNAL OF INBORN ERRORS OF METABOLISM AND SCREENING 2017. [DOI: 10.1177/2326409816685732] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Eva Richard
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
| | - Sandra Brasil
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
| | - Fátima Leal
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
| | - Rosa Navarrete
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
| | - Ana Vega
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
| | - María Jesús Ecay
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
| | - Lourdes R. Desviat
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
| | - Celia Pérez-Cerda
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
| | - Magdalena Ugarte
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
| | - Begoña Merinero
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
| | - Belén Pérez
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
- IdiPAZ, Madrid, Spain
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23
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Froese DS, Kopec J, Fitzpatrick F, Schuller M, McCorvie TJ, Chalk R, Plessl T, Fettelschoss V, Fowler B, Baumgartner MR, Yue WW. Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B12 Trafficking. J Biol Chem 2015; 290:29167-77. [PMID: 26483544 PMCID: PMC4705923 DOI: 10.1074/jbc.m115.683268] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Indexed: 11/06/2022] Open
Abstract
Conversion of vitamin B12 (cobalamin, Cbl) into the cofactor forms methyl-Cbl (MeCbl) and adenosyl-Cbl (AdoCbl) is required for the function of two crucial enzymes, mitochondrial methylmalonyl-CoA mutase and cytosolic methionine synthase, respectively. The intracellular proteins MMACHC and MMADHC play important roles in processing and targeting the Cbl cofactor to its destination enzymes, and recent evidence suggests that they may interact while performing these essential trafficking functions. To better understand the molecular basis of this interaction, we have mapped the crucial protein regions required, indicate that Cbl is likely processed by MMACHC prior to interaction with MMADHC, and identify patient mutations on both proteins that interfere with complex formation, via different mechanisms. We further report the crystal structure of the MMADHC C-terminal region at 2.2 Å resolution, revealing a modified nitroreductase fold with surprising homology to MMACHC despite their poor sequence conservation. Because MMADHC demonstrates no known enzymatic activity, we propose it as the first protein known to repurpose the nitroreductase fold solely for protein-protein interaction. Using small angle x-ray scattering, we reveal the MMACHC-MMADHC complex as a 1:1 heterodimer and provide a structural model of this interaction, where the interaction region overlaps with the MMACHC-Cbl binding site. Together, our findings provide novel structural evidence and mechanistic insight into an essential biological process, whereby an intracellular "trafficking chaperone" highly specific for a trace element cofactor functions via protein-protein interaction, which is disrupted by inherited disease mutations.
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Affiliation(s)
- D Sean Froese
- From the Division of Metabolism and Children's Research Center, University Children's, Hospital, CH-8032 Zurich, Switzerland, radiz - Rare Disease Initiative Zurich, Clinical Research Priority Program for Rare Diseases, University of Zurich, CH-8032 Zurich, Switzerland
| | - Jolanta Kopec
- the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom, and
| | - Fiona Fitzpatrick
- the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom, and
| | - Marion Schuller
- the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom, and
| | - Thomas J McCorvie
- the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom, and
| | - Rod Chalk
- the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom, and
| | - Tanja Plessl
- From the Division of Metabolism and Children's Research Center, University Children's, Hospital, CH-8032 Zurich, Switzerland
| | - Victoria Fettelschoss
- From the Division of Metabolism and Children's Research Center, University Children's, Hospital, CH-8032 Zurich, Switzerland
| | - Brian Fowler
- From the Division of Metabolism and Children's Research Center, University Children's, Hospital, CH-8032 Zurich, Switzerland
| | - Matthias R Baumgartner
- From the Division of Metabolism and Children's Research Center, University Children's, Hospital, CH-8032 Zurich, Switzerland, radiz - Rare Disease Initiative Zurich, Clinical Research Priority Program for Rare Diseases, University of Zurich, CH-8032 Zurich, Switzerland, the Zurich Center for Integrative Human Physiology, University of Zurich, 8057 Zurich, Switzerland
| | - Wyatt W Yue
- the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom, and
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24
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Caterino M, Pastore A, Strozziero MG, Di Giovamberardino G, Imperlini E, Scolamiero E, Ingenito L, Boenzi S, Ceravolo F, Martinelli D, Dionisi-Vici C, Ruoppolo M. The proteome of cblC defect: in vivo elucidation of altered cellular pathways in humans. J Inherit Metab Dis 2015; 38:969-79. [PMID: 25585586 DOI: 10.1007/s10545-014-9806-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 12/17/2014] [Accepted: 12/19/2014] [Indexed: 12/26/2022]
Abstract
Methylmalonic acidemia with homocystinuria, cobalamin deficiency type C (cblC) (MMACHC) is the most common inborn error of cobalamin metabolism. Despite a multidrug treatment, the long-term follow-up of early-onset patients is often unsatisfactory, with progression of neurological and ocular impairment. Here, the in-vivo proteome of control and MMACHC lymphocytes (obtained from patients under standard treatment with OHCbl, betaine, folate and L-carnitine) was quantitatively examined by two dimensional differential in-gel electrophoresis (2D-DIGE) and mass spectrometry. Twenty three proteins were found up-regulated and 38 proteins were down-regulated. Consistent with in vivo studies showing disturbance of glutathione metabolism, a deregulation in proteins involved in cellular detoxification, especially in glutathione metabolism was found. In addition, relevant changes were observed in the expression levels of proteins involved in intracellular trafficking and protein folding, energy metabolism, cytoskeleton organization and assembly. This study demonstrates relevant changes in the proteome profile of circulating lymphocytes isolated from treated cblC patients. Some results confirm previous observations in vivo on fibroblast, thus concluding that some dysregulation is ubiquitous. On the other hand, new findings could be tissue-specific. These observations expand our current understanding of the cblC disease and may ignite new research and therapeutic strategies to treat this disorder.
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25
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Liu YR, Ji YF, Wang YL, Zhang BA, Fang GY, Wang JT, Sun GF, Lu H. Clinical analysis of late-onset methylmalonic acidaemia and homocystinuria, cblC type with a neuropsychiatric presentation. J Neurol Neurosurg Psychiatry 2015; 86:472-5. [PMID: 25091368 DOI: 10.1136/jnnp-2014-308203] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Yan-ru Liu
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Yang-fei Ji
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Ya-li Wang
- Department of Psychiatry, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Bo-ai Zhang
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Gui-yuan Fang
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Jing-tao Wang
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Gui-fang Sun
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Hong Lu
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
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26
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Gherasim C, Ruetz M, Li Z, Hudolin S, Banerjee R. Pathogenic mutations differentially affect the catalytic activities of the human B12-processing chaperone CblC and increase futile redox cycling. J Biol Chem 2015; 290:11393-402. [PMID: 25809485 DOI: 10.1074/jbc.m115.637132] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Indexed: 11/06/2022] Open
Abstract
Human CblC catalyzes the elimination of the upper axial ligand in cobalamin or B12 derivatives entering the cell from circulation. This processing step is critical for assimilation of dietary cobalamin into the active cofactor forms that support the B12-dependent enzymes, methionine synthase and methylmalonyl-CoA mutase. Using a modified nitroreductase scaffold tailored to bind cobalamin and glutathione, CblC exhibits versatility in the mechanism by which it removes cyano versus alkyl ligands in cobalamin. In this study, we have characterized the effects of two pathogenic missense mutations at the same residue, R161G and R161Q, which are associated with early and late onset of the CblC disorder, respectively. We find that the R161Q and R161G CblC mutants display lower protein stability and decreased dealkylation but not decyanation activity, suggesting that cyanocobalamin might be therapeutically useful for patients carrying mutations at Arg-161. The mutant proteins also exhibit impaired glutathione binding. In the presence of physiologically relevant glutathione concentrations, stabilization of the cob(II)alamin derivative is observed, which occurs at the expense of increased oxidation of glutathione. Futile redox cycling, which is suppressed in wild-type human CblC, explains the reported increase in oxidative stress levels associated with the CblC disorder.
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Affiliation(s)
- Carmen Gherasim
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600
| | - Markus Ruetz
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600
| | - Zhu Li
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600
| | - Stephanie Hudolin
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600
| | - Ruma Banerjee
- From the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600
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27
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Rahmandar MH, Bawcom A, Romano ME, Hamid R. Cobalamin C deficiency in an adolescent with altered mental status and anorexia. Pediatrics 2014; 134:e1709-14. [PMID: 25367534 PMCID: PMC4533284 DOI: 10.1542/peds.2013-2711] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Although cobalamin (cbl) C deficiency is the most common inherited disorder of vitamin B12 metabolism, the late-onset form of the disease can be difficult to recognize because it has a broad phenotypic spectrum. In this report, we describe an adolescent female exposed to unknown illicit substances and sexual abuse who presented with psychosis, anorexia, seizures, and ataxia. The patient's diagnosis was delayed until a metabolic workup was initiated, revealing hyperhomocysteinemia, low normal plasma methionine, and methylmalonic aciduria. Ultimately, cblC deficiency was confirmed when molecular testing showed compound heterozygosity for mutations (c.271dupA and c.482G>A) in the MMACHC gene. This diagnosis led to appropriate treatment with hydroxocobalamin, betaine, and folate, which resulted in improvement of her clinical symptoms and laboratory values. This patient demonstrates a previously unrecognized presentation of late-onset cblC deficiency. Although neuropsychiatric symptoms are common in late-onset disease, seizures and cerebellar involvement are not. Furthermore, anorexia has not been previously described in these patients. This case emphasizes that inborn errors of metabolism should be part of the differential diagnosis for a teenager presenting with altered mental status, especially when the diagnosis is challenging or neurologic symptoms are unexplained. Correct diagnosis of this condition is important because treatment is available and can result in clinical improvement.(1.)
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Affiliation(s)
| | - Amanda Bawcom
- Division of Medical Genetics and Genomic Medicine, and
| | - Mary E. Romano
- Division of Adolescent and Young Adult Health, Department of Pediatrics, Monroe Carell Jr Children’s Hospital at Vanderbilt University, Nashville, Tennessee
| | - Rizwan Hamid
- Division of Medical Genetics and Genomic Medicine, and
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28
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Muntau AC, Leandro J, Staudigl M, Mayer F, Gersting SW. Innovative strategies to treat protein misfolding in inborn errors of metabolism: pharmacological chaperones and proteostasis regulators. J Inherit Metab Dis 2014; 37:505-23. [PMID: 24687294 DOI: 10.1007/s10545-014-9701-z] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 02/19/2014] [Accepted: 02/24/2014] [Indexed: 10/25/2022]
Abstract
To attain functionality, proteins must fold into their three-dimensional native state. The intracellular balance between protein synthesis, folding, and degradation is constantly challenged by genetic or environmental stress factors. In the last ten years, protein misfolding induced by missense mutations was demonstrated to be the seminal molecular mechanism in a constantly growing number of inborn errors of metabolism. In these cases, loss of protein function results from early degradation of missense-induced misfolded proteins. Increasing knowledge on the proteostasis network and the protein quality control system with distinct mechanisms in different compartments of the cell paved the way for the development of new treatment strategies for conformational diseases using small molecules. These comprise proteostasis regulators that enhance the capacity of the proteostasis network and pharmacological chaperones that specifically bind and rescue misfolded proteins by conformational stabilization. They can be used either alone or in combination, the latter to exploit synergistic effects. Many of these small molecule compounds currently undergo preclinical and clinical pharmaceutical development and two have been approved: saproterin dihydrochloride for the treatment of phenylketonuria and tafamidis for the treatment of transthyretin-related hereditary amyloidosis. Different technologies are exploited for the discovery of new small molecule compounds that belong to the still young class of pharmaceutical products discussed here. These compounds may in the near future improve existing treatment strategies or even offer a first-time treatment to patients suffering from nowadays-untreatable inborn errors of metabolism.
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Affiliation(s)
- Ania C Muntau
- Department of Molecular Pediatrics, Dr von Hauner Children's Hospital, Ludwig Maximilians University, Lindwurmstrasse 4, 80337, Munich, Germany,
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29
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Jeong J, Park J, Park J, Kim J. Processing of glutathionylcobalamin by a bovine B12 trafficking chaperone bCblC involved in intracellular B12 metabolism. Biochem Biophys Res Commun 2014; 443:173-8. [DOI: 10.1016/j.bbrc.2013.11.075] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 11/17/2013] [Indexed: 11/26/2022]
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30
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Hannibal L, DiBello PM, Jacobsen DW. Proteomics of vitamin B12 processing. Clin Chem Lab Med 2013; 51:477-88. [PMID: 23241609 DOI: 10.1515/cclm-2012-0568] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 10/23/2012] [Indexed: 12/18/2022]
Abstract
The causes of cobalamin (B12, Cbl) deficiency are multifactorial. Whether nutritional due to poor dietary intake, or functional due to impairments in absorption or intracellular processing and trafficking events, the major symptoms of Cbl deficiency include megaloblastic anemia, neurological deterioration and in extreme cases, failure to thrive and death. The common biomarkers of Cbl deficiency (hyperhomocysteinemia and methylmalonic acidemia) are extremely valuable diagnostic indicators of the condition, but little is known about the changes that occur at the protein level. A mechanistic explanation bridging the physiological changes associated with functional B12 deficiency with its intracellular processers and carriers is lacking. In this article, we will cover the effects of B12 deficiency in a cblC-disrupted background (also referred to as MMACHC) as a model of functional Cbl deficiency. As will be shown, major protein changes involve the cytoskeleton, the neurological system as well as signaling and detoxification pathways. Supplementation of cultured MMACHC-mutant cells with hydroxocobalamin (HOCbl) failed to restore these variants to the normal phenotype, suggesting that a defective Cbl processing pathway produces irreversible changes at the protein level.
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Affiliation(s)
- Luciana Hannibal
- Department of Pathobiology (NC2 – 104), Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
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31
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Deme JC, Miousse IR, Plesa M, Kim JC, Hancock MA, Mah W, Rosenblatt DS, Coulton JW. Structural features of recombinant MMADHC isoforms and their interactions with MMACHC, proteins of mammalian vitamin B12 metabolism. Mol Genet Metab 2012; 107:352-62. [PMID: 22832074 DOI: 10.1016/j.ymgme.2012.07.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 07/01/2012] [Indexed: 12/17/2022]
Abstract
The genes MMACHC and MMADHC encode critical proteins involved in the intracellular metabolism of cobalamin. Two clinical features, homocystinuria and methylmalonic aciduria, define inborn errors of these genes. Based on disease phenotypes, MMADHC acts at a branch point for cobalamin delivery, apparently exerting its function through interaction with MMACHC that demonstrates dealkylase and decyanase activities. Here we present biophysical analyses of MMADHC to identify structural features and to further characterize its interaction with MMACHC. Two recombinant tag-less isoforms of MMADHC (MMADHCΔ1-12 and MMADHCΔ1-61) were expressed and purified. Full length MMACHC and full length MMADHC were detected in whole cell lysates of human cells; by Western blotting, their molecular masses corresponded to purified recombinant proteins. By clear-native PAGE and by dynamic light scattering, recombinant MMADHCs were stable and monodisperse. Both species were monomeric, adopting extended conformations in solution. Circular dichroism and secondary structure predictions correlated with significant regions of disorder within the N-terminal domain of MMADHC. We found no evidence that MMADHC binds cobalamin. Phage panning against MMADHC predicted four binding regions on MMACHC, two of which overlap with predicted sites on MMACHC at which it may self-associate. Specific, concentration-dependent responses were observed for MMACHC binding to itself and to both MMADHC constructs. As estimated in the sub-micromolar range, the binding of MMACHC to itself was weaker compared to its interaction with either of the MMADHC isoforms. We propose that the function of MMADHC is exerted through its structured C-terminal domain via interactions with MMACHC.
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Affiliation(s)
- Justin C Deme
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
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32
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Froese DS, Krojer T, Wu X, Shrestha R, Kiyani W, von Delft F, Gravel RA, Oppermann U, Yue WW. Structure of MMACHC Reveals an Arginine-Rich Pocket and a Domain-Swapped Dimer for Its B12 Processing Function. Biochemistry 2012; 51:5083-90. [DOI: 10.1021/bi300150y] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | - Xuchu Wu
- Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Canada
| | | | | | | | - Roy A. Gravel
- Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Canada
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33
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Carrillo-Carrasco N, Chandler RJ, Venditti CP. Combined methylmalonic acidemia and homocystinuria, cblC type. I. Clinical presentations, diagnosis and management. J Inherit Metab Dis 2012; 35:91-102. [PMID: 21748409 PMCID: PMC4219318 DOI: 10.1007/s10545-011-9364-y] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 05/27/2011] [Accepted: 06/09/2011] [Indexed: 11/25/2022]
Abstract
Combined methylmalonic acidemia and homocystinuria, cblC type, is an inborn error of intracellular cobalamin metabolism with a wide spectrum of clinical manifestations that is stated to be the most common inherited disorder of cobalamin metabolism. This metabolic disease is caused by mutations in the MMACHC gene and results in impaired intracellular synthesis of adenosylcobalamin and methylcobalamin, cofactors for the methylmalonyl-CoA mutase and methionine synthase enzymes. Elevated methylmalonic acid and homocysteine with decreased methionine production are the biochemical hallmarks of this disorder. Awareness of the diverse clinical presentations associated with cblC disease is necessary to provide a timely diagnosis, to guide management of affected individuals and to establish a framework for the future treatment of individuals detected through expanded newborn screening. This article reviews the biochemistry, clinical presentations, genotype-phenotype correlations, diagnosis and management of cblC disease.
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Affiliation(s)
- Nuria Carrillo-Carrasco
- Organic Acid Research Section, Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Building 49, Room 4A18, Bethesda, MD 20892, USA
| | - Randy J. Chandler
- Organic Acid Research Section, Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Building 49, Room 4A18, Bethesda, MD 20892, USA
- Institute for Biomedical Sciences, The George Washington University, Washington, DC, USA
| | - Charles P. Venditti
- Organic Acid Research Section, Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Building 49, Room 4A18, Bethesda, MD 20892, USA
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34
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Combined methylmalonic aciduria and homocystinuria cblC type of a Taiwanese infant with c.609G>A and C.567dupT mutations in the MMACHC gene. Pediatr Neonatol 2011; 52:223-6. [PMID: 21835369 DOI: 10.1016/j.pedneo.2011.05.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Revised: 08/18/2010] [Accepted: 09/01/2010] [Indexed: 11/20/2022] Open
Abstract
Combined methylmalonic aciduria and homocystinuria, cobalamin (cbl)C type (cblC disease), the most common inborn error of vitamin B(12), is a rare disorder of intracellular cbl metabolism because of mutations in the MMACHC gene located in chromosome region 1p34.1. It has become possible to establish phenotype-genotype correlations and to observe ethnicity-related trends. This article provides detailed clinical manifestations and outcomes of a Taiwanese infant boy with early-onset cblC disease, heterozygous for c.609G>A and c.567dupT mutations, although there is limited information about cases with c.609G>A or c.567dupT mutation in the literature. He had no significant clinical abnormality during his neonatal period, whereas elevated C3 level was noted at newborn screening. He presented later with life-threatening manifestations and failure to thrive, which resolved through our treatment, although delayed development was still noted at 6 months of age. To date, all reported cblC patients with the c.609G>A mutation have been East Asians. Therefore, we suggest that c.609G>A should be included in the initial mutation screening tests for a cblC patient in East Asian populations.
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35
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Glutathione increases the binding affinity of a bovine B₁₂ trafficking chaperone bCblC for vitamin B₁₂. Biochem Biophys Res Commun 2011; 412:360-5. [PMID: 21821010 DOI: 10.1016/j.bbrc.2011.07.103] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 07/22/2011] [Indexed: 11/20/2022]
Abstract
Intracellular B(12) metabolism involves a B(12) trafficking chaperone CblC that is well conserved in mammals including human. The protein CblC is known to bind cyanocobalamin (CNCbl, vitamin B(12)) inducing the base-off transition and convert it into an intermediate that can be used in enzyme cofactor synthesis. The binding affinity of human CblC for CNCbl was determined to be K(d)=≈6-16 μM, which is relatively low considering sub-micromolar B(12) concentrations (0.03-0.7 μM) in normal cells. In the current study, we discovered that the base-off transition of CNCbl upon binding to bCblC, a bovine homolog of human CblC, is facilitated in the presence of reduced form of glutathione (GSH). In addition, GSH dramatically increases the binding affinity for CNCbl lowering the K(d) from 27.1 ± 0.2-0.24 ± 0.09 μM. The effect of GSH is due to conformational change of bCblC upon binding with GSH, which was indicated by limited proteolysis and urea-induced equilibrium denaturation of the protein. The results of this study suggest that GSH positively modulates bCblC by increasing the binding affinity for CNCbl, which would enhance functional efficiency of the protein.
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36
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Hannibal L, DiBello PM, Yu M, Miller A, Wang S, Willard B, Rosenblatt DS, Jacobsen DW. The MMACHC proteome: hallmarks of functional cobalamin deficiency in humans. Mol Genet Metab 2011; 103:226-39. [PMID: 21497120 PMCID: PMC3110603 DOI: 10.1016/j.ymgme.2011.03.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2011] [Revised: 03/08/2011] [Accepted: 03/08/2011] [Indexed: 12/13/2022]
Abstract
Cobalamin (Cbl, B(12)) is an essential micronutrient required to fulfill the enzymatic reactions of cytosolic methylcobalamin-dependent methionine synthase and mitochondrial adenosylcobalamin-dependent methylmalonyl-CoA mutase. Mutations in the MMACHC gene (cblC complementation group) disrupt processing of the upper-axial ligand of newly internalized cobalamins, leading to functional deficiency of the vitamin. Patients with cblC disease present with both hyperhomocysteinemia and methylmalonic acidemia, cognitive dysfunction, and megaloblastic anemia. In the present study we show that cultured skin fibroblasts from cblC patients export increased levels of both homocysteine and methylmalonic acid compared to control skin fibroblasts, and that they also have decreased levels of total intracellular folates. This is consistent with the clinical phenotype of functional cobalamin deficiency in vivo. The protein changes that accompany human functional Cbl deficiency are unknown. The proteome of control and cblC fibroblasts was quantitatively examined by two dimensional difference in-gel electrophoresis (2D-DIGE) and liquid chromatography-electrospray ionization-mass spectrometry (LC/ESI/MS). Major changes were observed in the expression levels of proteins involved in cytoskeleton organization and assembly, the neurological system and cell signaling. Pathway analysis of the differentially expressed proteins demonstrated strong associations with neurological disorders, muscular and skeletal disorders, and cardiovascular diseases in the cblC mutant cell lines. Supplementation of the cell cultures with hydroxocobalamin did not restore the cblC proteome to the patterns of expression observed in control cells. These results concur with the observed phenotype of patients with the cblC disorder and their sometimes poor response to treatment with hydroxocobalamin. Our findings could be valuable for designing alternative therapies to alleviate the clinical manifestation of the cblC disorder, as some of the protein changes detected in our study are common hallmarks of known pathologies such as Alzheimer's and Parkinson's diseases as well as muscular dystrophies.
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Affiliation(s)
- Luciana Hannibal
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Cleveland, OH 44195
- School of Biomedical Sciences, Kent State University, Kent, OH 44242
- Address correspondence to: Luciana Hannibal, Ph.D., Department of Pathobiology, NC2-104, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, Tel: 216-445-9761, Fax: 216-636-0104, , or Donald W. Jacobsen, Ph.D., Department of Cell Biology, NC-10, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, Tel: 216-444-8340, Fax: 216-444-9404,
| | - Patricia M. DiBello
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Cleveland, OH 44195
| | - Michelle Yu
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Cleveland, OH 44195
| | - Abby Miller
- Department of Clinical Pathology, Cleveland Clinic, Cleveland, OH 44195
| | - Sihe Wang
- Department of Clinical Pathology, Cleveland Clinic, Cleveland, OH 44195
| | - Belinda Willard
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Cleveland, OH 44195
| | | | - Donald W. Jacobsen
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Cleveland, OH 44195
- School of Biomedical Sciences, Kent State University, Kent, OH 44242
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44106
- Address correspondence to: Luciana Hannibal, Ph.D., Department of Pathobiology, NC2-104, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, Tel: 216-445-9761, Fax: 216-636-0104, , or Donald W. Jacobsen, Ph.D., Department of Cell Biology, NC-10, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, Tel: 216-444-8340, Fax: 216-444-9404,
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Koutmos M, Gherasim C, Smith JL, Banerjee R. Structural basis of multifunctionality in a vitamin B12-processing enzyme. J Biol Chem 2011; 286:29780-7. [PMID: 21697092 DOI: 10.1074/jbc.m111.261370] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
An early step in the intracellular processing of vitamin B(12) involves CblC, which exhibits dual reactivity, catalyzing the reductive decyanation of cyanocobalamin (vitamin B(12)), and the dealkylation of alkylcobalamins (e.g. methylcobalamin; MeCbl). Insights into how the CblC scaffold supports this chemical dichotomy have been unavailable despite it being the most common locus of patient mutations associated with inherited cobalamin disorders that manifest in both severe homocystinuria and methylmalonic aciduria. Herein, we report structures of human CblC, with and without bound MeCbl, which provide novel biochemical insights into its mechanism of action. Our results reveal that CblC is the most divergent member of the NADPH-dependent flavin reductase family and can use FMN or FAD as a prosthetic group to catalyze reductive decyanation. Furthermore, CblC is the first example of an enzyme with glutathione transferase activity that has a sequence and structure unrelated to the GST superfamily. CblC thus represents an example of evolutionary adaptation of a common structural platform to perform diverse chemistries. The CblC structure allows us to rationalize the biochemical basis of a number of pathological mutations associated with severe clinical phenotypes.
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Affiliation(s)
- Markos Koutmos
- Department of Biological Chemistry and the Life Sciences Institute, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, USA
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38
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Jogl G, Wang X, Mason SA, Kovalevsky A, Mustyakimov M, Fisher Z, Hoffman C, Kratky C, Langan P. High-resolution neutron crystallographic studies of the hydration of the coenzyme cob(II)alamin. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2011; 67:584-91. [PMID: 21636899 DOI: 10.1107/s090744491101496x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2011] [Accepted: 04/20/2011] [Indexed: 11/11/2022]
Abstract
The hydration of the coenzyme cob(II)alamin has been studied using high-resolution monochromatic neutron crystallographic data collected at room temperature to a resolution of 0.92 Å on the original D19 diffractometer with a prototype 4° × 64° detector at the high-flux reactor neutron source run by the Institute Laue-Langevin. The resulting structure provides hydrogen-bonding parameters for the hydration of biomacromolecules to unprecedented accuracy. These experimental parameters will be used to define more accurate force fields for biomacromolecular structure refinement. The presence of a hydrophobic bowl motif surrounded by flexible side chains with terminal functional groups may be significant for the efficient scavenging of ligands. The feasibility of extending the resolution of this structure to ultrahigh resolution was investigated by collecting time-of-flight neutron crystallographic data during commissioning of the TOPAZ diffractometer with a prototype array of 14 modular 2° × 21° detectors at the Spallation Neutron Source run by Oak Ridge National Laboratory.
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Affiliation(s)
- Gerwald Jogl
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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Jeong JJ, Ha TS, Kim JH. Protection of aquo/hydroxocobalamin from reduced glutathione by a B12 trafficking chaperone. BMB Rep 2011; 44:170-5. [DOI: 10.5483/bmbrep.2011.44.3.170] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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40
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Hannibal L, Smith CA, Jacobsen DW. The X-ray crystal structure of glutathionylcobalamin revealed. Inorg Chem 2011; 49:9921-7. [PMID: 20863098 DOI: 10.1021/ic101173b] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The first evidence of a complex between glutathione and cobalamin, glutathionylcobalamin (GSCbl), was presented by Wagner and Bernhauer more than 40 years ago (Ann. N.Y. Acad. Sci. 1964, 112, 580). More recently, NMR and EXAFS solution studies by Brown et al. (Biochemistry 1993, 32, 8421) and Scheuring et al. (Biochemistry 1994, 33, 6310), respectively, provided evidence that the glutathionyl moiety in GSCbl is bound to the cobalt center via a Co-S bond. Despite continued efforts, the structural analysis of glutathionylcobalamin in the solid state has remained elusive. Here, we report the first atomic resolution crystal structure of GSCbl, refined to a crystallographic R factor of 0.0683. The glutathione moiety is bound to the cobalt center through the sulfur atom as expected, with a Co-S bond distance of 2.295(1) Å. This distance agrees with the distance obtained from the EXAFS analysis of GSCbl (2.280(5) Å). However, the bond to the axial α-5,6-dimethylbenzimidazole base (DMB), 2.074(3) Å, is significantly shorter than that determined from the EXAFS measurements (Co-N3B = 2.15(3) Å). The corrin fold angle is 24.7°, the highest ever reported for a cobalamin structure, and points in the direction of the β face of the corrin, toward the glutathione (GS(-)). The GS(-) ligand has been modeled in two conformations, each featuring distinct hydrogen bonding interactions. In both conformations, the α-carboxylate group of the GS(-) ligand interacts with the generally rigid side chain a of the cobalamin molecule, resulting in two distinct conformations. A comparison with the structure of other thiolatocobalamins revealed high similarity in the positions of the atoms in the cysteinyl moiety, the fold of the corrin rings, and the Co-S bond distances.
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Affiliation(s)
- Luciana Hannibal
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA
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Plesa M, Kim J, Paquette SG, Gagnon H, Ng-Thow-Hing C, Gibbs BF, Hancock MA, Rosenblatt DS, Coulton JW. Interaction between MMACHC and MMADHC, two human proteins participating in intracellular vitamin B₁₂ metabolism. Mol Genet Metab 2011; 102:139-48. [PMID: 21071249 DOI: 10.1016/j.ymgme.2010.10.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 10/15/2010] [Accepted: 10/15/2010] [Indexed: 11/22/2022]
Abstract
The identification of eight genes involved in inherited cobalamin (Cbl) disorders has provided insight into the complexity of the vitamin B₁₂ trafficking pathway. Detailed knowledge about the structure, interaction, and physiological functions for many of the gene products, including the MMACHC and MMADHC proteins, is lacking. Having cloned, expressed, and purified MMACHC in Escherichia coli, we demonstrated its monodispersity by dynamic light scattering and measured its hydrodynamic radius, either alone or in complex with each of four vitamin B₁₂ derivatives. Using solution-phase intrinsic fluorescence and label-free, real-time surface plasmon resonance (SPR), MMACHC bound cyanocobalamin and hydroxycobalamin with similar low micromolar affinities (K(D) 6.4 and 9.8 μM, respectively); adenosylcobalamin and methylcobalamin also shared similar binding affinities for MMACHC (K(D) 1.7 and 1.4 μM, respectively). To predict specific regions of interaction between MMACHC and the proposed partner protein MMADHC, MMACHC was subjected to phage display. Five putative MMACHC-binding sites were identified. Finally, MMADHC was confirmed as a binding partner for MMACHC both in vitro (SPR) and in vivo (bacterial two-hybrid system).
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Affiliation(s)
- Maria Plesa
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
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42
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Wang F, Han L, Yang Y, Gu X, Ye J, Qiu W, Zhang H, Zhang Y, Gao X, Wang Y. Clinical, biochemical, and molecular analysis of combined methylmalonic acidemia and hyperhomocysteinemia (cblC type) in China. J Inherit Metab Dis 2010; 33 Suppl 3:S435-42. [PMID: 20924684 DOI: 10.1007/s10545-010-9217-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2009] [Revised: 08/10/2010] [Accepted: 09/21/2010] [Indexed: 11/29/2022]
Abstract
The most common inborn error of cobalamin (cbl) metabolism in China is the cblC type characterized by combined methylmalonic acidemia and hyperhomocysteinemia. The clinical presentation is relatively nonspecific, such as feeding difficulty, recurrent vomiting, hypotonia, lethargy, seizures, progressive developmental delay, and mental retardation, together with anemia and metabolic acidosis. More specific biochemical findings include high levels of propionylcarnitine (C3), free carnitine (C3/C0), and acetylcarnitine (C3/C2) measured by tandem mass spectrometry (MS/MS), elevation of methylmalonic acid (MMA) measured by gas chromatography-mass spectrometry (GC-MS), and increased total homocysteine with normal or decreased methionine. We report on 50 Chinese patients with combined methylmalonic acidemia and hyperhomocysteinemia. Forty-six belonged to the cblC complementation group. Mutation analysis of the MMACHC gene was performed to characterize the mutational spectrum of cblC deficiency, and 17 different mutations were found. Most were clustered in exons 3 and 4, accounting for 91.3% of all mutant alleles. Two mutations were novel, namely, c.315 C>G (p.Y105X) and c.470 G>C(p.W157S). In terms of genotype-phenotype correlation, the c.609 G>A mutation was associated with early-onset disease when homozygous. Unlike previous reports from other populations, c.609 G>A (p.W203X) was the most frequent cblC mutation detected in our study of Chinese patients, affecting 51 of 92 MMACHC alleles (55.4%). The high prevalence of this nonsense mutation could have potential therapeutic significance for Chinese cblC patients. Besides traditional approaches consisting of hydroxocobalamin injections, carnitine, betaine, and protein restriction, novel drugs that target premature termination codons may have a role in the future.
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Affiliation(s)
- Fei Wang
- Department of Pediatric Endocrinology and Genetic Metabolism, Shanghai Institute for Pediatric Research, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China
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Abstract
Vitamin B12 (cobalamin, Cbl) is an essential nutrient in human metabolism. Genetic diseases of vitamin B12 utilisation constitute an important fraction of inherited newborn disease. Functionally, B12 is the cofactor for methionine synthase and methylmalonyl CoA mutase. To function as a cofactor, B12 must be metabolised through a complex pathway that modifies its structure and takes it through subcellular compartments of the cell. Through the study of inherited disorders of vitamin B12 utilisation, the genes for eight complementation groups have been identified, leading to the determination of the general structure of vitamin B12 processing and providing methods for carrier testing, prenatal diagnosis and approaches to treatment.
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Froese D, Healy S, McDonald M, Kochan G, Oppermann U, Niesen F, Gravel R. Thermolability of mutant MMACHC protein in the vitamin B12-responsive cblC disorder. Mol Genet Metab 2010; 100:29-36. [PMID: 20219402 PMCID: PMC2923755 DOI: 10.1016/j.ymgme.2010.02.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 02/04/2010] [Accepted: 02/05/2010] [Indexed: 11/29/2022]
Abstract
Methylmalonic aciduria and homocystinuria, cblC type, is the most common inborn error of cellular vitamin B12 metabolism. We previously showed that the protein carrying the mutation responsible for late-onset cblC (MMACHC-R161Q), treatable with high dose OHCbl, is able to bind OHCbl with wild-type affinity, leaving undetermined the disease mechanism involved [Froese et al., Mechanism of responsiveness, Mol. Genet. Metab. (2009).]. To assess whether the mutation renders the protein unstable, we investigated the thermostability of the wild-type and mutant MMACHC proteins, either unbound or bound to different cobalamins (Cbl), using differential scanning fluorimetry. We found that MMACHC-wt and MMACHC-R161Q are both very thermolabile proteins in their apo forms, with melting temperatures (T(m)) of 39.3+/-1.0 and 37.1+/-0.7 degrees C, respectively; a difference confirmed by unfolding of MMACHC-R161Q but not MMACHC-wt by isothermal denaturation at 35 degrees C over 120 min. However, with the addition of OHCbl, MMACHC-wt becomes significantly stabilized (Delta T(m max)=8 degrees C, half-maximal effective ligand concentration, AC(50)=3 microM). We surveyed the effect of different cobalamins on the stabilization of the wild-type protein and found that AdoCbl was the most stabilizing, exerting a maximum increase in T(m) of approximately 16 degrees C, followed by MeCbl at approximately 13 degrees C, each evaluated at 50 microM cofactor. The other cobalamins stabilized in the order (CN)(2)Cbi>OHCbl>CNCbl. Interestingly, the AC(50)'s for AdoCbl, MeCbl, (CN)(2)Cbi and OHCbl were similar and ranged from 1-3 microM, which compares well with the K(d) of 6 microM for OHCbl [Froese et al., Mechanism of responsiveness, Mol. Genet. Metab. (2009).]. Unlike MMACHC-wt, the mutant protein MMACHC-R161Q is only moderately stabilized by OHCbl (Delta T(m max)=4 degrees C). The dose-response curve also shows a lower effectivity of OHCbl with respect to stabilization, with an AC(50) of 7 microM. MMACHC-R161Q showed the same order of stabilization as MMACHC-wt, but each cobalamin stabilized this mutant protein less than its wild-type counterpart. Additionally, MMACHC-R161Q had a higher AC(50) for each cobalamin form compared to MMACHC-wt. Finally, we show that MMACHC-R161Q is able to support the base-off transition for AdoCbl and CNCbl, indicating this mutant is not blocked in that respect. Taken together, our results suggest that protein stability, as well as propensity for ligand-induced stabilization, contributes to the disease mechanism in late-onset cblC disorder. Our results underscore the importance of cofactor stabilization of MMACHC and suggest that even small increases in the concentration of cobalamin complexed with MMACHC may have therapeutic benefit in children with the late-onset, vitamin responsive cblC disease.
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Affiliation(s)
- D.S. Froese
- Department of Biochemistry and Molecular Biology, University of Calgary, Alberta Children’s Hospital Research Institute for Child and Maternal Health, Calgary, Alta., Canada T2N 4N1
- Structural Genomics Consortium, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, United Kingdom
| | - S. Healy
- Department of Biochemistry and Molecular Biology, University of Calgary, Alberta Children’s Hospital Research Institute for Child and Maternal Health, Calgary, Alta., Canada T2N 4N1
| | - M. McDonald
- Department of Biochemistry and Molecular Biology, University of Calgary, Alberta Children’s Hospital Research Institute for Child and Maternal Health, Calgary, Alta., Canada T2N 4N1
| | - G. Kochan
- Structural Genomics Consortium, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, United Kingdom
| | - U. Oppermann
- Structural Genomics Consortium, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, United Kingdom
- Nuffield Department of Orthopedic Surgery, Rheumatology and Musculoskeletal Sciences, Botnar Research Center, Biomedical Research Unit, University of Oxford, Oxford, United Kingdom
| | - F.H. Niesen
- Structural Genomics Consortium, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, United Kingdom
| | - R.A. Gravel
- Department of Biochemistry and Molecular Biology, University of Calgary, Alberta Children’s Hospital Research Institute for Child and Maternal Health, Calgary, Alta., Canada T2N 4N1
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