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Lorenzini M, Guha N, Davison JE, Pitcher A, Pandya B, Kemp H, Lachmann R, Elliott PM, Murphy E. Isolated aortic root dilation in homocystinuria. J Inherit Metab Dis 2018; 41:109-115. [PMID: 28980096 PMCID: PMC5786652 DOI: 10.1007/s10545-017-0094-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 08/17/2017] [Accepted: 09/15/2017] [Indexed: 01/02/2023]
Abstract
BACKGROUND Vascular complications in homocystinuria have been known for many years, but there have been no reports to date on involvement of the ascending aorta. METHODS We conducted a cross-sectional study of patients with homocystinuria, known to a single metabolic centre, and evaluated in 2016 with a transthoracic echocardiogram. Aortic root dilation was defined as Z-score ≥ 2.0 SD, and graded mild (Z-score 2.0-3.0), moderate (Z-score 3.01-4.0) and severe (Z-score > 4.0). RESULTS The study population included 34 patients, median age of 44.3 years (IQR 33.3-52.2), 50% males, 69% diagnosed aged <18 years and 29% pyridoxine-responsive. Eight (24%) had a history of hypertension. Seven patients (21%) were found to have a dilation of the aortic root, mild in two cases (6%), moderate in four (12%) and severe in one (3%). None had dilation of the ascending aorta. Significant aortic regurgitation, secondary to moderate aortic root dilation, was documented in two patients. A single patient had significant mitral regurgitation due to prolapse of both valve leaflets, as well as mild aortic root dilation. Comparing patients with a dilation of the aortic root to those without, there were no significant clinical, laboratory or echocardiographic differences, with the only exception being that the diameter of the ascending aorta was larger in the group with a dilated aortic root, albeit within normal limits. CONCLUSIONS A subset of patients with homocystinuria have isolated dilation of the aortic root similar to that observed in Marfan syndrome.
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Affiliation(s)
- Massimiliano Lorenzini
- University College London Institute for Cardiovascular Science and Barts Heart Centre, St. Bartholomew's Hospital, London, UK
- Cardiology, Department of Experimental, Diagnostic and Specialty Medicine, Alma Mater Studiorum University of Bologna, Bologna, Italy
| | - Nishan Guha
- Department of Clinical Biochemistry, John Radcliffe Hospital and Nuffield Division of Clinical Laboratory Sciences, University of Oxford, Oxford, UK
| | - James E Davison
- Metabolic Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Alex Pitcher
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Bejal Pandya
- Adult Congenital Heart Disease Department, Barts Heart Centre, St. Bartholomew's Hospital, London, UK
| | - Helena Kemp
- Department of Clinical Biochemistry, North Bristol NHS Trust, Bristol, UK
| | - Robin Lachmann
- Charles Dent Metabolic Unit, National Hospital for Neurology and Neurosurgery, Queen Square, London, UK
| | - Perry M Elliott
- University College London Institute for Cardiovascular Science and Barts Heart Centre, St. Bartholomew's Hospital, London, UK
| | - Elaine Murphy
- Charles Dent Metabolic Unit, National Hospital for Neurology and Neurosurgery, Queen Square, London, UK.
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C-terminal propeptide is required for fibrillin-1 secretion and blocks premature assembly through linkage to domains cbEGF41-43. Proc Natl Acad Sci U S A 2014; 111:10155-60. [PMID: 24982166 DOI: 10.1073/pnas.1401697111] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Fibrillin microfibrils are 10-12 nm diameter, extracellular matrix assemblies that provide dynamic tissues of metazoan species with many of their biomechanical properties as well as sequestering growth factors and cytokines. Assembly of fibrillin monomers into microfibrils is thought to occur at the cell surface, with initial steps including proprotein processing, multimerization driven by the C terminus, and the head-to-tail alignment of adjacent molecules. At present the mechanisms that regulate microfibril assembly are still to be elucidated. We have used structure-informed protein engineering to create a recombinant, GFP-tagged version of fibrillin-1 (GFP-Fbn) to study this process. Using HEK293T cells transiently transfected with GFP-Fbn constructs, we show that (i) the C-terminal propeptide is an essential requirement for the secretion of full-length fibrillin-1 from cells; (ii) failure to cleave off the C-terminal propeptide blocks the assembly of fibrillin-1 into microfibrils produced by dermal fibroblasts; and (iii) the requirement of the propeptide for secretion is linked to the presence of domains cbEGF41-43, because either deletion or exchange of domains in this region leads to cellular retention. Collectively, these data suggest a mechanism in which the propeptide blocks a key site at the C terminus to prevent premature microfibril assembly.
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Fouladgar M, Mohammadzadeh S, Nayeri H. Electrochemical determination of homocysteine using carbon nanotubes modified paste electrode and isoprenaline as a mediator. RUSS J ELECTROCHEM+ 2014. [DOI: 10.1134/s1023193514030070] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Newton LAA, Sandhu K, Livingstone C, Leslie R, Davis J. Clinical diagnostics for homocysteine: a rogue amino acid? Expert Rev Mol Diagn 2014; 10:489-500. [DOI: 10.1586/erm.10.19] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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5
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Protein sulfhydryl group oxidation and mixed-disulfide modifications in stable and unstable human carotid plaques. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2013; 2013:403973. [PMID: 23431411 PMCID: PMC3575616 DOI: 10.1155/2013/403973] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 12/28/2012] [Indexed: 11/17/2022]
Abstract
Objectives. Oxidative stress has been implicated in the outcome of atherosclerotic plaques. However, at present, no data are available neither on the degree of plaque protein sulfhydryl groups oxidation nor on its relationship with plaque vulnerability. We investigated the entity of protein-SH oxidative modifications, focusing on low molecular weight thiols adduction, in human carotid plaque extracts in relation to plaque stability/instability. Methods. Plaque stability/instability was histologically assessed. The extent of protein-SH oxidative modifications was established by a differential proteomic approach on fluorescein-5-maleimide-labeled plaque extracts and corresponding plasma samples from 48 endarterectomized patients. The analysis on protein thiolation was performed by capillary zone electrophoresis. Results. We observed a higher protein-SH oxidation of both plasma-derived and topically expressed proteins in unstable plaques, partly due to higher levels of S-thiolation. Conversely, in plasma, none of the investigated parameters discriminated among patients with stable and unstable plaques. Conclusions. Our results suggest the presence of a more pronounced oxidative environment in unstable plaques. Identifying specific oxidative modifications and understanding their effects on protein function could provide further insight into the relevance of oxidative stress in atherosclerosis.
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Maclean KN, Greiner LS, Evans JR, Sood SK, Lhotak S, Markham NE, Stabler SP, Allen RH, Austin RC, Balasubramaniam V, Jiang H. Cystathionine protects against endoplasmic reticulum stress-induced lipid accumulation, tissue injury, and apoptotic cell death. J Biol Chem 2012; 287:31994-2005. [PMID: 22854956 DOI: 10.1074/jbc.m112.355172] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Cystathionine (R-S-(2-amino-2-carboxyethyl)-l-homocysteine) is a non-proteinogenic thioether containing amino acid. In mammals, cystathionine is formed as an intermediate of the transsulfuration pathway by the condensation of serine and homocysteine (Hcy) in a reaction catalyzed by cystathionine β-synthase (CBS). Cystathionine is subsequently converted to cysteine plus ammonia and α-ketobutyrate by the action of cystathionine γ-lyase (CGL). Pathogenic mutations in CBS result in CBS-deficient homocystinuria (HCU) which, if untreated, results in mental retardation, thromboembolic complications and connective tissue disorders. Currently there is no known function for cystathionine other than serving as an intermediate in transsulfuration and to date, the possible contribution of the abolition of cystathionine synthesis to pathogenesis in HCU has not been investigated. Using both mouse and cell-culture models, we have found that cystathionine is capable of blocking the induction of hepatic steatosis and kidney injury, acute tubular necrosis, and apoptotic cell death by the endoplasmic reticulum stress inducing agent tunicamycin. Northern and Western blotting analysis indicate that the protective effects of cystathionine occur without any obvious alteration of the induction of the unfolded protein response. Our data constitute the first experimental evidence that the abolition of cystathionine synthesis may contribute to the pathology of HCU and that this compound has therapeutic potential for disease states where ER stress is implicated as a primary initiating pathogenic factor.
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Affiliation(s)
- Kenneth N Maclean
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
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Hubmacher D, Sabatier L, Annis DS, Mosher DF, Reinhardt DP. Homocysteine modifies structural and functional properties of fibronectin and interferes with the fibronectin-fibrillin-1 interaction. Biochemistry 2011; 50:5322-32. [PMID: 21561146 DOI: 10.1021/bi200183z] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Homocystinuria is a genetic disorder resulting in elevated levels of homocysteine in plasma and tissues. Some of the skeletal and ocular symptoms such as long bone overgrowth, scoliosis, and ectopia lentis overlap with symptoms seen in Marfan syndrome. Marfan syndrome is caused by mutations in the extracellular matrix protein fibrillin-1. We previously showed that fibrillin-1 is a target for homocysteine and that the deposition of homocysteinylated fibrillin-1 in the extracellular matrix is compromised. Since the assembly of fibrillin-1 is critically dependent on fibronectin, we analyzed the consequences of fibronectin homocysteinylation and its interaction with fibrillin-1. Cellular fibronectin and proteolytic fragments were homocysteinylated and tested in various interaction assays with recombinant fibrillin-1 and heparin. Fibronectin homocysteinylation consistently compromised the fibronectin-fibrillin-1 interaction, while the interaction with heparin was not affected. Fibronectin homocysteinylation, but not cysteinylation, reduced the fibronectin dimers to monomers as shown by Western blotting. ELISA analyses of homocysteinylated fibronectin with three monoclonal antibodies demonstrated structural changes in the disulfide-containing FNI domains FNI(2), FNI(4), and FNI(9). Using fluorescently labeled fibronectin, we studied the consequence of fibronectin homocysteinylation on assembly in cell culture. Modified fibronectin showed deficiencies in denovo matrix incorporation and initial assembly. In conclusion, we define here characteristic structural changes of fibronectin upon homocysteinylation that translate into functional deficiencies in the fibronectin-fibrillin-1 interaction and in fibronectin assembly. Since fibronectin is a major organizer of various extracellular protein networks, these structural and functional alterations may contribute to the pathogenesis of homocystinuria and Marfan syndrome.
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Affiliation(s)
- Dirk Hubmacher
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
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Mudd SH. Hypermethioninemias of genetic and non-genetic origin: A review. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2011; 157C:3-32. [PMID: 21308989 DOI: 10.1002/ajmg.c.30293] [Citation(s) in RCA: 147] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
This review covers briefly the major conditions, genetic and non-genetic, sometimes leading to abnormally elevated methionine, with emphasis on recent developments. A major aim is to assist in the differential diagnosis of hypermethioninemia. The genetic conditions are: (1) Homocystinuria due to cystathionine β-synthase (CBS) deficiency. At least 150 different mutations in the CBS gene have been identified since this deficiency was established in 1964. Hypermethioninemia is due chiefly to remethylation of the accumulated homocysteine. (2) Deficient activity of methionine adenosyltransferases I and III (MAT I/III), the isoenzymes the catalytic subunit of which are encoded by MAT1A. Methionine accumulates because its conversion to S-adenosylmethionine (AdoMet) is impaired. (3) Glycine N-methyltrasferase (GNMT) deficiency. Disruption of a quantitatively major pathway for AdoMet disposal leads to AdoMet accumulation with secondary down-regulation of methionine flux into AdoMet. (4) S-adenosylhomocysteine (AdoHcy) hydrolase (AHCY) deficiency. Not being catabolized normally, AdoHcy accumulates and inhibits many AdoMet-dependent methyltransferases, producing accumulation of AdoMet and, thereby, hypermethioninemia. (5) Citrin deficiency, found chiefly in Asian countries. Lack of this mitochondrial aspartate-glutamate transporter may produce (usually transient) hypermethioninemia, the immediate cause of which remains uncertain. (6) Fumarylacetoacetate hydrolase (FAH) deficiency (tyrosinemia type I) may lead to hypermethioninemia secondary either to liver damage and/or to accumulation of fumarylacetoacetate, an inhibitor of the high K(m) MAT. Additional possible genetic causes of hypermethioninemia accompanied by elevations of plasma AdoMet include mitochondrial disorders (the specificity and frequency of which remain to be elucidated). Non-genetic conditions include: (a) Liver disease, which may cause hypermethioninemia, mild, or severe. (b) Low-birth-weight and/or prematurity which may cause transient hypermethioninemia. (c) Ingestion of relatively large amounts of methionine which, even in full-term, normal-birth-weight babies may cause hypermethioninemia.
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Affiliation(s)
- S Harvey Mudd
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, MD, USA.
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Hubmacher D, Cirulis JT, Miao M, Keeley FW, Reinhardt DP. Functional consequences of homocysteinylation of the elastic fiber proteins fibrillin-1 and tropoelastin. J Biol Chem 2009; 285:1188-98. [PMID: 19889633 DOI: 10.1074/jbc.m109.021246] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Homocystinuria caused by cystathionine-beta-synthase deficiency represents a severe form of homocysteinemias, which generally result in various degrees of elevated plasma homocysteine levels. Marfan syndrome is caused by mutations in fibrillin-1, which is one of the major constituents of connective tissue microfibrils. Despite the fundamentally different origins, both diseases share common clinical symptoms in the connective tissue such as long bone overgrowth, scoliosis, and ectopia lentis, whereas they differ in others. Fibrillin-1 contains approximately 13% cysteine residues and can be modified by homocysteine. We report here that homocysteinylation affects functional properties of fibrillin-1 and tropoelastin. We used recombinant fragments spanning the entire fibrillin-1 molecule to demonstrate that homocysteinylation, but not cysteinylation leads to abnormal self-interaction, which was attributed to a reduced amount of multimerization of the fibrillin-1 C terminus. The deposition of the fibrillin-1 network by human dermal fibroblasts was greatly reduced by homocysteine, but not by cysteine. Furthermore, homocysteinylation, but not cysteinylation of elastin-like polypeptides resulted in modified coacervation properties. In summary, the results provide new insights into pathogenetic mechanisms potentially involved in cystathionine-beta-synthase-deficient homocystinuria.
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Affiliation(s)
- Dirk Hubmacher
- Faculty of Medicine, Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 2B2, Canada
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Rubio-Aliaga I, Przemeck GKH, Fuchs H, Gailus-Durner V, Adler T, Hans W, Horsch M, Rathkolb B, Rozman J, Schrewe A, Wagner S, Hoelter SM, Becker L, Klopstock T, Wurst W, Wolf E, Klingenspor M, Ivandic BT, Busch DH, Beckers J, Hrabé de Angelis M. Dll1 haploinsufficiency in adult mice leads to a complex phenotype affecting metabolic and immunological processes. PLoS One 2009; 4:e6054. [PMID: 19562077 PMCID: PMC2699037 DOI: 10.1371/journal.pone.0006054] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Accepted: 05/26/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The Notch signaling pathway is an evolutionary conserved signal transduction pathway involved in embryonic patterning and regulation of cell fates during development and self-renewal. Recent studies have demonstrated that this pathway is integral to a complex system of interactions, involving as well other signal transduction pathways, and implicated in distinct human diseases. Delta-like 1 (Dll1) is one of the known ligands of the Notch receptors. The role of the Notch ligands is less well understood. Loss-of-function of Dll1 leads to embryonic lethality, but reduction of Delta-like 1 protein levels has not been studied in adult stage. METHODOLOGY/PRINCIPAL FINDINGS Here we present the haploinsufficient phenotype of Dll1 and a missense mutant Dll1 allele (Dll1(C413Y)). Haploinsufficiency leads to a complex phenotype with several biological processes altered. These alterations reveal the importance of Dll1 mainly in metabolism, energy balance and in immunology. The animals are smaller, lighter, with altered fat to lean ratio and have increased blood pressure and a slight bradycardia. The animals have reduced cholesterol and triglyceride levels in blood. At the immunological level a subtle phenotype is observed due to the effect and fine-tuning of the signaling network at the different levels of differentiation, proliferation and function of lymphocytes. Moreover, the importance of the proteolytic regulation of the Notch signaling network emphasized. CONCLUSIONS/SIGNIFICANCE In conclusion, slight alterations in one player of Notch signaling alter the entire organism, emphasizing the fine-tuning character of this pathway in a high number of processes.
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Affiliation(s)
- Isabel Rubio-Aliaga
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Gerhard K. H. Przemeck
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Helmut Fuchs
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Valérie Gailus-Durner
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Thure Adler
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
- Institute for Medical Microbiology, Immunology and Hygiene, Technische Universitaet Muenchen, Munich, Germany
| | - Wolfgang Hans
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Marion Horsch
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Birgit Rathkolb
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
- Chair for Molecular Animal Breeding and Biotechnology/LAFUGA, Gene Center, Ludwig-Maximilians-Universitaet Muenchen, Munich, Germany
| | - Jan Rozman
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
- Molecular Nutritional Medicine, Technische Universitaet Muenchen, Else Kroener-Fresenius Center, Freising-Weihenstephan, Germany
| | - Anja Schrewe
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
- Department of Medicine III, Division of Cardiology, University of Heidelberg, Heidelberg, Germany
| | - Sibylle Wagner
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Sabine M. Hoelter
- Institute of Developmental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Lore Becker
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
- Friedrich-Baur-Institute, Department of Neurology, Ludwig-Maximilians-Universitaet, Munich, Germany
| | - Thomas Klopstock
- Friedrich-Baur-Institute, Department of Neurology, Ludwig-Maximilians-Universitaet, Munich, Germany
| | - Wolfgang Wurst
- Institute of Developmental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
- Lehrstuhl fuer Entwicklungsgenetik, Technische Universitaet Muenchen, Freising-Weihenstephan, Germany
| | - Eckhard Wolf
- Chair for Molecular Animal Breeding and Biotechnology/LAFUGA, Gene Center, Ludwig-Maximilians-Universitaet Muenchen, Munich, Germany
| | - Martin Klingenspor
- Molecular Nutritional Medicine, Technische Universitaet Muenchen, Else Kroener-Fresenius Center, Freising-Weihenstephan, Germany
| | - Boris T. Ivandic
- Department of Medicine III, Division of Cardiology, University of Heidelberg, Heidelberg, Germany
| | - Dirk H. Busch
- Institute for Medical Microbiology, Immunology and Hygiene, Technische Universitaet Muenchen, Munich, Germany
| | - Johannes Beckers
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
- Lehrstuhl fuer Experimentelle Genetik, Technische Universitaet Muenchen, Freising-Weihenstephan, Germany
| | - Martin Hrabé de Angelis
- Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
- Lehrstuhl fuer Experimentelle Genetik, Technische Universitaet Muenchen, Freising-Weihenstephan, Germany
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Sundaramoorthy E, Maiti S, Brahmachari SK, Sengupta S. Predicting protein homocysteinylation targets based on dihedral strain energy and pKa of cysteines. Proteins 2008; 71:1475-83. [PMID: 18076028 DOI: 10.1002/prot.21846] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A multitude of complex diseases have been linked to elevated homocysteine levels; however, till date there is no plausible explanation for a single amino acid's involvement in so many diseases. Since homocysteine is a reactive thiol amino acid and the majority of plasma homocysteine is protein thiol bound, we hypothesized that homocysteine might bind to accessible cysteine residues in target proteins, thereby modulating its structure or function or both. The parameters that dictate homocysteine-protein interaction are not well understood, and the few known homocysteine binding proteins were identified by a candidate protein approach. In this study, we identified potential homocysteine interacting proteins based on cysteine content, solvent accessibility of cysteine residues, and dihedral strain energies and pKa of these cysteines. Pathway mapping of the cysteine-rich proteins revealed that proteins in the coagulation cascade, notch receptor-mediated signaling, LDL endocytosis, programmed cell death, and extracellular matrix proteins were significantly over-represented with cysteine-rich proteins, and we believe that homocysteine has a high probability to bind to proteins in these pathways. In fact, several clinical studies have implicated high homocysteine levels to be associated with diseases like thrombosis, neural tube defects, and so forth, which result from dysfunction of one or more of the proteins identified in our study. Further, we successfully validated our prediction parameters on the proteins that have already been experimentally shown to bind homocysteine, and our structural analysis argues a plausible explanation for these prior reported protein interactions with homocysteine that could not be previously explained.
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Affiliation(s)
- Elayanambi Sundaramoorthy
- Proteomics and Structural Biology Unit, Institute of Genomics and Integrative Biology, Delhi 110007, India
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Cordle J, Johnson S, Tay JZY, Roversi P, Wilkin M, Hernandez-Diaz B, Shimizu H, Jensen S, Whiteman P, Jin B, Redfield C, Baron M, Lea SM, Handford PA. A conserved face of the Jagged/Serrate DSL domain is involved in Notch trans-activation and cis-inhibition. Nat Struct Mol Biol 2008; 15:849-57. [PMID: 18660822 PMCID: PMC2669539 DOI: 10.1038/nsmb.1457] [Citation(s) in RCA: 189] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Accepted: 06/05/2008] [Indexed: 12/28/2022]
Abstract
The Notch receptor and its ligands are key components in a core metazoan signaling pathway that regulates the spatial patterning, timing and outcome of many cell-fate decisions. Ligands contain a disulfide-rich Delta/Serrate/LAG-2 (DSL) domain required for Notch trans-activation or cis-inhibition. Here we report the X-ray structure of a receptor binding region of a Notch ligand, the DSL-EGF3 domains of human Jagged-1 (J-1(DSL-EGF3)). The structure reveals a highly conserved face of the DSL domain, and we show, by functional analysis of Drosophila melanogster ligand mutants, that this surface is required for both cis- and trans-regulatory interactions with Notch. We also identify, using NMR, a surface of Notch-1 involved in J-1(DSL-EGF3) binding. Our data imply that cis- and trans-regulation may occur through the formation of structurally distinct complexes that, unexpectedly, involve the same surfaces on both ligand and receptor.
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Affiliation(s)
- Jemima Cordle
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Steven Johnson
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Joyce Zi Yan Tay
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Pietro Roversi
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Marian Wilkin
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Stopford Road, Manchester M13 9PT, UK
| | - Beatriz Hernandez-Diaz
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Stopford Road, Manchester M13 9PT, UK
| | - Hideyuki Shimizu
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Stopford Road, Manchester M13 9PT, UK
| | - Sacha Jensen
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Pat Whiteman
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Boquan Jin
- Department of Immunology, Fourth Military Medical University, 17 West Changle Road, Xi’an, Shaanxi 710032, PR China
| | - Christina Redfield
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Martin Baron
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Stopford Road, Manchester M13 9PT, UK
| | - Susan M. Lea
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Penny A. Handford
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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Krumdieck CL, Fernandez JR, Desmond RA, Kleinstein RN, Shipp MD, Prince CW. C677T methylene-H4-folate-reductase variant decreases binocular accommodation. Optom Vis Sci 2008; 85:196-200. [PMID: 18317335 DOI: 10.1097/opx.0b013e3181643e97] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE The C677T polymorphism of methylene tetrahydrofolate reductase (MTHFR) lowers the activity of this enzyme, producing moderate elevation of blood levels of homocysteine (Hcy) and lowering the levels of 5-methyl-tetrahydro-folic acid (5-MeTHFA), methionine (Meth), and S-adenosylmethionine (SAM). In this study we examined 100 apparently normal subjects of both sexes (average age 25.6 +/- 4.25) for the genotypic presence of the T allele and its association with accommodative amplitude (AA). METHODS The amplitude of accommodation was measured by the subjective "push-up" technique. DNA from buccal cells was genotyped for the C677T polymorphism of MTHFR by a PCR-restriction fragment length polymorphism genotyping assay. Descriptive statistics were obtained by frequency distribution and univariate analysis. Comparisons between monocular and binocular AA were obtained by t-test statistics or ANOVA. Associations between genotype and phenotype were analyzed using regression models. RESULTS The C677T polymorphism was associated with decreased binocular AA (p = 0.0087). Monocular AA was not associated with the MTHFR genotype. CONCLUSIONS Our results suggest a role for the C677T polymorphism in damaging the neural aspects of binocular vergence accommodation. The postulated neural damage could be due to the decreased formation of 5-MeTHFA and the defective synthesis of Meth, SAM and neurotransmitters or other methyl acceptors in nervous tissue of bearers of the C677T polymorphism. The differential effect upon monocular and binocular accommodation is hypothetically explained by a greater involvement of methylation reactions in vergence accommodation. A similar mechanism is proposed to explain the prevalent insufficient accommodation of Down's syndrome in which the blood levels of Meth and SAM are reduced.
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Affiliation(s)
- Carlos L Krumdieck
- Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
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Abstract
Fibrillin-1 is a 350 kDa calcium-binding protein which assembles to form 10-12 nm microfibrils in the extracellular matrix (ECM). The structure of fibrillin-1 is dominated by two types of disulfide-rich motifs, the calcium- binding epidermal growth factor-like (cbEGF) and transforming growth factor beta binding protein-like (TB) domains. Disruption of fibrillin-1 domain structure and function contributes to the pathogenic mechanisms underlying two inherited diseases with very different etiologies: Marfan syndrome (MFS) and homocystinuria (HC). MFS is a connective tissue disease caused by mutations in the fibrillin-1 gene FBN1. Many missense mutations cause variable degrees of fibrillin-1 domain misfolding, which may affect the delivery of fibrillin-1 to the ECM and/or its assembly into microfibrils. HC is a metabolic disorder which affects methionine metabolism and results in raised serum levels of the highly reactive thiol-containing amino acid homocysteine. Patients with HC often exhibit ocular and skeletal defects resembling the MFS phenotype, suggesting that elevated homocysteine levels may lead to chemical reduction of disulfide bonds within fibrillin-1 domains resulting in the loss of native structure. Protein misfolding therefore is implicated in pathogenic mechanisms underlying MFS and HC.
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Affiliation(s)
- Pat Whiteman
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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Hubmacher D, Tiedemann K, Bartels R, Brinckmann J, Vollbrandt T, Bätge B, Notbohm H, Reinhardt DP. Modification of the Structure and Function of Fibrillin-1 by Homocysteine Suggests a Potential Pathogenetic Mechanism in Homocystinuria. J Biol Chem 2005; 280:34946-55. [PMID: 16096271 DOI: 10.1074/jbc.m504748200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Homocystinuria, a disorder originating in defects in the methionine metabolism, is characterized by an elevated plasma concentration of homocysteine. Most patients have a defect in the cystathionine-beta-synthase, the key enzyme in the conversion of homocysteine to cysteine. Many abnormalities in the connective tissue of patients with homocystinuria resemble those seen in Marfan syndrome, caused by mutations in fibrillin-1. These observations led to the hypothesis that the structure and function of fibrillin-1 is compromised in patients with homocystinuria. To test this hypothesis we produced recombinant human fibrillin-1 fragments spanning the central portion of the molecule (8-Cys/transforming growth factor-beta binding domain 3 to calcium binding EGF domain 22) and extensively analyzed the potential of homocysteine to modify structural and functional properties of these proteins. Circular dichroism spectroscopy revealed moderate changes of their secondary structures after incubation with homocysteine. Equilibrium dialysis demonstrated a number of high affinity calcium binding sites in the tandemly repeated calcium binding epidermal growth factor-like domains 11-22. Calcium binding of homocysteine-modified fragments was completely abolished. Incubation of the recombinant proteins with homocysteine rendered the analyzed calcium binding EGF domains as well as the 8-Cys/transforming growth factor-beta binding domain 3 significantly more susceptible to proteolytic degradation. Furthermore, data were obtained demonstrating that homocysteine can covalently modify fibrillin-1 via disulfide bonds. These data strongly suggest that structural and functional modifications as well as degradation processes of fibrillin-1 in the connective tissues of patients with homocystinuria play a major role in the pathogenesis of this disorder.
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Affiliation(s)
- Dirk Hubmacher
- Faculty of Medicine, Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A2B2, Canada
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