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Schoenmakers E, Chatterjee K. Human Genetic Disorders Resulting in Systemic Selenoprotein Deficiency. Int J Mol Sci 2021; 22:12927. [PMID: 34884733 PMCID: PMC8658020 DOI: 10.3390/ijms222312927] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 11/26/2021] [Accepted: 11/27/2021] [Indexed: 01/01/2023] Open
Abstract
Selenium, a trace element fundamental to human health, is incorporated as the amino acid selenocysteine (Sec) into more than 25 proteins, referred to as selenoproteins. Human mutations in SECISBP2, SEPSECS and TRU-TCA1-1, three genes essential in the selenocysteine incorporation pathway, affect the expression of most if not all selenoproteins. Systemic selenoprotein deficiency results in a complex, multifactorial disorder, reflecting loss of selenoprotein function in specific tissues and/or long-term impaired selenoenzyme-mediated defence against oxidative and endoplasmic reticulum stress. SEPSECS mutations are associated with a predominantly neurological phenotype with progressive cerebello-cerebral atrophy. Selenoprotein deficiency due to SECISBP2 and TRU-TCA1-1 defects are characterized by abnormal circulating thyroid hormones due to lack of Sec-containing deiodinases, low serum selenium levels (low SELENOP, GPX3), with additional features (myopathy due to low SELENON; photosensitivity, hearing loss, increased adipose mass and function due to reduced antioxidant and endoplasmic reticulum stress defence) in SECISBP2 cases. Antioxidant therapy ameliorates oxidative damage in cells and tissues of patients, but its longer term benefits remain undefined. Ongoing surveillance of patients enables ascertainment of additional phenotypes which may provide further insights into the role of selenoproteins in human biological processes.
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Affiliation(s)
| | - Krishna Chatterjee
- Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke’s Hospital, University of Cambridge, Cambridge CB2 0QQ, UK;
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Schoenmakers E, Chatterjee K. Human Disorders Affecting the Selenocysteine Incorporation Pathway Cause Systemic Selenoprotein Deficiency. Antioxid Redox Signal 2020; 33:481-497. [PMID: 32295391 PMCID: PMC7409586 DOI: 10.1089/ars.2020.8097] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Significance: Generalized selenoprotein deficiency has been associated with mutations in SECISBP2, SEPSECS, and TRU-TCA1-1, 3 factors that are crucial for incorporation of the amino acid selenocysteine (Sec) into at least 25 human selenoproteins. SECISBP2 and TRU-TCA1-1 defects are characterized by a multisystem phenotype due to deficiencies of antioxidant and tissue-specific selenoproteins, together with abnormal thyroid hormone levels reflecting impaired hormone metabolism by deiodinase selenoenzymes. SEPSECS mutations are associated with a predominantly neurological phenotype with progressive cerebello-cerebral atrophy. Recent Advances: The recent identification of individuals with defects in genes encoding components of the selenocysteine insertion pathway has delineated complex and multisystem disorders, reflecting a lack of selenoproteins in specific tissues, oxidative damage due to lack of oxidoreductase-active selenoproteins and other pathways whose nature is unclear. Critical Issues: Abnormal thyroid hormone metabolism in patients can be corrected by triiodothyronine (T3) treatment. No specific therapies for other phenotypes (muscular dystrophy, male infertility, hearing loss, neurodegeneration) exist as yet, but their severity often requires supportive medical intervention. Future Directions: These disorders provide unique insights into the role of selenoproteins in humans. The long-term consequences of reduced cellular antioxidant capacity remain unknown, and future surveillance of patients may reveal time-dependent phenotypes (e.g., neoplasia, aging) or consequences of deficiency of selenoproteins whose function remains to be elucidated. The role of antioxidant therapies requires evaluation. Antioxid. Redox Signal. 33, 481-497.
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Affiliation(s)
- Erik Schoenmakers
- Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, United Kingdom
| | - Krishna Chatterjee
- Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, United Kingdom
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Rother M, Quitzke V. Selenoprotein synthesis and regulation in Archaea. Biochim Biophys Acta Gen Subj 2018; 1862:2451-2462. [DOI: 10.1016/j.bbagen.2018.04.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 04/09/2018] [Accepted: 04/10/2018] [Indexed: 01/23/2023]
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Labunskyy VM, Hatfield DL, Gladyshev VN. Selenoproteins: molecular pathways and physiological roles. Physiol Rev 2014; 94:739-77. [PMID: 24987004 DOI: 10.1152/physrev.00039.2013] [Citation(s) in RCA: 821] [Impact Index Per Article: 82.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Selenium is an essential micronutrient with important functions in human health and relevance to several pathophysiological conditions. The biological effects of selenium are largely mediated by selenium-containing proteins (selenoproteins) that are present in all three domains of life. Although selenoproteins represent diverse molecular pathways and biological functions, all these proteins contain at least one selenocysteine (Sec), a selenium-containing amino acid, and most serve oxidoreductase functions. Sec is cotranslationally inserted into nascent polypeptide chains in response to the UGA codon, whose normal function is to terminate translation. To decode UGA as Sec, organisms evolved the Sec insertion machinery that allows incorporation of this amino acid at specific UGA codons in a process requiring a cis-acting Sec insertion sequence (SECIS) element. Although the basic mechanisms of Sec synthesis and insertion into proteins in both prokaryotes and eukaryotes have been studied in great detail, the identity and functions of many selenoproteins remain largely unknown. In the last decade, there has been significant progress in characterizing selenoproteins and selenoproteomes and understanding their physiological functions. We discuss current knowledge about how these unique proteins perform their functions at the molecular level and highlight new insights into the roles that selenoproteins play in human health.
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Affiliation(s)
- Vyacheslav M Labunskyy
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; and Molecular Biology of Selenium Section, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Dolph L Hatfield
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; and Molecular Biology of Selenium Section, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Vadim N Gladyshev
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; and Molecular Biology of Selenium Section, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
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Zhao HD, Zhang WG, Sun MN, Duan QF, Li FL, Li H. The role of Sep (O-phosphoserine) tRNA: Sec (selenocysteine) synthase (SEPSECS) in proliferation, apoptosis and hormone secretion of trophoblast cells. Placenta 2013; 34:967-72. [DOI: 10.1016/j.placenta.2013.07.066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 07/22/2013] [Accepted: 07/23/2013] [Indexed: 01/23/2023]
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Paiardini A, Pascarella S. Structural mimicry between SLA/LP and Rickettsia surface antigens as a driver of autoimmune hepatitis: insights from an in silico study. Theor Biol Med Model 2013; 10:25. [PMID: 23575112 PMCID: PMC3636016 DOI: 10.1186/1742-4682-10-25] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 04/07/2013] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Autoimmune hepatitis (AIH) is a chronic, progressive liver disease, characterized by continuing hepatocellular inflammation and necrosis. A subgroup of AIH patients presents specific autoantibodies to soluble liver antigen/liver-pancreas (SLA/LP) protein, which is regarded as a highly specific diagnostic marker. Autoantigenic SLA/LP peptides are targeted by CD4+ T cells, and restricted by the allele HLA-DRB1*03:01, which confers disease susceptibility in Europeans and Americans. A positively charged residue at position 71 has been indicated as critical for AIH susceptibility in all of the HLA alleles identified to date. Though the exact molecular mechanisms underlying pathogenesis of AIH are not clear, molecular mimicry between SLA/LP and viral/bacterial antigens has been invoked. METHODS The immunodominant region of SLA/LP was used as query in databank searches to identify statistically significant similarities with viral/bacterial peptides. Homology modeling and docking was used to investigate the potential interaction of HLA-DRB1*03:01 with the identified peptides. By molecular mechanics means, the interactions and energy of binding at the HLA binding site was also scrutinized. RESULTS A statistically significant structural similarity between the immunodominant regions of SLA/LP and a region of the surface antigen PS 120 from Rickettsia spp. has been detected. The interaction of the SLA/LP autoepitope and the corresponding Rickettsia sequence with the allele HLA-DRB1*03:01 has been simulated. The obtained results predict for both peptides a similar binding mode and affinity to HLA-DRB1*03:01. A "hot spot" of interaction between HLA-DRB1*03:01 and PS 120 is located at the P4 binding pocket, and is represented by a salt bridge involving Lys at position 71 of the HLA protein, and Glu 795 of PS120 peptide. CONCLUSIONS These findings strongly support the notion that a molecular mimicry mechanism can trigger AIH onset. CD4+ T cells recognizing peptides of SLA/LP could indeed cross-react with foreign Rickettsia spp. antigens. Finally, the same analysis suggests a molecular explanation for the importance of position 71 in conferring the susceptibility of the allele HLA-DRB1*03:01 to AIH. The lack of a positive charge at such position could prevent HLA alleles from binding the foreign peptides and triggering the molecular mimicry event.
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Affiliation(s)
- Alessandro Paiardini
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”, Sapienza - Università di Roma, Roma, 00185, Italy
| | - Stefano Pascarella
- Dipartimento di Scienze Biochimiche “A. Rossi Fanelli”, Sapienza - Università di Roma, Roma, 00185, Italy
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Turanov AA, Xu XM, Carlson BA, Yoo MH, Gladyshev VN, Hatfield DL. Biosynthesis of selenocysteine, the 21st amino acid in the genetic code, and a novel pathway for cysteine biosynthesis. Adv Nutr 2011; 2:122-8. [PMID: 22332041 PMCID: PMC3065758 DOI: 10.3945/an.110.000265] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The biosynthetic pathway for selenocysteine (Sec), the 21st amino acid in the genetic code whose codeword is UGA, was recently determined in eukaryotes and archaea. Sec tRNA, designated tRNA([Ser]Sec), is initially aminoacylated with serine by seryl-tRNA synthetase and the resulting seryl moiety is converted to phosphoserine by O-phosphoseryl-tRNA kinase to form O-phosphoseryl-tRNA([Ser]Sec). Sec synthase (SecS) then uses O-phosphoseryl-tRNA([Ser]Sec) and the active donor of selenium, selenophosphate, to form Sec-tRNA([Ser]Sec). Selenophosphate is synthesized from selenide and ATP by selenophosphate synthetase 2 (SPS2). Sec was the last protein amino acid in eukaryotes whose biosynthesis had not been established and the only known amino acid in eukaryotes whose biosynthesis occurs on its tRNA. Interestingly, sulfide can replace selenide to form thiophosphate in the SPS2-catalyzed reaction that can then react with O-phosphoseryl-tRNA([Ser]Sec) in the presence of SecS to form cysteine-(Cys-)tRNA([Ser]Sec). This novel pathway of Cys biosynthesis results in Cys being decoded by UGA and replacing Sec in normally selenium-containing proteins (selenoproteins). The selenoprotein, thioredoxin reductase 1 (TR1), was isolated from cells in culture and from mouse liver for analysis of Cys/Sec replacement by MS. The level of Cys/Sec replacement in TR1 was proportional to the level of selenium in the diet of the mice. Elucidation of the biosynthesis of Sec and Sec/Cys replacement provides novel ways of regulating selenoprotein functions and ultimately better understanding of the biological roles of dietary selenium.
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Affiliation(s)
- Anton A. Turanov
- Division of Genetics, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston MA 02115
| | - Xue-Ming Xu
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Bradley A. Carlson
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Min-Hyuk Yoo
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Vadim N. Gladyshev
- Division of Genetics, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston MA 02115,To whom correspondence should be addressed. E-mail: ;
| | - Dolph L. Hatfield
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892,To whom correspondence should be addressed. E-mail: ;
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Palioura S, Herkel J, Simonović M, Lohse AW, Söll D. Human SepSecS or SLA/LP: selenocysteine formation and autoimmune hepatitis. Biol Chem 2011; 391:771-6. [PMID: 20623998 DOI: 10.1515/bc.2010.078] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Selenocysteine, the 21st genetically encoded amino acid, is the major form of the antioxidant trace element selenium in the human body. In eukaryotes and archaea its synthesis proceeds through a phosphorylated intermediate in a tRNA-dependent fashion. The final step of selenocysteine formation is catalyzed by O-phosphoseryl-tRNA:selenocysteinyl-tRNA synthase (SepSecS) that converts phosphoseryl-tRNA(Sec) to selenocysteinyl-tRNA(Sec). The human SepSecS protein is also known as soluble liver antigen/liver pancreas (SLA/LP), which represents one of the antigens of autoimmune hepatitis. Here we review the discovery of human SepSecS and the current understanding of the immunogenicity of SLA/LP in autoimmune hepatitis.
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Affiliation(s)
- Sotiria Palioura
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
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Mackay IR. A 50-year experience with autoimmune hepatitis: and where are we now? J Gastroenterol 2011; 46 Suppl 1:17-28. [PMID: 21072544 DOI: 10.1007/s00535-010-0325-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Accepted: 08/23/2010] [Indexed: 02/04/2023]
Abstract
BACKGROUND Autoimmune hepatitis (AIH) as chronic active hepatitis became recognized in the 1940s as a progressive hyperglobulinemic disease affecting younger women attributed to persisting virus infection of the liver: autoimmunity then was barely on the horizon. EARLY OBSERVATIONS The lupus erythematosus (LE) cell reported in 1948 signified the presence of antinuclear autoantibodies, promoting perceptions of autoimmunity in certain chronic diseases. Recognition of LE cells in chronic hepatitis led to the designation of 'lupoid hepatitis', with autoimmunity further substantiated by anti-cytoplasmic autoantibodies detected by complement fixation. Next a serum reactant with smooth muscle of rodent stomach was found to have a wider distribution and became identified as an autoantibody to filamentous (F) actin. Therapy with corticosteroids proved effective, particularly combined with azathioprine. Various trials showed greatly improved survival and established modern therapy of AIH. An HLA-based predisposition (B8, DR3) was the first pointer to a genetic etiology. RECENT ADVANCES Recombinant or purified autoantigenic substrates have led to automated assays, which, together with improved immunofluorescence procedures, allow serological confidence in diagnosis and institution of effective immunosuppressive therapies. The liver-kidney 'microsomal' autoantigen reactive with cytochrome P450 2D6 distinguishes two serological types of AIH that appear pathogenetically distinct. Molecular characterization of antigens and epitopes remains wanting in type 1 AIH. FUTURE PROSPECTS The challenge remains with both types of AIH to elucidate in molecular terms the genetic and environmental basis of pathogenesis from initiation to ultimate progression and cirrhosis (when inadequately treated). Advancing technologies are bringing this goal closer to being attainable.
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Affiliation(s)
- Ian R Mackay
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, 3800, Australia.
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Hellmann H, Mooney S. Vitamin B6: a molecule for human health? Molecules 2010; 15:442-59. [PMID: 20110903 PMCID: PMC6257116 DOI: 10.3390/molecules15010442] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 01/16/2010] [Accepted: 01/20/2010] [Indexed: 11/16/2022] Open
Abstract
Vitamin B6 is an intriguing molecule that is involved in a wide range of metabolic, physiological and developmental processes. Based on its water solubility and high reactivity when phosphorylated, it is a suitable co-factor for many biochemical processes. Furthermore the vitamin is a potent antioxidant, rivaling carotenoids or tocopherols in its ability to quench reactive oxygen species. It is therefore not surprising that the vitamin is essential and unquestionably important for the cellular metabolism and well-being of all living organisms. The review briefly summarizes the biosynthetic pathways of vitamin B6 in pro- and eukaryotes and its diverse roles in enzymatic reactions. Finally, because in recent years the vitamin has often been considered beneficial for human health, the review will also sum up and critically reflect on current knowledge how human health can profit from vitamin B6.
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Affiliation(s)
- Hanjo Hellmann
- Washington State University, Abelson 435, P.O. Box 66224, Pullman, WA, USA.
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Stock T, Rother M. Selenoproteins in Archaea and Gram-positive bacteria. Biochim Biophys Acta Gen Subj 2009; 1790:1520-32. [PMID: 19344749 DOI: 10.1016/j.bbagen.2009.03.022] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2009] [Revised: 03/23/2009] [Accepted: 03/23/2009] [Indexed: 01/23/2023]
Abstract
Selenium is an essential trace element for many organisms by serving important catalytic roles in the form of the 21st co-translationally inserted amino acid selenocysteine. It is mostly found in redox-active proteins in members of all three domains of life and analysis of the ever-increasing number of genome sequences has facilitated identification of the encoded selenoproteins. Available data from biochemical, sequence, and structure analyses indicate that Gram-positive bacteria synthesize and incorporate selenocysteine via the same pathway as enterobacteria. However, recent in vivo studies indicate that selenocysteine-decoding is much less stringent in Gram-positive bacteria than in Escherichia coli. For years, knowledge about the pathway of selenocysteine synthesis in Archaea and Eukarya was only fragmentary, but genetic and biochemical studies guided by analysis of genome sequences of Sec-encoding archaea has not only led to the characterization of the pathways but has also shown that they are principally identical. This review summarizes current knowledge about the metabolic pathways of Archaea and Gram-positive bacteria where selenium is involved, about the known selenoproteins, and about the respective pathways employed in selenoprotein synthesis.
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Affiliation(s)
- Tilmann Stock
- Molekulare Mikrobiologie und Bioenergetik, Institut für Molekulare Biowissenschaften, Goethe-Universität Frankfurt am Main, Max-von-Laue-Str. 9, D-60438 Frankfurt am Main, Germany
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Su D, Hohn MJ, Palioura S, Sherrer RL, Yuan J, Söll D, O'Donoghue P. How an obscure archaeal gene inspired the discovery of selenocysteine biosynthesis in humans. IUBMB Life 2009; 61:35-9. [PMID: 18798524 DOI: 10.1002/iub.136] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Selenocysteine (Sec) is the 21st genetically encoded amino acid found in organisms from all three domains of life. Sec biosynthesis is unique in that it always proceeds from an aminoacyl-tRNA precursor. Even though Sec biosynthesis in bacteria was established almost two decades ago, only recently the pathway was elucidated in archaea and eukaryotes. While other aspects of Sec biology have been reviewed previously (Allmang and Krol, Biochimie 2006;88:1561-1571, Hatfield et al., Prog Nucleic Acid Res Mol Biol 2006;81:97-142, Squires and Berry, IUBMB Life 2008;60:232-235), here we review the biochemistry and evolution of Sec biosynthesis and coding and show how the knowledge of an archaeal cysteine biosynthesis pathway helped to uncover the route to Sec formation in archaea and eukaryotes.
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Affiliation(s)
- Dan Su
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA.
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Allmang C, Wurth L, Krol A. The selenium to selenoprotein pathway in eukaryotes: more molecular partners than anticipated. Biochim Biophys Acta Gen Subj 2009; 1790:1415-23. [PMID: 19285539 DOI: 10.1016/j.bbagen.2009.03.003] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 03/03/2009] [Accepted: 03/05/2009] [Indexed: 01/23/2023]
Abstract
The amino acid selenocysteine (Sec) is the major biological form of the trace element selenium. Sec is co-translationally incorporated in selenoproteins. There are 25 selenoprotein genes in humans, and Sec was found in the active site of those that have been attributed a function. This review will discuss how selenocysteine is synthesized and incorporated into selenoproteins in eukaryotes. Sec biosynthesis from serine on the tRNA(Sec) requires four enzymes. Incorporation of Sec in response to an in-frame UGA codon, otherwise signaling termination of translation, is achieved by a complex recoding machinery to inform the ribosomes not to stop at this position on the mRNA. A number of the molecular partners acting in this machinery have been identified but their detailed mechanism of action has not been deciphered yet. Here we provide an overview of the literature in the field. Particularly striking is the higher than originally envisaged number of factors necessary to synthesize Sec and selenoproteins. Clearly, selenoprotein synthesis is an exciting and very active field of research.
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Affiliation(s)
- Christine Allmang
- Architecture et Réactivité de l'ARN - Université de Strasbourg, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
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Squires JE, Berry MJ. Eukaryotic selenoprotein synthesis: mechanistic insight incorporating new factors and new functions for old factors. IUBMB Life 2008; 60:232-5. [PMID: 18344183 DOI: 10.1002/iub.38] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Selenium is an essential micronutrient that has been linked to various aspects of human health. Selenium exerts its biological activity through the incorporation of the amino acid, selenocysteine (Sec), into a unique class of proteins termed selenoproteins. Sec incorporation occurs cotranslationally at UGA codons in archaea, prokaryotes, and eukaryotes. UGA codons specify Sec coding rather than termination by the presence of specific secondary structures in mRNAs termed selenocysteine insertion (SECIS) elements, and trans-acting factors that associate with SECIS elements. Herein, we discuss the various proteins known to function in eukaryotic selenoprotein biosynthesis, including several players whose roles have only been elucidated very recently.
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Affiliation(s)
- Jeffrey E Squires
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI 96813, USA.
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Ganichkin OM, Xu XM, Carlson BA, Mix H, Hatfield DL, Gladyshev VN, Wahl MC. Structure and catalytic mechanism of eukaryotic selenocysteine synthase. J Biol Chem 2007; 283:5849-65. [PMID: 18093968 DOI: 10.1074/jbc.m709342200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In eukaryotes and Archaea, selenocysteine synthase (SecS) converts O-phospho-L-seryl-tRNA [Ser]Sec into selenocysteyl-tRNA [Ser]Sec using selenophosphate as the selenium donor compound. The molecular mechanisms underlying SecS activity are presently unknown. We have delineated a 450-residue core of mouse SecS, which retained full selenocysteyl-tRNA [Ser]Sec synthesis activity, and determined its crystal structure at 1.65 A resolution. SecS exhibits three domains that place it in the fold type I family of pyridoxal phosphate (PLP)-dependent enzymes. Two SecS monomers interact intimately and together build up two identical active sites around PLP in a Schiff-base linkage with lysine 284. Two SecS dimers further associate to form a homotetramer. The N terminus, which mediates tetramer formation, and a large insertion that remodels the active site set SecS aside from other members of the family. The active site insertion contributes to PLP binding and positions a glutamate next to the PLP, where it could repel substrates with a free alpha-carboxyl group, suggesting why SecS does not act on free O-phospho-l-serine. Upon soaking crystals in phosphate buffer, a previously disordered loop within the active site insertion contracted to form a phosphate binding site. Residues that are strictly conserved in SecS orthologs but variant in related enzymes coordinate the phosphate and upon mutation corrupt SecS activity. Modeling suggested that the phosphate loop accommodates the gamma-phosphate moiety of O-phospho-l-seryl-tRNA [Ser]Sec and, after phosphate elimination, binds selenophosphate to initiate attack on the proposed aminoacrylyl-tRNA [Ser]Sec intermediate. Based on these results and on the activity profiles of mechanism-based inhibitors, we offer a detailed reaction mechanism for the enzyme.
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Affiliation(s)
- Oleg M Ganichkin
- Max-Planck-Institut für Biophysikalische Chemie, Zelluläre Biochemie/Makromolekulare Röntgenkristallographie, Am Fassberg 11, D-37077 Göttingen, Germany
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Xu XM, Carlson BA, Zhang Y, Mix H, Kryukov GV, Glass RS, Berry MJ, Gladyshev VN, Hatfield DL. New developments in selenium biochemistry: selenocysteine biosynthesis in eukaryotes and archaea. Biol Trace Elem Res 2007; 119:234-41. [PMID: 17916946 DOI: 10.1007/s12011-007-8003-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 12/14/2022]
Abstract
We used comparative genomics and experimental analyses to show that (1) eukaryotes and archaea, which possess the selenocysteine (Sec) protein insertion machinery contain an enzyme, O-phosphoseryl-transfer RNA (tRNA) [Ser]Sec kinase (designated PSTK), which phosphorylates seryl-tRNA [Ser]Sec to form O-phosphoseryl-tRNA [Ser]Sec and (2) the Sec synthase (SecS) in mammals is a pyridoxal phosphate-containing protein previously described as the soluble liver antigen (SLA). SecS uses the product of PSTK, O-phosphoseryl-tRNA[Ser]Sec, and selenophosphate as substrates to generate selenocysteyl-tRNA [Ser]Sec. Sec could be synthesized on tRNA [Ser]Sec from selenide, adenosine triphosphate (ATP), and serine using tRNA[Ser]Sec, seryl-tRNA synthetase, PSTK, selenophosphate synthetase, and SecS. The enzyme that synthesizes monoselenophosphate is a previously identified selenoprotein, selenophosphate synthetase 2 (SPS2), whereas the previously identified mammalian selenophosphate synthetase 1 did not serve this function. Monoselenophosphate also served directly in the reaction replacing ATP, selenide, and SPS2, demonstrating that this compound was the active selenium donor. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that contain selenoproteins.
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Affiliation(s)
- Xue-Ming Xu
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Institutes of Health, Bethesda, MD 20892, USA
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Xu XM, Carlson BA, Mix H, Zhang Y, Saira K, Glass RS, Berry MJ, Gladyshev VN, Hatfield DL. Biosynthesis of selenocysteine on its tRNA in eukaryotes. PLoS Biol 2007; 5:e4. [PMID: 17194211 PMCID: PMC1717018 DOI: 10.1371/journal.pbio.0050004] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Accepted: 11/01/2006] [Indexed: 12/02/2022] Open
Abstract
Selenocysteine (Sec) is cotranslationally inserted into protein in response to UGA codons and is the 21st amino acid in the genetic code. However, the means by which Sec is synthesized in eukaryotes is not known. Herein, comparative genomics and experimental analyses revealed that the mammalian Sec synthase (SecS) is the previously identified pyridoxal phosphate-containing protein known as the soluble liver antigen. SecS required selenophosphate and O-phosphoseryl-tRNA[Ser]Sec as substrates to generate selenocysteyl-tRNA[Ser]Sec. Moreover, it was found that Sec was synthesized on the tRNA scaffold from selenide, ATP, and serine using tRNA[Ser]Sec, seryl-tRNA synthetase, O-phosphoseryl-tRNA[Ser]Sec kinase, selenophosphate synthetase, and SecS. By identifying the pathway of Sec biosynthesis in mammals, this study not only functionally characterized SecS but also assigned the function of the O-phosphoseryl-tRNA[Ser]Sec kinase. In addition, we found that selenophosphate synthetase 2 could synthesize monoselenophosphate in vitro but selenophosphate synthetase 1 could not. Conservation of the overall pathway of Sec biosynthesis suggests that this pathway is also active in other eukaryotes and archaea that synthesize selenoproteins. Sec synthase, a conserved protein responsible for the biosynthesis of the rare 21st amino acid, selenocysteine, is identified in eukaryotes, and the underlying biochemical pathway is characterized. Biosynthesis of the 20 canonical amino acids is well established in eukaryotes. However, many eukaryotes also have a rare selenium-containing amino acid, selenocysteine, which is the 21st amino acid in the genetic code. Selenium is essential for human health, and its health benefits, including preventing cancer and heart disease and delaying aging, have been attributed to the presence of selenocysteine in protein. How selenocysteine is made in eukaryotes has not been established. To gain insight into its biosynthesis, we used computational analyses to search completely sequenced genomes for proteins that occur exclusively in organisms that utilize selenocysteine. This approach revealed a putative selenocysteine synthase, which had been previously identified as a pyridoxal phosphate–containing protein dubbed soluble liver antigen. We were able to characterize the activity of this synthase using selenophosphate and a tRNA aminoacylated with phosphoserine as substrates to generate selenocysteine. Moreover, identification of selenocysteine synthase allowed us to delineate the entire pathway of selenocysteine biosynthesis in mammals. Interestingly, selenocysteine synthase is present only in those archaea and eukaryotes that make selenoproteins, indicating that the newly defined pathway of selenocysteine biosynthesis is active in these domains of life.
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Affiliation(s)
- Xue-Ming Xu
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Bradley A Carlson
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Heiko Mix
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Yan Zhang
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Kazima Saira
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Richard S Glass
- Department of Chemistry, The University of Arizona, Tucson, Arizona, United States of America
| | - Marla J Berry
- Department of Cell and Molecular Biology, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America
| | - Vadim N Gladyshev
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Dolph L Hatfield
- Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail:
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Abstract
At the time of its discovery four decades ago, the genetic code was viewed as the result of a "frozen accident." Our current knowledge of the translation process and of the detailed structure of its components highlights the roles of RNA structure (in mRNA and tRNA), RNA modification (in tRNA), and aminoacyl-tRNA synthetase diversity in the evolution of the genetic code. The diverse assortment of codon reassignments present in subcellular organelles and organisms of distinct lineages has 'thawed' the concept of a universal immutable code; it may not be accidental that out of more than 140 amino acids found in natural proteins, only two (selenocysteine and pyrrolysine) are known to have been added to the standard 20-member amino acid alphabet. The existence of phosphoseryl-tRNA (in the form of tRNACys and tRNASec) may presage the discovery of other cotranslationally inserted modified amino acids.
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Affiliation(s)
- Alexandre Ambrogelly
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA
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Yuan J, Palioura S, Salazar JC, Su D, O'Donoghue P, Hohn MJ, Cardoso AM, Whitman WB, Söll D. RNA-dependent conversion of phosphoserine forms selenocysteine in eukaryotes and archaea. Proc Natl Acad Sci U S A 2006; 103:18923-7. [PMID: 17142313 PMCID: PMC1748153 DOI: 10.1073/pnas.0609703104] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The trace element selenium is found in proteins as selenocysteine (Sec), the 21st amino acid to participate in ribosome-mediated translation. The substrate for ribosomal protein synthesis is selenocysteinyl-tRNA(Sec). Its biosynthesis from seryl-tRNA(Sec) has been established for bacteria, but the mechanism of conversion from Ser-tRNA(Sec) remained unresolved for archaea and eukarya. Here, we provide evidence for a different route present in these domains of life that requires the tRNA(Sec)-dependent conversion of O-phosphoserine (Sep) to Sec. In this two-step pathway, O-phosphoseryl-tRNA(Sec) kinase (PSTK) converts Ser-tRNA(Sec) to Sep-tRNA(Sec). This misacylated tRNA is the obligatory precursor for a Sep-tRNA:Sec-tRNA synthase (SepSecS); this protein was previously annotated as SLA/LP. The human and archaeal SepSecS genes complement in vivo an Escherichia coli Sec synthase (SelA) deletion strain. Furthermore, purified recombinant SepSecS converts Sep-tRNA(Sec) into Sec-tRNA(Sec) in vitro in the presence of sodium selenite and purified recombinant E. coli selenophosphate synthetase (SelD). Phylogenetic arguments suggest that Sec decoding was present in the last universal common ancestor. SepSecS and PSTK coevolved with the archaeal and eukaryotic lineages, but the history of PSTK is marked by several horizontal gene transfer events, including transfer to non-Sec-decoding Cyanobacteria and fungi.
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Affiliation(s)
- Jing Yuan
- Departments of *Molecular Biophysics and Biochemistry and
| | | | | | - Dan Su
- Departments of *Molecular Biophysics and Biochemistry and
| | | | | | | | - William B. Whitman
- Department of Microbiology, University of Georgia, Athens, GA 30602-2605
| | - Dieter Söll
- Departments of *Molecular Biophysics and Biochemistry and
- Chemistry, Yale University, New Haven, CT 06520-8114; and
- To whom correspondence should be addressed. E-mail:
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22
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Allmang C, Krol A. Selenoprotein synthesis: UGA does not end the story. Biochimie 2006; 88:1561-71. [PMID: 16737768 DOI: 10.1016/j.biochi.2006.04.015] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Accepted: 04/24/2006] [Indexed: 11/15/2022]
Abstract
It is well established that the beneficial effects of the trace element selenium are mediated by its major biological product, the amino acid selenocysteine, present in the active site of selenoproteins. These fulfill different functions, as varied as oxidation-reduction of metabolites in bacteria, reduction of reactive oxygen species, control of the redox status of the cell or thyroid hormone maturation. This review will focus on the singularities of the selenocysteine biosynthesis pathway and its unique incorporation mechanism into eukaryal selenoproteins. Selenocysteine biosynthesis from serine is achieved on tRNA(Sec) and requires four proteins. As this amino acid is encoded by an in-frame UGA codon, otherwise signaling termination of translation, ribosomes must be told not to stop at this position in the mRNA. Several molecular partners acting in cis or in trans have been identified, but their knowledge has not enabled yet to firmly establish the molecular events underlying this mechanism. Data suggest that other, so far uncharacterized factors might exist. In this survey, we attempted to compile all the data available in the literature and to describe the latest developments in the field.
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Affiliation(s)
- C Allmang
- Institut de Biologie Moléculaire et Cellulaire, UPR 9002 du CNRS Architecture et Réactivité de l'ARN. Université Louis-Pasteur, 15, rue René-Descartes, 67084 Strasbourg Cedex, France
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Small-Howard A, Morozova N, Stoytcheva Z, Forry EP, Mansell JB, Harney JW, Carlson BA, Xu XM, Hatfield DL, Berry MJ. Supramolecular complexes mediate selenocysteine incorporation in vivo. Mol Cell Biol 2006; 26:2337-46. [PMID: 16508009 PMCID: PMC1430297 DOI: 10.1128/mcb.26.6.2337-2346.2006] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Selenocysteine incorporation in eukaryotes occurs cotranslationally at UGA codons via the interactions of RNA-protein complexes, one comprised of selenocysteyl (Sec)-tRNA([Ser]Sec) and its specific elongation factor, EFsec, and another consisting of the SECIS element and SECIS binding protein, SBP2. Other factors implicated in this pathway include two selenophosphate synthetases, SPS1 and SPS2, ribosomal protein L30, and two factors identified as binding tRNA([Ser]Sec), termed soluble liver antigen/liver protein (SLA/LP) and SECp43. We report that SLA/LP and SPS1 interact in vitro and in vivo and that SECp43 cotransfection increases this interaction and redistributes all three proteins to a predominantly nuclear localization. We further show that SECp43 interacts with the selenocysteyl-tRNA([Ser]Sec)-EFsec complex in vitro, and SECp43 coexpression promotes interaction between EFsec and SBP2 in vivo. Additionally, SECp43 increases selenocysteine incorporation and selenoprotein mRNA levels, the latter presumably due to circumvention of nonsense-mediated decay. Thus, SECp43 emerges as a key player in orchestrating the interactions and localization of the other factors involved in selenoprotein biosynthesis. Finally, our studies delineating the multiple, coordinated protein-nucleic acid interactions between SECp43 and the previously described selenoprotein cotranslational factors resulted in a model of selenocysteine biosynthesis and incorporation dependent upon both cytoplasmic and nuclear supramolecular complexes.
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Affiliation(s)
- Andrea Small-Howard
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, HI 96822, USA
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Wang CX, Teufel A, Cheruti U, Grötzinger J, Galle PR, Lohse AW, Herkel J. Characterization of human gene encoding SLA/LP autoantigen and its conserved homologs in mouse, fish, fly, and worm. World J Gastroenterol 2006; 12:902-7. [PMID: 16521218 PMCID: PMC4066155 DOI: 10.3748/wjg.v12.i6.902] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To approach the elusive function of the SLA/LP molecule, we have characterized genomic organization and conservation of the major antigenic and functional properties of the SLA/LP molecule in various species.
METHODS: By means of computational biology, we have characterized the complete SLA/LP gene, mRNA and deduced protein sequences in man, mouse, zebrafish, fly, and worm.
RESULTS: The human SLA/LP gene sequence of approximately 39 kb, which maps to chromosome 4p15.2, is organized in 11 exons, of which 10 or 11 are translated, depending on the splice variant. Homologous molecules were identified in several biological model organisms. The various homologous protein sequences showed a high degree of similarity or homology, notably at those residues that are of functional importance. The only domain of the human protein sequence that lacks significant homology with homologous sequences is the major antigenic epitope recognized by autoantibodies from autoimmune hepatitis (AIH) patients.
CONCLUSION: The SLA/LP molecule and its functionally relevant residues have been highly conserved throughout the evolution, suggesting an indispensable function of the molecule. The finding that the only non-conserved domain is the dominant antigenic epitope of the human SLA/LP sequence, suggests that SLA/LP autoimmunity is autoantigen-driven rather than being driven by molecular mimicry.
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Affiliation(s)
- Chun-Xia Wang
- Department of Medicine, University Medical Centre Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany.
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25
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Abstract
Autoantibodies indicate an immune reactive state, but in liver disease they lack pathogenicity and disease specificity. Antinuclear antibodies, smooth muscle antibodies, antibodies to liver/kidney microsome type 1, antimitochondrial antibodies, and perinuclear antineutrophil cytoplasmic antibodies constitute the standard serological repertoire that should be assessed in all liver diseases of undetermined cause. Antibodies to soluble liver antigen/liver pancreas, asialoglycoprotein receptor, actin, liver cytosol type 1, nuclear antigens specific to primary biliary cirrhosis, and pore complex antigens constitute an investigational repertoire that promises to have prognostic and diagnostic value. These autoantibodies may emerge as predictors of treatment response and outcome. Antibodies to histones, doubled-stranded DNA, chromatin, and lactoferrin constitute a supplemental repertoire, and they support the immune nature of the liver disease. Final diagnoses and treatment strategies do not depend solely on serological markers. Autoantibodies are floating variables, and their behavior does not correlate closely with disease activity. There are no minimum levels of significant seropositivity, especially in children. Over-interpretation is the major pitfall in the clinical application of the serological results. New autoantibodies will emerge as the search for target antigens and key pathogenic pathways continues.
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Affiliation(s)
- Albert J Czaja
- Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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Mizutani T, Shinoda M, Tanaka Y, Kuno T, Hattori A, Usui T, Kuno N, Osaka T. Autoantibodies against CYP2D6 and other drug-metabolizing enzymes in autoimmune hepatitis type 2. Drug Metab Rev 2005; 37:235-52. [PMID: 15747502 DOI: 10.1081/dmr-200028798] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Autoimmune hepatitis (AIH) is a disease of unknown etiology, characterized by liver-related autoantibodies. Autoimmune hepatitis is subdivided into two major types: AIH type 1 is characterized by the detection of ANA, SMA, ANCA, anti-ASGP-R, and anti-SLA/LP. Autoimmune hepatitis type 2 is characterized to be mainly related with drug-metabolizing enzymes as autoantigens, such as anti-LKM (liver-kidney microsomal antigen)-1 against CYP2D6, anti-LKM-2 against CYP2C9-tienilic acid, anti-LKM-3 against UGT1A, and anti-LC1 (liver cytosol antigen)-1 and anti-APS (autoimmune polyglandular syndrome type-1) against CYP1A2, CYP2A6, and others. Anti-LKM-1 sera inhibited CYP2D6 activity in vitro but did not inhibit cellular drug metabolism in vivo. CYP2D6 is the major target autoantigen of LKM-1 and expressed on plasma membrane (PM) of hepatocytes, suggesting a pathogenic role for anti-LKM-1 in liver injury as a trigger. Anti-CYP1A2 was observed in dihydralazine-induced hepatitis, and radiolabeled CYP1A2 disappeared from the PM with a half-life of less than 30 min, whereas microsomal CYP1A2 was stably radiolabeled for several hours. Main antigenic epitopes on CYP2D6 are aa 193-212, aa 257-269, and aa 321-351; and D263 is essential. The third epitope is located on the surface of the protein CYP2D6 and displays a hydrophobic patch that is situated between an aromatic residue (W316) and histidine (H326). Some drugs such as anticonvulsants (phenobarbital, phenytoin, and carbamazepine) and halothane are suggested to induce hepatitis with anti-CYP3A and anti-CYP2E1, respectively. Autoantibodies against CYP11A1, CYP17, and/or CYP21 involved in the synthesis of steroid hormones are also detected in patients with adrenal failure, gonadal failure, and/or Addison disease.
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Affiliation(s)
- Takaharu Mizutani
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan.
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Shinoda M, Tanaka Y, Kuno T, Matsufuji T, Matsufuji S, Murakami Y, Mizutani T. High levels of autoantibodies against drug-metabolizing enzymes in SLA/LP-positive AIH-1 sera. Autoimmunity 2005; 37:473-80. [PMID: 15621574 DOI: 10.1080/08916930400001891] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Autoimmune hepatitis type 1 (AIH-1) is characterized by the detection of smooth muscle autoantibodies, antinuclear antibodies and antineutrophil cytoplasmic autoantibodies, and AIH-2 is characterized by the presence of autoantibodies against LKM, which contain drug-metabolizing enzymes. In this study, we measured the levels of drug-metabolizing enzymes in AIH-1 patients (ANA-positive). We exhaustively investigated the level of autoantibodies against major CYPs and UDP-glucuronosyltransferases of typical phase II drug-metabolizing enzymes, a transporter (MDR1), and NADPH-cytochrome P450 reductase in 4 patients with AIH-1 and 6 controls, as a case report. Two (Patients 3 and 4) of the AIH patients exhibited high levels of autoantibodies, while two (Patients 1 and 2) of the patients and the controls did not. The levels of autoantibodies against CYP2C19, CYP2D6, CYP2E1, UGT1A6 and human liver microsomes in Patients 3 and 4 sera were over 2(3) times the levels in Patient 1, Patient 2 and the control sera. Meanwhile, the levels of autoantibodies against CYP1A2, CYP2A6, CYP2C9, UGT2B7, MDR1 and NADPH-cytochrome P450 reductase were 2-2(2) higher in Patients 3 and 4 than in the other subjects. We found that the pattern of elevation in the Patient 3 serum was not parallel with that in Patient 4. Thus, we found high levels of autoantibodies against drug-metabolizing enzymes in AIH-1 patients.
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Affiliation(s)
- Masakazu Shinoda
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Japan
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Cheng J, Liu Y, Hong Y, Wang L, Zhong YW, Dong J, Wang G. Identification and characterization of gene 10 transactivated by hepatitis C virus non-structural protein 5A with DNA microarray assay. Shijie Huaren Xiaohua Zazhi 2003; 11:935-938. [DOI: 10.11569/wcjd.v11.i7.935] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM To explore the new target genes transactivated by HCV NS5A, we conducted microarray assay on the hepatoblastoma HepG2 and HepG2 transfected by NS5A expressive vector.
METHODS Sequence specific primers were designed and synthesized according to the HCV-H strain of virus sequence. Polymerase chain reaction (PCR) was conducted to amplify the NS5A coding gene for the construction of expressive vector pcDNA3.1(-)-NS5A. Hepatoblastoma cell line HepG2 was transfected with plasmid DNA of pcDNA3.1(-)-NS5A, and total RNA was purified from it. Reverse transcribed cDNA were subjected to microarray assay. The coding gene transactivated by HCV NS5A was cloned by bioinformatics methods.
RESULTS The expressive vector had been constructed and approved correct. The RNA had been purified from HepG2 and HepG2 cells transfected with pcDNA3.1(-)-NS5A, respectively. The cDNA derived had been subjected to microarray assay. New gene named NS5ATP10 had been cloned in combination of molecular biological and bioinformatics methods.
CONCLUSION HCV NS5A is a potential transactivator. Microarray is an efficient and convenient method for analysis of differentially expressed genes. A new gene has been recognized as the new target transactivated by HCV NS5A protein. These results pave the way for study on the transactivation of HCV NS5A protein.
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Affiliation(s)
- Jun Cheng
- Gene Therapy Research Center, Institute of Infectious Diseases, 302 Hospital of PLA, Beijing 100039, China
| | - Yan Liu
- Gene Therapy Research Center, Institute of Infectious Diseases, 302 Hospital of PLA, Beijing 100039, China
| | - Yuan Hong
- Gene Therapy Research Center, Institute of Infectious Diseases, 302 Hospital of PLA, Beijing 100039, China
| | - Lin Wang
- Gene Therapy Research Center, Institute of Infectious Diseases, 302 Hospital of PLA, Beijing 100039, China
| | - Yan-Wei Zhong
- Gene Therapy Research Center, Institute of Infectious Diseases, 302 Hospital of PLA, Beijing 100039, China
| | - Jing Dong
- Gene Therapy Research Center, Institute of Infectious Diseases, 302 Hospital of PLA, Beijing 100039, China
| | - Gang Wang
- Gene Therapy Research Center, Institute of Infectious Diseases, 302 Hospital of PLA, Beijing 100039, China
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Cheng J, Li K, Lu YY, Wang L, Liu Y. Bioinformatics analysis of human hepatitis C virus core protein-binding protein 6 gene and protein. Shijie Huaren Xiaohua Zazhi 2003; 11:378-384. [DOI: 10.11569/wcjd.v11.i4.378] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM To investigate the structure and function of gene encoding human hepatitis C virus core protein-binding protein 6 (HCBP6) with yeast two-hybrid technique and bioinformatics methods.
METHODS Yeast two-hybrid technique and bioinformatics method were used to screen and identify the human HCBP6 gene and its amino acid sequences.
RESULTS Human HCBP6 cDNA and genomic DNA sequences were identified. Human HCBP6 coded for 456 nt and corresponding protein was composed of 152 amino acids. The promoter sequence of HCBP6 gene was identified and promoter motif was predicted by 3 different bioinformatics methods. No intron in HCBP6 gene was identified by homologous search of cDNA and genomic DNA sequence database. The hydrophilic domain was predicted by bioinformatics methods, and the functional domains were determined with online search tools. Mouse HCBP6 gene was identified on the basis of the mouse homologous DNA sequence database. However, all data obtained from bioinformatics analysis were preliminary and further study is required for confirmation.
CONCLUSION The bioinformatics is a powerful method for the analysis and prediction of a new gene and corresponding protein. Although the predicted result is not accurate, it provides valuable information for further study.
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Affiliation(s)
- Jun Cheng
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
| | - Ke Li
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
| | - Yin-Ying Lu
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
| | - Lin Wang
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
| | - Yan Liu
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
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Abstract
The report of the 1997 National Institutes of Health Consensus Development Conference on hepatitis C endorsed pretreatment liver biopsy. We revisit the following questions: Does liver histology help determine the urgency of, and predict the likelihood of response to, antiviral therapy, and can surrogate markers supplant histological assessment? Because the rate of progression of chronic hepatitis C is influenced by baseline histological grade/stage, patients can be stratified into those with moderate to severe hepatitis, who merit imminent therapy, and those with mild hepatitis, in whom therapy can be postponed until more effective/tolerable treatments become available. Less advanced baseline histology has been shown to be an independent predictor of responsiveness to antiviral therapy. Although the predictive value of biopsy is insufficient to withhold therapy from patients with advanced fibrosis, baseline biopsy helps gauge expectations for the outcome of therapy. Reports have been published recently suggesting that laboratory markers can predict distinctions between low-grade fibrosis and therapy-indicating septal fibrosis/cirrhosis. These indices, however, are insufficiently reliable to predict histological distinctions in populations with varying prevalences of fibrosis/cirrhosis or to provide anything more than broad qualitative distinctions, far short of the potential information in a liver biopsy. For most patients, the value of pretreatment liver biopsy outweighs its risks, provides information about the urgency of treatment, and should be retained. Studies to identify noninvasive laboratory markers of histological activity and stage, especially genetic predictors of accelerated disease progression, command a high priority.
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Affiliation(s)
- Jules L Dienstag
- Gastrointestinal Unit (Medical Services), Massachusetts General Hospital, Boston, MA 02114, USA.
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31
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Abstract
The molecular characterization of the autoreactivities associated with autoimmune liver disease will improve their diagnosis and enhance understanding of their pathogenic mechanisms. Surprisingly, little is known about the nature of the major autoreactivities associated with type 1 AIH, including homogeneous ANA and antibodies to microfilaments [3]. Type 1 AIH is, however, the prototype of autoimmune liver disease [103].
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Affiliation(s)
- Francesco B Bianchi
- Department of Internal Medicine, Cardioangiology, Hepatology, Alma Mater Studiorum, University of Bologna, Policlinico Sant'Orsola-Malpighi, via Massarenti, 9 40138 Bologna, Italy.
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32
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Affiliation(s)
- Albert J Czaja
- Division of Gastroenterology and Hepatology, Mayo Clinic and Mayo Foundation, Rochester, MN 55905, USA.
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33
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Abstract
Autoimmune hepatitis is as virulent in the elderly as in the young, and initial treatment should be similar. Antiphospholipid antibodies should be sought in all patients with a history of fetal loss or arterial or venous thrombosis. The C282Y mutation in the HFE hemochromatosis gene occurs more commonly in autoimmune hepatitis than in normal subjects, but it is not associated with distinctive features. Children with autoimmune hepatitis may have abnormal cholangiogram results, but the syndrome of autoimmune sclerosing cholangitis does not affect immediate prognosis. Bile duct changes, including destructive cholangitis, can be incidental findings that have no clinical expression or therapeutic consequence. In South America, DRB1*1301 is associated with protracted hepatitis A virus infection which may enhance exposure to hepatic self-antigens in children. Interferon gamma-inducible protein 10 may be an important chemokine that promotes liver damage by attracting activated T cells. Transcripts of Fas ligand are abnormally increased in autoimmune hepatitis, and apoptotic dysfunction may contribute to disease progression. Pregnancy is not contraindicated in autoimmune hepatitis, and cyclosporine may be effective as first-line therapy.
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Affiliation(s)
- Albert J Czaja
- Division of Gastroenterology and Hepatology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
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Ma Y, Okamoto M, Thomas MG, Bogdanos DP, Lopes AR, Portmann B, Underhill J, Dürr R, Mieli-Vergani G, Vergani D. Antibodies to conformational epitopes of soluble liver antigen define a severe form of autoimmune liver disease. Hepatology 2002; 35:658-64. [PMID: 11870381 DOI: 10.1053/jhep.2002.32092] [Citation(s) in RCA: 202] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Prevalence and clinical relevance of antibodies to soluble liver antigen (tRNP((Ser)Sec)/SLA) in autoimmune hepatitis (AIH) have been investigated using partially purified or prokaryotically expressed antigen. The aim of this study was to improve the detection of anti-tRNP((Ser)Sec)/SLA by establishing an immunoassay that was able to identify antibodies directed to conformational epitopes and to investigate the clinical implication of this autoantibody in autoimmune liver disease. By using eukaryotically expressed tRNP((Ser)Sec)/SLA as target in a radioligand assay (RLA), 81 patients with autoimmune liver disease (AILD) (33 type 1 AIH, 31 type 2 AIH, and 17 autoimmune sclerosing cholantitis [ASC]), 147 pathologic, and 56 healthy controls were investigated. RLA results were compared with those obtained using a commercial enzyme-linked immunosorbent assay (ELISA) and immunoblot. Reactivity to tRNP((Ser)Sec)/SLA was present in 58% of patients with type 1 and type 2 AIH, 41% with ASC, but in only 3 pathologic controls. RLA was similarly disease-specific but remarkably more sensitive than ELISA and immunoblot. A prospective study showed that anti-tRNP((Ser)Sec)/SLA-positive patients run a severe clinical course, having worse histology, needing longer to achieve remission, relapsing and requiring liver transplantation or dying more frequently than anti-tRNP((Ser)Sec)/SLA negative patients. Anti-tRNP((Ser)Sec)/SLA production was favored by the possession of DR3 and A1-B8-DR3 in AIH type 1 and ASC, and prevented by the possession of A2 in all 3 types of AILD, particularly in type 2 AIH. In conclusion, anticonformational tRNP((Ser)Sec)/SLA reactivity is frequent in type 1 and type 2 AIH and ASC, defining patients with a worse prognosis.
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Affiliation(s)
- Yun Ma
- Immunology Section, Institute of Hepatology, University College London, 69-75 Chenies Mews, London, WC1E 6HX, UK
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35
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Abstract
Premises for the subspecialty of hepatoimmunology include the recognition that the liver is a lymphoid organ with unique immunological properties. These properties ensure efficient innate defence against intestinal microbes and toxins, confer a particular capacity for induction of tolerance, and provide for apoptotic disposal of redundant lymphocytes. Pathological responses within the liver are elicited when: (i) hepatotropic viruses (hepatitis virus B and C) escape immune elimination and reside in hepatocytes; (ii) the liver becomes the site of autoimmune responses directed against either hepatocytes (autoimmune hepatitis) or biliary ductules (primary biliary cirrhosis); or (iii) the liver in the course of disposal of drugs generates neoantigens that provoke adverse allergic responses. Recent advances in the understanding of the immunopathogenesis of these entities are reviewed.
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Affiliation(s)
- Ian R Mackay
- Department of Biochemistry and MolecularBiology, Monash University, Clayton, Victoria, Australia.
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36
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Abstract
Hepatocyte injury and necrosis from many causes may result in pediatric liver disease. Influenced by other cell types in the liver, by its unique vascular arrangements, by lobular zonation, and by contributory effects of sepsis, reactive oxygen species and disordered hepatic architecture, the hepatocyte is prone to injury from exogenous toxins, from inborn errors of metabolism, from hepatotrophic viruses, and from immune mechanisms. Experimental studies on cultured hepatocytes or animal models must be interpreted with caution. Having discussed general concepts, this review describes immune mechanisms of liver injury, as seen in autoimmune hepatitis, hepatitis B and C infection, the anticonvulsant hypersensitivity syndrome, and autoimmune polyendocrinopathy. Of the monogenic disorders causing significant liver injury in childhood, alpha-1 antitrypsin deficiency and Niemann-Pick C disease demonstrate the effect of endoplasmic or endosomal retention of macromolecules. Tyrosinemia illustrates how understanding the biochemical defect leads to understanding cell injury, extrahepatic porphyric effects, oncogenesis, pharmacological intervention, and possible stem cell therapy. Pathogenesis of cirrhosis in galactosemia remains incompletely understood. In hereditary fructose intolerance, phosphate sequestration causes ATP depletion. Recent information about mitochondrial disease, NASH, disorders of glycosylation, Wilson's disease, and the progressive familial intrahepatic cholestases is discussed.
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Affiliation(s)
- M S Tanner
- Institute of Child Health, University of Sheffield Children's Hospital, Western Bank, UK
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Herkel J, Heidrich B, Nieraad N, Wies I, Rother M, Lohse AW. Fine specificity of autoantibodies to soluble liver antigen and liver/pancreas. Hepatology 2002; 35:403-8. [PMID: 11826415 DOI: 10.1053/jhep.2002.30699] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Autoantibodies to soluble liver antigen and liver pancreas (SLA/LP) have been described as specific markers for Autoimmune Hepatitis (AIH), occurring in about 20% of patients with AIH. The high degree of specificity for SLA/LP in autoimmune liver disease suggests a possible role in its pathogenesis. This study aims to map the exact epitope(s) recognized by SLA/LP autoantibodies and to assess the role of molecular mimicry between microbial antigens and self-epitopes. Using SLA/LP-reactive sera of 18 individual AIH patients and a pool of 15 patient sera, we found the dominant immune reactivity directed to peptide p395-414 and a less prominent immune response to 2 other epitopes adjacent to the dominant epitope. Immunodominance of peptide p395-414 was confirmed by absorption experiments. The SLA/LP autoantibodies of all tested AIH patients were mainly of the IgG1 type, suggesting that SLA/LP autoantibodies may arise by a common and specific underlying immune stimulus. Based on sequence homologies of the SLA/LP antigenic region with viral proteins, it was hypothesized that molecular mimicry may drive autoimmunity to SLA/LP. However, the homologous virus-derived peptides were not recognized by SLA/LP autoantibodies. Similarly, the only known procaryotic homologue, MJ0610 of Methanococcus jannaschii, was only weakly recognized by SLA/LP-positive sera. Thus, no evidence could be found for molecular mimicry being the causative mechanism for the development of SLA/LP autoantibodies. In conclusion, the exquisite epitope specificity and IgG subtype are evidence for the maturity of the SLA/LP autoantibody response; a specific autoantigen-driven process underlying the immunopathogenesis is likely.
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Affiliation(s)
- Johannes Herkel
- I. Department of Medicine, Johannes Gutenberg-Universität, Mainz, Germany
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