1
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Adams TM, Zhao P, Chapla D, Moremen KW, Wells L. Sequential in vitro enzymatic N-glycoprotein modification reveals site-specific rates of glycoenzyme processing. J Biol Chem 2022; 298:102474. [PMID: 36089065 PMCID: PMC9530959 DOI: 10.1016/j.jbc.2022.102474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 09/01/2022] [Accepted: 09/03/2022] [Indexed: 12/01/2022] Open
Abstract
N-glycosylation is an essential eukaryotic posttranslational modification that affects various glycoprotein properties, including folding, solubility, protein–protein interactions, and half-life. N-glycans are processed in the secretory pathway to form varied ensembles of structures, and diversity at a single site on a glycoprotein is termed ‘microheterogeneity’. To understand the factors that influence glycan microheterogeneity, we hypothesized that local steric and electrostatic factors surrounding each site influence glycan availability for enzymatic modification. We tested this hypothesis via expression of reporter N-linked glycoproteins in N-acetylglucosaminyltransferase MGAT1-null HEK293 cells to produce immature Man5GlcNAc2 glycoforms (38 glycan sites total). These glycoproteins were then sequentially modified in vitro from high mannose to hybrid and on to biantennary, core-fucosylated, complex structures by a panel of N-glycosylation enzymes, and each reaction time course was quantified by LC-MS/MS. Substantial differences in rates of in vitro enzymatic modification were observed between glycan sites on the same protein, and differences in modification rates varied depending on the glycoenzyme being evaluated. In comparison, proteolytic digestion of the reporters prior to N-glycan processing eliminated differences in in vitro enzymatic modification. Furthermore, comparison of in vitro rates of enzymatic modification with the glycan structures found on the mature reporters expressed in WT cells correlated well with the enzymatic bottlenecks observed in vivo. These data suggest higher order local structures surrounding each glycosylation site contribute to the efficiency of modification both in vitro and in vivo to establish the spectrum of microheterogeneity in N-linked glycoproteins.
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Affiliation(s)
- Trevor M Adams
- Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602
| | - Peng Zhao
- Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602
| | - Digantkumar Chapla
- Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602
| | - Kelley W Moremen
- Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602.
| | - Lance Wells
- Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602.
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2
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Chen Q, Zhang Y, Zhang K, Liu J, Pan H, Wang X, Li S, Hu D, Lin Z, Zhao Y, Hou G, Guan F, Li H, Liu S, Ren Y. Profiling the Bisecting N-acetylglucosamine Modification in Amniotic Membrane via Mass Spectrometry. GENOMICS, PROTEOMICS & BIOINFORMATICS 2022; 20:648-656. [PMID: 35123071 PMCID: PMC9880894 DOI: 10.1016/j.gpb.2021.09.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 08/30/2021] [Accepted: 10/11/2021] [Indexed: 01/31/2023]
Abstract
Bisecting N-acetylglucosamine (GlcNAc), a GlcNAc linked to the core β-mannose residue via a β1,4 linkage, is a special type of N-glycosylation that has been reported to be involved in various biological processes, such as cell adhesion and fetal development. This N-glycan structure is abundant in human trophoblasts, which is postulated to be resistant to natural killer cell-mediated cytotoxicity, enabling a mother to nourish a fetus without rejection. In this study, we hypothesized that the human amniotic membrane, which serves as the last barrier for the fetus, may also express bisected-type glycans. To test this hypothesis, glycomic analysis of the human amniotic membrane was performed, and bisected N-glycans were detected. Furthermore, our proteomic data, which have been previously employed to explore human missing proteins, were analyzed and the presence of bisecting GlcNAc-modified peptides was confirmed. A total of 41 glycoproteins with 43 glycopeptides were found to possess a bisecting GlcNAc, and 25 of these glycoproteins were reported to exhibit this type of modification for the first time. These results provide insights into the potential roles of bisecting GlcNAc modification in the human amniotic membrane, and can be beneficial to functional studies on glycoproteins with bisecting GlcNAc modifications and functional studies on immune suppression in human placenta.
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Affiliation(s)
| | | | | | - Jie Liu
- BGI-Shenzhen, Shenzhen 518083, China
| | | | | | - Siqi Li
- BGI-Shenzhen, Shenzhen 518083, China
| | - Dandan Hu
- BGI-Shenzhen, Shenzhen 518083, China
| | | | - Yun Zhao
- BGI-Shenzhen, Shenzhen 518083, China
| | | | - Feng Guan
- Joint International Research Laboratory of Glycobiology and Medical Chemistry, College of Life Sciences, Northwest University, Xi’an 710069, China
| | - Hong Li
- Shenzhen Seventh People's Hospital, Shenzhen 518081, China
| | - Siqi Liu
- BGI-Shenzhen, Shenzhen 518083, China,Corresponding authors.
| | - Yan Ren
- BGI-Shenzhen, Shenzhen 518083, China,Institute of Interdisciplinary Integrative Medicine Research, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China,Corresponding authors.
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3
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Brás-Costa C, Chaves AFA, Cajado-Carvalho D, da Silva Pires D, Andrade-Silva D, Serrano SMT. Profilings of subproteomes of lectin-binding proteins of nine Bothrops venoms reveal variability driven by different glycan types. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2022; 1870:140795. [PMID: 35662639 DOI: 10.1016/j.bbapap.2022.140795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 05/23/2022] [Accepted: 05/27/2022] [Indexed: 06/15/2023]
Abstract
Snake venom proteomes have long been investigated to explore a multitude of biologically active components that are used for prey capture and defense, and are involved in the pathological effects observed upon mammalian envenomation. Glycosylation is a major protein post-translational modification in venoms and contributes to the diversification of proteomes. We have shown that Bothrops venoms are markedly defined by their content of glycoproteins, and that most N-glycan structures of eight Bothrops venoms contain sialic acid, while bisected N-acetylglucosamine was identified in Bothrops cotiara venom. To further investigate the mechanisms involved in the generation of different venoms by related snakes, here the glycoproteomes of nine Bothrops venoms (Bothrops atrox, B. cotiara, Bothrops erythromelas, Bothrops fonsecai, B. insularis, Bothrops jararaca, Bothrops jararacussu, Bothrops moojeni and Bothrops neuwiedi) were comparatively analyzed by enrichment with three lectins of different specificities, recognizing bisecting N-acetylglucosamine- and sialic acid-containing glycoproteins, and mass spectrometry. The lectin capture strategy generated venom fractions enriched with several glycoproteins, including metalloprotease, serine protease, and L- amino acid oxidase, in addition to various types of low abundant enzymes. The different contents of lectin-enriched proteins underscore novel aspects of the variability of the glycoprotein subproteomes of Bothrops venoms and point to the role of distinct types of glycan chains in generating different venoms by closely related snake species.
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Affiliation(s)
- Carolina Brás-Costa
- Laboratory of Applied Toxinology, Center of Toxins, Immune-Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - Alison Felipe Alencar Chaves
- Laboratory of Applied Toxinology, Center of Toxins, Immune-Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - Daniela Cajado-Carvalho
- Laboratory of Applied Toxinology, Center of Toxins, Immune-Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - David da Silva Pires
- Laboratory of Cell Cycle, Center of Toxins, Immune-Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - Débora Andrade-Silva
- Laboratory of Applied Toxinology, Center of Toxins, Immune-Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - Solange M T Serrano
- Laboratory of Applied Toxinology, Center of Toxins, Immune-Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil.
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4
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Klarić TS, Salopek M, Micek V, Gornik Kljaić O, Lauc G. Post-natal developmental changes in the composition of the rat neocortical N-glycome. Glycobiology 2020; 31:636-648. [PMID: 33242084 DOI: 10.1093/glycob/cwaa108] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/04/2020] [Accepted: 11/17/2020] [Indexed: 12/27/2022] Open
Abstract
Asparagine-linked glycosylation (N-glycosylation) plays a key role in many neurodevelopmental processes, including neural cell adhesion, neurite outgrowth and axon targeting. However, little is known about the dynamics of N-glycosylation during brain development and, in particular, how the N-glycome of the developing neocortex differs from that of the adult. The aim of this study, therefore, was to perform a thorough characterization of N-glycosylation in both the adult and neonatal rat neocortex in order to gain insights into the types of changes occurring in the N-glycome during neurodevelopment. To this end, we used hydrophilic interaction ultraperformance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry to compare the adult neocortical N-glycome with that of 24- and 48-h neonates. We report that the abundance of complex N-glycans is significantly lower in adults compared with neonates. Furthermore, the proportion of charged complex N-glycans is also greatly reduced. This decrease in the abundance of complex N-glycans is offset by a corresponding increase in the proportion of truncated and, to a lesser extent, hybrid N-glycans. Lastly, we report that although the proportion of oligomannose N-glycans remains constant at around 24%, the distribution of high-mannose subtypes shifts from predominantly large subtypes in neonates to smaller subtypes in the adult. In summary, our findings indicate that N-glycan synthesis in the rat neocortex is fundamentally different in neonates compared with adults with a general shift occurring from large, sialylated N-glycans towards smaller, neutral structures as neonates develop into adults, coupled with a parallel shift towards smaller oligomannose structures.
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Affiliation(s)
- Thomas S Klarić
- Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia
| | - Matija Salopek
- Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia
| | - Vedran Micek
- Laboratory Animals Unit, Institute for Medical Research and Occupational Health, Zagreb, Croatia
| | - Olga Gornik Kljaić
- Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia
| | - Gordan Lauc
- Faculty of Pharmacy and Biochemistry, University of Zagreb, Zagreb, Croatia.,Genos Glycoscience Research Laboratory, Zagreb, Croatia
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5
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Chen Q, Tan Z, Guan F, Ren Y. The Essential Functions and Detection of Bisecting GlcNAc in Cell Biology. Front Chem 2020; 8:511. [PMID: 32719771 PMCID: PMC7350706 DOI: 10.3389/fchem.2020.00511] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 05/18/2020] [Indexed: 12/11/2022] Open
Abstract
The N-glycans of mammalian glycoproteins vary greatly in structure, and the biological importance of these variations is mostly unknown. It is widely acknowledged that the bisecting N-acetylglucosamine (GlcNAc) structure, a β1,4-linked GlcNAc attached to the core β-mannose residue, represents a special type of N-glycosylated modification, and it has been reported to be involved in various biological processes, such as cell adhesion, fertilization and fetal development, neuritogenesis, and tumor development. In particular, the occurrence of N-glycans with a bisecting GlcNAc modification on proteins has been proven, with many implications for immune biology. Due to the essential functions of bisecting GlcNAc structures, analytical approaches to this modification are highly required. The traditional approach that has been used for bisecting GlcNAc determinations is based on the lectin recognition of Phaseolus vulgaris erythroagglutinin (PHA-E); however, poor binding specificity hinders the application of this method. With the development of mass spectrometry (MS) with high resolution and improved sensitivity and accuracy, MS-based glycomic analysis has provided precise characterization and quantification for glycosylation modification. In this review, we first provide an overview of the bisecting GlcNAc structure and its biological importance in neurological systems, immune tolerance, immunoglobulin G (IgG), and tumor metastasis and development and then summarize approaches to its determination by MS for performing precise functional studies. This review is valuable for those readers who are interested in the importance of bisecting GlcNAc in cell biology.
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Affiliation(s)
- Qiushi Chen
- Clinical Laboratory of BGI Health, BGI-Shenzhen, Shenzhen, China
| | - Zengqi Tan
- Joint International Research Laboratory of Glycobiology and Medical Chemistry, College of Life Sciences, Northwest University, Xi'an, China
| | - Feng Guan
- Joint International Research Laboratory of Glycobiology and Medical Chemistry, College of Life Sciences, Northwest University, Xi'an, China
| | - Yan Ren
- Clinical Laboratory of BGI Health, BGI-Shenzhen, Shenzhen, China
- Institute of Interdisciplinary Integrative Medicine Research, Shanghai University of Traditional Chinese Medicine, Shanghai, China
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6
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Yan S, Wang H, Schachter H, Jin C, Wilson IBH, Paschinger K. Ablation of N-acetylglucosaminyltransferases in Caenorhabditis induces expression of unusual intersected and bisected N-glycans. Biochim Biophys Acta Gen Subj 2018; 1862:2191-2203. [PMID: 29981898 PMCID: PMC6173287 DOI: 10.1016/j.bbagen.2018.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 06/30/2018] [Accepted: 07/04/2018] [Indexed: 12/17/2022]
Abstract
The modification in the Golgi of N-glycans by N-acetylglucosaminyltransferase I (GlcNAc-TI, MGAT1) can be considered to be a hallmark of multicellular eukaryotes as it is found in all metazoans and plants, but rarely in unicellular organisms. The enzyme is key for the normal processing of N-glycans to either complex or paucimannosidic forms, both of which are found in the model nematode Caenorhabditis elegans. Unusually, this organism has three different GlcNAc-TI genes (gly-12, gly-13 and gly-14); therefore, a complete abolition of GlcNAc-TI activity required the generation of a triple knock-out strain. Previously, the compositions of N-glycans from this mutant were described, but no detailed structures. Using an off-line HPLC-MALDI-TOF-MS approach combined with exoglycosidase digestions and MS/MS, we reveal that the multiple hexose residues of the N-glycans of the gly-12;gly-13;gly-14 triple mutant are not just mannose, but include galactoses in three different positions (β-intersecting, β-bisecting and α-terminal) on isomeric forms of Hex4-8HexNAc2 structures; some of these structures are fucosylated and/or methylated. Thus, the N-glycomic repertoire of Caenorhabditis is even wider than expected and exhibits a large degree of plasticity even in the absence of key glycan processing enzymes from the Golgi apparatus.
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Affiliation(s)
- Shi Yan
- Department für Chemie, Universität für Bodenkultur, 1190 Wien, Austria,Institut für Parasitologie, Veterinärmedizinische Universität Wien, 1210 Wien, Austria
| | - Huijie Wang
- Department für Chemie, Universität für Bodenkultur, 1190 Wien, Austria
| | - Harry Schachter
- Hospital for Sick Children and University of Toronto, Toronto, ON M5G 1X8, Canada
| | - Chunsheng Jin
- Institutionen för Biomedicin, Göteborgs universitet, 405 30 Göteborg, Sweden
| | - Iain B. H. Wilson
- Department für Chemie, Universität für Bodenkultur, 1190 Wien, Austria,To whom correspondence should be addressed:
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7
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McCarthy C, Saldova R, Wormald MR, Rudd PM, McElvaney NG, Reeves EP. The Role and Importance of Glycosylation of Acute Phase Proteins with Focus on Alpha-1 Antitrypsin in Acute and Chronic Inflammatory Conditions. J Proteome Res 2014; 13:3131-43. [DOI: 10.1021/pr500146y] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Cormac McCarthy
- Respiratory
Research Division, Royal College of Surgeons in Ireland, Beaumont
Hospital, Dublin 9, Ireland
| | - Radka Saldova
- NIBRT
GlycoScience Group, The National Institute for Bioprocessing Research
and Training, University College Dublin, Dublin 4, Ireland
| | - Mark R Wormald
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, Oxford OX1 3QU, U.K
| | - Pauline M. Rudd
- NIBRT
GlycoScience Group, The National Institute for Bioprocessing Research
and Training, University College Dublin, Dublin 4, Ireland
| | - Noel G. McElvaney
- Respiratory
Research Division, Royal College of Surgeons in Ireland, Beaumont
Hospital, Dublin 9, Ireland
| | - Emer P. Reeves
- Respiratory
Research Division, Royal College of Surgeons in Ireland, Beaumont
Hospital, Dublin 9, Ireland
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8
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Rosenbaum EE, Vasiljevic E, Brehm KS, Colley NJ. Mutations in four glycosyl hydrolases reveal a highly coordinated pathway for rhodopsin biosynthesis and N-glycan trimming in Drosophila melanogaster. PLoS Genet 2014; 10:e1004349. [PMID: 24785692 PMCID: PMC4006722 DOI: 10.1371/journal.pgen.1004349] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 03/18/2014] [Indexed: 01/16/2023] Open
Abstract
As newly synthesized glycoproteins move through the secretory pathway, the asparagine-linked glycan (N-glycan) undergoes extensive modifications involving the sequential removal and addition of sugar residues. These modifications are critical for the proper assembly, quality control and transport of glycoproteins during biosynthesis. The importance of N-glycosylation is illustrated by a growing list of diseases that result from defects in the biosynthesis and processing of N-linked glycans. The major rhodopsin in Drosophila melanogaster photoreceptors, Rh1, is highly unique among glycoproteins, as the N-glycan appears to be completely removed during Rh1 biosynthesis and maturation. However, much of the deglycosylation pathway for Rh1 remains unknown. To elucidate the key steps in Rh1 deglycosylation in vivo, we characterized mutant alleles of four Drosophila glycosyl hydrolases, namely α-mannosidase-II (α-Man-II), α-mannosidase-IIb (α-Man-IIb), a β-N-acetylglucosaminidase called fused lobes (Fdl), and hexosaminidase 1 (Hexo1). We have demonstrated that these four enzymes play essential and unique roles in a highly coordinated pathway for oligosaccharide trimming during Rh1 biosynthesis. Our results reveal that α-Man-II and α-Man-IIb are not isozymes like their mammalian counterparts, but rather function at distinct stages in Rh1 maturation. Also of significance, our results indicate that Hexo1 has a biosynthetic role in N-glycan processing during Rh1 maturation. This is unexpected given that in humans, the hexosaminidases are typically lysosomal enzymes involved in N-glycan catabolism with no known roles in protein biosynthesis. Here, we present a genetic dissection of glycoprotein processing in Drosophila and unveil key steps in N-glycan trimming during Rh1 biosynthesis. Taken together, our results provide fundamental advances towards understanding the complex and highly regulated pathway of N-glycosylation in vivo and reveal novel insights into the functions of glycosyl hydrolases in the secretory pathway.
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Affiliation(s)
- Erica E. Rosenbaum
- Department of Ophthalmology & Visual Sciences and Department of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Eva Vasiljevic
- Department of Ophthalmology & Visual Sciences and Department of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Kimberley S. Brehm
- Department of Ophthalmology & Visual Sciences and Department of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Nansi Jo Colley
- Department of Ophthalmology & Visual Sciences and Department of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail:
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9
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Damerow M, Rodrigues JA, Wu D, Güther MLS, Mehlert A, Ferguson MAJ. Identification and functional characterization of a highly divergent N-acetylglucosaminyltransferase I (TbGnTI) in Trypanosoma brucei. J Biol Chem 2014; 289:9328-39. [PMID: 24550396 PMCID: PMC3979372 DOI: 10.1074/jbc.m114.555029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Trypanosoma brucei expresses a diverse repertoire of N-glycans, ranging from oligomannose and paucimannose structures to exceptionally large complex N-glycans. Despite the presence of the latter, no obvious homologues of known β1–4-galactosyltransferase or β1–2- or β1–6-N-acetylglucosaminyltransferase genes have been found in the parasite genome. However, we previously reported a family of putative UDP-sugar-dependent glycosyltransferases with similarity to the mammalian β1–3-glycosyltransferase family. Here we characterize one of these genes, TbGT11, and show that it encodes a Golgi apparatus resident UDP-GlcNAc:α3-d-mannoside β1–2-N-acetylglucosaminyltransferase I activity (TbGnTI). The bloodstream-form TbGT11 null mutant exhibited significantly modified protein N-glycans but normal growth in vitro and infectivity to rodents. In contrast to multicellular organisms, where the GnTI reaction is essential for biosynthesis of both complex and hybrid N-glycans, T. brucei TbGT11 null mutants expressed atypical “pseudohybrid” glycans, indicating that TbGnTII activity is not dependent on prior TbGnTI action. Using a functional in vitro assay, we showed that TbGnTI transfers UDP-GlcNAc to biantennary Man3GlcNAc2, but not to triantennary Man5GlcNAc2, which is the preferred substrate for metazoan GnTIs. Sequence alignment reveals that the T. brucei enzyme is far removed from the metazoan GnTI family and suggests that the parasite has adapted the β3-glycosyltransferase family to catalyze β1–2 linkages.
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Affiliation(s)
- Manuela Damerow
- From the Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom and
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10
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Schachter H. Complex N-glycans: the story of the "yellow brick road". Glycoconj J 2013; 31:1-5. [PMID: 24178944 DOI: 10.1007/s10719-013-9507-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 10/14/2013] [Indexed: 11/25/2022]
Abstract
The synthesis of complex asparagine-linked glycans (N-glycans) involves a multi-step process that starts with a five mannose N-glycan structure: [Manα1-6(Manα1-3)Manα1-6][Manα1-3]-R where R = Manβ1-4GlcNAcβ1-4GlcNAcβ1-Asn-protein. N-acetylglucosaminyltransferase I (GlcNAc-TI) first catalyzes addition of GlcNAc in β1-2 linkage to the Manα1-3-R terminus of the five-mannose structure. Mannosidase II then removes two Man residues exposing the Manα1-6 terminus that serves as a substrate for GlcNAc-T II and addition of a second GlcNAcβ1-2 residue. The resulting structure is the complex N-glycan: GlcNAcβ1-2Manα1-6(GlcNAcβ1-2Manα1-3)-R. This structure is the precursor to a large assortment of branched complex N-glycans involving four more N-acetylglucosaminyltransferases. This short review describes the experiments (done in the early 1970s) that led to the discovery of GlcNAc-TI and II.
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Affiliation(s)
- Harry Schachter
- Molecular Structure and Function Program, Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada, M5G 1X8,
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11
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Nemčovičová I, Nemčovič M, Šesták S, Plšková M, Wilson IBH, Mucha J. Expression, purification and preliminary crystallographic analysis of Drosophila melanogaster lysosomal α-mannosidase. Acta Crystallogr Sect F Struct Biol Cryst Commun 2012; 68:965-70. [PMID: 22869134 PMCID: PMC3412785 DOI: 10.1107/s1744309112029375] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Accepted: 06/28/2012] [Indexed: 11/10/2022]
Abstract
The lysosomal α-mannosidases are class II mannosidases that belong to glycoside hydrolase family 38 and play an important role in the degradation of asparagine-linked carbohydrates of glycoproteins. Based on peptide similarity to human and bovine lysosomal mannosidase (LM), recombinant α-mannosidase from Drosophila melanogaster (dLM408) was cloned and heterologously expressed in Pichia pastoris. The recombinant form of dLM408 designed for structural analysis lacks the transmembrane domain and was crystallized using standard vapour-diffusion and counter-diffusion techniques. The crystals grew as flat plates and as tetragonal bipyramids, respectively. The plate-shaped crystals exhibited the symmetry of space group P2(1)2(1)2(1) and diffracted to a minimum d-spacing of 3.5 Å.
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Affiliation(s)
- I. Nemčovičová
- Department of Cellular Biology, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA
- Department of Glycobiology, Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38 Bratislava, Slovakia
| | - M. Nemčovič
- Department of Glycobiology, Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38 Bratislava, Slovakia
| | - S. Šesták
- Department of Glycobiology, Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38 Bratislava, Slovakia
| | - M. Plšková
- Department of Glycobiology, Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38 Bratislava, Slovakia
| | - I. B. H. Wilson
- Department für Chemie, Universität für Bodenkultur, Muthgasse 18, A-1190 Wien, Austria
| | - J. Mucha
- Department of Glycobiology, Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38 Bratislava, Slovakia
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12
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Cao J, Li Y, Xia W, Reddig K, Hu W, Xie W, Li HS, Han J. A Drosophila metallophosphoesterase mediates deglycosylation of rhodopsin. EMBO J 2011; 30:3701-13. [PMID: 21804530 DOI: 10.1038/emboj.2011.254] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Accepted: 07/01/2011] [Indexed: 11/09/2022] Open
Abstract
Oligosaccharide chains of newly synthesized membrane receptors are trimmed and modified to optimize their trafficking and/or signalling before delivery to the cell surface. For most membrane receptors, the functional significance of oligosaccharide chain modification is unknown. During the maturation of Rh1 rhodopsin, a Drosophila light receptor, the oligosaccharide chain is trimmed extensively. Neither the functional significance of this modification nor the enzymes mediating this process are known. Here, we identify a dmppe (Drosophila metallophosphoesterase) mutant with incomplete deglycosylation of Rh1, and show that the retained oligosaccharide chain does not affect Rh1 localization or signalling. The incomplete deglycosylation, however, renders Rh1 more sensitive to endocytic degradation, and causes morphological and functional defects in photoreceptors of aged dmppe flies. We further demonstrate that the dMPPE protein functions as an Mn(2+)/Zn(2+)-dependent phosphoesterase and mediates in vivo dephosphorylation of α-Man-II. Most importantly, the dephosphorylated α-Man-II is required for the removal of the Rh1 oligosaccharide chain. These observations suggest that the glycosylation status of membrane proteins is controlled through phosphorylation/dephosphorylation, and that MPPE acts as the phosphoesterase in this regulation.
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Affiliation(s)
- Jinguo Cao
- Institute of Life Science, The Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, China
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13
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Kuntz DA, Nakayama S, Shea K, Hori H, Uto Y, Nagasawa H, Rose DR. Structural Investigation of the Binding of 5-Substituted Swainsonine Analogues to Golgi α-Mannosidase II. Chembiochem 2010; 11:673-80. [DOI: 10.1002/cbic.200900750] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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14
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Karg SR, Frey AD, Kallio PT. Reduction of N-linked xylose and fucose by expression of rat beta1,4-N-acetylglucosaminyltransferase III in tobacco BY-2 cells depends on Golgi enzyme localization domain and genetic elements used for expression. J Biotechnol 2010; 146:54-65. [PMID: 20083147 DOI: 10.1016/j.jbiotec.2010.01.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Revised: 12/23/2009] [Accepted: 01/12/2010] [Indexed: 11/26/2022]
Abstract
Plant-specific N-glycosylation, such as the introduction of core alpha1,3-fucose and beta1,2-xylose residues, is a major obstacle to the utilization of plant cell- or plant-derived recombinant therapeutic proteins. The beta1,4-N-acetylglucosaminyltransferase III (GnTIII) introduces a bisecting GlcNAc residue into N-glycans, which exerts a high level of substrate mediated control over subsequent modifications, for example inhibiting mammalian core fucosylation. Based on similar findings in plants, we used Nicotianatabacum BY-2 cells to study the effects of localization and expression levels of GnTIII in the remodeling of the plant N-glycosylation pathway. The N-glycans produced by the cells expressing GnTIII were partially bisected and practically devoid of the paucimannosidic type which is typical for N-glycans produced by wildtype BY-2 suspension cultured cells. The proportion of human-compatible N-glycans devoid of fucose and xylose could be increased from an average of 4% on secreted protein from wildtype cells to as high as 59% in cells expressing chimeric GnTIII, named GnTIII(A.th.) replacing its native localization domain with the cytoplasmic tail, transmembrane, and stem region of Arabidopsis thaliana mannosidase II. The changes in N-glycosylation observed were dependent on the catalytic activity of GnTIII, as the expression of catalytically inactive GnTIII mutants did not show a significant effect on N-glycosylation.
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Affiliation(s)
- Saskia R Karg
- Institute of Microbiology, ETH Zurich, CH-8093 Zürich, Switzerland.
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15
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A long-wavelength fluorescent substrate for continuous fluorometric determination of alpha-mannosidase activity: resorufin alpha-D-mannopyranoside. Anal Biochem 2009; 399:7-12. [PMID: 20026005 DOI: 10.1016/j.ab.2009.11.039] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 11/05/2009] [Accepted: 11/13/2009] [Indexed: 11/21/2022]
Abstract
A simple and reliable continuous assay for measurement of alpha-mannosidase activity is described and demonstrated for analysis with two recombinant human enzymes using the new substrate resorufin alpha-d-mannopyranoside (Res-Man). The product of enzyme reaction, resorufin, exhibits fluorescence emission at 585 nm with excitation at 571 nm and has a pK(a) of 5.8, allowing continuous measurement of fluorescence turnover at or near physiological pH values for human lysosomal and Drosophila Golgi alpha-mannosidases. The assay performed using recombinant Drosophila Golgi alpha-mannosidase (dGMII) has been shown to give the kinetic parameters K(m) of 200 microM and V(max) of 11 nmol/min per nmol dGMII. Methods for performing the assay using several concentrations of the known alpha-mannosidase inhibitor swainsonine are also presented, demonstrating a potential for use of the assay as a simple method for high-throughput screening of inhibitors potentially useful in cancer treatment.
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16
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Iizuka M, Ogawa S, Takeuchi A, Nakakita S, Kubo Y, Miyawaki Y, Hirabayashi J, Tomita M. Production of a recombinant mouse monoclonal antibody in transgenic silkworm cocoons. FEBS J 2009; 276:5806-20. [PMID: 19740109 DOI: 10.1111/j.1742-4658.2009.07262.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the present study, we describe the production of transgenic silkworms expressing a recombinant mouse mAb in their cocoons. Two transgenic lines, L- and H-, were generated that carried cDNAs encoding the L- and H-chains of a mouse IgG mAb, respectively, under the control of the enhancer-linked sericin-1 promoter. Cocoon protein analysis indicated that the IgG L- or H-chain was secreted into the cocoons of each line. We also produced a transgenic line designated L/H, which carried both cDNAs, by crossing the L- and H-lines. This line efficiently produced the recombinant mAb as a fully assembled H(2)L(2) tetramer in its cocoons, with negligible L- or H-chain monomer and H-chain dimer production. Thus, the H(2)L(2) tetramer was synthesized in, and secreted from, the middle silk gland cells. Crossing of the L/H-line with a transgenic line expressing a baculovirus-derived trans-activator produced a 2.4-fold increase in mAb expression. The recombinant mAb was extracted from the cocoons with a buffer containing 3 m urea and purified by protein G affinity column chromatography. The antigen-binding affinity of the purified recombinant mAb was identical to that of the native mAb produced by a hybridoma. Analysis of the structure of the N-glycans attached to the recombinant mAb revealed that the mAb contained high mannose-, hybrid- and complex-type N-glycans. By contrast, insect-specific paucimannose-type glycans were not detected. Fucose residues alpha-1,3- and alpha-1,6-linked to the core N-acetylglucosamine residue, both of which are found in insect N-glycans, were not observed in the N-glycans of the mAb.
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Kuntz DA, Zhong W, Guo J, Rose DR, Boons GJ. The molecular basis of inhibition of Golgi alpha-mannosidase II by mannostatin A. Chembiochem 2009; 10:268-77. [PMID: 19101978 PMCID: PMC3956299 DOI: 10.1002/cbic.200800538] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Indexed: 11/10/2022]
Abstract
Mannostatin A is a potent inhibitor of the mannose-trimming enzyme, Golgi alpha-mannosidase II (GMII), which acts late in the N-glycan processing pathway. Inhibition of this enzyme provides a route to blocking the transformation-associated changes in cancer cell surface oligosaccharide structures. Here, we report on the synthesis of new Mannostatin derivatives and analyze their binding in the active site of Drosophila GMII by X-ray crystallography. The results indicate that the interaction with the backbone carbonyl of Arg876 is crucial to the high potency of the inhibitor-an effect enhanced by the hydrophobic interaction between the thiomethyl group and an aromatic pocket vicinal to the cleavage site. The various structures indicate that differences in the hydration of protein-ligand complexes are also important determinants of plasticity as well as selectivity of inhibitor binding.
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Affiliation(s)
- Douglas A. Kuntz
- Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada M5G 1L7. Fax: 416-581-7562
| | - Wei Zhong
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602. Fax: 706-542-4412
| | - Jun Guo
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602. Fax: 706-542-4412
| | - David R. Rose
- Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada M5G 1L7. Fax: 416-581-7562
| | - Geert-Jan Boons
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602. Fax: 706-542-4412
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18
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Chen R, Pawlicki M, Hamilton B, Tolbert T. Enzyme-Catalyzed Synthesis of a Hybrid N-Linked Oligosaccharide using N-Acetylglucosaminyltransferase I. Adv Synth Catal 2008. [DOI: 10.1002/adsc.200800265] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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19
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Zhong W, Kuntz DA, Ember B, Singh H, Moremen KW, Rose DR, Boons GJ. Probing the substrate specificity of Golgi alpha-mannosidase II by use of synthetic oligosaccharides and a catalytic nucleophile mutant. J Am Chem Soc 2008; 130:8975-83. [PMID: 18558690 PMCID: PMC3982601 DOI: 10.1021/ja711248y] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Inhibition of Golgi alpha-mannosidase II (GMII), which acts late in the N-glycan processing pathway, provides a route to blocking cancer-induced changes in cell surface oligosaccharide structures. To probe the substrate requirements of GMII, oligosaccharides were synthesized that contained an alpha(1,3)- or alpha(1,6)-linked 1-thiomannoside. Surprisingly, these oligosaccharides were not observed in X-ray crystal structures of native Drosophila GMII (dGMII). However, a mutant enzyme in which the catalytic nucleophilic aspartate was changed to alanine (D204A) allowed visualization of soaked oligosaccharides and led to the identification of the binding site for the alpha(1,3)-linked mannoside of the natural substrate. These studies also indicate that the conformational change of the bound mannoside to a high-energy B 2,5 conformation is facilitated by steric hindrance from, and the formation of strong hydrogen bonds to, Asp204. The observation that 1-thio-linked mannosides are not well tolerated by the catalytic site of dGMII led to the synthesis of a pentasaccharide containing the alpha(1,6)-linked Man of the natural substrate and the beta(1,2)-linked GlcNAc moiety proposed to be accommodated by the extended binding site of the enzyme. A cocrystal structure of this compound with the D204A enzyme revealed the molecular interactions with the beta(1,2)-linked GlcNAc. The structure is consistent with the approximately 80-fold preference of dGMII for the cleavage of substrates containing a nonreducing beta(1,2)-linked GlcNAc. By contrast, the lysosomal mannosidase lacks an equivalent GlcNAc binding site and kinetic analysis indicates oligomannoside substrates without non-reducing-terminal GlcNAc modifications are preferred, suggesting that selective inhibitors for GMII could exploit the additional binding specificity of the GlcNAc binding site.
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20
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Rothman JE. The Golgi apparatus: roles for distinct 'cis' and 'trans' compartments. CIBA FOUNDATION SYMPOSIUM 2008:120-37. [PMID: 6295718 DOI: 10.1002/9780470720745.ch7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The Golgi apparatus seems to consist of distinct cis and trans compartments that are proposed to act sequentially to refine the protein export of the endoplasmic reticulum by removing escaped endoplasmic reticulum proteins. Refinement may be a multi-stage process that employs a principle akin to fractional distillation; the stack of cisternae comprising the cis Golgi may be the plates in this distillation tower. The trans Golgi, consisting of the last one or two cisternae, may be the receiver that collects from the cis Golgi only its most refined fraction for later distribution to specific locations throughout the cell.
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Crispin M, Aricescu AR, Chang VT, Jones EY, Stuart DI, Dwek RA, Davis SJ, Harvey DJ. Disruption of alpha-mannosidase processing induces non-canonical hybrid-type glycosylation. FEBS Lett 2007; 581:1963-8. [PMID: 17466984 DOI: 10.1016/j.febslet.2007.04.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Revised: 04/03/2007] [Accepted: 04/06/2007] [Indexed: 11/27/2022]
Abstract
Golgi alpha-mannosidase II is essential for the efficient formation of complex-type glycosylation. Here, we demonstrate that the disruption of Golgi alpha-mannosidase II activity by swainsonine in human embryonic kidney cells is capable of inducing a novel class of hybrid-type glycosylation containing a partially processed mannose moiety. The discovery of 'Man(6)-based' hybrid-type glycans reveals a broader in vivo specificity of N-acetylglucosaminyltransferase I, further defines the arm-specific tolerance of core alpha1-6 fucosyltransferase to terminal alpha1-2 mannose residues, and suggests that disruption of Golgi alpha-mannosidase II activity is capable of inducing potentially 'non-self' structures.
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Affiliation(s)
- Max Crispin
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Headington, Oxford OX3 7BN, UK.
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22
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Rouwendal GJA, Wuhrer M, Florack DEA, Koeleman CAM, Deelder AM, Bakker H, Stoopen GM, van Die I, Helsper JPFG, Hokke CH, Bosch D. Efficient introduction of a bisecting GlcNAc residue in tobacco N-glycans by expression of the gene encoding human N-acetylglucosaminyltransferase III. Glycobiology 2007; 17:334-44. [PMID: 17179169 DOI: 10.1093/glycob/cwl078] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In this study, we show that introduction of human N-acetylglucosaminyltransferase (GnT)-III gene into tobacco plants leads to highly efficient synthesis of bisected N-glycans. Enzymatically released N-glycans from leaf glycoproteins of wild-type and transgenic GnT-III plants were profiled by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) in native form. After labeling with 2-aminobenzamide, profiling was performed using normal-phase high-performance liquid chromatography with fluorescence detection, and glycans were structurally characterized by MALDI-TOF/TOF-MS and reverse-phase nano-liquid chromatography-MS/MS. These analyses revealed that most of the complex-type N-glycans in the plants expressing GnT-III were bisected and carried at least two terminal N-acetylglucosamine (GlcNAc) residues in contrast to wild-type plants, where a considerable proportion of N-glycans did not contain GlcNAc residues at the nonreducing end. Moreover, we have shown that the majority of N-glycans of an antibody produced in a plant expressing GnT-III is also bisected. This might improve the efficacy of therapeutic antibodies produced in this type of transgenic plant.
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Affiliation(s)
- Gerard J A Rouwendal
- Business Unit Bioscience, Plant Research International BV, Wageningen University and Research Centre, Droevendaalsesteeg 1 6708 PB Wageningen, The Netherlands.
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23
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Gordon RD, Sivarajah P, Satkunarajah M, Ma D, Tarling CA, Vizitiu D, Withers SG, Rini JM. X-ray Crystal Structures of Rabbit N-acetylglucosaminyltransferase I (GnT I) in Complex with Donor Substrate Analogues. J Mol Biol 2006; 360:67-79. [PMID: 16769084 DOI: 10.1016/j.jmb.2006.04.058] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Revised: 04/24/2006] [Accepted: 04/25/2006] [Indexed: 10/24/2022]
Abstract
The Golgi-resident glycosyltransferase, UDP-N-acetyl-d-glucosamine:alpha-3-d-mannoside beta-1,2-N-acetylglucosaminyltransferase I (GnT I), initiates the conversion of high-mannose oligosaccharides to complex and hybrid structures in the biosynthesis of N-linked glycans. Reported here are the X-ray crystal structures of GnT I in complex with UDP-CH2-GlcNAc (a non-hydrolyzable C-glycosidic phosphonate), UDP-2-deoxy-2-fluoro-glucose, UDP-glucose and UDP. Collectively, these structures provide evidence for the importance of the GlcNAc moiety and its N-acetyl group in donor substrate binding, as well as insight into the role played by the flexible 318-330 loop in substrate binding and product release. In addition, the UDP-CH2-GlcNAc complex reveals a well-defined glycerol molecule poised for nucleophilic attack on the C1 atom of the donor substrate analogue. The position and orientation of this glycerol molecule have allowed us to model the binding of the Manalpha1,3Manbeta1 moiety of the acceptor substrate and, based on the model, to suggest a rationalization for the main determinants of GnT I acceptor specificity.
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Affiliation(s)
- Roni D Gordon
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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24
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Nakajima M, Imamura H, Shoun H, Wakagi T. Unique metal dependency of cytosolic alpha-mannosidase from Thermotoga maritima, a hyperthermophilic bacterium. Arch Biochem Biophys 2003; 415:87-93. [PMID: 12801516 DOI: 10.1016/s0003-9861(03)00222-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
A putative cytosolic alpha-mannosidase gene from a hyperthermophilic marine bacterium Thermotoga maritima was cloned and expressed in Escherichia coli. The purified recombinant enzyme appeared to be a homodimer of a 110-kDa subunit. The enzyme showed metal-dependent ability to hydrolyze p-nitrophenyl-alpha-D-mannopyranoside. In the absence of a metal, the enzyme was inactive. Cobalt and cadmium supported high activity (60 U/mg at 70 degrees C), while the activity with zinc and chromium was poor. Cobalt (0.8 mol) bound to 1 mol monomer with a K(d) of 70 microM. The optimum pH and temperature were 6.0 and 80 degrees C, respectively. The activity was inhibited by swainsonine, but not by 1-deoxymannojirimycin, which is in agreement with the features of cytosolic alpha-mannosidase.
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Affiliation(s)
- Masahiro Nakajima
- Department of Biotechnology, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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25
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Moremen KW. Golgi alpha-mannosidase II deficiency in vertebrate systems: implications for asparagine-linked oligosaccharide processing in mammals. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1573:225-35. [PMID: 12417404 DOI: 10.1016/s0304-4165(02)00388-4] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The maturation of N-glycans to complex type structures on cellular and secreted proteins is essential for the roles that these structures play in cell adhesion and recognition events in metazoan organisms. Critical steps in the biosynthetic pathway leading from high mannose to complex structures include the trimming of mannose residues by processing mannosidases in the endoplasmic reticulum (ER) and Golgi complex. These exo-mannosidases comprise two separate families of enzymes that are distinguished by enzymatic characteristics and sequence similarity. Members of the Class 2 mannosidase family (glycosylhydrolase family 38) include enzymes involved in trimming reactions in N-glycan maturation in the Golgi complex (Golgi mannosidase II) as well as catabolic enzymes in lysosomes and cytosol. Studies on the biological roles of complex type N-glycans have employed a variety of strategies including the treatment of cells with glycosidase inhibitors, characterization of human patients with enzymatic defects in processing enzymes, and generation of mouse models for the enzyme deficiency by selective gene disruption approaches. Corresponding studies on Golgi mannosidase II have employed swainsonine, an alkaloid natural plant product that causes "locoism", a phenocopy of the lysosomal storage disease, alpha-mannosidosis, as a result of the additional targeting of the broad-specificity lysosomal mannosidase by this compound. The human deficiency in Golgi mannosidase II is characterized by congenital dyserythropoietic anemia with splenomegaly and various additional abnormalities and complications. Mouse models for Golgi mannosidase II deficiency recapitulate many of the pathological features of the human disease and confirm that the unexpectedly mild effects of the enzyme deficiency result from a tissue-specific and glycoprotein substrate-specific alternate pathway for synthesis of complex N-glycans. In addition, the mutant mice develop symptoms of a systemic autoimmune disorder as a consequence of the altered glycosylation. This review will discuss the biochemical features of Golgi mannosidase II and the consequences of its deficiency in mammalian systems as a model for the effects of alterations in vertebrate N-glycan maturation during development.
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Affiliation(s)
- Kelley W Moremen
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA.
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Schachter H, Jaeken J. Carbohydrate-deficient glycoprotein syndrome type II. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1455:179-92. [PMID: 10571011 DOI: 10.1016/s0925-4439(99)00054-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The carbohydrate-deficient glycoprotein syndromes (CDGS) are a group of autosomal recessive multisystemic diseases characterized by defective glycosylation of N-glycans. This review describes recent findings on two patients with CDGS type II. In contrast to CDGS type I, the type II patients show a more severe psychomotor retardation, no peripheral neuropathy and a normal cerebellum. The CDGS type II serum transferrin isoelectric focusing pattern shows a large amount (95%) of disialotransferrin in which each of the two glycosylation sites is occupied by a truncated monosialo-monoantennary N-glycan. Fine structure analysis of this glycan suggested a defect in the Golgi enzyme UDP-GlcNAc:alpha-6-D-mannoside beta-1,2-N-acetylglucosaminyltransferase II (GnT II; EC 2.4.1.143) which catalyzes an essential step in the biosynthetic pathway leading from hybrid to complex N-glycans. GnT II activity is reduced by over 98% in fibroblast and mononuclear cell extracts from the CDGS type II patients. Direct sequencing of the GnT II coding region from the two patients identified two point mutations in the catalytic domain of GnT II, S290F (TCC to TTC) and H262R (CAC to CGC). Either of these mutations inactivates the enzyme and probably also causes reduced expression. The CDG syndromes and other congenital defects in glycan synthesis as well as studies of null mutations in the mouse provide strong evidence that the glycan moieties of glycoproteins play essential roles in the normal development and physiology of mammals and probably of all multicellular organisms.
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Affiliation(s)
- H Schachter
- Department of Biochemistry, University of Toronto Medical School, and Department of Structural Biology and Biochemistry, Hospital for Sick Children, Ont, Canada
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Tulsiani DR, Abou-Haila A, Loeser CR, Pereira BM. The biological and functional significance of the sperm acrosome and acrosomal enzymes in mammalian fertilization. Exp Cell Res 1998; 240:151-64. [PMID: 9596988 DOI: 10.1006/excr.1998.3943] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mammalian spermatozoon undergoes continuous modifications during spermatogenesis, maturation in the epididymis, and capacitation in the female reproductive tract. Only the capacitated spermatozoa are capable of binding the zona-intact egg and undergoing the acrosome reaction. The fertilization process is a net result of multiple molecular events which enable ejaculated spermatozoa to recognize and bind to the egg's extracellular coat, the zona pellucida (ZP). Sperm-egg interaction is a species-specific event which is initiated by the recognition and binding of complementary molecule(s) present on sperm plasma membrane (receptor) and the surface of the ZP (ligand). This is a carbohydrate-mediated event which initiates a signal transduction cascade resulting in the exocytosis of acrosomal contents. This step is believed to be a prerequisite which enables the acrosome reacted spermatozoa to penetrate the ZP and fertilize the egg. This review focuses on the formation and contents of the sperm acrosome as well as the mechanisms underlying the induction of the acrosome reaction. Special emphasis has been laid on the synthesis, processing, substrate specificity, and mechanism of action of the acid glycohydrolases present within the acrosome. The hydrolytic action of glycohydrolases and proteases released at the site of sperm-zona binding, along with the enhanced thrust generated by the hyperactivated beat pattern of the bound spermatozoon, are important factors regulating the penetration of ZP. We have discussed the most recent studies which have attempted to explain signal transduction pathways leading to the acrosomal exocytosis.
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Affiliation(s)
- D R Tulsiani
- Center for Reproductive Biology Research, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2633, USA
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29
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Schachter H, Tan J, Sarkar M, Yip B, Chen S, Dunn J, Jaeken J. Defective glycosyltransferases are not good for your health. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 435:9-27. [PMID: 9498061 DOI: 10.1007/978-1-4615-5383-0_2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- H Schachter
- Hospital for Sick Children, Toronto, Ont., Canada
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Chui D, Oh-Eda M, Liao YF, Panneerselvam K, Lal A, Marek KW, Freeze HH, Moremen KW, Fukuda MN, Marth JD. Alpha-mannosidase-II deficiency results in dyserythropoiesis and unveils an alternate pathway in oligosaccharide biosynthesis. Cell 1997; 90:157-67. [PMID: 9230311 DOI: 10.1016/s0092-8674(00)80322-0] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Alpha-mannosidase-II (alphaM-II) catalyzes the first committed step in the biosynthesis of complex asparagine-linked (N-linked) oligosaccharides (N-glycans). Genetic deficiency of alphaM-II should abolish complex N-glycan production as reportedly does inhibition of alphaM-II by swainsonine. We find that mice lacking a functional alphaM-II gene develop a dyserythropoietic anemia concurrent with loss of erythrocyte complex N-glycans. Unexpectedly, nonerythroid cell types continued to produce complex N-glycans by an alternate pathway comprising a distinct alpha-mannosidase. These studies reveal cell-type-specific variations in N-linked oligosaccharide biosynthesis and an essential role for alphaM-II in the formation of erythroid complex N-glycans. alphaM-II deficiency elicits a phenotype in mice that correlates with human congenital dyserythropoietic anemia type II.
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Affiliation(s)
- D Chui
- Howard Hughes Medical Institute and Division of Cellular and Molecular Medicine, University of California San Diego, La Jolla 92093, USA
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32
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Abstract
Glycoproteins generally exist as populations of glycosylated variants (glycoforms) of a single polypeptide. Although the same glycosylation machinery is available to all proteins that enter the secretory pathway in a given cell, most glycoproteins emerge with characteristic glycosylation patterns and heterogeneous populations of glycans at each glycosylation site. The factors that control the composition of the glycoform populations and the role that heterogeneity plays in the function of glycoproteins are important questions for glycobiology. A full understanding of the implications of glycosylation for the structure and function of a protein can only be reached when a glycoprotein is viewed as a single entity. Individual glycoproteins, by virtue of their unique structures, can selectively control their own glycosylation by modulating interactions with the glycosylating enzymes in the cell. Examples include protein-specific glycosylation within the immunoglobulins and immunoglobulin superfamily and site-specific processing in ribonuclease, Thy-1, IgG, tissue plasminogen activator, and influenza A hemagglutinin. General roles for the range of sugars on glycoproteins such as the leukocyte antigens include orientating the molecules on the cell surface. A major role for specific sugars is in recognition by lectins, including chaperones involved in protein folding. In addition, the recognition of identical motifs in different glycans allows a heterogeneous population of glycoforms to participate in specific biological interactions.
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Affiliation(s)
- P M Rudd
- Department of Biochemistry, University of Oxford, U.K
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33
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Altmann F, März L. Processing of asparagine-linked oligosaccharides in insect cells: evidence for alpha-mannosidase II. Glycoconj J 1995; 12:150-5. [PMID: 7620332 DOI: 10.1007/bf00731359] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The occurrence of alpha-D-mannosidase II activity in insect cells was studied using pyridylaminated oligosaccharides as substrates and two-dimensional HPLC and glycosidase digestion for the analysis of products. GlcNAcMan5GlcNAc2 was converted to GlcNAcMan3GlcNAc2 by each of the three cell lines investigated (Bm-N, Sf-21, and Mb-0503). The respective activity was highest in Bm-N cells which were used for further experiments. Man5GlcNAc2 was not degraded by the Bm-N cell homogenate. Thus, this alpha-mannosidase essentially exhibits the same substrate specificity as mammalian and plant Golgi alpha-mannosidase II. The alpha-mannosidase II-like activity from Bm-N cells exhibits a pH optimum of 6.0-6.5, has no requirement for divalent metal ions, and is highly sensitive to swainsonine. The alpha 1,6-linked mannosyl residue is removed first as deduced from the elution time on reversed phase HPLC of the intermediate product. The same branch preference was found with alpha-mannosidase II from mung bean seedlings and Xenopus liver. Upon ultracentrifugation of Bm-N cell homogenate, 72% of the mannosidase acting on the GlcNAcMan5GlcNAc2 substrate was found in the microsomal pellet indicating the enzyme to be membrane-bound.
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Affiliation(s)
- F Altmann
- Institut für Chemie der Universität für Bodenkultur Wien, Vienna
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34
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Chapter 5 Biosynthesis 4b. Substrate Level Controls for N-Glycan Assembly. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s0167-7306(08)60595-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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35
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Chapter 5 Biosynthesis 7. How Can N-Linked Glycosylation and Processing Inhibitors be Used to Study Carbohydrate Synthesis and Function. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s0167-7306(08)60599-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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36
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Novak A, Lowden JA. GM2 ganglioside activator occurs in multiple forms. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1199:209-14. [PMID: 8123670 DOI: 10.1016/0304-4165(94)90117-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The protein which activates the hydrolysis of GM2 ganglioside by hexosaminidase A was purified from human kidney. The GM2 activator had a molecular mass of 28 kDa by gel filtration and was resolved into three major bands using polyacrylamide gel electrophoresis in the presence of SDS with molecular masses of 23, 22 and 21 kDa. These three bands corresponded respectively to strongly binding, weakly binding and non-binding fractions of GM2 activator chromatographed through concanavalin A-Sepharose, indicating that GM2 activator exists in multiple glycosylated forms.
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Affiliation(s)
- A Novak
- Division of Neurosciences, Hospital for Sick Children, Toronto, Canada
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37
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Tachibana H, Seki K, Murakami H. Identification of hybrid-type carbohydrate chains on the light chain of human monoclonal antibody specific to lung adenocarcinoma. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1182:257-63. [PMID: 8399360 DOI: 10.1016/0925-4439(93)90067-b] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The carbohydrate chains on the light chains of human monoclonal antibody HB4C5 reactive to human lung adenocarcinoma tissue have been characterized. The HB4C5 antibody consists of two kinds of light chains (30 kDa and 32 kDa). Each chain has different carbohydrates of varying molecular masses linked to the variable regions. The 30 kDa light chain has been confirmed to be the active species for antibody binding. The carbohydrates on the light chains were characterized by lectin blot analysis combined with glycosidase treatment. A carbohydrate chain linked to the active 30 kDa light-chain species, and one of a few carbohydrate phenotypes on the 32 kDa light-chain species is characterized as "hybrid type". A sialylated complex-type carbohydrate could also bind to the 32 kDa light-chain species. Nucleotide sequence analysis revealed that one potential N-glycosylation site is located in the complementarity determining region 1 of the light chain, although no such site was found in the variable region of the heavy chain.
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Affiliation(s)
- H Tachibana
- Graduate School of Genetic Resources Technology, Kyushu University, Fukuoka, Japan
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38
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Amatayakul-Chantler S, Dwek RA, Tennent GA, Pepys MB, Rademacher TW. Molecular characterization of Limulus polyphemus C-reactive protein. II. Asparagine-linked oligosaccharides. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 214:99-110. [PMID: 8508812 DOI: 10.1111/j.1432-1033.1993.tb17901.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The N-linked oligosaccharides of C-reactive protein (CRP) from the arachnid Limulus polyphemus, the horseshoe crab, were characterized after their release by hydrazinolysis, re-N-acetylation, and reduction with NaB3H4. High-voltage paper electrophoresis of the reduced oligosaccharides revealed only neutral species. Gel-permeation chromatography on Bio-Gel P4 yielded five fractions. The oligosaccharide fractions were further fractionated using high-voltage borate paper electrophoresis and Dionex BioLC ion-exchange chromatography. The oligosaccharides were structurally characterized by sequential exoglycosidase digestion, fragmentation by acetolysis and methylation analysis. Three major structures were found, of which two were the biantennary oligomannose type with compositions Man5GlcNAc2 (B-1), Man4GlcNAc2 (C-3) and one was the monoantennary structure Man3GlcNAc2 (D-1). The biantennary oligomannose structures B-1 and C-3 contained the structural unit Man alpha 6Man alpha 6R. This unusual arrangement of mannose linkages suggests a biosynthetic pathway in Limulus which differs from that reported in mammals, plants and the parasitic protozoa.
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39
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Houri JJ, Ogier-Denis E, Bauvy C, Aubery M, Sapin C, Trugnan G, Codogno P. Swainsonine is a useful tool to monitor the intracellular traffic of N-linked glycoproteins as a function of the state of enterocytic differentiation of HT-29 cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 205:1169-74. [PMID: 1577000 DOI: 10.1111/j.1432-1033.1992.tb16887.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
After treatment with swainsonine, an inhibitor of both lysosomal alpha-mannosidase and Golgi alpha-mannosidase-II activities, analysis of [3H]mannose-labeled glycans showed that HT-29 cells, derived from a human colonic adenocarcinoma, displayed distinct patterns of N-glycan expression, depending upon their state of enterocytic differentiation. In differentiated HT-29 cells hybrid-type chains were detected, whereas undifferentiated HT-29 cells accumulated high-mannose-type oligosaccharide, despite our demonstration of Golgi alpha-mannosidase-II activity in both cell populations. Pulse/chase experiments carried out in the presence of swainsonine revealed that the persistence of high-mannose-type chains in undifferentiated HT-29 cells was the result of the stabilization of glycoproteins substituted with these glycans. These data suggest that in undifferentiated HT-29 cells, glycoproteins with high-mannose-type oligosaccharides are delivered to a degradative compartment containing swainsonine-sensitive alpha-mannosidase(s), whereas in differentiated HT-29 cells glycoproteins enter a compartment in which alpha-mannosidase II (Golgi apparatus) is present. Thus, this apparent dual effect of swainsonine on N-glycan trimming may reflect differences in the intracellular traffic of glycoproteins as a function of the state of enterocytic differentiation of HT-29 cells.
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Affiliation(s)
- J J Houri
- Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 180, Université René Descartes, Paris, France
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40
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Chawla D, Animashaun T, Hughes RC. Interactions of Bowringia mildbraedii agglutinin with complex- and hybrid-type glycans. FEBS Lett 1992; 298:291-6. [PMID: 1544463 DOI: 10.1016/0014-5793(92)80079-v] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Affinity chromatography on Bowringia mildbraedii agglutinin (BMA) Sepharose of glycopeptides confirmed a previous report using oligosaccharides (Animashaun, T. and Hughes, R. C. (1989) J. Biol. Chem. 264,4657-4663) that high affinity binding requires the sequence Man alpha 1---2 Man alpha 1----6 Man alpha 1----6 Man beta 1----4. However, moderate binding was still exhibited by structures lacking this sequence provided the oligosaccharide core sequence Man alpha 1----3[Man alpha 1----6]Man beta 1----4GlcNAc was present. This moderate binding was not affected by substitution with N-acetylglucosamine at C2 and C4, respectively, of the Man alpha 1----3 and Man beta 1----4 residues and BMA Sepharose should prove to be a useful tool for the isolation of bisected or non-bisected hybrid-type glycans.
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Affiliation(s)
- D Chawla
- National Institute for Medical Research, The Ridgeway, Mill Hill, London, UK
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41
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Shoreibah M, Hindsgaul O, Pierce M. Purification and characterization of rat kidney UDP-N-acetylglucosamine: alpha-6-D-mannoside beta-1,6-N-acetylglucosaminyltransferase. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50674-3] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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42
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Mori E, Takasaki S, Hedrick JL, Wardrip NJ, Mori T, Kobata A. Neutral oligosaccharide structures linked to asparagines of porcine zona pellucida glycoproteins. Biochemistry 1991; 30:2078-87. [PMID: 1998670 DOI: 10.1021/bi00222a012] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
N-Linked sugar chains were liberated by hydrazinolysis from porcine zona pellucida glycoproteins obtained from ovarian follicular oocytes. Neutral sugar chains were separated from acidic ones by paper electrophoresis and fractionated with a serial lectin column chromatography and Bio-Gel P-4 column chromatography. Their structural analysis by sequential glycosidase digestion in combination with methylation analysis revealed that the neutral sugar chains are of bi-, tri-, and tetraantennary complex type with a fucosylated trimannosyl core. Twenty-six percent of the sugar chains contain N-acetyllactosamine repeating structures in their outer chain moieties. Only linear N-acetyllactosamine repeats, the maximum size of which is hexasaccharide, are detected. A characteristic feature is that 39% of the sugar chains contain N-acetylglucosamine residues at their nonreducing termini in spite of the absence of bisected sugar chains. This study provided, for the first time, the substantial information about the sugar chain structures of mammalian zona pellucida glycoproteins.
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Affiliation(s)
- E Mori
- Department of Immunology and Biochemistry, University of Tokyo, Japan
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43
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Olafson RW, Thomas JR, Ferguson MA, Dwek RA, Chaudhuri M, Chang KP, Rademacher TW. Structures of the N-linked oligosaccharides of Gp63, the major surface glycoprotein, from Leishmania mexicana amazonensis. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)38336-x] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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44
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Structural heterogeneity of sugar chains in immunoglobulin G. Conformation of immunoglobulin G molecule and substrate specificities of glycosyltransferases. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39283-x] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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45
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Tulsiani DR, Coleman VD, Touster O. Asparagine-linked glycoprotein biosynthesis in rat brain: identification of glucosidase I, glucosidase II, and and endomannosidase (glucosyl mannosidase). Arch Biochem Biophys 1990; 277:114-21. [PMID: 2407194 DOI: 10.1016/0003-9861(90)90558-g] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Previous studies from this laboratory provided evidence, largely based upon the presence of a novel alpha-D-mannosidase, suggesting that the biosynthesis of N-linked glycoproteins may be different in brain as compared to other tissues (Tulsiani, D. R. P., and Touster, O. (1985) J. Biol. Chem. 260, 13,081-13,087). In the present report we describe studies on the enzymes involved in early processing reactions. These studies indicate that the brain, like other tissues, contains glucosidases I and II. The two glucosidases were separated as distinct activities with some overlapping by chromatography on a DE-52 column. The differential inhibition studies and substrate specificity studies support our conclusion that, as in other tissues, rat brain glucosidase I cleaves alpha 1,2-linked terminal glucosyl residues, whereas glucosidase II prefers alpha 1,3-linked glucosyl residues. In addition to these two processing glucosidases, we have characterized an endo enzyme (glucosyl mannosidase) in rat brain. The endomannosidase cleaves a disaccharide (glucosyl alpha 1,3-mannose) from monoglucosylated oligosaccharides (GlcMan7-9GlcNAc). Little or no activity was observed when di- or triglucosylated oligosaccharide was used as a substrate. The pH optimum of the glucosyl mannosidase is 6.2-6.8. The enzyme appears to be an intrinsic microsomal membrane component, since washing of the microsomal membranes with salt solution did not release the enzyme in soluble form. A mixture of Triton X-100 and sodium deoxycholate is required for complete solubilization of the enzyme. The solubilized enzyme is eluted from a Bio-Gel A-1.5m column as a single peak with an apparent molecular weight of 380,000.
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Affiliation(s)
- D R Tulsiani
- Department of Molecular Biology, Vanderbilt University, Nashville, Tennessee 37235
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46
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Cacan R, Lepers A, Belard M, Verbert A. Catabolic pathway of oligosaccharide-diphospho-dolichol. Subcellular sites of the degradation of the oligomannoside moiety. EUROPEAN JOURNAL OF BIOCHEMISTRY 1989; 185:173-9. [PMID: 2530086 DOI: 10.1111/j.1432-1033.1989.tb15099.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The degradation of oligosaccharide-diphospho-dolichol leads to the release of oligosaccharide material ranging from (Glc)3(Man)9(GlcNAc)2-P to (Man)3 species and further smaller species. The subcellular location of the glucosidases and mannosidases involved in this catabolic process has been investigated on the basis of their differential sensitivity towards specific inhibitors (castanospermine, deoxymannojirimycin and swainsonine). The results indicate that the first steps of degradation down to the (Man)6 species occurs in the rough endoplasmic reticulum. This result is supported by the fact that the (Man)6 species is the end product when lipid-intermediate-derived glucosylated oligosaccharides are incubated with purified rough endoplasmic reticulum membranes. Swainsonine and lysosomotropic agents (chloroquine and ammonium chloride) do not affect the degradation process, thus indicating that neither Golgi apparatus nor lysosomes are involved in this catabolism. The observation of the same degradation pattern of the released oligosaccharide material in mannosidosis fibroblasts, lacking lysosomal mannosidases, confirms these results. Finally, the subcellular distribution of the released oligosaccharide material indicates that the oligomannosides larger than (Man)6 species are sequestered in the particulate fraction whereas, in contrast, oligomannosides smaller than (Man)6 species are found predominantly in the cytosol. Taken altogether, the experiments demonstrate that the first steps of the degradation of oligosaccharide-diphospho-dolichol occurs in the rough endoplasmic reticulum producing oligomannosides of the (Man)6 species which are then translocated to the cytoplasm to be further degraded.
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Affiliation(s)
- R Cacan
- Laboratoire de Chimie Biologique de l'Université des Sciences et Techniques de Lille Flandres-Artois, Villeneuve d'Ascq, France
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47
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Brockhausen I, Hull E, Hindsgaul O, Schachter H, Shah RN, Michnick SW, Carver JP. Control of Glycoprotein Synthesis. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)60451-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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48
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Identification of an N-Acetylglucosaminyltransferase in Dictyostelium discoideum That Transfers an “Intersecting” N-Acetylglucosamine Residue to High Mannose Oligosaccharides. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)81636-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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49
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Shao MC, Wold F. The Effect of the Protein Matrix on Glycoprotein Processing by Oviduct Golgi Enzymes. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83340-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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50
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Gyves PW, Gesundheit N, Stannard BS, DeCherney GS, Weintraub BD. Alterations in the Glycosylation of Secreted Thyrotropin during Ontogenesis. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)83319-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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