201
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Misaki R, Nagaya H, Fujiyama K, Yanagihara I, Honda T, Seki T. N-linked glycan structures of mouse interferon-β produced by Bombyx mori larvae. Biochem Biophys Res Commun 2003; 311:979-86. [PMID: 14623278 DOI: 10.1016/j.bbrc.2003.10.094] [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: 10/26/2022]
Abstract
The full-length mouse interferon-beta (mIFN-beta) cDNA, including the secretion signal peptide coding region under control of the polyhedrin promoter, was introduced into Bombyx mori nucleopolyhedrovirus (BmNPV). Recombinant mIFN-beta (rmIFN-beta) was accumulated in the haemolymph of infected silkworm larvae. Western blot analysis showed isoforms of rmIFN-beta, suggesting that rmIFN-beta is glycosylated. The glycan structures of purified rmIFN-beta were determined. The N-glycans were liberated by hydrazinolysis and the resulting oligosaccharides were labeled with 2-aminopyridine. The pyridylaminated (PA) glycans were purified by gel filtration, reversed-phase HPLC, and size-fractionation HPLC. The structures of the PA-sugar chains were identified by a combination of two-dimensional PA-sugar chain mapping, MS analysis, and exoglycosidase digestions.
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Affiliation(s)
- Ryo Misaki
- The International Center for Biotechnology, Osaka University, 2-1 Yamada-oka, Suita, 565-0871, Osaka, Japan
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202
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Louie KA, Dadgari JM, DeBoer BM, Weisbuch H, Snow PM, Cheevers WP, Douvas A, McMillan M. Caprine arthritis-encephalitis virus-infected goats can generate human immunodeficiency virus-gp120 cross-reactive antibodies(1). Virology 2003; 315:217-23. [PMID: 14592773 DOI: 10.1016/s0042-6822(03)00523-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Lentiviruses display surprisingly disparate clinical manifestations in their specific hosts, share complex genetic structures, and exhibit extensive diversity, particularly in their envelope genes. The envelope protein, gp135, of caprine arthritis-encephalitis virus (CAEV) has minimal primary sequence homology to gp120, the envelope protein of human immunodeficiency virus (HIV). Nevertheless, they bear certain similarities in that they both possess five variable regions, both are heavily glycosylated, and both share short sequence motifs. We establish a further relationship and demonstrate that some goats, infected with CAEV, possess gp135-specific antibodies which cross-react with gp120 from several HIV strains, provided the protein is expressed in insect cells. We show that, although the cross-reactivity of these immunoglobulins depends on the level of glycosylation, nevertheless, some antibodies recognize the protein epitopes on gp120, at least some of which are linear in character. Further characterization of this unexpected cross-reaction will define its potential therapeutic utility.
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Affiliation(s)
- Katherine A Louie
- Department of Microbiology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
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203
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Müthing J, Kemminer SE, Conradt HS, Sagi D, Nimtz M, Kärst U, Peter-Katalinić J. Effects of buffering conditions and culture pH on production rates and glycosylation of clinical phase I anti-melanoma mouse IgG3 monoclonal antibody R24. Biotechnol Bioeng 2003; 83:321-34. [PMID: 12783488 DOI: 10.1002/bit.10673] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
R24, a mouse IgG3 monoclonal antibody (MAb) against ganglioside GD3 (Neu5Acalpha8Neu5Acalpha3Gal beta4Glcbeta1Cer), can block tumor growth as reported in a series of clinical trials in patients with metastatic melanoma. The IgG molecule basically contains an asparagine-linked biantennary complex type oligosaccharide on the C(H)2 domain of each heavy chain, which is necessary for its in vivo effector function. The purpose of this study was to investigate the biotechnological production and particularly the glycosylation of this clinically important MAb in CO(2)/HCO(3) (-) (pH 7.4, 7.2, and 6.9) and HEPES buffered serum-free medium. Growth, metabolism, and IgG production of hybridoma cells (ATCC HB-8445) were analyzed on a 2-L bioreactor scale using fed-batch mode. Specific growth rates (mu) and MAb production rates (q(IgG)) varied significantly with maximum product yields at pH 6.9 (q(IgG) = 42.9 microg 10(-6) cells d(-1), mu = 0.30 d(-1)) and lowest yields in pH 7.4 adjusted batches (q(IgG) = 10.8 microg 10(-6) cells d(-1), mu = 0.40 d(-1)). N-glycans were structurally characterized by high pH anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF), and electrospray-ionization quadrupole time-of-flight (ESI-QTOF) mass spectrometry (MS). The highest relative amounts of agalacto and monogalacto biantennary complex type oligosaccharides were detected in the pH 7.2 (46% and 38%, respectively) and pH 6.9 (44% and 40%, respectively) cultivations and the uppermost quantities of digalacto (fully galactosylated) structures in the pH 7.4 (32%) and the HEPES (26%) buffered fermentation. In the experiments with HEPES buffering, antibodies with a molar Neu5Ac/Neu5Gc ratio of 3.067 were obtained. The fermentations at pH 7.2 and 6.9 resulted in almost equal molar Neu5Ac/Neu5Gc ratios of 1.008 and 0.985, respectively, while the alkaline shift caused a moderate overexpression of Neu5Ac deduced from the Neu5Ac/Neu5Gc quotient of 1.411. Different culture buffering gave rise to altered glycosylation pattern of the MAb R24. Consequently, a detailed molecular characterization of MAb glycosylation is generally recommended as a part of the development of MAbs for targeted in vivo immunotherapy to assure biochemical consistency of product lots and oligosaccharide-dependent biological activity.
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Affiliation(s)
- Johannes Müthing
- Institute for Medical Physics and Biophysics, Laboratory for Biomedical Analysis, University of Münster, D-48149 Münster, Germany.
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204
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Samyn-Petit B, Wajda Dubos JP, Chirat F, Coddeville B, Demaizieres G, Farrer S, Slomianny MC, Theisen M, Delannoy P. Comparative analysis of the site-specific N-glycosylation of human lactoferrin produced in maize and tobacco plants. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:3235-42. [PMID: 12869199 DOI: 10.1046/j.1432-1033.2003.03706.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have compared the site-by-site N-glycosylation status of human lactoferrin (Lf) produced in maize, a monocotyledon, and in tobacco, used as a model dicotyledon. Maize and tobacco plants were stably transformed and recombinant Lf was purified from both seeds and leaves. N-glycopeptides were generated by trypsin digestion of recombinant Lf and purified by reverse-phase HPLC. The N-glycosylation pattern of each site was determined by mass spectrometry. Our results indicated that the N-glycosylation patterns of recombinant Lf produced in maize and tobacco share common structural features. In particular, both N-glycosylation sites of each recombinant Lf are mainly substituted by typical plant paucimannose-type N-glycans, with beta1,2-xylose and alpha1,3-linked fucose at the proximal N-acetylglucosamine. However, tobacco Lf shows a significant amount of processed N-glycans with one or two beta1,2GlcNAc linked to the trimannose core, which are weakly expressed in maize Lf. Finally, no Lewisa epitope was observed on tobacco Lf.
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Affiliation(s)
- Bénédicte Samyn-Petit
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, Laboratoire de Chimie Biologique, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France
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205
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Furuhashi M, Suganuma N. Effect of additional N-glycosylation signal in the N-terminal region on intracellular function of the human gonadotropin alpha-subunit. Endocr J 2003; 50:245-53. [PMID: 12940452 DOI: 10.1507/endocrj.50.245] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
hCG, LH, FSH, and TSH are a family of heterodimeric glycoprotein hormones that contain a common alpha-subunit, but differ in their hormone-specific beta-subunits. The alpha-subunit has two N-glycosylation sites at Asn52 and Asn78. To obtain more information on the relationship between the structure and function of the alpha-subunit, we introduced a novel N-glycosylation site in the N-terminal region by mutating Asp3 and Gln5 into Asn and Thr, respectively. Glycosylation mutants were expressed alone or with hCGbeta-subunit in Chinese hamster ovary cells. New N-linked oligosaccharides were efficiently added to the wild-type and mutant alpha-subunits lacking N-glycan at Asn52 (alpha deltaAsn1), Asn78 (alpha deltaAsn2), and both (alpha deltaAsn(1 + 2)). The new sugar chain did not affect secretion and assembly except that 1) it increased the intracellular degradation of alpha deltaAsn(1 + 2), and 2) it augmented the assembly of alpha deltaAsn1 with hCGbeta-subunit. Amino acid changes generated the attachment of O-glycosylation in free alpha-subunit but not in assembled form. These data indicate that the newly introduced N-glycosylation consensus sequence is functional, and that the N-terminal region of the alpha-subunit is flexible and can be modified without affecting the intracellular function. Furthermore, amino acid sequences in the N-terminus are involved in the O-glycosylation in free alpha-subunit.
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Affiliation(s)
- Madoka Furuhashi
- Department of Obstetrics and Gynecology, Japanese Red Cross Nagoya First Hospital, Nagoya 453-8511, Japan
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206
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Herr AB, White CL, Milburn C, Wu C, Bjorkman PJ. Bivalent binding of IgA1 to FcalphaRI suggests a mechanism for cytokine activation of IgA phagocytosis. J Mol Biol 2003; 327:645-57. [PMID: 12634059 DOI: 10.1016/s0022-2836(03)00149-9] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
FcalphaRI, the receptor specific for the Fc region of immunoglobulin A (IgA), is responsible for IgA-mediated phagocytosis, oxidative burst, and antibody-dependent cellular cytotoxicity. Using the techniques of analytical ultracentrifugation and equilibrium gel-filtration, we show that two FcalphaRI molecules bind to a single Fcalpha homodimer. Surface plasmon resonance studies confirm the 2:1 stoichiometry of binding, with equilibrium dissociation constants of 176 nM and 431 nM for the first and second binding events, respectively. The binding affinity decreases at acidic pH in a manner consistent with protonation of a single histidine residue in the binding site. A thermodynamic analysis indicates that the histidine residue does not participate in a salt-bridge in the complex; in fact, less than 10% of the free energy of binding was contributed by electrostatic interactions. The bivalent, pH-dependent interaction between FcalphaRI and IgA has important implications for cytokine-dependent phagocytosis of IgA and the FcalphaRI-mediated degradation or recycling of IgA.
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Affiliation(s)
- Andrew B Herr
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
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207
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Barnes LM, Bentley CM, Dickson AJ. Stability of protein production from recombinant mammalian cells. Biotechnol Bioeng 2003; 81:631-9. [PMID: 12529877 DOI: 10.1002/bit.10517] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
One of the most important criteria for successful generation of a therapeutic protein from a recombinant cell is to obtain a cell line that maintains stability of production. If this is not achieved it can generate problems for process yields, effective use of time and money, and for regulatory approval of products. However, selection of a cell line that sustains stability of production over the required time period may be difficult to achieve during development of a therapeutic protein. There are several studies in the literature that have reported on the instability of protein production from recombinant cell lines. The causes of instability of production are varied and, in many cases, the exact molecular mechanisms are unknown. The production of proteins by cells is modulated by molecular events at levels ranging from transcription, posttranscriptional processing, translation, posttranslational processing, to secretion. There is potential for regulation of stability of protein production at many or all of these stages. In this study we review published information on stability of protein production for three industrially important cell lines: hybridoma, Chinese hamster ovary (CHO), and nonsecreting (NS0) myeloma cell lines. We highlight the most likely molecular loci at which instability may be engendered and indicate other areas of protein production that may affect stability from mammalian cells. We also outline approaches that could help to overcome the problems associated with unpredictable expression levels and maximized production, and indicate the consequences these might have for stability of production.
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Affiliation(s)
- Louise M Barnes
- 2.205 School of Biological Sciences, University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, United Kingdom.
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208
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Massotte D. G protein-coupled receptor overexpression with the baculovirus-insect cell system: a tool for structural and functional studies. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1610:77-89. [PMID: 12586382 DOI: 10.1016/s0005-2736(02)00720-4] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
G protein-coupled receptors, whose topology shows seven transmembrane domains, form the largest known family of receptors involved in higher organism signal transduction. These receptors are generally of low natural abundance and overexpression is usually a prerequisite to their structural or functional characterisation. The baculovirus-insect cell system constitutes a versatile tool for the maximal production of receptors. This heterologous expression system also provides interesting alternatives for receptor functional studies in a well-controlled cellular context.
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Affiliation(s)
- Dominique Massotte
- Laboratoire de Biologie et Génomique Structurales, UMR 7104, IGBMC, 1 rue Laurent Fries, BP 10142, F-67404 Illkirch Cedex, France.
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209
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Hollister J, Grabenhorst E, Nimtz M, Conradt H, Jarvis DL. Engineering the protein N-glycosylation pathway in insect cells for production of biantennary, complex N-glycans. Biochemistry 2002; 41:15093-104. [PMID: 12475259 PMCID: PMC3612895 DOI: 10.1021/bi026455d] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Insect cells, like other eucaryotic cells, modify many of their proteins by N-glycosylation. However, the endogenous insect cell N-glycan processing machinery generally does not produce complex, terminally sialylated N-glycans such as those found in mammalian systems. This difference in the N-glycan processing pathways of insect cells and higher eucaryotes imposes a significant limitation on their use as hosts for baculovirus-mediated recombinant glycoprotein production. To address this problem, we previously isolated two transgenic insect cell lines that have mammalian beta1,4-galactosyltransferase or beta1,4-galactosyltransferase and alpha2,6-sialyltransferase genes. Unlike the parental insect cell line, both transgenic cell lines expressed the mammalian glycosyltransferases and were able to produce terminally galactosylated or sialylated N-glycans. The purpose of the present study was to investigate the structures of the N-glycans produced by these transgenic insect cell lines in further detail. Direct structural analyses revealed that the most extensively processed N-glycans produced by the transgenic insect cell lines were novel, monoantennary structures with elongation of only the alpha1,3 branch. This led to the hypothesis that the transgenic insect cell lines lacked adequate endogenous N-acetylglucosaminyltransferase II activity for biantennary N-glycan production. To test this hypothesis and further extend the N-glycan processing pathway in Sf9 cells, we produced a new transgenic line designed to constitutively express a more complete array of mammalian glycosyltransferases, including N-acetylglucosaminyltransferase II. This new transgenic insect cell line, designated SfSWT-1, has higher levels of five glycosyltransferase activities than the parental cells and supports baculovirus replication at normal levels. In addition, direct structural analyses showed that SfSWT-1 cells could produce biantennary, terminally sialylated N-glycans. Thus, this study provides new insight on the glycobiology of insect cells and describes a new transgenic insect cell line that will be widely useful for the production of more authentic recombinant glycoproteins by baculovirus expression vectors.
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Affiliation(s)
- Jason Hollister
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071
| | - Eckart Grabenhorst
- Protein Glycosylation, Gesellschaft für Biotechnologische Forschung mbH, Braunschweig, Germany
| | - Manfred Nimtz
- Protein Glycosylation, Gesellschaft für Biotechnologische Forschung mbH, Braunschweig, Germany
| | - Harald Conradt
- Protein Glycosylation, Gesellschaft für Biotechnologische Forschung mbH, Braunschweig, Germany
| | - Donald L. Jarvis
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming 82071
- To whom correspondence should be addressed. Phone: 307-766-4383. Fax: 307-766-5098.
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210
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Boorsma M, Hoenke S, Marrero A, Fischer R, Bailey JE, Renner WA, Bachmann MF. Bioprocess applications of a Sindbis virus-based temperature-inducible expression system. Biotechnol Bioeng 2002; 79:602-9. [PMID: 12209807 DOI: 10.1002/bit.10311] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The production and study of toxic proteins requires inducible expression systems with low basal level expression and high inducibility. Here, we describe bioprocess applications of the pCytTS temperature-regulatable Sindbis virus replicon-based expression system. We used green fluorescent protein as a marker protein to optimize the selection of stable transfected clones with increased expression levels. Using the optimized protocol, clones were constructed that produced the growth-inhibiting, anti-viral protein interferon beta (beta-IFN). Selected clones were analyzed for temperature-dependent beta-IFN production in adherent and suspension cultures in serum free medium. Specific expression levels were around 1.0 x 10(5) IU/10(6) cells/day (0.5 microg/10(6) cells/day) in suspension cultures and over 1.5 x 10(6) IU/mL/day (7.5 microg/mL/day) in hollow fiber reactors using adherent cells. Hexahistidine-tagged beta-IFN purified from T-flask cultures was highly glycosylated and showed high specific activity. beta-IFN mRNA amplified by the viral replicase for 10 days did not show an accumulation of mutations. These data suggest the applicability of the pCytTS-inducible expression system for the production of high-quality glycoproteins in different reactors.
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Affiliation(s)
- M Boorsma
- Cytos Biotechnology AG, Wagistrasse 21, CH-8952, Zurich-Schlieren, Switzerland
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211
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Biomedical vignette. J Biomed Sci 2002. [DOI: 10.1007/bf02254983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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212
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Establishment of a human somatic hybrid cell line for recombinant protein production. J Biomed Sci 2002. [DOI: 10.1007/bf02254991] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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213
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Abstract
In recent years, the number of recombinant proteins used for therapeutic applications has increased dramatically. Many of these applications involve complex glycoproteins and antibodies with relatively high production needs. These demands have driven the development of a variety of improvements in protein expression technology, particularly involving mammalian and microbial culture systems.
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Affiliation(s)
- Dana C Andersen
- Cell Culture & Fermentation Research & Development, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
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214
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Callewaert N, Vervecken W, Van Hecke A, Contreras R. Use of a meltable polyacrylamide matrix for sodium dodecyl sulfate-polyacrylamide gel electrophoresis in a procedure for N-glycan analysis on picomole amounts of glycoproteins. Anal Biochem 2002; 303:93-5. [PMID: 11906155 DOI: 10.1006/abio.2001.5514] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Nico Callewaert
- Department of Molecular Biology, Unit for Fundamental and Applied Molecular Biology, Ghent University, Flanders Interuniversity Institute for Biotechnology, K.L.-Ledeganckstraat 35, B-9000 Ghent, Belgium
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215
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Korke R, Rink A, Seow TK, Chung MCM, Beattie CW, Hu WS. Genomic and proteomic perspectives in cell culture engineering. J Biotechnol 2002; 94:73-92. [PMID: 11792453 DOI: 10.1016/s0168-1656(01)00420-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
In the last few years, the number of biologics produced by mammalian cells have been steadily increasing. The advances in cell culture engineering science have contributed significantly to this increase. A common path of product and process development has emerged in the last decade and the host cell lines frequently used have converged to only a few. Selection of cell clones, their adaptation to a desired growth environment, and improving their productivity has been key to developing a new process. However, the fundamental understanding of changes during the selection and adaptation process is still lacking. Some cells may undergo irreversible alteration at the genome level, some may exhibit changes in their gene expression pattern, while others may incur neither genetic reconstruction nor gene expression changes, but only modulation of various fluxes by changing nutrient/metabolite concentrations and enzyme activities. It is likely that the selection of cell clones and their adaptation to various culture conditions may involve alterations not only in cellular machinery directly related to the selected marker or adapted behavior, but also those which may or may not be essential for selection or adaptation. The genomic and proteomic research tools enable one to globally survey the alterations at mRNA and protein levels and to unveil their regulation. Undoubtedly, a better understanding of these cellular processes at the molecular level will lead to a better strategy for 'designing' producing cells. Herein the genomic and proteomic tools are briefly reviewed and their impact on cell culture engineering is discussed.
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Affiliation(s)
- Rashmi Korke
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA
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216
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Abstract
Myeloma expression systems have been utilized successfully for the production of various recombinant proteins. In particular, myeloma cell lines have been exploited to express a variety of different antibodies for diagnostic applications as well as in the treatment of various human diseases. The use of myeloma cells for antibody production is advantageous because they are professional immunoglobulin-secreting cells and are able to make proper post-translational modifications. Proper glycosylation has been shown to be important for antibody function. Advances in genetic engineering and molecular biology techniques have made it possible to isolate murine and human variable regions of almost any desired specificity. Antibodies and antibody variants produced in myeloma cells have been extremely helpful in elucidating the amino acid residues and structural motifs that contribute to antibody function. Because of their domain nature, immunoglobulin genes can be easily manipulated to produce chimeric or humanized antibodies. These antibodies are less immunogenic in humans and also retain their specificity for antigen and biologic properties. In addition, novel proteins in which antibodies are fused to non-immunoglobulin sequences as well as secretory IgA have been produced in myeloma cells.
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Affiliation(s)
- Esther M Yoo
- Department of Microbiology, Immunology and Molecular Genetics and the Molecular Biology Institute, University of California Los Angeles, 611 S. Charles Young Drive, Los Angeles, CA 90095, USA
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217
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Abstract
The first patents of biopharmaceuticals derived from recombinant DNA will expire shortly, which raises the possibility of marketing generic products ('biogenerics') with limited documentation, similar to that which occurs with conventional pharmaceuticals. We propose the term off-patent biotechnological products (OPBPs) as an alternative to biogenerics when describing such products. It is questionable whether the majority of OPBPs can be classified as similar to the innovator products, considering the size and complexity of the molecules and the many factors that influence biological activity. There are three classes of OPBPs, each of which needs to meet different regulatory demands when seeking marketing authorization.
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Affiliation(s)
- Huub Schellekens
- Central Laboratory Animal Institute, Dept of Innovation Studies, Utrecht University, PO Box 80.190, 3508 TD, Utrecht, The Netherlands.
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218
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Affiliation(s)
- Benjamin G Davis
- Dyson Perrins Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QY, UK.
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219
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Barroso B, Dijkstra R, Geerts M, Lagerwerf F, van Veelen P, de Ru A. On-line high-performance liquid chromatography/mass spectrometric characterization of native oligosaccharides from glycoproteins. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2002; 16:1320-1329. [PMID: 12112260 DOI: 10.1002/rcm.723] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
An on-line high-performance liquid chromatography/mass spectrometry (HPLC/MS) method is described for the rapid characterization of any type of oligosaccharide released from glycoproteins. The procedure can be applied without further manipulation to fractions collected from a high-performance anion-exchange chromatography-pulse amperometric detection (HPAEC-PAD) system commonly used for glycosylation mapping of glycoproteins, or to a pool of oligosaccharides directly released from glycoproteins. The system consists of a porous graphitized high-performance chromatography column (Hypercarb) coupled to a quadrupole time-of-flight (TOF) mass spectrometer. Oligosaccharides are eluted from the column with a gradient of ammonium acetate/acetonitrile and directly identified following in-source fragmentation. Some applications of the method are presented, as well as information about the spectra and fragmentation behavior observed for N- and O-linked oligosaccharides released from some recombinant glycoproteins. Low femtomole limits of detection are achieved using proper miniaturization.
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Affiliation(s)
- Begona Barroso
- Pharming Group N.V., Archimedesweg 4, 2333 CN Leiden, The Netherlands.
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220
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Petersen L, Jensen KJ. A new, efficient glycosylation method for oligosaccharide synthesis under neutral conditions: preparation and use of new DISAL donors. J Org Chem 2001; 66:6268-75. [PMID: 11559173 DOI: 10.1021/jo0057654] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Efficient, stereoselective glycosylation methods are required for the synthesis of complex oligosaccharides as tools in glycobiology. All glycosylation methods, which have found wide acceptance, rely on Lewis acid activation of glycosyl donors prior to glycosylation. Here, we present a new and efficient method for glycosylation under neutral or mildly basic conditions. Glycosides of methyl 2-hydroxy-3,5-dinitrobenzoate (DISAL) and its para regioisomer, methyl 4-hydroxy-3,5-dinitrobenzoate, were prepared by nucleophilic aromatic substitution. In a first demonstration of their potential as glycosyl donors, stereospecific glycosylation of methanol was achieved. In the glycosylation of more hindered alcohols, the beta-donor proved more reactive, and alpha-glucosides were predominantly formed. Glycosylation of protected monosaccharides, with free 6-OH or 3-OH, proceeded smoothly in 1-methyl-2-pyrrolidinone (NMP) at 40-60 degrees C in the absence of Lewis acids and bases in good to excellent yields. Glycosylation of 3-OH gave the alpha-linked disaccharide only.
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Affiliation(s)
- L Petersen
- Department of Chemistry, Building 201, Kemitorvet, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
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221
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Wallis GL, Swift RJ, Atterbury R, Trappe S, Rinas U, Hemming FW, Wiebe MG, Trinci AP, Peberdy JF. The effect of pH on glucoamylase production, glycosylation and chemostat evolution of Aspergillus niger. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1527:112-22. [PMID: 11479027 DOI: 10.1016/s0304-4165(01)00145-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effect of ambient pH on production and glycosylation of glucoamylase (GAM) and on the generation of a morphological mutant produced by Aspergillus niger strain B1 (a transformant containing an additional 20 copies of the homologous GAM glaA gene) was studied. We have shown that a change in the pH from 4 to 5.4 during continuous cultivation of the A. niger B1 strain instigates or accelerates the spontaneous generation of a morphological mutant (LB). This mutant strain produced approx. 50% less extracellular protein and GAM during both chemostat and batch cultivation compared to another strain with parental-type morphology (PS). The intracellular levels of GAM were also lower in the LB strain. In addition, cultivation of the original parent B1 strain in a batch-pulse bioreactor at pH 5.5 resulted in a 9-fold drop in GAM production and a 5-fold drop in extracellular protein compared to that obtained at pH 4. Glycosylation analysis of the glucoamylases purified from shake-flask cultivation showed that both principal forms of GAM secreted by the LB strain possessed enhanced galactosylation (2-fold), compared to those of the PS. Four diagnostic methods (immunostaining, mild methanolysis, mild acid hydrolysis and beta-galactofuranosidase digestion) provided evidence that the majority of this galactose was of the furanoic conformation. The GAMs produced during batch-pulse cultivation at pH 5.5 similarly showed an approx. 2-fold increase in galactofuranosylation compared to pH 4. Interestingly, in both cases the increased galactofuranosylation appears primarily restricted to the O-linked glycan component. Ambient pH therefore regulates both GAM production and influences its glycosylation.
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Affiliation(s)
- G L Wallis
- School of Biological, University of Nottingham, UK.
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222
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Li P, Gao XG, Arellano RO, Renugopalakrishnan V. Glycosylated and phosphorylated proteins--expression in yeast and oocytes of Xenopus: prospects and challenges--relevance to expression of thermostable proteins. Protein Expr Purif 2001; 22:369-80. [PMID: 11482998 DOI: 10.1006/prep.2001.1431] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phosphorylation and glycosylation are important posttranslational events in the biosynthesis of proteins. The different degrees of phosphorylation and glycosylation of proteins have been an intriguing phenomenon. Advances in genetic engineering have made it possible to control the degree of glycosylation and phosphorylation of proteins. Structural biology of phosphorylated and glycosylated proteins has been advancing at a much slower pace due to difficulties in using high-resolution NMR studies in solution phase. Major difficulties have arisen from the inherent mobilities of phosphorylated and glycosylated side chains. This paper reviews molecular and structural biology of phosphorylated and glycosylated proteins expressed in eukaryotic expression systems which are especially suited for large-scale production of these proteins. In our laboratory, we have observed that eukaryotic expression systems are particularly suited for the expression of thermostable light-activated proteins, e.g., bacteriorhodopsins and plastocyanins.
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Affiliation(s)
- P Li
- Shanghai Research Center of Biotechnology, Chinese Academy of Sciences, Shanghai 200233, People's Republic of China
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223
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Samyn-Petit B, Gruber V, Flahaut C, Wajda-Dubos JP, Farrer S, Pons A, Desmaizieres G, Slomianny MC, Theisen M, Delannoy P. N-glycosylation potential of maize: the human lactoferrin used as a model. Glycoconj J 2001; 18:519-27. [PMID: 12151713 DOI: 10.1023/a:1019640312730] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In order to determine the N-glycosylation potential of maize, a monocotyledon expression system for the production of recombinant glycoproteins, human lactoferrin was used as a model. The human lactoferrin coding sequence was inserted into the pUC18 plasmid under control of the wheat glutenin promoter. Maize was stably transformed and recombinant lactoferrin was purified from the fourth generation seeds. Glycosylation was analysed by gas chromatography, lectin detection, glycosidase digestions and mass spectrometry. The results indicated that both N-glycosylation sites of recombinant lactoferrin are mainly substituted by typical plant paucimannose-type glycans, with beta1,2-xylose and alpha1,3-linked fucose at the proximal N-acetylglucosamine, and that complex-type glycans with Lewis(a) determinants are not present in maize recombinant lactoferrin.
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Affiliation(s)
- B Samyn-Petit
- Meristem Therapeutics, 8 rue des Frères Lumière, 63100 Clermont-Ferrand, France
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224
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Baker KN, Rendall MH, Hills AE, Hoare M, Freedman RB, James DC. Metabolic control of recombinant protein N-glycan processing in NS0 and CHO cells. Biotechnol Bioeng 2001; 73:188-202. [PMID: 11257601 DOI: 10.1002/bit.1051] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Chinese hamster ovary and murine myeloma NS0 cells are currently favored host cell types for the production of therapeutic recombinant proteins. In this study, we compared N-glycan processing in GS-NS0 and GS-CHO cells producing the same model recombinant glycoprotein, tissue inhibitor of metalloproteinases 1. By manipulation of intracellular nucleotide-sugar content, we examined the feasibility of implementing metabolic control strategies aimed at reducing the occurrence of murine-specific glycan motifs on NS0-derived recombinant proteins, such as Galalpha1,3Galbeta1,4GlcNAc. Although both CHO and NS0-derived oligosaccharides were predominantly of the standard complex type with variable sialylation, 30% of N-glycan antennae associated with NS0-derived TIMP-1 terminated in alpha1,3-linked galactose residues. Furthermore, NS0 cells conferred a greater proportion of terminal N-glycolylneuraminic (sialic) acid residues as compared with the N-acetylneuraminic acid variant. Inclusion of the nucleotide-sugar precursors, glucosamine (10 mM, plus 2 mM uridine) and N-acetylmannosamine (20 mM), in culture media were shown to significantly increase the intracellular pools of UDP-N-acetylhexosamine and CMP-sialic acid, respectively, in both NS0 and CHO cells. The elevated UDP-N-acetylhexosamine content induced by the glucosamine/uridine treatment was associated with an increase in the antennarity of N-glycans associated with TIMP-1 produced in CHO cells but not N-glycans associated with TIMP-1 from NS0 cells. In addition, elevated UDP-N-acetylhexosamine content was associated with a slight decrease in sialylation in both cell lines. The elevated CMP-sialic acid content induced by N-acetylmannosamine had no effect on the overall level of sialylation of TIMP-1 produced by both CHO and NS0 cells, although the ratio of N-glycolylneuraminic acid:N-acetylneuraminic acid associated with NS0-derived TIMP-1 changed from 1:1 to 1:2. These data suggest that manipulation of nucleotide-sugar metabolism can promote changes in N-glycan processing that are either conserved between NS0 and CHO cells or specific to either NS0 cells or CHO cells.
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Affiliation(s)
- K N Baker
- Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
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225
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Abstract
This unit reviews the stages involved in protein production in mammalian cells using a stable-expression approach. Choice of cell type is discussed, as is transfection of the host cells, methods for selection and amplification of transformants, and growth of cells at appropriate scale for protein production. Since post-transcriptional modification and intracellular protein transportation are important features of recombinant-protein production in mammalian cells, some description of these mechanisms is included.
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Affiliation(s)
- D Gray
- Chiron Corporation, Emeryville, California, USA
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226
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Abstract
Chemical tools have proven indispensable for studies in glycobiology. Synthetic oligosaccharides and glycoconjugates provide materials for correlating structure with function. Synthetic mimics of the complex assemblies found on cell surfaces can modulate cellular interactions and are under development as therapeutic agents. Small molecule inhibitors of carbohydrate biosynthetic and processing enzymes can block the assembly of specific oligosaccharide structures. Inhibitors of carbohydrate recognition and biosynthesis can reveal the biological functions of the carbohydrate epitope and its cognate receptors. Carbohydrate biosynthetic pathways are often amenable to interception with synthetic unnatural substrates. Such metabolic interference can block the expression of oligosaccharides or alter the structures of the sugars presented on cells. Collectively, these chemical approaches are contributing great insight into the myriad biological functions of oligosaccharides.
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Affiliation(s)
- C R Bertozzi
- Departments of Chemistry and Molecular and Cell Biology and Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA
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227
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Bakker H, Bardor M, Molthoff JW, Gomord V, Elbers I, Stevens LH, Jordi W, Lommen A, Faye L, Lerouge P, Bosch D. Galactose-extended glycans of antibodies produced by transgenic plants. Proc Natl Acad Sci U S A 2001; 98:2899-904. [PMID: 11226338 PMCID: PMC30237 DOI: 10.1073/pnas.031419998] [Citation(s) in RCA: 193] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2000] [Indexed: 01/03/2023] Open
Abstract
Plant-specific N-glycosylation can represent an important limitation for the use of recombinant glycoproteins of mammalian origin produced by transgenic plants. Comparison of plant and mammalian N-glycan biosynthesis indicates that beta1,4-galactosyltransferase is the most important enzyme that is missing for conversion of typical plant N-glycans into mammalian-like N-glycans. Here, the stable expression of human beta1,4-galactosyltransferase in tobacco plants is described. Proteins isolated from transgenic tobacco plants expressing the mammalian enzyme bear N-glycans, of which about 15% exhibit terminal beta1,4-galactose residues in addition to the specific plant N-glycan epitopes. The results indicate that the human enzyme is fully functional and localizes correctly in the Golgi apparatus. Despite the fact that through the modified glycosylation machinery numerous proteins have acquired unusual N-glycans with terminal beta1,4-galactose residues, no obvious changes in the physiology of the transgenic plants are observed, and the feature is inheritable. The crossing of a tobacco plant expressing human beta1,4-galactosyltransferase with a plant expressing the heavy and light chains of a mouse antibody results in the expression of a plantibody that exhibits partially galactosylated N-glycans (30%), which is approximately as abundant as when the same antibody is produced by hybridoma cells. These results are a major step in the in planta engineering of the N-glycosylation of recombinant antibodies.
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Affiliation(s)
- H Bakker
- Plant Research International, Wageningen University and Research Centre, P. O. Box 16, 6700AA, Wageningen, The Netherlands
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228
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Kaufmann H, Mazur X, Marone R, Bailey JE, Fussenegger M. Comparative analysis of two controlled proliferation strategies regarding product quality, influence on tetracycline-regulated gene expression, and productivity. Biotechnol Bioeng 2001. [DOI: 10.1002/1097-0290(20010320)72:6<592::aid-bit1024>3.0.co;2-j] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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229
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He X, Agnihotri G, Liu Hw HW. Novel enzymatic mechanisms in carbohydrate metabolism. Chem Rev 2000; 100:4615-62. [PMID: 11749360 DOI: 10.1021/cr9902998] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- X He
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712
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230
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Koeller KM, Wong CH. Synthesis of complex carbohydrates and glycoconjugates: enzyme-based and programmable one-pot strategies. Chem Rev 2000; 100:4465-94. [PMID: 11749355 DOI: 10.1021/cr990297n] [Citation(s) in RCA: 347] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- K M Koeller
- Department of Chemistry, The Scripps Research Institute and Skaggs Institute for Chemical Biology, 10550 North Torrey Pines Road, La Jolla, California 92037
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231
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Renucci M, Tirard A, Charpin P, Augier R, Strambi A. c-Fos-related antigens in the central nervous system of an insect, Acheta domesticus. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2000; 45:139-148. [PMID: 11223933 DOI: 10.1002/1520-6327(200012)45:4<139::aid-arch1>3.0.co;2-n] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Fos-related antigens (Fra) were detected in the nuclei of neurones in young adult Acheta domesticus female crickets by immunohistochemical analysis, using an antibody that recognizes the amino-acid sequence 127-152 of c-Fos protein. Specificity of Fra immunoreactivity was confirmed by Western blot analysis of nuclear extracts from neural tissues. A major immunoreactive doublet with an apparent molecular mass of 52,000/54,000 Da was detected in nuclear extracts. Immunostaining of the 52,000/54,000 Da doublet showed variations in intensity during the first 5 days following the imaginal molt. Staining was more intense between day 2 and day 4 when ecdysteroid titers were high. Expression of Fra was low in allatectomized (i.e., deprived of juvenile hormone and ecdysteroids) and ovariectomized (i.e., deprived of ecdysteroids) females as compared to control females. These results show the involvement of hormone-regulated process in expression of Fra. The effect of nociceptive stimulation on Fra expression was tested. Twenty minutes after removal of the ovipositor, a supplementary band with an apparent molecular mass of 70,000 Da appeared in the nuclear extracts, then decreased and disappeared totally after 45 min. Several other Fos-related antigens with different temporal patterns of expression were also detected.
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Affiliation(s)
- M Renucci
- CNRS, Laboratoire de Neurobiologie, Marseille, France.
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232
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Koeller KM, Wong CH. Complex carbohydrate synthesis tools for glycobiologists: enzyme-based approach and programmable one-pot strategies. Glycobiology 2000; 10:1157-69. [PMID: 11087708 DOI: 10.1093/glycob/10.11.1157] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The ultimate goal in complex carbohydrate synthesis is to develop synthetic tools which are simple and easily accessible to glycobiologists. This review will describe methods which have the potential to reach this goal, with particular focus on enzymatic and computer-based one-pot approaches for the preparation of complex carbohydrates and glycoconjugates.
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Affiliation(s)
- K M Koeller
- Department of Chemistry, The Scripps Research Institute and Skaggs Institute for Chemical Biology, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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233
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Andersen DC, Bridges T, Gawlitzek M, Hoy C. Multiple cell culture factors can affect the glycosylation of Asn-184 in CHO-produced tissue-type plasminogen activator. Biotechnol Bioeng 2000; 70:25-31. [PMID: 10940860 DOI: 10.1002/1097-0290(20001005)70:1<25::aid-bit4>3.0.co;2-q] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Human tissue-type plasminogen activator (t-PA) contains a variably occupied glycosylation site at Asn-184 in naturally produced t-PA and in t-PA produced in recombinant Chinese hamster ovary (CHO) cells. The presence of an oligosaccharide at this site has previously been shown to reduce specific activity and fibrin binding. In this report, the site occupancy of t-PA is shown to increase gradually over the course of batch and fed-batch CHO cultures. Additional cell culture factors, including butyrate and temperature, are also shown to influence the degree of glycosylation. In each of these cases, conditions with decreased growth rate correlate with increased site occupancy. Investigations using quinidine and thymidine to manipulate the cell cycle distribution of cultures further support this correlation between site occupancy and growth state. Comparison of the cell cycle distribution across the range of cell culture factors investigated shows a consistent relationship between site occupancy and the fraction of cells in the G(0)/G(1) phase of the cell cycle. These results support a correlation between growth state and site occupancy, which fundamentally differs from site occupancy trends previously observed and illustrates the importance of the growth profile of CHO cultures in producing consistently glycosylated recombinant glycoproteins.
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Affiliation(s)
- D C Andersen
- Department of Manufacturing Sciences, Genentech, Inc., One DNA Way, South San Francisco, California 94080-4990, USA.
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234
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Sheffield WP, Marques JA, Bhakta V, Smith IJ. Modulation of clearance of recombinant serum albumin by either glycosylation or truncation. Thromb Res 2000; 99:613-21. [PMID: 10974348 DOI: 10.1016/s0049-3848(00)00286-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Albumin is an abundant non-glycosylated plasma protein with a slow clearance profile. It has been employed as a fusion partner in efforts to slow the clearance of small antithrombotic proteins like hirudin. In the present study, the in vivo clearance of recombinant rabbit serum albumin (rRSA), of mutant rRSAs containing consensus sequences for N-linked glycosylation (D494N and V14T variants), and of mutant mini-proteins truncated at albumin domain boundaries (rRSAs 1-185, 1-377, or 378-584) was examined. Mean terminal catabolic half-lives (t(0.5)cat) in rabbits for plasma-derived RSA, rRSA, and the V14T variant did not differ significantly (range 4. 32-4.76 days). In contrast, mean t(0.5)cat was reduced to 2.87 days for the D494N variant and to less than 0.071 days for all mini-proteins. The mini-proteins were found in the urine in tissue distribution experiments, suggesting a renal route of clearance. Our results suggest that all three internally repeated albumin domains are required to maintain the slow in vivo clearance profile of albumin, and that albumin glycosylation can be associated with an acceleration of clearance. This information could be used to design fusion proteins, including those with antithrombotic properties, with predictably altered in vivo half-lives less than that of serum albumin.
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Affiliation(s)
- W P Sheffield
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
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235
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Effect of aPMR1 disruption on the processing of heterologous glycoproteins secreted in the yeastSaccharomyces cerevisiae. BIOTECHNOL BIOPROC E 2000. [DOI: 10.1007/bf02942179] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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236
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Abstract
The recognition of complex carbohydrates and glycoconjugates as mediators of important biological processes has stimulated investigation into their therapeutic potential. New approaches for the simplification of glycoconjugate synthesis are overcoming the limitations of existing methods and providing a diverse array of these biomolecules. As the accessibility of glycoconjugates increases, carbohydrate-based constructs are becoming available for analysis as medicinal agents in a wide range of therapies.
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Affiliation(s)
- K M Koeller
- Department of Chemistry, The Scripps Research Institute and Skaggs Institute for Chemical Biology, La Jolla, CA 92037, USA
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237
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Van den Nieuwenhof IM, Koistinen H, Easton RL, Koistinen R, Kämäräinen M, Morris HR, Van Die I, Seppälä M, Dell A, Van den Eijnden DH. Recombinant glycodelin carrying the same type of glycan structures as contraceptive glycodelin-A can be produced in human kidney 293 cells but not in chinese hamster ovary cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:4753-62. [PMID: 10903509 DOI: 10.1046/j.1432-1327.2000.01528.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have produced human recombinant glycodelin in human kidney 293 cells and in Chinese hamster ovary (CHO) cells. Structural analyses by lectin immunoassays and fast atom bombardment mass spectrometry showed that recombinant human glycodelin produced in CHO cells contains only typical CHO-type glycans and is devoid of any of the N, N'-diacetyllactosediamine (lacdiNAc)-based chains previously identified in glycodelin-A (GdA). By contrast, human kidney 293 cells produced recombinant glycodelin with the same type of carbohydrate structures as GdA. The presence of a beta1-->4-N-acetylgalactosaminyltransferase functioning in the synthesis of lacdiNAc-based glycans in human kidney 293 cells is concluded to be the cause of the occurrence of lacdiNAc-based glycans on glycodelin produced in these cells. Furthermore, human kidney 293 cells were found to be particularly suited for the production of recombinant glycodelin when they were cultured in high glucose media. Lowering the glucose concentration and the addition of glucosamine resulted in higher relative amounts of oligomannosidic-type glycans and complex glycans with truncated antennae. Human glycodelin is an attractive candidate for the development of a contraceptive agent, and this study gives valuable information for selecting the proper expression system and cell culture conditions for the production of a correctly glycosylated recombinant form.
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Affiliation(s)
- I M Van den Nieuwenhof
- Department of Medical Chemistry, Faculty of Medicine, Vrije Universiteit, Amsterdam, The Netherlands.
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238
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Gawlitzek M, Ryll T, Lofgren J, Sliwkowski MB. Ammonium alters N-glycan structures of recombinant TNFR-IgG: degradative versus biosynthetic mechanisms. Biotechnol Bioeng 2000; 68:637-46. [PMID: 10799988 DOI: 10.1002/(sici)1097-0290(20000620)68:6<637::aid-bit6>3.0.co;2-c] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The effect of ammonium on the glycosylation pattern of the recombinant immunoadhesin tumor necrosis factor-IgG (TNFR-IgG) produced by Chinese hamster ovary cells is elucidated in this study. TNFR-IgG is a chimeric IgG fusion protein bearing one N-linked glycosylation site in the Fc region and three complex-type N-glycans in the TNF-receptor portion of each monomer. The ammonium concentration of batch suspension cultures was adjusted with glutamine and/or NH(4)Cl. The amount of galactose (Gal) and N-acetylneuraminic acid (NANA) residues on TNFR-IgG correlated in a dose-dependent manner with the ammonium concentration under which the N-linked oligosaccharides were synthesized. As ammonium increased from 1 to 15 mM, a concomitant decrease of up to 40% was observed in terminal galactosylation and sialylation of the molecule. Cell culture supernatants contained measurable beta-galactosidase and sialidase activity, which increased throughout the culture. The beta-galactosidase, but not the sialidase, level was proportional to the ammonium concentration. No loss of N-glycans was observed in incubation studies using beta-galactosidase and sialidase containing cell culture supernatants, suggesting that the ammonium effect was biosynthetic and not degradative. Several biosynthetic mechanisms were investigated. Ammonium (a weak base) is known to affect the pH of acidic intracellular compartments (e.g., trans-Golgi) as well as intracellular nucleotide sugar pools (increases UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine). Ammonium might also affect the expression rates of beta1, 4-galactosyltransferase (beta1,4-GT) and alpha2,3-sialyltransferase (alpha2,3-ST). To separate these mechanisms, experiments were designed using chloroquine (changes intracellular pH) and glucosamine (increases UDP-GNAc pool [sum of UDP-GlcNAc and UDP-GalNAc]). The ammonium effect on TNFR-IgG oligosaccharide structures could be mimicked only by chloroquine, another weak base. No differences in N-glycosylation were found in the product synthesized in the presence of glucosamine. No differences in beta1, 4-galactosyltransferase (beta1,4-GT) and alpha2,3-sialyltransferase (alpha2,3-ST) messenger RNA (mRNA) and enzyme levels were observed in cells cultivated in the presence or absence of 13 mM NH(4)Cl. pH titration of endogenous CHO alpha2,3-ST and beta-1,4-GT revealed a sharp optimum at pH 6.5, the reported trans-Golgi pH. Thus, at pH 7.0 to 7.2, a likely trans-Golgi pH range in the presence of 10 to 15 mM ammonium, activities for both enzymes are reduced to 50% to 60%. Consequently, ammonium seems to alter the carbohydrate biosynthesis of TNFR-IgG by a pH-mediated effect on glycosyltransferase activity.
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Affiliation(s)
- M Gawlitzek
- Process Sciences, Genentech, Inc., South San Francisco, California 94080, USA.
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239
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Abstract
Glycosylation of proteins represents one of the most important post-(co-)translational events in view of the ubiquity of the phenomenon. In most cases, the covalently linked glycans are involved in the functioning of these biomolecules in biological systems. Detailed information on the carbohydrate moieties including monosaccharide composition, anomeric configurations, type of glycosidic linkages and attachment sites at the protein is indispensable in describing the ultimate structure of a specific glycoprotein. This chapter presents a general strategy for the structural characterization of glycoproteins/glycopeptides focussed on the glycan part. Some of the techniques commonly used, like enzyme treatments, separation methods, chemical analyses, mass spectrometry and nuclear magnetic resonance spectroscopy are briefly reviewed.
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Affiliation(s)
- G J Gerwig
- Bijvoet Center for Biomolecular Research, Department of Bio-Organic Chemistry, Utrecht University, Utrecht, The Netherlands
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240
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Morrison CJ, Easton RL, Morris HR, McMaster WR, Piret JM, Dell A. Modification of a recombinant GPI-anchored metalloproteinase for secretion alters the protein glycosylation. Biotechnol Bioeng 2000; 68:407-21. [PMID: 10745209 DOI: 10.1002/(sici)1097-0290(20000520)68:4<407::aid-bit6>3.0.co;2-s] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The N-linked glycans of recombinant leishmanolysin (GP63) expressed as a glycosylphosphatidylinositol (GPI)-anchored membrane protein or modified for secretion in Chinese hamster ovary (CHO) cells were analyzed by fast atom bombardment-mass spectrometry (FAB-MS). The glycans isolated from both membrane and secreted protein were predominantly complex biantennary structures. However other aspects of the glycan profiles showed striking differences. The degree of sialylation of the membrane form was greatly reduced and the core fucosylation of biantennary structures was increased compared to the secreted form. Glycans isolated from membrane expressed protein also contained a higher proportion of lactosamine repeats. Residence times in the secretory pathway were similar for both secreted and membrane protein. Glycosylation differences may therefore be due to differences in protein conformation and accessibility to glycosyltransferases or glycosidases. These differences in glycosylation represent an important factor when considering modifying membrane expressed proteins for secreted production.
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Affiliation(s)
- C J Morrison
- Biotechnology Laboratory, University of British Columbia, Vancouver, British Columbia, Canada
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241
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Bragonzi A, Distefano G, Buckberry LD, Acerbis G, Foglieni C, Lamotte D, Campi G, Marc A, Soria MR, Jenkins N, Monaco L. A new Chinese hamster ovary cell line expressing alpha2,6-sialyltransferase used as universal host for the production of human-like sialylated recombinant glycoproteins. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1474:273-82. [PMID: 10779678 DOI: 10.1016/s0304-4165(00)00023-4] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Chinese hamster ovary (CHO) cells are widely employed to produce glycosylated recombinant proteins. Our group as well as others have demonstrated that the sialylation defect of CHO cells can be corrected by transfecting the alpha2,6-sialyltransferase (alpha2,6-ST) cDNA. Glycoproteins produced by such CHO cells display both alpha2,6- and alpha2,3-linked terminal sialic acid residues, similar to human glycoproteins. Here, we have established a CHO cell line stably expressing alpha2,6-ST, providing a universal host for further transfections of human genes. Several relevant parameters of the universal host cell line were studied, demonstrating that the alpha2,6-ST transgene was stably integrated into the CHO cell genome, that transgene expression was stable in the absence of selective pressure, that the recombinant sialyltransferase was correctly localized in the Golgi and, finally, that the bioreactor growth parameters of the universal host were comparable to those of the parental cell line. A second step consisted in the stable transfection into the universal host of cDNAs for human glycoproteins of therapeutic interest, i.e. interferon-gamma and the tissue inhibitor of metalloproteinases-1. Interferon-gamma purified from the universal host carried 40.4% alpha2,6- and 59.6% alpha2,3-sialic acid residues and showed improved pharmacokinetics in clearance studies when compared to interferon-gamma produced by normal CHO cells.
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Affiliation(s)
- A Bragonzi
- DIBIT, Department of Biological and Technological Research, San Raffaele Scientific Institute, via Olgettina 58, 20132 Milan, Italy
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242
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Kumagai MH, Donson J, della-Cioppa G, Grill LK. Rapid, high-level expression of glycosylated rice alpha-amylase in transfected plants by an RNA viral vector. Gene 2000; 245:169-74. [PMID: 10713457 DOI: 10.1016/s0378-1119(00)00015-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Tobamoviral vectors have been developed for the heterologous expression of glycoproteins in plants. The rice alpha-amylase gene (OS103) was placed under the transcriptional control of a tobamovirus subgenomic promoter in a RNA viral vector. One to two weeks after inoculation, transfected Nicotiana benthamiana plants accumulated glycosylated alpha-amylase to levels of at least 5% total soluble protein. The 46kDa recombinant enzyme was purified, and its structural and biological properties were analyzed. Post-translational modifications of the secreted protein were compared to rice alpha-amylase expressed in amylolytic strains of Pichia pastoris and Saccharomyces cerevisiae. Endo-H analysis revealed that the alpha-amylase was moderately glycosylated in transfected plants and hyperglycosylated in yeast.
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243
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Ohta M, Ohnishi T, Ioannou YA, Hodgson ME, Matsuura F, Desnick RJ. Human alpha-N-acetylgalactosaminidase: site occupancy and structure of N-linked oligosaccharides. Glycobiology 2000; 10:251-61. [PMID: 10704524 DOI: 10.1093/glycob/10.3.251] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Human alpha-N-acetylgalactosaminidase (alpha-GalNAc; also known as alpha-galactosidase B) is the lysosomal exoglycohydrolase that cleaves alpha-N-acetylgalactosaminyl moieties in glycoconjugates. Mutagenesis studies indicated that the first five (N124, N177, N201, N359, and N385) of the six potential N-glycosylation sites were occupied. Site 3 occupancy was important for enzyme function and stability. Characterization of the N-linked oligosaccharide structures on the secreted enzyme overexpressed in Chinese hamster ovary cells revealed highly heterogeneous structures consisting of complex (approximately 53%), hybrid (approximately 12%), and high mannose-type (approximately 33%) oligosaccharides. The complex structures were mono-, bi-, 2,4-tri-, 2,6-tri-, and tetraantennary, among which the biantennary structures were most predominant (approximately 53%). Approximately 80% of the complex oligo-saccharides had a core-region fucose and 50% of the complex oligosaccharides were sialylated exclusively with alpha-2,3-linked sialic acid residues. The majority of hybrid type oligo-saccharides were GalGlcNAcMan(6)GlcNAc-Fuc(0-1)GlcNAc. Approximately 54% of the hybrid oligosaccharide were phosphorylated and one-third of these structures were further sialylated, the latter representing unique phosphorylated and sialylated structures. Of the high mannose oligosaccharides, Man(5-7)GlcNAc(2) were the predominant species (approximately 90%) and about 50% of the high mannose oligosaccharides were phosphorylated, exclusively as monoesters whose positions were determined. Comparison of the oligosaccharide structures of alpha-GalNAc and alpha-galactosidase A, an evolutionary-related and highly homologous exoglycosidase, indicated that alpha-GalNAc had more completed complex chains, presumably due to differences in enzyme structure/domains, rate of biosynthesis, and/or aggregation of the overexpressed recombinant enzymes.
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Affiliation(s)
- M Ohta
- Department of Biotechnology, Fukuyama University, Fukuyama, Hiroshima 729-0292, Japan
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244
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Mueller PP, Schlenke P, Nimtz M, Conradt HS, Hauser H. Recombinant glycoprotein product quality in proliferation-controlled BHK-21 cells. Biotechnol Bioeng 1999; 65:529-36. [PMID: 10516578 DOI: 10.1002/(sici)1097-0290(19991205)65:5<529::aid-bit5>3.0.co;2-m] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We analyzed product quality to determine the applicability of proliferation-controlled mammalian cells for recombinant pharmaceutical protein production. Baby hamster kidney (BHK)-21 cells were engineered to express a dicistronic, stabilized, self-selecting growth control system consisting of a beta-estradiol-activatable transcription factor IRF-1 fusion protein. IRF-1 activity led to a reduced growth rate, whereas productivity, protein integrity, and glycosylation pattern of the industrially relevant secreted pharmaceutical glycoprotein erythropoietin remained consistent, showing that this technique has the potential for improving the consistency of high-quality pharmaceutical products and thus warrants further development.
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Affiliation(s)
- P P Mueller
- Department of Gene Regulation and Differentiation, GBF-National Research Center for Biotechnology, Mascheroder Weg 1, D-38124 Braunschweig, Germany.
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245
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Wolff MW, Murhammer DW, Jarvis DL, Linhardt RJ. Electrophoretic analysis of glycoprotein glycans produced by lepidopteran insect cells infected with an immediate early recombinant baculovirus encoding mammalian beta1,4-galactosyltransferase. Glycoconj J 1999; 16:753-6. [PMID: 11133014 DOI: 10.1023/a:1007131611378] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Glycosylation, the most extensive co- and post-translational modification of eukaryotic cells, can significantly affect biological activity and is particularly important for recombinant glycoproteins in human therapeutic applications. The baculovirus-insect cell expression system is a popular tool for the expression of heterologous proteins and has an excellent record of producing high levels of biologically active eukaryotic proteins. Insect cells are capable of glycosylation, but their N-glycosylation pathway is truncated in comparison with the pathway of mammalian cells. A previous study demonstrated that an immediate early recombinant baculovirus could be used to extend the insect cell N-glycosylation pathway by contributing bovine beta-1,4 galactosyltransferase (GalT) immediately after infection. Lectin blotting assays indicated that this ectopically expressed enzyme could transfer galactose to an N-linked glycan on a foreign glycoprotein expressed later in infection. In the current study, glycans were isolated from total Sf-9 cell glycoproteins after infection with the immediate early recombinant baculovirus encoding GalT, fluorescently conjugated and analyzed by electrophoresis in combination with exoglycosidase digestion. These direct analyses clearly demonstrated that Sf-9 cells infected with this recombinant baculovirus can synthesize galactosylated N-linked glycans.
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Affiliation(s)
- M W Wolff
- Department of Chemical and Biochemical Engineering, University of Wyoming, Laramie 82071, USA
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246
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Pirie-Shepherd SR. Role of carbohydrate on angiostatin in the treatment of cancer. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 1999; 134:553-60. [PMID: 10595781 DOI: 10.1016/s0022-2143(99)90093-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- S R Pirie-Shepherd
- Surgical Research Laboratory, Children's Hospital, Boston, MA 02115, USA
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247
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Imperiali B, O'Connor SE. Effect of N-linked glycosylation on glycopeptide and glycoprotein structure. Curr Opin Chem Biol 1999; 3:643-9. [PMID: 10600722 DOI: 10.1016/s1367-5931(99)00021-6] [Citation(s) in RCA: 324] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Asparagine-linked glycosylation is an enzyme-catalyzed, co-translational protein modification reaction that has the capacity to influence either the protein folding process or the stability of the native glycoprotein conjugate. Advances in both glycoconjugate chemical synthesis and glycoprotein expression methods have increased the availability of these once elusive biopolymers. The application of spectroscopic methods to these proteins has begun to illuminate the various ways in which the saccharide affects the structure, function and stability of the proteins.
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Affiliation(s)
- B Imperiali
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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248
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Wallis GL, Swift RJ, Hemming FW, Trinci AP, Peberdy JF. Glucoamylase overexpression and secretion in Aspergillus niger: analysis of glycosylation. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1472:576-86. [PMID: 10564772 DOI: 10.1016/s0304-4165(99)00188-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We have studied the effects of overexpression and secretion of a homologous model glycoprotein, glucoamylase (GAM-1), on glycosylation in a single gene copy wild-type parent and multiple gene copy transformants of Aspergillus niger. In batch culture the B36 strain, which possess 80 additional copies of the GAM glaA gene, secreted about 5-8-fold more protein and GAM-1 than the parent strain (N402). A comparison of the glycosylation of GAM-1 secreted by the parent strain with that secreted by the multiple copy and hyper-secreting B36 strain showed that both the N-linked and O-linked glycan composition was very similar. Short oligomannose N-linked glycans were found (Man(7-8)GlcNAc(2)). O-Linked glycans were comprised of short (1-3 residues) oligosaccharide chains of mannose and galactose. Evidence is presented that this galactose is present in the novel galactofuranose conformation. This glycan composition of GAM-1 differed from that of a commercially available (A. niger) GAM source. Microsomes prepared from the mycelium showed a 2-3-fold co-ordinated increase in the activity of the dolichol phosphate:glycosyltransferases. Similar results were obtained from strains B1 (20 copies of glaA) and N402 when grown at a low dilution rate in a chemostat, although both the levels of GAM secretion and the activities of the dolichol phosphate:glycosyltransferases were lower than found in batch culture. These data suggest that A. niger is capable of secreting large amounts of a single glycoprotein combined with higher activity levels of the dolichol phosphate:glycosyltransferases without an increase in the heterogeneity of the glycan structures. Thus, from a biotechnological viewpoint, protein glycosylation may not be a bottleneck to enhanced glycoprotein production using A. niger.
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Affiliation(s)
- G L Wallis
- School of Biomedical Science (Biochemistry), The Medical School, Queens Medical Centre, The University of Nottingham, Nottingham, UK
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249
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Chapman TL, Heikeman AP, Bjorkman PJ. The inhibitory receptor LIR-1 uses a common binding interaction to recognize class I MHC molecules and the viral homolog UL18. Immunity 1999; 11:603-13. [PMID: 10591185 DOI: 10.1016/s1074-7613(00)80135-1] [Citation(s) in RCA: 267] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
LIR-1 is a class I MHC receptor related to natural killer inhibitory receptors (KIRs). Binding of LIR-1 or KIRs to class I molecules results in inhibitory signals. Unlike individual KIRs, LIR-1 recognizes many class I alleles and also binds UL18, a human cytomegalovirus class I MHC homolog. Here, we show that LIR-1 interacts with the relatively nonpolymorphic alpha3 domain of class I proteins and the analogous region of UL18 using its N-terminal immunoglobulin-like domain. The >1000-fold higher affinity of LIR-1 for UL18 than for class I illustrates how a viral protein competes with host proteins to subvert the host immune response. LIR-1 recognition of class I molecules resembles the CD4-class II MHC interaction more than the KIR-class I interaction, implying a functional distinction between LIR-1 and KIRs.
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Affiliation(s)
- T L Chapman
- Graduate Option in Biochemistry, Howard Hughes Medical Institute, California Institute of Technology, Pasadena 91125, USA
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250
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Cayli A, Hirschmann F, Wirth M, Hauser H, Wagner R. Cell lines with reduced UDP-N-acetylhexosamine pool in the presence of ammonium. Biotechnol Bioeng 1999; 65:192-200. [PMID: 10458740 DOI: 10.1002/(sici)1097-0290(19991020)65:2<192::aid-bit9>3.0.co;2-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The glycosylation of pharmaglycoproteins from recombinant cell lines can be affected by an uncontrolled accumulation of ammonium in the medium. Glucosamine-6-phosphate isomerase (GPI) has been proposed as the key enzyme responsible for elevating the intracellular UDP-N-acetylhexosamine pool (UDPGNAc) by accepting ammonium from the medium of cultured mammalian cells. As previously reported, the increased UDPGNAc pool then affects the N-glycan complexity in glycoproteins. To understand the entry of extracellular ammonium into the cellular metabolism, GPI has been isolated to homogeneity from BHK-21 cells and characterized. Thus, the complete pathway by which ammonium enters the cellular metabolism was elucidated. To reduce the negative effects of ammonium, GPI was inhibited using two different strategies. First, the addition of mannose to the culture media and, second, antisense RNA expression. In both cases, the cellular UDPGNAc pool was suppressed in the presence of high ammonium concentrations in the medium. However, constant suppression of the UDPGNAc pool could not be achieved by antisense RNA expression because antisense clones were apparently unstable. Further studies showed that the main reason for instability was the inducibility of GPI by its substrate ammonium. GPI was induced to a factor of two under ammonium-containing medium conditions. We propose gene knockout technology for GPI repression to obtain cell lines consisting of an UDPGNAc pool unaffected by the presence of ammonium.
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Affiliation(s)
- A Cayli
- Department of Cell Culture Technology, Gesellschaft für Biotechnologische Forschung mbH, Mascheroder Weg 1, D-38124 Braunschweig, Germany
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