16 results found
Calle B, Bineva-Todd G, Marchesi A, et al., 2021, Benefits of chemical sugar modifications introduced by click chemistry for glycoproteomic analyses, Journal of the American Society for Mass Spectrometry, Vol: 32, Pages: 2366-2375, ISSN: 1044-0305
Mucin-type O-glycosylation is among the most complex post-translational modifications. Despite mediating many physiological processes, O-glycosylation remains understudied compared to other modifications, simply because the right analytical tools are lacking. In particular, analysis of intact O-glycopeptides by mass spectrometry is challenging for several reasons; O-glycosylation lacks a consensus motif, glycopeptides have low charge density which impairs ETD fragmentation, and the glycan structures modifying the peptides are unpredictable. Recently, we introduced chemically modified monosaccharide analogs that allowed selective tracking and characterization of mucin-type O-glycans after bioorthogonal derivatization with biotin-based enrichment handles. In doing so, we realized that the chemical modifications used in these studies have additional benefits that allow for improved analysis by tandem mass spectrometry. In this work, we built on this discovery by generating a series of new GalNAc analog glycopeptides. We characterized the mass spectrometric signatures of these modified glycopeptides and their MOE signature residues left by bioorthogonal enrichment reagents. Our data indicate that chemical methods for glycopeptide profiling offer opportunities to optimize attributes such as increased charge state, higher charge density, and predictable fragmentation behavior.
Cioce A, Bineva-Todd G, Agbay A, et al., 2021, Optimization of metabolic oligosaccharide engineering with Ac4GalNAlk and Ac4GlcNAlk by an engineered pyrophosphorylase, ACS Chemical Biology, ISSN: 1554-8929
Metabolic oligosaccharide engineering (MOE) has fundamentally contributed to our understanding of protein glycosylation. Efficient MOE reagents are activated into nucleotide-sugars by cellular biosynthetic machineries, introduced into glycoproteins and traceable by bioorthogonal chemistry. Despite their widespread use, the metabolic fate of many MOE reagents is only beginning to be mapped. While metabolic interconnectivity can affect probe specificity, poor uptake by biosynthetic salvage pathways may impact probe sensitivity and trigger side reactions. Here, we use metabolic engineering to turn the weak alkyne-tagged MOE reagents Ac4GalNAlk and Ac4GlcNAlk into efficient chemical tools to probe protein glycosylation. We find that bypassing a metabolic bottleneck with an engineered version of the pyrophosphorylase AGX1 boosts nucleotide-sugar biosynthesis and increases bioorthogonal cell surface labeling by up to two orders of magnitude. A comparison with known azide-tagged MOE reagents reveals major differences in glycoprotein labeling, substantially expanding the toolbox of chemical glycobiology.
Cioce A, Malaker SA, Schumann B, 2021, Generating orthogonal glycosyltransferase and nucleotide sugar pairs as next-generation glycobiology tools., Curr Opin Chem Biol, Vol: 60, Pages: 66-78
Protein glycosylation fundamentally impacts biological processes. Nontemplated biosynthesis introduces unparalleled complexity into glycans that needs tools to understand their roles in physiology. The era of quantitative biology is a great opportunity to unravel these roles, especially by mass spectrometry glycoproteomics. However, with high sensitivity come stringent requirements on tool specificity. Bioorthogonal metabolic labeling reagents have been fundamental to studying the cell surface glycoproteome but typically enter a range of different glycans and are thus of limited specificity. Here, we discuss the generation of metabolic 'precision tools' to study particular subtypes of the glycome. A chemical biology tactic termed bump-and-hole engineering generates mutant glycosyltransferases that specifically accommodate bioorthogonal monosaccharides as an enabling technique of glycobiology. We review the groundbreaking discoveries that have led to applying the tactic in the living cell and the implications in the context of current developments in mass spectrometry glycoproteomics.
Debets MF, Tastan OY, Wisnovsky SP, et al., 2020, Metabolic precision labeling enables selective probing of O-linked N-acetylgalactosamine glycosylation, Proceedings of the National Academy of Sciences of USA, Vol: 117, Pages: 25293-25301, ISSN: 0027-8424
Protein glycosylation events that happen early in the secretory pathway are often dysregulated during tumorigenesis. These events can be probed, in principle, by monosaccharides with bioorthogonal tags that would ideally be specific for distinct glycan subtypes. However, metabolic interconversion into other monosaccharides drastically reduces such specificity in the living cell. Here, we use a structure-based design process to develop the monosaccharide probe GalNAzMe that is specific for cancer-relevant Ser/Thr-N-acetylgalactosamine (O-GalNAc) glycosylation. By virtue of a branched N-acylamide side chain, GalNAzMe is not interconverted by epimerization to the corresponding N-acetylglucosamine analog by the epimerase GALE like conventional GalNAc-based probes. GalNAzMe enters O-GalNAc glycosylation but does not enter other major cell surface glycan types including Asn(N)-linked glycans. We transfect cells with the engineered pyrophosphorylase mut-AGX1 to biosynthesize the nucleotide-sugar donor UDP-GalNAzMe from a sugar-1-phosphate precursor. Tagged with a bioorthogonal azide group, GalNAzMe serves as an O-glycan specific reporter in superresolution microscopy, chemical glycoproteomics, a genome-wide CRISPR knock-out (KO) screen, and imaging of intestinal organoids. Additional ectopic expression of an engineered glycosyltransferase, BH-GalNAc-T2, boosts labeling in a programmable fashion by increasing incorporation of GalNAzMe into the cell surface glycoproteome. Alleviating the need for GALE-KO cells in metabolic labeling experiments, GalNAzMe is a precision tool that allows a detailed view into the biology of a major type of cancer-relevant protein glycosylation.
Zol-Hanlon MI, Schumann B, 2020, Open questions in chemical glycobiology, Communications Chemistry, Vol: 3, Pages: 1-5, ISSN: 2399-3669
Schumann B, Malaker S, Wisnovsky S, et al., 2020, Bump-and-hole engineering identifies specific substrates of glycosyltransferases in living cells, Molecular Cell, Vol: 78, Pages: 824-834.e15, ISSN: 1097-2765
Studying posttranslational modifications classically relies on experimental strategies that oversimplify the complex biosynthetic machineries of living cells. Protein glycosylation contributes to essential biological processes, but correlating glycan structure, underlying protein, and disease-relevant biosynthetic regulation is currently elusive. Here, we engineer living cells to tag glycans with editable chemical functionalities while providing information on biosynthesis, physiological context, and glycan fine structure. We introduce a non-natural substrate biosynthetic pathway and use engineered glycosyltransferases to incorporate chemically tagged sugars into the cell surface glycome of the living cell. We apply the strategy to a particularly redundant yet disease-relevant human glycosyltransferase family, the polypeptide N-acetylgalactosaminyl transferases. This approach bestows a gain-of-chemical-functionality modification on cells, where the products of individual glycosyltransferases can be selectively characterized or manipulated to understand glycan contribution to major physiological processes.
Choi J, Wagner LJS, Timmermans SBPE, et al., 2019, Engineering Orthogonal Polypeptide GalNAc-Transferase and UDP-Sugar Pairs, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 141, Pages: 13442-13453, ISSN: 0002-7863
Kaplonek P, Khan N, Reppe K, et al., 2018, Improving vaccines against Streptococcus pneumoniae using synthetic glycans, Proceedings of the National Academy of Sciences, Vol: 115, Pages: 13353-13358, ISSN: 0027-8424
<jats:p><jats:italic>Streptococcus pneumoniae</jats:italic> remains a deadly disease in small children and the elderly even though conjugate and polysaccharide vaccines based on isolated capsular polysaccharides (CPS) are successful. The most common serotypes that cause infection are used in vaccines around the world, but differences in geographic and demographic serotype distribution compromises protection by leading vaccines. The medicinal chemistry approach to glycoconjugate vaccine development has helped to improve the stability and immunogenicity of synthetic vaccine candidates for several serotypes leading to the induction of higher levels of specific protective antibodies. Here, we show that marketed CPS-based glycoconjugate vaccines can be improved by adding synthetic glycoconjugates representing serotypes that are not covered by existing vaccines. Combination (coformulation) of synthetic glycoconjugates with the licensed vaccines Prevnar13 (13-valent) and Synflorix (10-valent) yields improved 15- and 13-valent conjugate vaccines, respectively, in rabbits. A pentavalent semisynthetic glycoconjugate vaccine containing five serotype antigens (sPCV5) elicits antibodies with strong in vitro opsonophagocytic activity. This study illustrates that synthetic oligosaccharides can be used in coformulation with both isolated polysaccharide glycoconjugates to expand protection from existing vaccines and each other to produce precisely defined multivalent conjugated vaccines.</jats:p>
Schumann B, Reppe K, Kaplonek P, et al., 2018, Development of an efficacious, semisynthetic glycoconjugate vaccine candidate against Streptococcus pneumoniae serotype 1, ACS Central Science, Vol: 4, Pages: 357-361, ISSN: 2374-7943
Infections with Streptococcus pneumoniae are a major health burden. Glycoconjugate vaccines based on capsular polysaccharides (CPSs) successfully protect from infection, but not all pneumococcal serotypes are covered with equal potency. Marketed glycoconjugate vaccines induce low levels of functional antibodies against the highly invasive serotype 1 (ST1), presumably due to the obscuring of protective epitopes during chemical activation and conjugation to carrier proteins. Synthetic oligosaccharide antigens can be designed to carry linkers for site-selective protein conjugation while keeping protective epitopes intact. Here, we developed an efficacious semisynthetic ST1 glycoconjugate vaccine candidate. A panel of synthetic oligosaccharides served to reveal a critical role of the rare aminosugar, 2-acetamido-4-amino-2,4,6-trideoxy-d-galactose (d-AAT), for ST1 immune recognition. A monovalent ST1 trisaccharide carrying d-AAT at the nonreducing end induced a strong antibacterial immune response in rabbits and outperformed the ST1 component of the multivalent blockbuster vaccine Prevenar 13, paving the way for a more efficacious vaccine.
Qin C, Schumann B, Zou X, et al., 2018, Total Synthesis of a Densely Functionalized Plesiomonas shigelloides Serotype 51 Aminoglycoside Trisaccharide Antigen., J Am Chem Soc, Vol: 140, Pages: 3120-3127
Plesiomonas shigelloides, a pathogen responsible for frequent outbreaks of severe travelers' diarrhea, causes grave extraintestinal infections. Sepsis and meningitis due to P. shigelloides are associated with a high mortality rate as antibiotic resistance increases and vaccines are not available. Carbohydrate antigens expressed by pathogens are often structurally unique and are targets for developing vaccines and diagnostics. Here, we report a total synthesis of the highly functionalized trisaccharide repeating unit 2 from P. shigelloides serotype 51 from three monosaccharides. A judicious choice of building blocks and reaction conditions allowed for the four amino groups adorning the sugar rings to be installed with two N-acetyl (Ac) groups, rare acetamidino (Am), and d-3-hydroxybutyryl (Hb) groups. The strategy for the differentiation of amino groups in trisaccharide 2 will serve well for the syntheses of other complex glycans.
Schumann B, Hahm HS, Parameswarappa SG, et al., 2017, A semisynthetic Streptococcus pneumoniae serotype 8 glycoconjugate vaccine, Science Translational Medicine, Vol: 9, Pages: 1-12, ISSN: 1946-6234
Glycoconjugate vaccines based on capsular polysaccharides (CPSs) of pathogenic bacteria such as Streptococcus pneumoniae successfully protect from disease but suffer from incomplete coverage, are troublesome to manufacture from isolated CPSs, and lack efficacy against certain serotypes. Defined, synthetic oligosaccharides are an attractive alternative to isolated CPSs but require the identification of immunogenic and protective oligosaccharide antigens. We describe a medicinal chemistry strategy based on a combination of automated glycan assembly (AGA), glycan microarray–based monoclonal antibody (mAb) reverse engineering, and immunological evaluation in vivo to uncover a protective glycan epitope (glycotope) for S. pneumoniae serotype 8 (ST8). All four tetrasaccharide frameshifts of ST8 CPS were prepared by AGA and used in glycan microarray experiments to identify the glycotopes recognized by antibodies against ST8. One tetrasaccharide frameshift that was preferentially recognized by a protective, CPS-directed mAb was conjugated to the carrier protein CRM197. Immunization of mice with this semisynthetic glycoconjugate followed by generation and characterization of a protective mAb identified protective and nonprotective glycotopes. Immunization of rabbits with semisynthetic ST8 glycoconjugates containing protective glycotopes induced an antibacterial immune response. Coformulation of ST8 glycoconjugates with the marketed 13-valent glycoconjugate vaccine Prevnar 13 yielded a potent 14-valent S. pneumoniae vaccine. Our strategy presents a facile approach to develop efficient semisynthetic glycoconjugate vaccines.
Schumann B, Parameswarappa SG, Lisboa MP, et al., 2016, Nucleophile-Directed Stereocontrol Over Glycosylations Using Geminal-Difluorinated Nucleophiles., Angew Chem Int Ed Engl, Vol: 55, Pages: 14431-14434
The glycosylation reaction is the key transformation in oligosaccharide synthesis, but it is still difficult to control in many cases. Stereocontrol during cis-glycosidic linkage formation relies almost exclusively on tuning the glycosylating agent or the reaction conditions. Herein, we use nucleophile-directed stereocontrol to manipulate the stereoselectivity of glycosylation reactions. Placing two fluorine atoms in close proximity to the hydroxy group of an aliphatic amino alcohol lowers the oxygen nucleophilicity and reverses the stereoselectivity of glycosylations to preferentially form the desired cis-glycosides with a broad set of substrates. This concept was applied to the design of a cis-selective linker for automated glycan assembly. Fluorination of an amino alcohol linker does not impair glycan immobilization and lectin binding as illustrated by glycan microarray experiments. These fluorinated linkers enable the facile generation of α-terminating synthetic glycans for the formation of glycoconjugates.
Anish C, Schumann B, Pereira CL, et al., 2014, Chemical Biology Approaches to Designing Defined Carbohydrate Vaccines, CHEMISTRY & BIOLOGY, Vol: 21, Pages: 38-50, ISSN: 1074-5521
Schumann B, Pragani R, Anish C, et al., 2014, Synthesis of conjugation-ready zwitterionic oligosaccharides by chemoselective thioglycoside activation, CHEMICAL SCIENCE, Vol: 5, Pages: 1992-2002, ISSN: 2041-6520
Dimmer KS, Papic D, Schumann B, et al., 2012, A crucial role for Mim2 in the biogenesis of mitochondrial outer membrane proteins, JOURNAL OF CELL SCIENCE, Vol: 125, Pages: 3464-3473, ISSN: 0021-9533
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