Mass spectrometric rearrangement reactions have been reported for a large variety of compounds such as peptides, lipids, and carbohydrates. In the case of carbohydrates this phenomenon has been... Show moreMass spectrometric rearrangement reactions have been reported for a large variety of compounds such as peptides, lipids, and carbohydrates. In the case of carbohydrates this phenomenon has been described as internal residue loss. Resulting fragment ions may be misinterpreted as fragments arising from conventional glycosidic bond cleavages, which may result in incorrect structural assignment. Therefore, awareness of the occurrence of glycan rearrangements is important for avoiding misinterpretation of tandem mass spectra. In this review mass spectrometric rearrangements of both derivatized and underivatized (native) oligosaccharide structures are discussed. Similar phenomena have been reported for glycopeptides, labeled glycan structures and other biomolecules containing a carbohydrate part. Rearrangements in oligosaccharides and glycoconjugates have been observed with different types of mass spectrometers. Most of the observed carbohydrate rearrangement reactions appear to be linked to the presence of a proton. Hence, tandem mass spectrometric analysis of alkali adducts or deprotonated ions often prevents rearrangement reactions, while they may happen with high efficacy with protonated glycoconjugates. (C) 2011 Wiley Periodicals, Inc., Mass Spec Rev 30:664-680, 2011 Show less
Guhr, T.; Bloem, J.; Derksen, N.I.L.; Wuhrer, M.; Koenderman, A.H.L.; Aalberse, R.C.; Rispens, T. 2011
Glycans present on glycoproteins from the eggs of the parasite Schistosoma mansoni are mediators of various immune responses of the human host, including T-cell modulation and granuloma formation,... Show moreGlycans present on glycoproteins from the eggs of the parasite Schistosoma mansoni are mediators of various immune responses of the human host, including T-cell modulation and granuloma formation, and they are the target of glycan-specific antibodies. Here we have analyzed the glycosylation of kappa-5, a major glycoprotein antigen from S. mansoni eggs using a targeted approach of lectin purification followed by mass spectrometry of glycopeptides as well as released glycans. We demonstrate that kappa-5 has four fully occupied N-glycosylation sites carrying unique triantennary glycans composed of a difucosylated and xylosylated core region, and immunogenic GalNAc beta 1-4GlcNAc (LDN) termini. Furthermore, we show that the kappa-5 specific IgE antibodies in sera of S. mansoni-infected individuals are directed against the core region of the kappa-5 glycans. Whereas two previously analyzed immunomodulatory egg glycoproteins, IPSE/alpha-1 and omega-1, both express diantennary N-glycans with a difucosylated core and one or two Gal beta 1-4(Fuc alpha 1-3)GlcNAc (Lewis X) antennae, the kappa-5 glycosylation appears unique among the major soluble egg antigens of S. mansoni. The distinct structural and antigenic properties of kappa-5 glycans suggest a specific role for kappa-5 in schistosome egg immunogenicity. Molecular & Cellular Proteomics 10: 10.1074/mcp.M110.005710, 1-14, 2011. Show less
We have recently shown that IgG1 directed against antigens thought to be involved in the pathogenesis of rheumatoid arthritis harbor different glycan moieties on their Fc-tail, as compared with... Show moreWe have recently shown that IgG1 directed against antigens thought to be involved in the pathogenesis of rheumatoid arthritis harbor different glycan moieties on their Fc-tail, as compared with total sera IgG1. Given the crucial roles of Fc-linked N-glycans for the structure and biological activity of IgG, Fc-glycosylation of antibodies is receiving considerable interest. However, so far little is known about the signals and factors that could influence the composition of these carbohydrate structures on secreted IgG produced by B lymphocytes. Here we show that both "environmental" factors, such as all-trans retinoic acid (a natural metabolite of vitamin A), as well as factors stimulating the innate immune system (i.e. CpG oligodeoxynucleotide, a ligand for toll-like receptor 9) or coming from the adaptive immune system (i.e. interleukin-21, a T-cell derived cytokine) can modulate IgG1 Fc-glycosylation. These factors affect Fc-glycan profiles in different ways. CpG oligodeoxynucleotide and interleukin-21 increase Fc-linked galactosylation and reduce bisecting N-acetylglucosamine levels, whereas all-trans retinoic acid significantly decreases galactosylation and sialylation levels. Moreover, these effects appeared to be stable and specific for secreted IgG1 as no parallel changes of the corresponding glycans in the cellular glycan pool were observed. Interestingly, several other cytokines and molecules known to affect B-cell biology and antibody production did not have an impact on IgG1 Fc-coupled glycan profiles. Together, these data indicate that different stimuli received by B cells during their activation and differentiation can modulate the Fc-linked glycosylation of secreted IgG1 without affecting the general cellular glycosylation machinery. Our study, therefore, furthers our understanding of the regulation of IgG1 glycosylation at the cellular level. Molecular & Cellular Proteomics 10: 10.1074/mcp.M110.004655, 1-12, 2011. Show less
Selman, M.H.J.; Hemayatkar, M.; Deelder, A.M.; Wuhrer, M. 2011
Solid-phase extraction microtips are important devices in modern bioanalytics, as they allow miniaturized sample preparation for mass spectrometric analysis. Here we introduce the use of cotton... Show moreSolid-phase extraction microtips are important devices in modern bioanalytics, as they allow miniaturized sample preparation for mass spectrometric analysis. Here we introduce the use of cotton wool for the preparation of filter-free HILIC SPE microtips. To this end, pieces of cotton wool pads (approximately 500 mu g) were packed into 10 mu L pipet tips. The performance of the tips was evaluated for microscale purification of tryptic IgG Fe N-glycopeptides. Cotton wool HILIC SPE microtips allowed the removal of salts, most nonglycosylated peptides, and detergents such as SDS from glycoconjugate samples. MALDI-TOF-MS glycopeptide profiles were very repeatable with different tips as well as reused tips, and very similar profiles were obtained with different brands of cotton wool pads. In addition, we used cotton HILIC microtips to purify N-glycans after N-glycosidase F treatment of IgG and transferrin followed by MALDI-TOF-MS detection. In conclusion, we establish cotton wool microtips for glycan and glycopeptide purification with subsequent mass spectrometric detection. Show less
Wang, J.; Bax, M.; Balog, C.I.A.; Stavenhagen, K.; Koeleman, C.A.M.; Scherer, H.U.; ... ; Wuhrer, M. 2011
N-glycosylation of the immunoglobulin Fc moiety influences its biological activity by, for example, modulating the interaction with Fc receptors. Changes in IgG glycosylation have been found to be... Show moreN-glycosylation of the immunoglobulin Fc moiety influences its biological activity by, for example, modulating the interaction with Fc receptors. Changes in IgG glycosylation have been found to be associated with various inflammatory diseases. Here we evaluated for the first time IgG Fc N-glycosylation changes in well-defined antibody-mediated autoimmune diseases, that is, the neurological disorders Lambert-Eaton myasthenic syndrome and myasthenia gravis, with antibodies to muscle nicotinic acetylcholine receptors or muscle-specific kinase. IgGs were purified from serum or plasma by protein A affinity chromatography and digested with trypsin. Glycopeptides were purified and analyzed by MALDI-FTICR-MS. Glycoform distributions of both IgG1 and IgG2 were determined for 229 patients and 56 controls. We observed an overall age and sex dependency of IgG Fc N-glycosylation, which was in accordance with literature. All three disease groups showed lower levels of IgG2 galactosylation compared to controls. In addition, LEMS patients showed lower IgG1 galactosylation. Notably, the galactosylation differences were not paralleled by a difference in IgG sialylation. Moreover, the level of IgG core-fucosylation and bisecting N-acetylglucosamine were evaluated. The control and disease groups revealed similar levels of IgG Fc core-fucosylation. Interestingly, LEMS patients below 50 years showed elevated levels of bisecting N-acetylglucosamine on IgG1 and IgG2, demonstrating for the first time the link of changes in the level of bisecting N-acetylglucosamine with disease. Show less
Ruhaak, L.R.; Hennig, R.; Huhn, C.; Borowiak, M.; Dolhain, R.J.E.M.; Deelder, A.M.; ... ; Wuhrer, M. 2010
High throughput methods for oligosaccharide analysis are required when searching for glycan based biomarkers Next to mass spectrometry based methods which allow fast and reproducible analysis of... Show moreHigh throughput methods for oligosaccharide analysis are required when searching for glycan based biomarkers Next to mass spectrometry based methods which allow fast and reproducible analysis of such compounds further separation based techniques are needed which allow for quantitative analysis Here an optimized sample preparation method for N glycan profiling by multiplexed capillary gel electrophoresis with laser induced fluorescence detection (CGE LIF) was developed, enabling high throughput glycosylation analysis First, glycans are released enzymatically from denatured plasma glycoproteins Second, glycans are labeled with APTS using 2-picoline borane as a nontoxic and efficient reducing agent Reaction conditions are optimized for a high labeling efficiency short handling times and only limited loss of sialic acids Third samples are subjected to hydrophilic interaction chromatography (HILIC) purification at the 96 well plate format Subsequently, purified APTS labeled N glycans are analyzed by CGE LIF using a 48-capillary DNA sequencer The method was found to be robust and suitable for high-throughput glycan analysis Even though the method comprises two overnight incubations, 96 samples can be analyzed with an overall labor allocation time of 2 5 h The method was applied to serum samples from a pregnant woman, which were sampled during first second and third trimesters of pregnancy, as well as 6 weeks 3 months, and 6 months postpartum Alterations in the glycosylation patterns were observed with gestation and time after delivery Show less
The development of medical interventions for the preservation of disease-free longevity would be facilitated by markers that predict healthy aging. Altered protein N-glycosylation patterns have... Show moreThe development of medical interventions for the preservation of disease-free longevity would be facilitated by markers that predict healthy aging. Altered protein N-glycosylation patterns have been found with increasing age and several disease states. Here we investigate whether glycans derived from the total glycoprotein pool in plasma mark familial longevity and distinguish healthy from unhealthy aging. Total plasma N-glycan profiles of 2396 middle aged participants in the Leiden Longevity Study (LLS) were obtained by glycan release, labeling and subsequent HPLC analysis with fluorescence detection. After normalization and batch correction, several regression strategies were applied to evaluate associations between glycan patterns, familial longevity and healthy aging. Two N-glycan features (LC-7 and LC-8) were identified to be more abundant in plasma of the offspring of long-lived individuals as compared to controls. These results were not confounded by the altered lipid status or glucose homeostasis of the offspring. Furthermore, a decrease in levels of LC-8 was associated with the occurrence of myocardial infarction (p = 0.049, coefficient = -0.065), indicating that plasma glycosylation patterns do not only mark familial longevity, but may also reflect healthy aging. In conclusion, we describe two glycan features, of which increased levels mark familial longevity while decreased levels of one of these features mark the presence of cardiovascular disease. Show less
Wuhrer, M.; Remoortere, A. van; Balog, C.I.A.; Deelder, A.M.; Hokke, C.H. 2010
Characterization of protein-carbohydrate interactions at the molecular level is important for understanding many glycan-mediated processes. Here we present a method for the identification of glycan... Show moreCharacterization of protein-carbohydrate interactions at the molecular level is important for understanding many glycan-mediated processes. Here we present a method for the identification of glycan ligands of carbohydrate-binding proteins. The glycans released from natural sources are labeled with biotinamidocaproyl hydrazide (BACH) and subsequently fractionated by high-performance liquid chromatography. Glycan fractions are screened for binding to carbohydrate-binding proteins (CBPs) using a microtitration plate binding assay; CBPs are immobilized, BACH-glycan fractions are added, and bound BACH-glycans are detected using alkaline phosphatase-conjugated streptavidin. The glycan structures in binding fractions are studied by (tandem) mass spectrometry, exoglycosidase treatment, and rechromatography, thereby revealing the glycan motifs recognized by the CBPs. Subsequent surface plasmon resonance experiments using a reverse setup with immobilization of the BACH-glycan ligands on streptavidin-coated surfaces provide more information on glycan-CBP interactions via association and dissociation curves. The presented method is easy and fast, and the required instrumentation is available in many laboratories. The assay is very sensitive given that both the mass spectrometric analysis and the microtitration plate binding assay can be performed on femtomole amounts of BACH-glycans. This approach should be generally applicable to study and structurally identify carbohydrate ligands of anti-glycan antibodies and lectins. (C) 2010 Elsevier Inc. All rights reserved. Show less
Lonardi, E.; Balog, C.I.A.; Deelder, A.M.; Wuhrer, M. 2010
Glycan microarrays are emerging as increasingly used screening tools with a high potential for unraveling protein-carbohydrate interactions: probing hundreds or even thousands of glycans in... Show moreGlycan microarrays are emerging as increasingly used screening tools with a high potential for unraveling protein-carbohydrate interactions: probing hundreds or even thousands of glycans in parallel, they provide the researcher with a vast amount of data in a short time-frame, while using relatively small amounts of analytes. Natural glycan microarrays focus on the glycans' repertoire of natural sources, including both well-defined structures as well as still-unknown ones. This article compares different natural glycan microarray strategies. Glycan probes may comprise oligosaccharides from glycoproteins as well as glycolipids and polysaccharides. Oligosaccharides may be purified from scarce biological samples that are of particular relevance for the carbohydrate-binding protein to be studied. We give an overview of strategies for glycan isolation, derivatization, fractionation, immobilization and structural characterization. Detection methods such as fluorescence analysis and surface plasmon resonance are summarized. The importance of glycan density and multivalency is discussed. Furthermore, some applications of natural glycan microarrays for studying lectin and antibody binding are presented. Show less
Eggink, D.; Melchers, M.; Wuhrer, M.; Montfort, T. van; Dey, A.K.; Naaijkens, B.A.; ... ; Sanders, R.W. 2010
Background: Markers for longevity that reflect the health condition and predict healthy aging are extremely scarce. Such markers are, however, valuable in aging research. It has been shown... Show moreBackground: Markers for longevity that reflect the health condition and predict healthy aging are extremely scarce. Such markers are, however, valuable in aging research. It has been shown previously that the N-glycosylation pattern of human immunoglobulin G (IgG) is age-dependent. Here we investigate whether N-linked glycans reflect early features of human longevity. Methodology/Principal Findings: The Leiden Longevity Study (LLS) consists of nonagenarian sibling pairs, their offspring, and partners of the offspring serving as control. IgG subclass specific glycosylation patterns were obtained from 1967 participants in the LLS by MALDI-TOF-MS analysis of tryptic IgG Fc glycopeptides. Several regression strategies were applied to evaluate the association of IgG glycosylation with age, sex, and longevity. The degree of galactosylation of IgG decreased with increasing age. For the galactosylated glycoforms the incidence of bisecting GlcNAc increased as a function of age. Sex-related differences were observed at ages below 60 years. Compared to males, younger females had higher galactosylation, which decreased stronger with increasing age, resulting in similar galactosylation for both sexes from 60 onwards. In younger participants (<60 years of age), but not in the older age group (>60 years), decreased levels of non-galactosylated glycoforms containing a bisecting GlcNAc reflected early features of longevity. Conclusions/Significance: We here describe IgG glycoforms associated with calendar age at all ages and the propensity for longevity before middle age. As modulation of IgG effector functions has been described for various IgG glycosylation features, a modulatory effect may be expected for the longevity marker described in this study. Show less
Most methods for the analysis of oligosaccharides from biological sources require a glycan derivatization step: glycans may be derivatized to introduce a chromophore or fluorophore, facilitating... Show moreMost methods for the analysis of oligosaccharides from biological sources require a glycan derivatization step: glycans may be derivatized to introduce a chromophore or fluorophore, facilitating detection after chromatographic or electrophoretic separation. Derivatization can also be applied to link charged or hydrophobic groups at the reducing end to enhance glycan separation and mass-spectrometric detection. Moreover, derivatization steps such as permethylation aim at stabilizing sialic acid residues, enhancing mass-spectrometric sensitivity, and supporting detailed structural characterization by ( tandem) mass spectrometry. Finally, many glycan labels serve as a linker for oligosaccharide attachment to surfaces or carrier proteins, thereby allowing interaction studies with carbohydrate-binding proteins. In this review, various aspects of glycan labeling, separation, and detection strategies are discussed. Show less
Bruggink, C.; Poorthuis, B.J.H.M.; Piraud, M.; Froissart, R.; Deelder, A.M.; Wuhrer, M. 2010
Urine, amniotic fluid and ascitic fluid samples of galactosialidosis patients were analyzed and structurally characterized for free oligosaccharides using capillary high-performance anion-exchange... Show moreUrine, amniotic fluid and ascitic fluid samples of galactosialidosis patients were analyzed and structurally characterized for free oligosaccharides using capillary high-performance anion-exchange chromatography with pulsed amperometric detection and online mass spectrometry. In addition to the expected endo-beta-N-acetylglucosaminidase-cleaved products of complex-type sialylated N-glycans, O-sulfated oligosaccharide moieties were detected. Moreover, novel carbohydrate moieties with reducing-end hexose residues were detected. On the basis of structural features such as a hexose-N-acetylhexosamine-hexose-hexose consensus sequence and di-sialic acid units, these oligosaccharides are thought to represent, at least in part, glycan moieties of glycosphingolipids. In addition, C-1-oxidized, aldohexonic acid-containing versions of most of these oligosaccharides were observed. These observations suggest an alternative catabolism of glycosphingolipids in galactosialidosis patients: oligosaccharide moieties from glycosphingolipids would be released by a hitherto unknown ceramide glycanase activity. The results show the potential and versatility of the analytical approach for structural characterization of oligosaccharides in various body fluids. Show less
Scherer, H.U.; Woude, D. van der; Ioan-Facsinay, A.; Bannoudi, H. el; Trouw, L.A.; Wang, J.; ... ; Toes, R.E.M. 2010
Objective. Anti-citrullinated protein antibodies ( ACPA) exhibit unique specificity for rheumatoid arthritis. However, it is incompletely understood whether and how ACPA contribute to disease... Show moreObjective. Anti-citrullinated protein antibodies ( ACPA) exhibit unique specificity for rheumatoid arthritis. However, it is incompletely understood whether and how ACPA contribute to disease pathogenesis. The Fc part of human IgG carries 2 N-linked glycan moieties that are crucial for the structural stability of the antibody and that modulate both its binding affinity to Fc gamma receptors and its ability to activate complement. We undertook this study to analyze Fc glycosylation of IgG1 ACPA in serum and synovial fluid ( SF) in order to further characterize the immune response to citrullinated antigens. Methods. ACPA were isolated by affinity purification using cyclic citrullinated peptides as antigen. IgG1 Fc glycosylation was analyzed by mass spectrometry. ACPA IgG1 glycan profiles were compared with glycan profiles of total serum IgG1 obtained from 85 well-characterized patients. Glycan profiles of paired SF and serum samples were available from 11 additional patients. Results. Compared with the pool of serum IgG1, ACPA IgG1 lacked terminal sialic acid residues. In SF, ACPA were highly agalactosylated and lacked sialic acid residues, a feature that was not detected for total SF IgG1. Moreover, differential ACPA glycan profiles were detected in rheumatoid factor (RF)-positive and RF-negative patients. Conclusion. ACPA IgG1 exhibit a specific Fc-linked glycan profile that is distinct from that of total serum IgG1. Moreover, Fc glycosylation of ACPA differs markedly between SF and serum. Since Fc glycosylation directly affects the recruitment of Fc-mediated effector mechanisms, these data could further our understanding of the contribution of ACPA to disease pathogenesis. Show less
Analysis of N-glycans is often performed by LC coupled to fluorescence detection. The N-glycans are usually labeled by reductive amination with a fluorophore containing a primary amine to allow... Show moreAnalysis of N-glycans is often performed by LC coupled to fluorescence detection. The N-glycans are usually labeled by reductive amination with a fluorophore containing a primary amine to allow fluorescence detection. Moreover, many of the commonly applied labels also allow improved mass spectrometric detection of oligosaccharides. For reductive amination, the amine group of the label reacts with the reducing-end aldehyde group of the oligosaccharide to form a Schiff base, which is reduced to a secondary amine. Here, we propose the use of 2-picoline-borane as the reducing agent, as a non-toxic alternative to the extensively used, but toxic sodium cyanoborohydride. Using dextran oligosaccharides and plasma N-glycans, we demonstrate similar labeling efficacies for 2-picoline-borane and sodium cyanoborohydride. Therefore, 2-picoline-borane is a non-toxic alternative to sodium cyanoborohydride for the labeling of oligosaccharides. Show less
