The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Cornelis H Hokke - One of the best experts on this subject based on the ideXlab platform.
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micro array assisted analysis of anti schistosome glycan antibodies elicited by protective vaccination with irradiated cercariae
The Journal of Infectious Diseases, 2019Co-Authors: Y Michelle Y Yang, Angela Van Diepen, Alan R Wilson, Steffan R L Thomas, Thomas M Kariuki, Cornelis H HokkeAbstract:Baboons vaccinated with radiation-attenuated cercariae develop high levels of protection against schistosome infection, correlating to high antibody titres towards schistosome antigens with unknown molecular identity. Using a microarray consisting of glycans isolated from different life-stages of schistosomes, we studied the anti-glycan immunoglobulin (Ig) G and IgM responses in vaccinated and challenged baboons over a time course of 25 weeks. Anti-glycan IgM responses developed early after vaccination, but did not rise in response to later vaccinations. In contrast, anti-glycan IgG developed more slowly, but was boosted by all five subsequent vaccinations. High IgM and IgG levels against O-Glycans and glycosphingolipid glycans of cercariae were observed. At the time of challenge, while most antibody levels decreased in the absence of vaccination, IgG towards a subset of glycans containing multiple-fucosylated motifs remained high until 6 weeks post-challenge during challenge parasite elimination, suggesting a possible role of this IgG in protection.
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novel o linked methylated glycan antigens decorate secreted immunodominant glycoproteins from the intestinal nematode heligmosomoides polygyrus
International Journal for Parasitology, 2016Co-Authors: James P Hewitson, Linh D Nguyen, Angela Van Diepen, Cornelis H Smit, Carolien A M Koeleman, Henry J Mcsorley, Janice Murray, Rick M Maizels, Cornelis H HokkeAbstract:Glycan molecules from helminth parasites have been associated with diverse biological functions ranging from interactions with neighbouring host cell populations to down-modulation of specific host immunity. Glycoproteins secreted by the intestinal nematode Heligmosomoides polygyrus are of particular interest as the excretory–secretory products (termed HES) of this parasite contain both heat-labile and heat-stable components with immunomodulatory effects. We used MALDI-TOF-MS and LC–MS/MS to analyse the repertoire of N- and O-linked glycans released from Heligmosomoides polygyrus excretory–secretory products by PNGase A and F, β-elimination and hydrazinolysis revealing a broad range of structures including novel methylhexose- and methylfucose-containing glycans. Monoclonal antibodies to two immunodominant glycans of H. polygyrus, previously designated Glycans A and B, were found to react by glycan array analysis to a methyl-hexose-rich fraction and to a sulphated LacDiNAc (LDN; GalNAcβ1–4GlcNAc) structure, respectively. We also analysed the glycan repertoire of a major glycoprotein in Heligmosomoides polygyrus excretory–secretory products, VAL-2, which contains many glycan structures present in Heligmosomoides polygyrus excretory–secretory products including Glycan A. However, it was found that this set of glycans is not responsible for the heat-stable immunomodulatory properties of Heligmosomoides polygyrus excretory–secretory products, as revealed by the inability of VAL-2 to inhibit allergic lung inflammation. Taken together, these studies reveal that H. polygyrus secretes a diverse range of antigenic glycoconjugates, and provides a framework to explore the biological and immunomodulatory roles they may play within the mammalian host.
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differential anti glycan antibody responses in schistosoma mansoni infected children and adults studied by shotgun glycan microarray
PLOS Neglected Tropical Diseases, 2012Co-Authors: Angela Van Diepen, Cornelis H Smit, Loes Van Egmond, Narcis B Kabatereine, Angela Pinot De Moira, David W Dunne, Cornelis H HokkeAbstract:Background Schistosomiasis (bilharzia) is a chronic and potentially deadly parasitic disease that affects millions of people in (sub)tropical areas. An important partial immunity to Schistosoma infections does develop in disease endemic areas, but this takes many years of exposure and maturation of the immune system. Therefore, children are far more susceptible to re-infection after treatment than older children and adults. This age-dependent immunity or susceptibility to re-infection has been shown to be associated with specific antibody and T cell responses. Many antibodies generated during Schistosoma infection are directed against the numerous glycans expressed by Schistosoma. The nature of glycan epitopes recognized by antibodies in natural schistosomiasis infection serum is largely unknown. Methodology/Principal Findings The binding of serum antibodies to glycans can be analyzed efficiently and quantitatively using glycan microarray approaches. Very small amounts of a large number of glycans are presented on a solid surface allowing binding properties of various glycan binding proteins to be tested. We have generated a so-called shotgun glycan microarray containing natural N-glycan and lipid-glycan fractions derived from 4 different life stages of S. mansoni and applied this array to the analysis of IgG and IgM antibodies in sera from children and adults living in an endemic area. This resulted in the identification of differential glycan recognition profiles characteristic for the two different age groups, possibly reflecting differences in age or differences in length of exposure or infection. Conclusions/Significance Using the shotgun glycan microarray approach to study antibody response profiles against schistosome-derived glycan elements, we have defined groups of infected individuals as well as glycan element clusters to which antibody responses are directed in S. mansoni infections. These findings are significant for further exploration of Schistosoma glycan antigens in relation to immunity.
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serum antibody screening by surface plasmon resonance using a natural glycan microarray
Glycoconjugate Journal, 2008Co-Authors: Arjen R De Boer, Andre M Deelder, Cornelis H Hokke, Manfred WuhrerAbstract:A surface plasmon resonance (SPR) based natural glycan microarray was developed for screening of interactions between glycans and carbohydrate-binding proteins (CBPs). The microarray contained 144 glycan samples and allowed the real-time and simultaneous screening for recognition by CBPs without the need of fluorescent labeling. Glycans were released from their natural source and coupled by reductive amination with the fluorescent labels 2-aminobenzamide (2AB) or anthranilic acid (AA) followed by high-performance liquid chromatography (HPLC) fractionation making use of the fluorescent tag. The released and labeled glycans, in addition to fluorescently labeled synthetic glycans and (neo)glycoproteins, were printed on an epoxide-activated chip at fmol amounts. This resulted in covalent immobilization, with the epoxide groups forming covalent bonds to the secondary amine groups present on the fluorescent glycoconjugates. The generated SPR glycan array presented a subset of the glycan repertoire of the human parasite Schistosoma mansoni. In order to demonstrate the usefulness of the array in the simultaneous detection of glycan-specific serum antibodies, the anti-glycan antibody profiles from sera of S. mansoni-infected individuals as well as from non-endemic uninfected controls were recorded. The SPR screening was sensitive for differences between infection sera and control sera, and revealed antibody titers and antibody classes (IgG or IgM). All SPR analyses were performed with a single SPR array chip, which required regeneration and blocking of the chip before the application of a serum sample. Our results indicate that SPR-based arrays constructed from glycans of natural or synthetic origin, pure or as mixture, can be used for determining serum antibody profiles as possible markers for the infection status of an individual.
Manfred Wuhrer - One of the best experts on this subject based on the ideXlab platform.
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mass spectrometric o glycan analysis after combined o glycan release by beta elimination and 1 phenyl 3 methyl 5 pyrazolone labeling
Biochimica et Biophysica Acta, 2012Co-Authors: Gerhild Zauner, Andre M Deelder, Carolien A M Koeleman, Manfred WuhrerAbstract:Abstract Background Analysis of protein glycosylation is an important first step towards establishing the functions of glycans in health and disease. In contrast to N-glycans which are generally enzymatically released for analysis, there is no corresponding enzyme for O-Glycan liberation. Therefore, O-Glycans are generally released by chemical methods involving tedious procedures. Methods Here, a straightforward method for the combined release and labeling of O-linked glycans from glycoproteins is described. Dimethylamine serves as the releasing agent, and 1-phenyl-3-methyl-5-pyrazolone (PMP) is employed for a prompt reaction with the reducing end of the freshly released O-Glycan structures via an aldol condensation followed by a Michael-type addition resulting in a 2:1 stoichiometry of PMP per glycan. Samples are analyzed by nanoLC coupled to mass spectrometry. Results Mucin from bovine submaxillary gland was used as a model protein to evaluate and optimize the approach that was further applied to bile salt stimulated lipase (BSSL) isolated from human milk. Next to previously reported O-Glycan structures two additional oligosaccharides could be detected for BSSL. General Significance In conclusion, the facile protocol established is suitable for the analysis of complex O-linked oligosaccharides from various biological samples. This article is part of a Special Issue entitled Glycoproteomics.
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serum antibody screening by surface plasmon resonance using a natural glycan microarray
Glycoconjugate Journal, 2008Co-Authors: Arjen R De Boer, Andre M Deelder, Cornelis H Hokke, Manfred WuhrerAbstract:A surface plasmon resonance (SPR) based natural glycan microarray was developed for screening of interactions between glycans and carbohydrate-binding proteins (CBPs). The microarray contained 144 glycan samples and allowed the real-time and simultaneous screening for recognition by CBPs without the need of fluorescent labeling. Glycans were released from their natural source and coupled by reductive amination with the fluorescent labels 2-aminobenzamide (2AB) or anthranilic acid (AA) followed by high-performance liquid chromatography (HPLC) fractionation making use of the fluorescent tag. The released and labeled glycans, in addition to fluorescently labeled synthetic glycans and (neo)glycoproteins, were printed on an epoxide-activated chip at fmol amounts. This resulted in covalent immobilization, with the epoxide groups forming covalent bonds to the secondary amine groups present on the fluorescent glycoconjugates. The generated SPR glycan array presented a subset of the glycan repertoire of the human parasite Schistosoma mansoni. In order to demonstrate the usefulness of the array in the simultaneous detection of glycan-specific serum antibodies, the anti-glycan antibody profiles from sera of S. mansoni-infected individuals as well as from non-endemic uninfected controls were recorded. The SPR screening was sensitive for differences between infection sera and control sera, and revealed antibody titers and antibody classes (IgG or IgM). All SPR analyses were performed with a single SPR array chip, which required regeneration and blocking of the chip before the application of a serum sample. Our results indicate that SPR-based arrays constructed from glycans of natural or synthetic origin, pure or as mixture, can be used for determining serum antibody profiles as possible markers for the infection status of an individual.
Carolien A M Koeleman - One of the best experts on this subject based on the ideXlab platform.
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novel o linked methylated glycan antigens decorate secreted immunodominant glycoproteins from the intestinal nematode heligmosomoides polygyrus
International Journal for Parasitology, 2016Co-Authors: James P Hewitson, Linh D Nguyen, Angela Van Diepen, Cornelis H Smit, Carolien A M Koeleman, Henry J Mcsorley, Janice Murray, Rick M Maizels, Cornelis H HokkeAbstract:Glycan molecules from helminth parasites have been associated with diverse biological functions ranging from interactions with neighbouring host cell populations to down-modulation of specific host immunity. Glycoproteins secreted by the intestinal nematode Heligmosomoides polygyrus are of particular interest as the excretory–secretory products (termed HES) of this parasite contain both heat-labile and heat-stable components with immunomodulatory effects. We used MALDI-TOF-MS and LC–MS/MS to analyse the repertoire of N- and O-linked glycans released from Heligmosomoides polygyrus excretory–secretory products by PNGase A and F, β-elimination and hydrazinolysis revealing a broad range of structures including novel methylhexose- and methylfucose-containing glycans. Monoclonal antibodies to two immunodominant glycans of H. polygyrus, previously designated Glycans A and B, were found to react by glycan array analysis to a methyl-hexose-rich fraction and to a sulphated LacDiNAc (LDN; GalNAcβ1–4GlcNAc) structure, respectively. We also analysed the glycan repertoire of a major glycoprotein in Heligmosomoides polygyrus excretory–secretory products, VAL-2, which contains many glycan structures present in Heligmosomoides polygyrus excretory–secretory products including Glycan A. However, it was found that this set of glycans is not responsible for the heat-stable immunomodulatory properties of Heligmosomoides polygyrus excretory–secretory products, as revealed by the inability of VAL-2 to inhibit allergic lung inflammation. Taken together, these studies reveal that H. polygyrus secretes a diverse range of antigenic glycoconjugates, and provides a framework to explore the biological and immunomodulatory roles they may play within the mammalian host.
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n glycosylation profiling of colorectal cancer cell lines reveals association of fucosylation with differentiation and caudal type homebox 1 cdx1 villin mrna expression
Molecular & Cellular Proteomics, 2016Co-Authors: Stephanie Holst, Andre M Deelder, Carolien A M Koeleman, Anna J M Deuss, Gabi W Van Pelt, Sandra J Van Vliet, Juan J Garciavallejo, Wilma E Mesker, Rob A E M Tollenaar, Yoann RomboutsAbstract:Various cancers such as colorectal cancer (CRC) are associated with alterations in protein glycosylation. CRC cell lines are frequently used to study these (glyco)biological changes and their mechanisms. However, differences between CRC cell lines with regard to their glycosylation have hitherto been largely neglected. Here, we comprehensively characterized the N-glycan profiles of 25 different CRC cell lines, derived from primary tumors and metastatic sites, in order to investigate their potential as glycobiological tumor model systems and to reveal glycans associated with cell line phenotypes. We applied an optimized, high-throughput membrane-based enzymatic glycan release for small sample amounts. Released glycans were derivatized to stabilize and differentiate between α2,3- and α2,6-linked N-acetylneuraminic acids, followed by N-glycosylation analysis by MALDI-TOF(/TOF)-MS. Our results showed pronounced differences between the N-glycosylation patterns of CRC cell lines. CRC cell line profiles differed from tissue-derived N-glycan profiles with regard to their high-mannose N-glycan content but showed a large overlap for complex type N-glycans, supporting their use as a glycobiological cancer model system. Importantly, we could show that the high-mannose N-glycans did not only occur as intracellular precursors but were also present at the cell surface. The obtained CRC cell line N-glycan features were not clearly correlated with mRNA expression levels of glycosyltransferases, demonstrating the usefulness of performing the structural analysis of glycans. Finally, correlation of CRC cell line glycosylation features with cancer cell markers and phenotypes revealed an association between highly fucosylated glycans and CDX1 and/or villin mRNA expression that both correlate with cell differentiation. Together, our findings provide new insights into CRC-associated glycan changes and setting the basis for more in-depth experiments on glycan function and regulation.
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mass spectrometric o glycan analysis after combined o glycan release by beta elimination and 1 phenyl 3 methyl 5 pyrazolone labeling
Biochimica et Biophysica Acta, 2012Co-Authors: Gerhild Zauner, Andre M Deelder, Carolien A M Koeleman, Manfred WuhrerAbstract:Abstract Background Analysis of protein glycosylation is an important first step towards establishing the functions of glycans in health and disease. In contrast to N-glycans which are generally enzymatically released for analysis, there is no corresponding enzyme for O-Glycan liberation. Therefore, O-Glycans are generally released by chemical methods involving tedious procedures. Methods Here, a straightforward method for the combined release and labeling of O-linked glycans from glycoproteins is described. Dimethylamine serves as the releasing agent, and 1-phenyl-3-methyl-5-pyrazolone (PMP) is employed for a prompt reaction with the reducing end of the freshly released O-Glycan structures via an aldol condensation followed by a Michael-type addition resulting in a 2:1 stoichiometry of PMP per glycan. Samples are analyzed by nanoLC coupled to mass spectrometry. Results Mucin from bovine submaxillary gland was used as a model protein to evaluate and optimize the approach that was further applied to bile salt stimulated lipase (BSSL) isolated from human milk. Next to previously reported O-Glycan structures two additional oligosaccharides could be detected for BSSL. General Significance In conclusion, the facile protocol established is suitable for the analysis of complex O-linked oligosaccharides from various biological samples. This article is part of a Special Issue entitled Glycoproteomics.
Zhongfu Wang - One of the best experts on this subject based on the ideXlab platform.
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anthranilic acid as a versatile fluorescent tag and linker for functional glycomics
Bioconjugate Chemistry, 2018Co-Authors: Yuyang Zhu, Yi Lasanajak, Zhongfu Wang, Xueyun Liu, Ying Zhang, Xuezheng SongAbstract:The advancement of glycoscience is critically dependent on the access to a large number of glycans for their functional study. Naturally occurring glycans are considered a viable source for diverse and biologically relevant glycan libraries. A mixture of free reducing glycans released from natural sources can be fluorescently tagged and separated by chromatography to produce a natural glycan library. Anthranilic acid (AA) has been widely used to fluorescently tag reducing glycans for HPLC or LC/MS analysis. However, AA conjugated glycans are not efficiently immobilized on microarray slides due to the lack of a primary alkylamine functional group. In this study, we have developed simple and efficient chemistry for bioconjugation and further functionalization of glycan-AA conjugates. This new approach enables quick preparation of glycan microarrays and neoglycoproteins from glycan-AA conjugates, which can be separated by weak anion exchange (WAX) and C18 reversed-phase HPLC.
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quantitative o glycomics based on improvement of the one pot method for nonreductive o glycan release and simultaneous stable isotope labeling with 1 d0 d5 phenyl 3 methyl 5 pyrazolone followed by mass spectrometric analysis
Journal of Proteomics, 2017Co-Authors: Chengjian Wang, Ying Zhang, Ping Zhang, Linjuan Huang, Wanjun Jin, Shan Qiang, Zhongfu WangAbstract:Abstract Rapid, simple and versatile methods for quantitative analysis of glycoprotein O -glycans are urgently required for current studies on protein O -glycosylation patterns and the search for disease O -glycan biomarkers. Relative quantitation of O -glycans using stable isotope labeling followed by mass spectrometric analysis represents an ideal and promising technique. However, it is hindered by the shortage of reliable nonreductive O -glycan release methods as well as the too large or too small inconstant mass difference between the light and heavy isotope form derivatives of O -glycans, which results in difficulties during the recognition and quantitative analysis of O -glycans by mass spectrometry. Herein we report a facile and versatile O -glycan relative quantification strategy, based on an improved one-pot method that can quantitatively achieve nonreductive release and in situ chromophoric labeling of intact mucin-type O -glycans in one step. In this study, the one-pot method is optimized and applied for quantitative O -glycan release and tagging with either non-deuterated (d 0 -) or deuterated (d 5 -) 1-phenyl-3-methyl-5-pyrazolone (PMP). The obtained O -glycan derivatives feature a permanent 10-Da mass difference between the d 0 - and d 5 -PMP forms, allowing complete discrimination and comparative quantification of these isotopically labeled O -glycans by mass spectrometric techniques. Moreover, the d 0 - and d 5 -PMP derivatives of O -glycans also have a relatively high hydrophobicity as well as a strong UV adsorption, especially suitable for high-resolution separation and high-sensitivity detection by RP-HPLC-UV. We have refined the conditions for the one-pot reaction as well as the corresponding sample purification approach. The good quantitation feasibility, reliability and linearity of this strategy have been verified using bovine fetuin and porcine stomach mucin as model O -glycoproteins. Additionally, we have also successfully applied this method to the quantitative O -glycomic comparison between perch and salmon eggs by ESI-MS, MS/MS and online RP-HPLC-UV-ESI-MS/MS, demonstrating its excellent applicability to various complex biological samples. Biological significance O -Linked glycoproteins, generated via a widely existing glycosylation modification process on serine (Ser) or threonine (Thr) residues of nascent proteins, play essential roles in a series of biological processes. As a type of informational molecule, the O -glycans of these glycoproteins participate directly in these biological mechanisms. Thus, the characteristic differences or changes of O -glycans in expression level usually relate to pathologies of many diseases and represent an important opportunity to uncover the functional mechanisms of various glycoprotein O -glycans. The novel strategy introduced here provides a simple and versatile analytical method for the precise quantitation of glycoprotein O -glycans by mass spectrometry, enabling rapid evaluation of the differences or changes of O -glycans in expression level. It is attractive for the field of quantitative/comparative O -glycomics, which has great significance for exploring the complex structure-function relationship of O -glycans, as well as for the search of O -glycan biomarkers of some major diseases and O -glycan related targets of some drugs.
Richard D. Cummings - One of the best experts on this subject based on the ideXlab platform.
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Fluorescent Glycosylamides Produced by Microscale Derivatization of Free Glycans for Natural Glycan Microarrays
2015Co-Authors: Xuezheng Song, Yi Lasanajak, David F Smith, Baoyun Xia, Richard D. CummingsAbstract:A novel strategy for creating naturally derived glycan microarrays has been developed. Glycosylamines are prepared from free reducing glycans and stabilized by reaction with acryloyl chloride to generate a glycosylamide in which the reducing monosaccharide has a closed-ring structure. Ozonolysis of the protected glycan yields an active aldehyde, to which a bifunctional fluorescent linker is coupled by reductive amination. The fluorescent derivatives are easily coupled through a residual primary alkylamine to generate glycan microarrays. This strategy preserves structural features of glycans required for antibody recognition and allows development of natural arrays of fluorescent glycans in which the cyclic pyranose structure of the reducing-end sugar residue is retained
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structural characterization by multistage mass spectrometry msn of human milk glycans recognized by human rotaviruses
Molecular & Cellular Proteomics, 2014Co-Authors: David J Ashline, Yi Lasanajak, Liya Hu, Sasirekha Ramani, B Venkataram V Prasad, Xuezheng Song, Richard D. Cummings, Ying Yu, Mary K. Estes, David F SmithAbstract:We have shown that recombinant forms of VP8* domains of the human rotavirus outer capsid spike protein VP4 from human neonatal strains (N155(G10P[11]) and RV3(G3P[6]) and a bovine strain (B223) recognize unique glycans within the repertoire of human milk glycans. The accompanying study by Yu et al.2, describes a human milk glycan shotgun glycan microarray that led to the identification of 32 specific glycans in the human milk tagged glycan library that were recognized by these human rotaviruses. These microarray analyses also provided a variety of metadata about the recognized glycan structures compiled from anti-glycan antibody and lectin binding before and after specific glycosidase digestions, along with compositional information from mass analysis by matrix-assisted laser desorption ionization-mass spectrometry. To deduce glycan sequence and utilize information predicted by analyses of metadata from each glycan, 28 of the glycan targets were retrieved from the tagged glycan library for detailed sequencing using sequential disassembly of glycans by ion-trap mass spectrometry. Our aim is to obtain a deeper structural understanding of these key glycans using an orthogonal approach for structural confirmation in a single ion trap mass spectrometer. This sequential ion disassembly strategy details the complexities of linkage and branching in multiple compositions, several of which contained isomeric mixtures including several novel structures. The application of this approach exploits both library matching with standard materials and de novo approaches. This combination together with the metadata generated from lectin and antibody-binding data before and after glycosidase digestions provide a heretofore-unavailable level of analytical detail to glycan structure analysis. The results of these studies showed that, among the 28 glycan targets analyzed, 27 unique structures were identified, and 23 of the human milk glycans recognized by human rotaviruses represent novel structures not previously described as glycans in human milk. The functional glycomics analysis of human milk glycans provides significant insight into the repertoire of glycans comprising the human milk metaglycome.
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a sialylated glycan microarray reveals novel interactions of modified sialic acids with proteins and viruses
Journal of Biological Chemistry, 2011Co-Authors: Xuezheng Song, Yi Lasanajak, Xi Chen, Hongzhi Cao, Vinod K Tiwari, Mary M Tappert, Gillian M Air, Harshal A Chokhawala, Haojie Zheng, Richard D. CummingsAbstract:Many glycan-binding proteins in animals and pathogens recognize sialic acid or its modified forms, but their molecular recognition is poorly understood. Here we describe studies on sialic acid recognition using a novel sialylated glycan microarray containing modified sialic acids presented on different glycan backbones. Glycans terminating in β-linked galactose at the non-reducing end and with an alkylamine-containing fluorophore at the reducing end were sialylated by a one-pot three-enzyme system to generate α2–3- and α2–6-linked sialyl glycans with 16 modified sialic acids. The resulting 77 sialyl glycans were purified and quantified, characterized by mass spectrometry, covalently printed on activated slides, and interrogated with a number of key sialic acid-binding proteins and viruses. Sialic acid recognition by the sialic acid-binding lectins Sambucus nigra agglutinin and Maackia amurensis lectin-I, which are routinely used for detecting α2–6- and α2–3-linked sialic acids, are affected by sialic acid modifications, and both lectins bind glycans terminating with 2-keto-3-deoxy-d-glycero-d-galactonononic acid (Kdn) and Kdn derivatives stronger than the derivatives of more common N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc). Three human parainfluenza viruses bind to glycans terminating with Neu5Ac or Neu5Gc and some of their derivatives but not to Kdn and its derivatives. Influenza A virus also does not bind glycans terminating in Kdn or Kdn derivatives. An especially novel aspect of human influenza A virus binding is its ability to equivalently recognize glycans terminated with either α2–6-linked Neu5Ac9Lt or α2–6-linked Neu5Ac. Our results demonstrate the utility of this sialylated glycan microarray to investigate the biological importance of modified sialic acids in protein-glycan interactions.
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glycan gimmickry by parasitic helminths a strategy for modulating the host immune response
Glycobiology, 2010Co-Authors: I Van Die, Richard D. CummingsAbstract:Parasitic helminths (worms) co-evolved with vertebrate immune systems to enable long-term survival of worms in infected hosts. Among their survival strategies, worms use their glycans within glycoproteins and glycolipids, which are abundant on helminth surfaces and in their excretory/ secretory products, to regulate and suppress host immune responses. Many helminths express unusual and antigenic (nonhost-like) glycans, including those containing polyfucose, tyvelose, terminal GalNAc, phosphorylcholine, methyl groups, and sugars in unusual linkages. In addition, some glycan antigens are expressed that share structural features with those in their intermediate and vertebrate hosts (hostlike glycans), including Le X (Galβ1-4[Fucα1-3]GlcNAc-), LDNF (GalNAcβ1-4[Fucα1-3]GlcNAc-), LDN (GalNAcβ14GlcNAc-), and Tn (GalNAcα1-O-Thr/Ser) antigens. The expression of host-like glycan determinants is remarkable and suggests that helminths may gain advantages by synthesizing such glycans. The expression of host-like glycans by parasites previously led to the concept of “molecular mimicry,” in which molecules are either derived from the pathogen or acquired from the host to evade recognition by the host immune system. However, recent discoveries into the potential of host glycan-binding proteins (GBPs), such as C-type lectin receptors and galectins, to functionally interact with various host-like helminth glycans provide new insights. Host GBPs through their interactions with wormderived glycans participate in shaping innate and adaptive immune responses upon infection. We thus propose an alternative concept termed “glycan gimmickry,” which is defined as an active strategy of parasites to use their glycans to target GBPs within the host to promote their survival.
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galectin 1 2 and 3 exhibit differential recognition of sialylated glycans and blood group antigens
Journal of Biological Chemistry, 2008Co-Authors: Sean R Stowell, David F Smith, Connie M Arthur, Padmaja Mehta, Kristen A Slanina, Ola Blixt, Hakon Leffler, Richard D. CummingsAbstract:Human galectins have functionally divergent roles, although most of the members of the galectin family bind weakly to the simple disaccharide lactose (Galbeta1-4Glc). To assess the specificity of galectin-glycan interactions in more detail, we explored the binding of several important galectins (Gal-1, Gal-2, and Gal-3) using a dose-response approach toward a glycan microarray containing hundreds of structurally diverse glycans, and we compared these results to binding determinants on cells. All three galectins exhibited differences in glycan binding characteristics. On both the microarray and on cells, Gal-2 and Gal-3 exhibited higher binding than Gal-1 to fucose-containing A and B blood group antigens. Gal-2 exhibited significantly reduced binding to all sialylated glycans, whereas Gal-1 bound alpha2-3- but not alpha2-6-sialylated glycans, and Gal-3 bound to some glycans terminating in either alpha2-3- or alpha2-6-sialic acid. The effects of sialylation on Gal-1, Gal-2, and Gal-3 binding to cells also reflected differences in cellular sensitivity to Gal-1-, Gal-2-, and Gal-3-induced phosphatidylserine exposure. Each galectin exhibited higher binding for glycans with poly-N-acetyllactosamine (poly(LacNAc)) sequences (Galbeta1-4GlcNAc)(n) when compared with N-acetyllactosamine (LacNAc) glycans (Galbeta1-4GlcNAc). However, only Gal-3 bound internal LacNAc within poly(LacNAc). These results demonstrate that each of these galectins mechanistically differ in their binding to glycans on the microarrays and that these differences are reflected in the determinants required for cell binding and signaling. The specific glycan recognition by each galectin underscores the basis for differences in their biological activities.
