Insight into Glycan Diversity and Evolutionary Lineage Based on Comparative Avio-N-glycomics and Sialic Acid Analysis of 88 Egg Whites of Galloanserae

MALDI glycotyping of O-antigens from a single colony of gram-negative bacteria

Polypeptide-targeted MALDI-TOF MS for microbial species identification has revolutionized microbiology. However, no practical MALDI-TOF MS identification method for O-antigen polysaccharides, a major indicator for epidemiological classification within a species of gram-negative bacteria, is available. We describe a simple MALDI glycotyping method for O-antigens that simultaneously identifies the molecular mass of the repeating units and the monosaccharide composition of the O-antigen. We analyzed the Escherichia coli O1, O6, and O157-type strains. Conventional species identification based on polypeptide patterns and O-antigen polysaccharide typing can be performed in parallel from a single colony using our MALDI-TOF MS workflow. Moreover, subtyping within the same O-antigen and parallel colony-specific O-antigen determination from mixed strains, including the simultaneous identification of multiple strains-derived O-antigens within selected colony, were performed. In MALDI glycotyping of two Enterobacteriaceae strains, a Citrobacter freundii strain serologically cross-reactive with E. coli O157 gave a MALDI spectral pattern identical to E. coli O157. On the other hand, an Edwardsiella tarda strain with no reported O-antigen cross-reactivity gave a MALDI spectral pattern of unknown O-antigen repeating units. The method described in this study allows the parallel and rapid identification of microbial genera, species, and serotypes of surface polysaccharides using a single MALDI-TOF MS instrument.

Glycoblotting-Based Ovo-Sulphoglycomics Reveals Phosphorylated N-Glycans as a Possible Host Factor of AIV Prevalence in Waterfowls

Sulfated N-glycans play a crucial role in the interaction between influenza A virus (IAV) and its host. These glycans have been found to enhance viral replication, highlighting their significance in IAV propagation. This study investigated the expression of acidic N-glycans, specifically sulfated and phosphorylated glycans, in the egg whites of 72 avian species belonging to the Order Anseriformes (waterfowls). We used the glycoblotting-based sulphoglycomics approach to elucidate the diversity of acidic N-glycans and infer their potential role in protecting embryos from infections. Family-specific variations in sulfated and phosphorylated N-glycan profiles were identified in waterfowl egg whites. Different waterfowl species exhibited distinct expressions of sulfated trans-Gal(+) and trans-Gal(-) N-glycan structures. Additionally, species-specific expression of phosphorylated N-glycans was observed. Furthermore, it was found that waterfowl species with high avian influenza virus (AIV) prevalence displayed a higher abundance of phosphorylated hybrid and high-mannose N-glycans on their egg whites. These findings shed light on the importance of phosphorylated and sulfated N-glycans in understanding the role of acidic glycans in IAV propagation.

Glycoblotting enables seamless and straightforward workflow for MALDI-TOF/MS-based sulphoglycomics of N- and O-glycans

Sulfated N- and O-glycans exist in trace levels which are challenging to detect, especially when abundant neutral and sialylated glycans are present. Current matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS)-based sulfoglycomics approaches effectively utilize permethylation to discriminate sulfated glycans from sialyl-glycans. And a charge-based separation to isolate the sulfated glycans from the rest of the permethylated neutral and sialyl-glycans. However, these approaches suffer from concomitant sample losses during cleanup steps. Herein, we describe Glycoblotting as a straightforward complementary method with seamless glycan purification, enrichment, methylation, and labeling on a single platform to address sulfated glycan enrichment, sialic acid methylation, and sample loss. Glycoblottings' on-bead chemoselective ligation of reducing sugars with hydrazide showed excellent recovery of sulfated glycans, allowing the detection of more sulfated glycan species. On-bead methyl esterification of sialic acid using 3-methyl-1-p-tolyltriazene (MTT) effectively discriminates sulfated glycans from sialyl-glycans. Furthermore, we have shown that using MTT as a methylating agent allowed us to simultaneously detect and differentiate sulfate from phosphate groups in isobaric N-glycan species. We believe that Glycoblotting will contribute significantly to the MALDI-TOF MS-based Sulphoglycomics workflow.

Galectin-4 Is Involved in the Structural Changes of Glycosphingolipid Glycans in Poorly Differentiated Gastric Cancer Cells with High Metastatic Potential

Gastric cancer with peritoneal dissemination is difficult to treat surgically, and frequently recurs and metastasizes. Currently, there is no effective treatment for this disease, and there is an urgent need to elucidate the molecular mechanisms underlying peritoneal dissemination and metastasis. Our previous study demonstrated that galectin-4 participates in the peritoneal dissemination of poorly differentiated gastric cancer cells. In this study, the glycan profiles of cell surface proteins and glycosphingolipids (GSLs) of the original (wild), galectin-4 knockout (KO), and rescue cells were investigated to understand the precise mechanisms involved in the galectin-4-mediated regulation of associated molecules, especially with respect to glycosylation. Glycan analysis of the NUGC4 wild type and galectin-4 KO clones with and without peritoneal metastasis revealed a marked structural change in the glycans of neutral GSLs, but not in N-glycan. Furthermore, mass spectrometry (MS) combined with glycosidase digestion revealed that this structural change was due to the presence of the lacto-type (β1-3Galactosyl) glycan of GSL, in addition to the neolacto-type (β1-4Galactosyl) glycan of GSL. Our results demonstrate that galectin-4 is an important regulator of glycosylation in cancer cells and galectin-4 expression affects the glycan profile of GSLs in malignant cancer cells with a high potential for peritoneal dissemination.

Direct MALDI Glycotyping of Glycoproteins toward Practical Subtyping of Biological Samples

The rapid analysis of glycan patterns (glycoforms) of glycoproteins can accelerate their quality control and biomarker discovery. We have focused on the direct analysis of glycoprotein glycoforms using matrix-assisted laser desorption/ionization in-source decay mass spectrometry (MALDI-ISDMS), called MALDI glycotyping. Our results show that the 1,5-diaminonaphthalene (DAN)/2,5-dihydroxybenzoic acid (DHB)/Na matrix can directly analyze the glycoforms in the femtomolar range of intact glycoproteins. The addition of DAN improved the morphology of the solid matrix due to the mixture of DAN and DHB, which significantly contribute to the high sensitivity of this direct analysis. Adding DAN significantly improved the sensitivity of the glycan precursor ions in the TOF/TOF analysis because of its enhanced fragmentation effect as an efficient UV-MALDI matrix. Further, practical glycoform analysis (glycotyping) of diluted biological samples containing glycoproteins, such as egg whites, was also successfully achieved.

Mouse tissue glycome atlas 2022 highlights inter-organ variation in major N-glycan profiles

This study presents "mouse tissue glycome atlas" representing the profiles of major N-glycans of mouse glycoproteins that may define their essential functions in the surface glycocalyx of mouse organs/tissues and serum-derived extracellular vesicles (exosomes). Cell surface glycocalyx composed of a variety of N-glycans attached covalently to the membrane proteins, notably characteristic "N-glycosylation patterns" of the glycocalyx, plays a critical role for the regulation of cell differentiation, cell adhesion, homeostatic immune response, and biodistribution of secreted exosomes. Given that the integrity of cell surface glycocalyx correlates significantly with maintenance of the cellular morphology and homeostatic immune functions, dynamic alterations of N-glycosylation patterns in the normal glycocalyx caused by cellular abnormalities may serve as highly sensitive and promising biomarkers. Although it is believed that inter-organs variations in N-glycosylation patterns exist, information of the glycan diversity in mouse organs/tissues remains to be elusive. Here we communicate for the first-time N-glycosylation patterns of 16 mouse organs/tissues, serum, and serum-derived exosomes of Slc:ddY mice using an established solid-phase glycoblotting platform for the rapid, easy, and high throughput MALDI-TOFMS-based quantitative glycomics. The present results elicited occurrence of the organ/tissue-characteristic N-glycosylation patterns that can be discriminated to each other. Basic machine learning analysis using this N-glycome dataset enabled classification between 16 mouse organs/tissues with the highest F1 score (69.7-100%) when neural network algorithm was used. A preliminary examination demonstrated that machine learning analysis of mouse lung N-glycome dataset by random forest algorithm allows for the discrimination of lungs among the different mouse strains such as the outbred mouse Slc:ddY, inbred mouse DBA/2Crslc, and systemic lupus erythematosus model mouse MRL-lpr/lpr with the highest F1 score (74.5-83.8%). Our results strongly implicate importance of "human organ/tissue glycome atlas" for understanding the crucial and diversified roles of glycocalyx determined by the organ/tissue-characteristic N-glycosylation patterns and the discovery research for N-glycome-based disease-specific biomarkers and therapeutic targets.

Effects of N-linked glycans of bilirubin oxidase on direct electron transfer-type bioelectrocatalysis

Bilirubin oxidase from Myrothecium verrucaria (mBOD) is a promising enzyme for catalyzing the four-electron reduction of dioxygen into water and realizes direct electron transfer (DET)-type bioelectrocatalysis. It has two N-linked glycans (N-glycans), and N472 and N482 are known as binding sites. Both binding sites located on opposite side of the type I (T1) Cu, which is the electrode-active site of BOD. We investigated the effect of N-glycans on DET-type bioelectrocatalysis by performing electrochemical measurements using electrodes with controlled surface charges. Two types of BODs with different N-glycans, mBOD and recombinant BOD overexpressed in Pichia pastoris (pBOD), and their deglycosylated forms (dg-mBOD and dg-pBOD) were used in this study. Kinetic analysis of the steady-state catalytic waves revealed that both size and composition of N-glycans affected the orientation of adsorbed BODs on the electrodes. Interestingly, the most favorable orientation was achieved with pBOD, which has the largest N-glycans. Furthermore, the effect of the orientation control by the N-glycans is cooperative with electrostatic interaction.

Antiadhesive nanosome elicits role of glycocalyx of tumor cell-derived exosomes in the organotropic cancer metastasis

Despite emerging importance of tumor cells-derived exosomes in cancer metastasis, the heterogeneity of exosome populations has largely hampered systemic characterization of their molecular composition, biogenesis, and functions. This study communicates a novel method for predicting and targeting pre-metastatic sites based on an exosome model "fluorescent cancer glyconanosomes" displaying N-glycans of cultured tumor cells. Glycoblotting by antiadhesive quantum dots provides a nice tool to shed light on the pivotal functions of the glycocalyx reconstructed from four cancer cell types without bias due to other compositions of exosomes. In vivo imaging revealed that circulation, clearance, and organotropic biodistribution of cancer glyconanosomes in mice depend strongly on cancer cell-type-specific N-glycosylation patterns, the compositions of key glycotypes, particularly dominant abundances of high mannose-type N-glycans and the position-specific sialylation. Notably, organ biodistribution of cancer glyconanosomes is reproducible artificially by mimicking cancer cell-type-specific N-glycosylation patterns, demonstrating that nanosomal glycoblotting method serves as promising tools for predicting and targeting pre-metastatic sites determined by the glycocalyx of extracellular vesicles disseminated from the primary cancer site.

Respiratory mucus as a virus-host range determinant

Efficient penetration of the mucus layer is needed for respiratory viruses to avoid mucociliary clearance prior to infection. Many respiratory viruses bind to glycans on the heavily glycosylated mucins that give mucus its gel-like characteristics. Influenza viruses, some paramyxoviruses, and coronaviruses avoid becoming trapped in the mucus by releasing themselves by means of their envelope-embedded enzymes that destroy glycan receptors. For efficient infection, receptor binding and destruction need to be in balance with the host receptor repertoire. Establishment in a novel host species requires resetting of the balance to adapt to the different glycan repertoire encountered. Growing understanding of species-specific mucosal glycosylation patterns and the dynamic interaction with respiratory viruses identifies the mucus layer as a major host-range determinant and barrier for zoonotic transfer.

Modified Sialic Acids on Mucus and Erythrocytes Inhibit Influenza A Virus Hemagglutinin and Neuraminidase Functions

Sialic acids (Sia) are the primary receptors for influenza viruses and are widely displayed on cell surfaces and in secreted mucus. Sia may be present in variant forms that include O-acetyl modifications at C-4, C-7, C-8, and C-9 positions and N-acetyl or N-glycolyl at C-5. They can also vary in their linkages, including α2-3 or α2-6 linkages. Here, we analyze the distribution of modified Sia in cells and tissues of wild-type mice or in mice lacking CMP-N-acetylneuraminic acid hydroxylase (CMAH) enzyme, which synthesizes N-glycolyl (Neu5Gc) modifications. We also examined the variation of Sia forms on erythrocytes and in saliva from different animals. To determine the effect of Sia modifications on influenza A virus (IAV) infection, we tested for effects on hemagglutinin (HA) binding and neuraminidase (NA) cleavage. We confirmed that 9-O-acetyl, 7,9-O-acetyl, 4-O-acetyl, and Neu5Gc modifications are widely but variably expressed in mouse tissues, with the highest levels detected in the respiratory and gastrointestinal (GI) tracts. Secreted mucins in saliva and surface proteins of erythrocytes showed a high degree of variability in display of modified Sia between different species. IAV HAs from different virus strains showed consistently reduced binding to both Neu5Gc- and O-acetyl-modified Sia; however, while IAV NAs were inhibited by Neu5Gc and O-acetyl modifications, there was significant variability between NA types. The modifications of Sia in mucus may therefore have potent effects on the functions of IAV and may affect both pathogens and the normal flora of different mucosal sites.IMPORTANCE Sialic acids (Sia) are involved in numerous different cellular functions and are receptors for many pathogens. Sia come in chemically modified forms, but we lack a clear understanding of how they alter interactions with microbes. Here, we examine the expression of modified Sia in mouse tissues, on secreted mucus in saliva, and on erythrocytes, including those from IAV host species and animals used in IAV research. These Sia forms varied considerably among different animals, and their inhibitory effects on IAV NA and HA activities and on bacterial sialidases (neuraminidases) suggest a host-variable protective role in secreted mucus.

Identification of the Duck Egg White N-Glycoproteome and Insight into the Course of Biological Evolution

Protein glycosylation is a ubiquitous posttranslational modification that modulates protein properties, thereby influencing bioactivities within a system. Duck egg white (DEW) proteins exhibit diverse biological properties compared with their chicken egg white (CEW) counterparts, which might be related to glycosylation. N-Glycoproteome analysis of DEW was conducted, and a total of 231 N-glycosites from 68 N-glycoproteins were identified. Gene ontology analysis was used to elucidate the biofunctions of DEW N-glycoproteins and compare them with those of CEW, which showed that the differences mostly involved molecular functions and biological processes. The biological functions of DEW N-glycoproteins were illuminated through bioinformatics analysis and comparison with CEW orthologues, which showed different allergenicities and antibacterial abilities. These divergences might be initiated by specific alterations in glycosylation, which can enhance the proteolysis resistance and protein steric hindrance. These results provide new insights for discovering the effects of N-glycosylation on biofunctions during the divergence of homologous proteins.

Identification of serum N-glycoproteins as a biological correlate underlying chronic stress response in mice

Glycosylation is a post-translational protein modification in eukaryotes and plays an important role in controlling several diseases. N-glycan structure is emerging as a new paradigm for biomarker discovery of neuropsychiatric disorders. However, the relationship between N-glycosylation pattern and depression is not well elucidated to date. This study aimed to explore whether serum N-glycan structures are altered in depressive-like behavior using a stress based mouse model. We used two groups of BALB/c mice; (i) treated group exposed to chronic unpredictable mild stress (CUMS) as a model of depression, and (ii) control group. Behavioral tests in mice (e.g., sucrose preference test, forced swimming test, and fear conditioning test) were used to evaluate the threshold level to which mice displayed a depressive-like phenotype. Serum N-glycans were analyzed carefully using glycoblotting followed by Matrix-assisted laser desorption ionization-time of flight/mass spectrometry (MALDI-TOF/MS) to exhibit N-glycan expression levels and to illustrate the changes in the N-glycome profile. N-glycan expression levels were commonly altered in the depressive-like model and correlated well with the behavioral data. Our results indicated that sialylated N-glycan was identified as a biomarker associated with depressive symptoms, which may have utility as a candidate biomarker for the clinical diagnosis and monitoring of depression.

Bacterial density rather than diversity correlates with hatching success across different avian species

Bacterial communities within avian nests are considered an important determinant of egg viability, potentially selecting for traits that confer embryos with protection against trans-shell infection. A high bacterial density on the eggshell increases hatching failure, whether this effect could be due to changes in bacterial community or just a general increase in bacterial density. We explored this idea using intra- and interspecific comparisons of the relationship between hatching success and eggshell bacteria characterized by culture and molecular techniques (fingerprinting and high-throughput sequencing). We collected information for 152 nests belonging to 17 bird species. Hatching failures occurred more frequently in nests with higher density of aerobic mesophilic bacteria on their eggshells. Bacterial community was also related to hatching success, but only when minority bacterial operational taxonomic units were considered. These findings support the hypothesis that bacterial density is a selective agent of embryo viability, and hence a proxy of hatching failure only within species. Although different avian species hold different bacterial densities or assemblages on their eggs, the association between bacteria and hatching success was similar for different species. This result suggests that interspecific differences in antibacterial defenses are responsible for keeping the hatching success at similar levels in different species.

Glycoblotting of Egg White Reveals Diverse N-Glycan Expression in Quail Species

The glycan part of glycoproteins is known to be involved in the structure and modulatory functions of glycoproteins, serving as ligands for cell-to-cell interactions, and as specific ligands for cell-to-microbe interactions. It is believed that intraspecies and interspecies variations in glycosylation exist. As an approach to better understand glycan diversity, egg whites (EW) from four different quail species are studied by the well-established glycoblotting procedure, a glycan enrichment and analysis method. N-Glycans were classified and the profiles were established for quail egg white samples which showed 21 relevant glycan peaks; 18 peaks were expressed significantly, and 10 glycan peaks are found to be abundant in certain species. The result establishes glycan profiles for Blue Scaled, Bobwhite, Japanese, and Mountain Quail egg whites and shows a unique difference among glycan expressions, particularly, high mannose in Japanese Quail and tetra-antennary glycan structure for other quail species.

Healthy human serum N-glycan profiling reveals the influence of ethnic variation on the identified cancer-relevant glycan biomarkers

Background

Most glycomics studies have focused on understanding disease mechanisms and proposing serum markers for various diseases, yet the influence of ethnic variation on the identified glyco-biomarker remains poorly addressed. This study aimed to investigate the inter-ethnic serum N-glycan variation among US origin control, Japanese, Indian, and Ethiopian healthy volunteers.

Methods

Human serum from 54 healthy subjects of various ethnicity and 11 Japanese hepatocellular carcinoma (HCC) patients were included in the study. We employed a comprehensive glycoblotting-assisted MALDI-TOF/MS-based quantitative analysis of serum N-glycome and fluorescence HPLC-based quantification of sialic acid species. Data representing serum N-glycan or sialic acid levels were compared among the ethnic groups using SPSS software.

Results

Total of 51 N-glycans released from whole serum glycoproteins could be reproducibly quantified within which 33 glycoforms were detected in all ethnicities. The remaining N-glycans were detected weakly but exclusively either in the Ethiopians (13 glycans) or in all the other ethnic groups (5 glycans). Highest abundance (p < 0.001) of high mannose, core-fucosylated, hyperbranched/hypersialylated N-glycans was demonstrated in Ethiopians. In contrast, only one glycan (m/z 2118) significantly differed among all ethnicities being highest in Indians and lowest in Ethiopians. Glycan abundance trend in Ethiopians was generally close to that of Japanese HCC patients. Glycotyping analysis further revealed ethnic-based disparities mainly in the branched and sialylated structures. Surprisingly, some of the glycoforms greatly elevated in the Ethiopian subjects have been identified as serum biomarkers of various cancers. Sialic acid level was significantly increased primarily in Ethiopians, compared to the other ethnicities.

Conclusion

The study revealed ethnic-specific differences in healthy human serum N-glycome with highest abundance of most glycoforms in the Ethiopian ethnicity. The results strongly emphasized the need to consider ethnicity matching for accurate glyco-biomarker identification. Further large-scale study employing various ethnic compositions is needed to verify the current result.

A glycomics approach to discover novel renal biomarkers in birds by administration of cisplatin and diclofenac to chickens

Avian species have a unique renal structure and abundant blood flow into the kidneys. Although many birds die due to nephrotoxicity caused by chemicals, there are no early biomarkers for renal lesions. Uric acid level in blood, which is generally used as a renal biomarker, is altered when the kidney function is damaged by over 70%. Therefore, early biomarkers for kidney injury in birds are needed. In humans, glycomics has been at the forefront of biological and medical sciences, and glycans are used as biomarkers of diseases, such as carcinoma. In this study, a glycomics approach was used to screen for renal biomarkers in chicken. First, a chicken model of kidney damage was generated by injection of diclofenac or cisplatin, which cause acute interstitial nephritis (AIN) and acute tubular necrosis (ATN), respectively. The nephrotoxicity levels were determined by a blood chemical test and histopathological analysis. The plasma N-glycans were then analyzed to discover renal biomarkers in birds. Levels of 14 glycans increased between pre- and post administration in kidney-damaged chickens in the diclofenac group, and some of these glycans had the same presumptive composition as those in human renal carcinoma patients. Glycan levels did not change remarkably in the cisplatin group. It is possible that there are changes in glycan expression due to AIN, but they do not reflect ATN. Although further research is needed in other species of birds, glycans are potentially useful biomarkers for AIN in avian species.

Topological N-glycosylation and site-specific N-glycan sulfation of influenza proteins in the highly expressed H1N1 candidate vaccines

The outbreak of a pandemic influenza H1N1 in 2009 required the rapid generation of high-yielding vaccines against the A/California/7/2009 virus, which were achieved by either addition or deletion of a glycosylation site in the influenza proteins hemagglutinin and neuraminidase. In this report, we have systematically evaluated the glycan composition, structural distribution and topology of glycosylation for two high-yield candidate reassortant vaccines (NIBRG-121xp and NYMC-X181A) by combining various enzymatic digestions with high performance liquid chromatography and multiple-stage mass spectrometry. Proteomic data analyses of the full-length protein sequences determined 9 N-glycosylation sites of hemagglutinin, and defined 6 N-glycosylation sites and the glycan structures of low abundance neuraminidase, which were occupied by high-mannose, hybrid and complex-type N-glycans. A total of ~300 glycopeptides were analyzed and manually validated by tandem mass spectrometry. The specific N-glycan structure and topological location of these N-glycans are highly correlated to the spatial protein structure and the residential ligand binding. Interestingly, sulfation, fucosylation and bisecting N-acetylglucosamine of N-glycans were also reliably identified at the specific glycosylation sites of the two influenza proteins that may serve a crucial role in regulating the protein structure and increasing the protein abundance of the influenza virus reassortants.

Rapid screening for specific glycosylation and pathogen interactions on a 78 species avian egg white glycoprotein microarray

There is an urgent need for discovery of novel antimicrobials and carbohydrate-based anti-adhesive strategies are desirable as they may not promote resistance. Discovery of novel anti-adhesive molecules from natural product libraries will require the use of a high throughput screening platform. Avian egg white (EW) provides nutrition for the embryo and protects against infection, with glycosylation responsible for binding certain pathogens. In this study, a microarray platform of 78 species of avian EWs was developed and profiled for glycosylation using a lectin panel with a wide range of carbohydrate specificities. The dominating linkages of sialic acid in EWs were determined for the first time using the lectins MAA and SNA-I. EW glycosylation similarity among the different orders of birds did not strictly depend on phylogenetic relationship. The interactions of five strains of bacterial pathogens, including Escherichia coli, Staphylococcus aureus and Vibrio cholera, identified a number of EWs as potential anti-adhesives, with some as strain- or species-specific. Of the two bacterial toxins examined, shiga-like toxin 1 subunit B bound to ten EWs with similar glycosylation more intensely than pigeon EW. This study provides a unique platform for high throughput screening of natural products for specific glycosylation and pathogen interactions. This platform may provide a useful platform in the future for discovery of anti-adhesives targeted for strain and species specificity.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012

This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.

N-Glycomic and Microscopic Subcellular Localization Analyses of NPP1, 2 and 6 Strongly Indicate that trans-Golgi Compartments Participate in the Golgi to Plastid Traffic of Nucleotide Pyrophosphatase/Phosphodiesterases in Rice

Nucleotide pyrophosphatase/phosphodiesterases (NPPs) are widely distributed N-glycosylated enzymes that catalyze the hydrolytic breakdown of numerous nucleotides and nucleotide sugars. In many plant species, NPPs are encoded by a small multigene family, which in rice are referred to NPP1-NPP6 Although recent investigations showed that N-glycosylated NPP1 is transported from the endoplasmic reticulum (ER)-Golgi system to the chloroplast through the secretory pathway in rice cells, information on N-glycan composition and subcellular localization of other NPPs is still lacking. Computer-assisted analyses of the amino acid sequences deduced from different Oryza sativa NPP-encoding cDNAs predicted all NPPs to be secretory glycoproteins. Confocal fluorescence microscopy observation of cells expressing NPP2 and NPP6 fused with green fluorescent protein (GFP) revealed that NPP2 and NPP6 are plastidial proteins. Plastid targeting of NPP2-GFP and NPP6-GFP was prevented by brefeldin A and by the expression of ARF1(Q71L), a dominant negative mutant of ADP-ribosylation factor 1 that arrests the ER to Golgi traffic, indicating that NPP2 and NPP6 are transported from the ER-Golgi to the plastidial compartment. Confocal laser scanning microscopy and high-pressure frozen/freeze-substituted electron microscopy analyses of transgenic rice cells ectopically expressing the trans-Golgi marker sialyltransferase fused with GFP showed the occurrence of contact of Golgi-derived membrane vesicles with cargo and subsequent absorption into plastids. Sensitive and high-throughput glycoblotting/mass spectrometric analyses showed that complex-type and paucimannosidic-type glycans with fucose and xylose residues occupy approximately 80% of total glycans of NPP1, NPP2 and NPP6. The overall data strongly indicate that the trans-Golgi compartments participate in the Golgi to plastid trafficking and targeting mechanism of NPPs.

Large-Scale Glycomics of Livestock: Discovery of Highly Sensitive Serum Biomarkers Indicating an Environmental Stress Affecting Immune Responses and Productivity of Holstein Dairy Cows

Because various stresses strongly influence the food productivity of livestock, biomarkers to indicate unmeasurable environmental stress in domestic animals are of increasing importance. Thermal comfort is one of the basic principles of dairy cow welfare that enhances productivity. To discover sensitive biomarkers that monitor such environmental stresses in dairy cows, we herein performed, for the first time, large-scale glycomics on 336 lactating Holstein cow serum samples over 9 months between February and October. Glycoblotting combined with MALDI-TOF/MS and DMB/HPLC allowed for comprehensive glycomics of whole serum glycoproteins. The results obtained revealed seasonal alterations in serum N-glycan levels and their structural characteristics, such as an increase in high-mannose type N-glycans in spring, the occurrence of di/triantennary complex type N-glycans terminating with two or three Neu5Gc residues in summer and autumn, and N-glycans in winter dominantly displaying Neu5Ac. A multivariate analysis revealed a correlation between the serum expression levels of these season-specific glycoforms and productivity.

Application of glyco-blotting for identification of structures of polysaccharides causing membrane fouling in a pilot-scale membrane bioreactor treating municipal wastewater

A new approach for the analysis of polysaccharides in membrane bioreactor (MBR) is proposed in this study. Enrichment of polysaccharides by glyco-blotting, in which polysaccharides are specifically collected via interactions between the aldehydes in the polysaccharides and aminooxy groups on glycoblotting beads, enabled MALDI-TOF/MS analysis at a high resolution. Structures of polysaccharides extracted from fouled membranes used in a pilot-scale MBR treating municipal wastewater and those in the supernatant of the mixed liquor suspension in the MBR were investigated. It was found that the overlap between polysaccharides found in the supernatants and those extracted from the fouled membrane was rather limited, suggesting that polysaccharides that dominate in supernatants may not be important in membrane fouling in MBRs. Analysis using a bacterial carbohydrate database suggested that capsular polysaccharides (CPS) and/or lipo-polysaccharides (LPS) produced by gram-negative bacteria are key players in the evolution of membrane fouling in MBRs.

Effect of ganglioside GM3 synthase gene knockout on the glycoprotein N-glycan profile of mouse embryonic fibroblast

The structural and clinical significance of cellular glycoproteins and glycosphingolipids (GSLs) are often separately discussed. Considering the biosynthetic pathway of glycoconjugates, glycans of cell-surface glycoproteins and GSLs might partially share functions in maintaining cellular homeostatis. The purpose of this study is to establish a general and comprehensive glycomics protocol for cellular GSLs and N-glycans of glycoproteins. To test the feasibility of a glycoblotting-based protocol, whole glycans released both from GSLs and glycoproteins were profiled concurrently by using GM3 synthase-deficient mouse embryonic fibroblast GM3(-/-). GM3(-/-) cells did not synthesize GM3 or any downstream product of GM3 synthase. Instead, expression levels of o-series gangliosides involving GM1-b and GD1-α increased dramatically, whereas a-/b-series gangliosides were predominantly detected in wild-type (WT) cells. We also discovered that glycoprotein N-glycan profiles of GM3(-/-) cells are significantly altered as compared to WT cells, although GM3 synthase is responsible only for GSLs synthesis and is not associated with glycoprotein N-glycan biosynthesis. The present approach allows for high-throughput profiling of cellular glycomes enriched by different classes of glycoconjugates, and our results demonstrated that gene knockout of the enzymes responsible for GSL biosynthesis significantly influences the N-glycans of glycoproteins.

Effects of single genetic damage in carbohydrate-recognizing proteins in mouse serum N-glycan profile revealed by simple glycotyping analysis

Gene knock-out of C-type lectin receptors expressed in dendritic cells induced significant alteration of serum N-glycans compared with that of gender-matched controls. Glycotyping analysis suggested that putative-core fucosylation is strongly influenced by differences in the dominant mechanisms after carbohydrate recognition by pattern-recognition receptors, endocytosis of ligands, or induction of cytokines/chemokines. However, the loss of galectin-9, a ligand for T-helper type 1-specific cell-surface molecule, did not affect most N-glycan profiles. Interestingly, lack of the Chst3 gene (chondroitin 6-sulfotransferase) appeared to influence markedly the expression of most N-glycans, especially highly modified glycoforms bearing multiple Neu5Gc, Fuc, and LacNAc units. In contrast, genetic mutations in B4galnt1 and B4galnt2 (GalNAc transferase, responsible for the synthesis of many gangliosides) induced no discernable alteration. These results indicate that the biosynthesis of N-glycans of serum glycoproteins can be affected not only by direct genetic mutations in the glycosyltransferases but also by changes in metabolite availability in sugar nucleotide synthesis and Golgi N-glycosylation pathways caused concertedly in whole cells, tissues, and organs by milder deficiencies in immune cell-surface lectins. Many common chronic conditions, such as autoimmunity, metabolic syndrome, and aging/dementia result.

Alternative glycosylation modulates function of IgG and other proteins - implications on evolution and disease

BACKGROUND

Nearly all membrane and secreted proteins, as well as numerous intracellular proteins are glycosylated. However, contrary to proteins which are defined by their individual genetic templates, glycans are encoded in a complex dynamic network of hundreds of genes which participate in the complex biosynthetic pathway of protein glycosylation.

SCOPE OF REVIEW

This review summarizes present knowledge about the importance of alternative glycosylation of IgG and other proteins.

MAJOR CONCLUSIONS

Numerous proteins depend on correct glycosylation for proper function. Very good example for this is the alternative glycosylation of IgG whose effector functions can be completely changed by the addition or removal of a single monosaccharide residue from its glycans.

GENERAL SIGNIFICANCE

The change in the structure of a protein requires mutations in DNA and subsequent selection in the next generation, while even slight alterations in activity or intracellular localization of one or more biosynthetic enzymes are sufficient for the creation of novel glycan structures, which can then perform new functions. Glycome composition varies significantly between individuals, which makes them slightly or even significantly different in their ability to execute specific molecular pathways with numerous implications for development and progression of various diseases. This article is part of a Special Issue entitled Glycoproteomics.