Distinctive characteristics of MALDI-Q/TOF and TOF/TOF tandem mass spectrometry for sequencing of permethylated complex type N-glycans

Species-Specific N-Glycomes and Methylation Patterns of Oysters Crassostrea gigas and Ostrea edulis and Their Possible Consequences for the Norovirus-HBGA Interaction

Noroviruses, the major cause of acute viral gastroenteritis, are known to bind to histo-blood group antigens (HBGAs), including ABH groups and Lewis-type epitopes, which decorate the surface of erythrocytes and epithelial cells of their host tissues. The biosynthesis of these antigens is controlled by several glycosyltransferases, the distribution and expression of which varies between tissues and individuals. The use of HBGAs as ligands by viruses is not limited to humans, as many animal species, including oysters, which synthesize similar glycan epitopes that act as a gateway for viruses, become vectors for viral infection in humans. Here, we show that different oyster species synthesize a wide range of N-glycans that share histo-blood A-antigens but differ in the expression of other terminal antigens and in their modification by O-methyl groups. In particular, we show that the N-glycans isolated from Crassostrea gigas and Ostrea edulis exhibit exquisite methylation patterns in their terminal N-acetylgalactosamine and fucose residues in terms of position and number, adding another layer of complexity to the post-translational glycosylation modifications of glycoproteins. Furthermore, modeling of the interactions between norovirus capsid proteins and carbohydrate ligands strongly suggests that methylation has the potential to fine-tune the recognition events of oysters by virus particles.

Mass Spectrometry Imaging for Glycome in the Brain

Glycans are diverse structured biomolecules that play crucial roles in various biological processes. Glycosylation, an enzymatic system through which various glycans are bound to proteins and lipids, is the most common and functionally crucial post-translational modification process. It is known to be associated with brain development, signal transduction, molecular trafficking, neurodegenerative disorders, psychopathologies, and brain cancers. Glycans in glycoproteins and glycolipids expressed in brain cells are involved in neuronal development, biological processes, and central nervous system maintenance. The composition and expression of glycans are known to change during those physiological processes. Therefore, imaging of glycans and the glycoconjugates in the brain regions has become a “hot” topic nowadays. Imaging techniques using lectins, antibodies, and chemical reporters are traditionally used for glycan detection. However, those techniques offer limited glycome detection. Mass spectrometry imaging (MSI) is an evolving field that combines mass spectrometry with histology allowing spatial and label-free visualization of molecules in the brain. In the last decades, several studies have employed MSI for glycome imaging in brain tissues. The current state of MSI uses on-tissue enzymatic digestion or chemical reaction to facilitate successful glycome imaging. Here, we reviewed the available literature that applied MSI techniques for glycome visualization and characterization in the brain. We also described the general methodologies for glycome MSI and discussed its potential use in the three-dimensional MSI in the brain.

A mass spectrometry-based glycotope-centric cellular glycomics is the more fruitful way forward to see the forest for the trees

The nature of protein glycosylation renders cellular glycomics a very challenging task in having to deal with all the disparate glycans carried on membrane glycoproteins. Rapid mapping by mass spectrometry analysis provides only a coarse sketch of the glycomic complexity based primarily on glycosyl compositions, whereby the missing high-resolution structural details require a combination of multi-mode separations and multi-stages of induced fragmentation to gain sufficiently discriminative precision, often at the expenses of throughput and sensitivity. Given the available technology and foreseeable advances in the near future, homing in on resolving the terminal fucosylated, sialylated and/or sulfated structural units, or glycotopes, maybe a more pragmatic and ultimately more rewarding approach to gain insights into myriad biological processes mediated by these terminal coding units carried on important glycoproteins, to be decoded by a host of endogenous glycan-binding proteins and antibodies. A broad overview of recent technical advances and limitations in cellular glycomics is first provided as a backdrop to the propounded glycotope-centric approach based on advanced nanoLC-MS2/MS3 analysis of permethylated glycans. To prioritize analytical focus on the more tangible glycotopes is akin to first identifying the eye-catching and characteristic-defining flowers and fruits of the glyco-forest, to see the forest for the trees. It has the best prospects of attaining the much-needed balance in sensitivity, structural precision and analytical throughput to match advances in other omics.

Parallel On-Target Derivatization for Mass Calibration and Rapid Profiling of N-Glycans by MALDI-TOF MS

Glycosylation is an important post-translational modification of proteins, and abnormal glycosylation is involved in a variety of diseases. Accurate and rapid profiling of N-glycans by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) is still technically challenging and hampered mainly by mass drift of instrument, manual identification of spectrum peaks, and poor cocrystallization with traditional matrices besides low ionization efficiency of analytes. In the present study, a parallel on-target derivatization strategy (POTDS), on the basis of two rationally combined matrices, i.e., 3-hydrazinobenzoic acid plus DHB (DHB/3HBA) and quinoline-3-carbohydrazide plus DHB (DHB/Q3CH), was proposed for mass calibration and rapid detection of reducing N-glycans. Both DHB/3HBA and DHB/Q3CH show high derivatization efficiency and can improve the ionization efficiency of reducing N-glycans significantly. For mass calibration, in combination with dextrans, DHB/3HBA and DHB/Q3CH prove to be highly sensitive matrices facilitating both MS and MS² calibration for N-glycans in dual polarities. For rapid identification, the regular mass difference observed for each N-glycan labeled with Q3CH and 3HBA respectively can eliminate the occurrence of false positives and promote automated identification of N-glycans in complex samples. For relative quantitation, the acid-base pair of DHB/Q3CH generates a concentrated cocrystallization of glycan-matrix mixtures at the edge of the droplet uniformly, exhibiting good linearity (R² > 0.998) and accuracy (RSD ≤ 10%). Furthermore, the established POTDS was successfully utilized to assess N-glycans of serum from HCC patients, revealing potential for biomarker discovery in clinical practice.

Advancing Solutions to the Carbohydrate Sequencing Challenge

Carbohydrates possess a variety of distinct features with stereochemistry playing a particularly important role in distinguishing their structure and function. Monosaccharide building blocks are defined by a high density of chiral centers. Additionally, the anomericity and regiochemistry of the glycosidic linkages carry important biological information. Any carbohydrate-sequencing method needs to be precise in determining all aspects of this stereodiversity. Recently, several advances have been made in developing fast and precise analytical techniques that have the potential to address the stereochemical complexity of carbohydrates. This perspective seeks to provide an overview of some of these emerging techniques, focusing on those that are based on NMR and MS-hybridized technologies including ion mobility spectrometry and IR spectroscopy.

Tailoring N-Glycan Biosynthesis for Production of Therapeutic Proteins in Saccharomyces cerevisiae

The ability to control and adjust the N-glycosylation pathway of Saccharomyces cerevisiae is a key step toward production of therapeutic glycoproteins such as antibodies or erythropoietin. The focus of this chapter is to describe the road from yeast-type N-glycosylation to human-type complex N-glycosylation. The chapter describes the cell engineering and provides the detailed analytical procedures required to perform glycan analysis using MALDI-TOF mass spectrometry.

Systems glycomics of adult zebrafish identifies organ-specific sialylation and glycosylation patterns

The emergence of zebrafish Danio rerio as a versatile model organism provides the unique opportunity to monitor the functions of glycosylation throughout vertebrate embryogenesis, providing insights into human diseases caused by glycosylation defects. Using a combination of chemical modifications, enzymatic digestion and mass spectrometry analyses, we establish here the precise glycomic profiles of eight individual zebrafish organs and demonstrate that the protein glycosylation and glycosphingolipid expression patterns exhibits exquisite specificity. Concomitant expression screening of a wide array of enzymes involved in the synthesis and transfer of sialic acids shows that the presence of organ-specific sialylation motifs correlates with the localized activity of the corresponding glycan biosynthesis pathways. These findings provide a basis for the rational design of zebrafish lines expressing desired glycosylation profiles.

Distinct substrate specificities of human GlcNAc-6-sulfotransferases revealed by mass spectrometry-based sulfoglycomic analysis

Sulfated glycans are known to be involved in several glycan-mediated cell adhesion and recognition pathways. Our mRNA transcript analyses on the genes involved in synthesizing GlcNAc-6-O-sulfated glycans in human colon cancer tissues indicated that GlcNAc6ST-2 (CHST4) is preferentially expressed in cancer cells compared with nonmalignant epithelial cells among the three known major GlcNAc-6-O-sulfotransferases. On the contrary, GlcNAc6ST-3 (CHST5) was only expressed in nonmalignant epithelial cells, whereas GlcNAc6ST-1 (CHST2) was expressed equally in both cancerous and nonmalignant epithelial cells. These results suggest that 6-O-sulfated glycans that are synthesized only by GlcNAc6ST-2 may be highly colon cancer-specific, as supported by immunohistochemical staining of cancer cells using the MECA-79 antibody known to be relatively specific to the enzymatic reaction products of GlcNAc6ST-2. By more precise MS-based sulfoglycomic analyses, we sought to further infer the substrate specificities of GlcNAc6STs via a definitive mapping of various sulfo-glycotopes and O-glycan structures expressed in response to overexpression of transfected GlcNAc6STs in the SW480 colon cancer cell line. By detailed MS/MS sequencing, GlcNAc6ST-3 was shown to preferentially add sulfate onto core 2-based O-glycan structures, but it does not act on extended core 1 structures, whereas GlcNAc6ST-1 prefers core 2-based O-glycans to extended core 1 structures. In contrast, GlcNAc6ST-2 could efficiently add sulfate onto both extended core 1- and core 2-based O-glycans, leading to the production of unique sulfated extended core 1 structures such as R-GlcNAc(6-SO3-)β1-3Galβ1-4GlcNAc(6-SO3-)β1-3Galβ1-3GalNAcα, which are good candidates to be targeted as cancer-specific glycans.

Mass spectrometry for protein sialoglycosylation

Sialic acids are a family of structurally unique and negatively charged nine-carbon sugars, normally found at the terminal positions of glycan chains on glycoproteins and glycolipids. The glycosylation of proteins is a universal post-translational modification in eukaryotic species and regulates essential biological functions, in which the most common sialic acid is N-acetyl-neuraminic acid (2-keto-5-acetamido-3,5-dideoxy-D-glycero-D-galactononulopyranos-1-onic acid) (Neu5NAc). Because of the properties of sialic acids under general mass spectrometry (MS) conditions, such as instability, ionization discrimination, and mixed adducts, the use of MS in the analysis of protein sialoglycosylation is still challenging. The present review is focused on the application of MS related methodologies to the study of both N- and O-linked sialoglycans. We reviewed MS-based strategies for characterizing sialylation by analyzing intact glycoproteins, proteolytic digested glycopeptides, and released glycans. The review concludes with future perspectives in the field.

Identifying Specific and Differentially Linked Glycosyl Residues in Mammalian Glycans by Targeted LC-MS Analysis

Glycans, which are widespread in nature, consist of a large number of monosaccharides linked via glycosidic bonds. Due to the complex nature of glycan structures on glycoproteins, assessing the configuration and positions of the glycosidic linkages of a glycan is a subject of considerable interest. In this study, a method for accomplishing this using partially O-methylated alditols (PMAs) from glycans combined with LC-MS analysis is reported. N-Glycans were first per-methylated with methyl iodide, and the levels of methylation were further confirmed by MALDI-TOF. PMAs were then produced via complete hydrolysis and reduction. PMAs derived from Fetuin N-glycan and Lewis^a antigen carbohydrates were successfully detected by LC-MS analysis. This analysis can be performed without the need for an additional derivatization step for GC analysis, and should be suitable for use in conjunction with a LC-MS-based analysis platform.

Novel ionic liquid matrices for qualitative and quantitative detection of carbohydrates by matrix assisted laser desorption/ionization mass spectrometry

Analysis of carbohydrates based on matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is still challenging and researchers have been devoting themselves to efficient matrices discovery. In the present study, the design, synthesis, qualitative and quantitative performance of non-derivative ionic liquid matrices (ILMs) were reported. DHB/N-methylaniline (N-MA) and DHB/N-ethylaniline (N-EA), performing best for carbohydrate detection, have been screened out. The limit of detection for oligosaccharide provided by DHB/N-MA and DHB/N-EA were as low as 10 fmol. DHB/N-MA and DHB/N-EA showed significantly higher ion generation efficiency than DHB. The comparison of capacity to probe polysaccharide between these two ILMs and DHB also revealed their powerful potential. Their outstanding performance were probably due to lower proton affinities and stronger UV absorption at λ = 355 nm. What is more, taking DHB/N-MA as an example, quantitative analysis of fructo-oligosaccharide mixtures extracted and identified from rice noodles has been accomplished sensitively using an internal standard method. Overall, DHB/N-MA and DHB/N-EA exhibited excellent performance and might be significant sources as the carbohydrate matrices.

Characterization of IgG glycosylation in rheumatoid arthritis patients by MALDI-TOF-MSn and capillary electrophoresis

An analytical method based on the combination of multistage mass spectrometry (MSⁿ) and capillary electrophoresis (CE) was developed for the analysis of immunoglobulin G (IgG) glycosylation in rheumatoid arthritis (RA) patients. It has been recently suggested that IgG glycosylation defect may be involved in RA immunopathogenesis. Complete characterization of glycans, including both qualitative and quantitative analysis, requires a combination of different techniques, and accurate, robust, sensitive, and high-throughput methodologies are important for analysis of clinical samples. In the present study, N-glycosylation of IgG in RA patients and in healthy people was characterized through identification of the released glycans using multistage matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MSⁿ), and quantitation by CE. Assignment of the IgG N-glycan structures was made through branching pattern analysis by MSⁿ with high-throughput. Further accurate quantitation indicated that galactosylation and sialylation of IgG N-glycans in RA cases were significantly lower than in healthy subjects. The results indicate that CE coupled with MSⁿ can identify abnormal glycosylation of IgG in RA patients compared with healthy people, and that the present work is useful for RA mechanism studies and RA diagnosis. Graphical Abstract Qualitative and quantitative analysis of IgG glycosylation in rheumatoid arthritis patients by MALDI-TOF-MSⁿ and capillary electrophoresis.

Current landscape of protein glycosylation analysis and recent progress toward a novel paradigm of glycoscience research

This review covers the basics and some applications of methodologies for the analysis of glycoprotein glycans. Analytical techniques used for glycoprotein glycans, including liquid chromatography (LC), capillary electrophoresis (CE), mass spectrometry (MS), and high-throughput analytical methods based on microfluidics, were described to supply the essentials about biopharmaceutical and biomarker glycoproteins. We will also describe the MS analysis of glycoproteins and glycopeptides as well as the chemical and enzymatic releasing methods of glycans from glycoproteins and the chemical reactions used for the derivatization of glycans. We hope the techniques have accommodated most of the requests from glycoproteomics researchers.

Efficient Mapping of Sulfated Glycotopes by Negative Ion Mode nanoLC-MS/MS-Based Sulfoglycomic Analysis of Permethylated Glycans

We have previously developed the enabling techniques for sulfoglycomics based on mass spectrometry (MS) analysis of permethylated glycans, which preserves the attractive features of more reliable MS/MS sequencing compared with that performed on native glycans, while providing an easy way to separate and hence enrich the sulfated glycans. Unlike LC-MS/MS analysis of native glycans in negative ion mode that has been more widely in use, the characteristics and potential benefits of similar applications based on permethylated sulfated glycans have not been fully investigated. We report here the important features of reverse phase-based nanoLC-MS/MS analysis of permethylated sulfated glycans in negative ion mode and demonstrate that complementary sets of diagnostic fragment ions afforded can allow rapid identification of various fucosylated, sialylated, sulfated glycotopes and definitive determination of the location of sulfate in a way difficult to achieve by other means. A parallel acquisition of both higher collision energy and trap-based MS(2) coupled with a product dependent MS(3) is conceivably the most productive sulfoglycomic workflow currently possible and the manually curated fragmentation characteristics presented here will allow future developments in automating data analysis.

Mass spectrometry-based N-linked glycomic profiling as a means for tracking pancreatic cancer metastasis

The aberrant glycosylation profile on the surface of cancer cells has been recognized for its potential diagnostic value towards assessing tumor progression. In this study, we initially investigate N-glycan profiles on the surface of normal (HPDE) and cancerous (Capan-1, Panc-1, and MIA PaCa-2) pancreatic cell lines, which are from different sites of pancreatic tumor. The enzymatically deglycosylated total N-glycans are permethylated via a quantitative solid-phase method and then analyzed by using MALDI-TOF MS and MALDI-QIT-TOF MS. We demonstrate that the level of high-mannose type glycans is higher among Capan-1 cells-pancreatic cancer cells that have metastasized to the liver-than that observed among Panc-1 and MIA PaCa-2 cells-pancreatic cancer cells from the pancreas duct head and tail regions, respectively. Furthermore, the relative abundance of highly-branched sialyted N-glycans is significantly up-regulated on Panc-1 and MIA PaCa-2 pancreatic cancer cells compared to that of normal HPDE pancreas cells. Taken together, these results indicate that specific N-glycosylation profile changes in pancreatic cancer cells can be used to not only distinguish between normal and cancerous cells but also provide more information on their location and metastatic potential.

Quantitation of permethylated N-glycans through multiple-reaction monitoring (MRM) LC-MS/MS

The important biological roles of glycans and their implications in disease development and progression have created a demand for the development of sensitive quantitative glycomics methods. Quantitation of glycans existing at low abundance is still analytically challenging. In this study, an N-linked glycans quantitation method using multiple-reaction monitoring (MRM) on a triple quadrupole instrument was developed. Optimum normalized collision energy (CE) for both sialylated and fucosylated N-glycan was determined to be 30%, whereas it was found to be 35% for either fucosylated or sialylated N-glycans. The optimum CE for mannose and complex type N-glycan was determined to be 35%. Additionally, the use of three transitions was shown to facilitate reliable quantitation. A total of 88 N-glycan compositions in human blood serum were quantified using this MRM approach. Reliable detection and quantitation of these glycans was achieved when the equivalence of 0.005 μL of blood serum was analyzed. Accordingly, N-glycans down to the 100th of a μL level can be reliably quantified in pooled human blood serum, spanning a dynamic concentration range of three orders of magnitude. MRM was also effectively utilized to quantitatively compare the expression of N-glycans derived from brain-targeting breast carcinoma cells (MDA-MB-231BR) and metastatic breast cancer cells (MDA-MB-231). Thus, the described MRM method of permethylated N-glycan enables a rapid and reliable identification and quantitation of glycans derived from glycoproteins purified or present in complex biological samples.

A single arabinan chain is attached to the phosphatidylinositol mannosyl core of the major immunomodulatory mycobacterial cell envelope glycoconjugate, lipoarabinomannan

Lipoarabinomannan (LAM) is composed of a phosphatidylinositol anchor followed by a mannan followed by an arabinan that may be capped with various motifs including oligosaccharides of mannose. A related polymer, lipomannan (LM), is composed of only the phosphatidylinositol and mannan core. Both the structure and the biosynthesis of LAM have been studied extensively. However, fundamental questions about the branching structure of LM and the number of arabinan chains on the mannan backbone in LAM remain. LM and LAM molecules produced by three different glycosyltransferase mutants of Mycobacterium smegmatis were used here to investigate these questions. Using an MSMEG_4241 mutant that lacks the α-(1,6)-mannosyltransferase used late in LM elongation, we showed that the reducing end region of the mannan that is attached to inositol has 5-7 unbranched α-6-linked-mannosyl residues followed by two or three α-6-linked mannosyl residues branched with single α-mannopyranose residues at O-2. After these branched mannosyl residues, the α-6-linked mannan chain is terminated with an α-mannopyranose at O-2 rather than O-6 of the penultimate residue. Analysis of the number of arabinans attached to the mannan core of LM in two other mutants (ΔembC and ΔMSMEG_4247) demonstrated exactly one arabinosyl substitution of the mannan core suggestive of the arabinosylation of a linear LM precursor with ∼10-12 mannosyl residues followed by additional mannosylation of the core and arabinosylation of a single arabinosyl "primer." Thus, these studies suggest that only a single arabinan chain attached near the middle of the mannan core is present in mature LAM and allow for an updated working model of the biosynthetic pathway of LAM and LM.

Electron capture dissociation of divalent metal-adducted sulfated N-glycans released from bovine thyroid stimulating hormone

Sulfated N-glycans released from bovine thyroid stimulating hormone (bTSH) were ionized with the divalent metal cations Ca(2+), Mg(2+), and Co by electrospray ionization (ESI). These metal-adducted species were subjected to infrared multiphoton dissociation (IRMPD) and electron capture dissociation (ECD) and the corresponding fragmentation patterns were compared. IRMPD generated extensive glycosidic and cross-ring cleavages, but most product ions suffered from sulfonate loss. Internal fragments were also observed, which complicated the spectra. ECD provided complementary structural information compared with IRMPD, and all observed product ions retained the sulfonate group, allowing sulfonate localization. To our knowledge, this work represents the first application of ECD towards metal-adducted sulfated N-glycans released from a glycoprotein. Due to the ability of IRMPD and ECD to provide complementary structural information, the combination of the two strategies is a promising and valuable tool for glycan structural characterization. The influence of different metal ions was also examined. Calcium adducts appeared to be the most promising species because of high sensitivity and ability to provide extensive structural information.

Increasing the depth of mass spectrometry-based glycomic coverage by additional dimensions of sulfoglycomics and target analysis of permethylated glycans

Hog or porcine gastric mucin resembles the human source in carrying not only blood group antigens but also the rather rare α4-GlcNAc-capped terminal epitope functionally implicated in protection against Helicobacter pylori infection. Being more readily available and reasonably well characterized, it serves as a good reagent for immunobiological studies, as well as a standard for analytical methodology developments. Current approaches in mass spectrometry (MS)-based glycomic mapping remain vastly inadequate in revealing the full complexity of glycosylation, particularly for cases such as the extremely heterogeneous O-glycosylation of mucosal mucins that can be further sulfated. We demonstrate here a novel concerted workflow that extends the conventional matrix-assisted laser desorption/ionization–mass spectrometry (MALDI-MS) mapping of permethylated glycans in positive ion mode to include a further step of sulfoglycomic analysis in negative ion mode. This was facilitated by introducing a mixed-mode solid-phase extraction step, which allows direct cleanup and simultaneous fractionation of the permethylated glycans into separate non-sulfated and sulfated pools in one single step. By distinct MALDI-MS/MS fragmentation patterns, all previously known structural features of porcine gastric mucin including the terminal epitopes and location of sulfates could be readily defined. We additionally showed that both arms of the core 2 structures could be extended via 6-O-sulfated GlcNAc to yield a series of disulfated O-glycans not previously reported, thus expanding its current glycomic coverage. However, a targeted LC-MSn analysis was required and best suited to dig even deeper into validating the occurrence of very minor structural isomers carrying the Lewis Y epitope implicated by positive antibody binding.

The usefulness of hydrazine derivatives for mass spectrometric analysis of carbohydrates

Over the last years, extensive studies have evaluated glycans from different biological samples and validated the importance of glycosylation as one of the most important post-translational modifications of proteins. Although a number of new methods for carbohydrate analysis have been published and there has been significant progress in their identification, the development of new approaches to study these biomolecules and understand their role in living systems are still vivid challenges that intrigue glycobiologists. In the last decade, the success in analyses of oligosaccharides has been driven mainly by the development of innovative, highly sensitive mass spectrometry techniques. For enhanced mass spectrometry detection, carbohydrate molecules are often derivatized. Besides, the type of labeling can influence the fragmentation pattern and make the structural analysis less complicated. In this regard, in 2003 we introduced the low scale, simple non-reductive tagging of glycans employing phenylhydrazine (PHN) as the derivatizing reagent. PHN-labeled glycans showed increased detection and as reported previously they can be analyzed by HPLC, ESI, or MALDI immediately after derivatization. Under tandem mass spectrometry conditions, PHN-derivatives produced useful data for the structural elucidation of oligosaccharides. This approach of analysis has helped to reveal new isomeric structures for glycans of known/unknown composition and has been successfully applied for the profiling of N-glycans obtained from serum samples and cancer cells. The efficacy of this labeling has also been evaluated for different substituted hydrazine reagents. This review summarizes all types of reducing-end labeling based on hydrazone-linkage that have been used for mass spectrometric analyses of oligosaccharides. This review is also aimed at correcting some past misconceptions or interpretations reported in the literature.

N-glycosylamine-mediated isotope labeling for mass spectrometry-based quantitative analysis of N-linked glycans

N-linked glycosylation is a major protein modification involved in many essential cellular functions. Methods capable of quantitative glycan analysis are highly valuable and have been actively pursued. Here we describe a novel N-glycosylamine-based strategy for isotopic labeling of N-linked glycans for quantitative analysis by use of mass spectrometry (MS). This strategy relies on the primary amine group on the reducing end of freshly released N-linked glycans for labeling, and eliminates the need for the harsh labeling reaction conditions and/or tedious cleanup procedures required by existing methods. By using NHS-ester amine chemistry we used this strategy to label N-linked glycans from a monoclonal antibody with commercially available tandem mass tags (TMT). Only duplex experiments can be performed with currently available TMT reagents, because quantification is based on the intensity of intact labeled glycans. Under mild reaction conditions, greater than 95% derivatization was achieved in 30 min and the labeled glycans, when kept at -20 °C, were stable for more than 10 days. By performing glycan release, TMT labeling, and LC-MS analysis continuously in a single volatile aqueous buffer without cleanup steps, we were able to complete the entire analysis in less than 2 h. Quantification was highly accurate and the dynamic range was large. Compared with previously established methods, N-glycosylamine-mediated labeling has the advantages of experimental simplicity, efficient labeling, and preserving glycan integrity.

Distribution of the Galβ1-4Gal epitope among birds: species-specific loss of the glycan structure in chicken and its relatives

The Galβ1-4Gal epitope is rarely found in mammals, and the natural antibody against Galβ1-4Gal is rich in human. In contrast, we have previously demonstrated the presence of Galβ1-4Gal in pigeon and ostrich, and the absence of this epitope in chicken. Here, to further investigate the expression of this glycan among birds, egg white glycoproteins and egg yolk IgG from nine species of birds, namely, chicken, duck, emu, guineafowl, ostrich, peafowl, pigeon, quail, and turkey, were analyzed by western blot using an anti-(Galβ1-4Gal) antibody. The results indicated that some egg white glycoproteins from emu, ostrich, and quail, and heavy chains of IgG from all of the birds, except chicken and quail, were stained with the antibody. The presence of Galβ1-4Gal on N-glycans of IgGs from guineafowl, peafowl, and turkey were confirmed by mass spectrometry (MS), MS/MS, and MS(n) analyses. In quail, the presence of Galβ1-4Gal was confirmed by detecting the activities of UDP-galactose: β-galactoside β1,4-galactosyltransferase (β4GalT(Gal)) in various tissues, and by detecting Galβ1-4Gal by western blotting. In contrast, bamboo partridge, which is a close relative of chicken, did not show any detectable activities of β4GalT(Gal) or Galβ1-4Gal on glycoproteins. Because quail, peafowl, turkey, chicken, and bamboo partridge belong to the same family, i.e., Phasianidae, expression of Galβ1-4Gal was most likely differentiated within this family. Considering that Galβ1-4Gal is also expressed in ostrich, emu, and pigeon, which are phylogenetically distant relatives within modern birds, Galβ1-4Gal expression appears to be widely distributed among birds, but might have been abolished in the ancestors of chicken and bamboo partridge.

Advanced mass spectrometry and chemical analyses reveal the presence of terminal disialyl motif on mouse B-cell glycoproteins

The occurrence of a terminal disialyl motif on mammalian O-glycans is increasingly being identified through recent mass spectrometry (MS)-based glycomic profiling. In most cases, it is carried on simple core 1 structures in which both the galactose and N-acetyl galactosamine can be disialylated. In contrast, a disialyl motif on N-glycans is less readily revealed by MS mapping, since additional MS/MS analysis is required to determine the distribution of the various sialic acids on typically multisialylated complex type N-glycans. In our MS-based glycomic screening, we found that a mouse B lymphoma cell line, BCL1, ranks among those that have the highest amount of disialyl motif on its O-glycans, including those carried on CD45. More intriguingly, detailed chemical and MS/MS analyses unambiguously showed that the Neu5Gcα2-8Neu5Gc disialyl motif is also present on the N-glycans and that it can be carried on the termini of polylactosaminoglycan chains, which can be further sulfated on the proximal GlcNAc, occurring alongside other monosialylated sulfated LacNAc termini. Upon silencing the expression of mouse α2,8-sialyltransferase VI (ST8Sia VI), the overall disialyl content decreases significantly, but more so for that on the N-glycans than the O-glycans. ST8Sia VI was further shown to be the most significantly upregulated ST8Sia during plasma cell differentiation, which coincides with increasing content of the disialyl motif. Increasing terminal disialylation without leading to polysialylation may thus have important biological consequences awaiting further investigation. Likewise, the expression of mono- and disialylated sulfated LacNAc may constitute novel recognition codes modulating B-cell activation and differentiation.

A combined system for engineering glycosylation efficiency and glycan structure in Saccharomyces cerevisiae

We describe a novel synthetic N-glycosylation pathway to produce recombinant proteins carrying human-like N-glycans in Saccharomyces cerevisiae, at the same time addressing glycoform and glycosylation efficiency. The Δalg3 Δalg11 double mutant strain, in which the N-glycans are not matured to their native high-mannose structure, was used. In this mutant strain, lipid-linked Man(3)GlcNAc(2) is built up on the cytoplasmic side of the endoplasmic reticulum, flipped by an artificial flippase into the ER lumen, and then transferred with high efficiency to the nascent polypeptide by a protozoan oligosaccharyltransferase. Protein-bound Man(3)GlcNAc(2) serves directly as a substrate for Golgi apparatus-targeted human N-acetylglucosaminyltransferases I and II. Our results confirmed the presence of the complex human-like N-glycan structure GlcNAc(2)Man(3)GlcNAc(2) on the secreted monoclonal antibody HyHEL-10. However, due to the interference of Golgi apparatus-localized mannosyltransferases, heterogeneity of N-linked glycans was observed.

Electron detachment dissociation of underivatized chloride-adducted oligosaccharides

Chloride anion attachment has previously been shown to aid determination of saccharide anomeric configuration and generation of linkage information in negative ion post-source decay MALDI tandem mass spectrometry. Here, we employ electron detachment dissociation (EDD) and collision activated dissociation (CAD) for the structural characterization of underivatized oligosaccharides bearing a chloride ion adduct. Both neutral and sialylated oligosaccharides are examined, including maltoheptaose, an asialo biantennary glycan (NA2), disialylacto-N-tetraose (DSLNT), and two LS tetrasaccharides (LSTa and LSTb). Gas-phase chloride-adducted species are generated by negative ion mode electrospray ionization. EDD and CAD spectra of chloride-adducted oligosaccharides are compared to the corresponding spectra for doubly deprotonated species not containing a chloride anion to assess the role of chloride adduction in the stimulation of alternative fragmentation pathways and altered charge locations allowing detection of additional product ions. In all cases, EDD of singly chloridated and singly deprotonated species resulted in an increase in observed cross-ring cleavages, which are essential to providing saccharide linkage information. Glycosidic cleavages also increased in EDD of chloride-adducted oligosaccharides to reveal complementary structural information compared to traditional (non-chloride-assisted) EDD and CAD. Results indicate that chloride adduction is of interest in alternative anion activation methods such as EDD for oligosaccharide structural characterization.

MALDI in-source decay, from sequencing to imaging

Matrix-assisted laser desorption/ionization (MALDI) is now a mature method allowing the identification and, more challenging, the quantification of biopolymers (proteins, nucleic acids, glycans, etc). MALDI spectra show mostly intact singly charged ions. To obtain fragments, the activation of singly charged precursors is necessary, but not efficient above 3.5 kDa, thus making MALDI MS/MS difficult for large species. In-source decay (ISD) is a prompt fragmentation reaction that can be induced thermally or by radicals. As fragments are formed in the source, precursor ions cannot be selected; however, the technique is not limited by the mass of the analyzed compounds and pseudo MS3 can be performed on intense fragments. The discovery of new matrices that enhance the ISD yield, combined with the high sensitivity of MALDI mass spectrometers, and software development, opens new perspectives. We first review the mechanisms involved in the ISD processes, then discuss ISD applications like top-down sequencing and post-translational modifications (PTMs) studies, and finally review MALDI-ISD tissue imaging applications.

Structural Characterization of Carbohydrates by Fourier Transform Tandem Mass Spectrometry

Fourier transform tandem mass spectrometry (MS/MS) provides high mass accuracy, high sensitivity, and analytical versatility and has therefore emerged as an indispensable tool for structural elucidation of biomolecules. Glycosylation is one of the most common posttranslational modifications, occurring in ~50% of proteins. However, due to the structural diversity of carbohydrates, arising from non-template driven biosynthesis, achievement of detailed structural insight is highly challenging. This review briefly discusses carbohydrate sample preparation and ionization methods, and highlights recent developments in alternative high-resolution MS/MS strategies, including infrared multiphoton dissociation (IRMPD), electron capture dissociation (ECD), and electron detachment dissociation (EDD), for carbohydrates with a focus on glycans and proteoglycans from mammalian glycoproteins.

MS-based glycomic strategies for probing the structural details of polylactosaminoglycan chain on N-glycans and glycoproteomic identification of its protein carriers

Most MS-based glycomic and glycoproteomic analyses focus on identifying changes in terminal glyco-epitopes represented by sialylation and fucosylation at specific positions of the terminal N-acetyllactosamine units. Much less attention was accorded to the underlying linear or branched poly-N-acetyllactosamine extension from the N-glycan trimannosyl core other than a simple inference of its presence due to mass data and hence glycosyl compositional assignment. Using the EA.hy926 cell line derived from human umbilical vein endothelial cells (HUVEC), we have systematically investigated the MALDI- and ESI-MS-based methodologies for probing the structural details of endothelial polylactosaminoglycans at both MS and MS(2) levels in conjunction with the use of endo-β-galactosidase to identify branching motifs and initiation sites. We showed that the polylactosaminoglycan chains on the N-glycans of EA.hy926 were less sialylated and fucosylated but more extended and branched than those of human umbilical vein endothelial cells, thus demonstrating a fundamental glycomic difference. For EA.hy926 that was investigated in more details, its polylactosaminoglycan chains were shown to be not restricted to extending from a specific antenna including the biologically important 6-arm position. Finally, experimental conditions for glycopeptide enrichment by tomato lectin were further optimized, which led to identification of over 40 candidate endothelial membrane protein carriers of polylactosaminoglycans by proteomic analysis.

Glycoproteomics analysis to identify a glycoform on haptoglobin associated with lung cancer

Glycosylation is a common protein modification that is of interest in current cancer research because altered carbohydrate moieties are often found during cancer progress. A search for biomarkers in human lung cancer serum samples using glycoproteomic approaches identified fucosylated haptoglobin (Hp) significantly increased in serum of each subtype of lung cancer compared to normal donors. In addition, MS provided evidence of an increase of Hp fucosylation; the glycan structure was determined to be an α 2,6-linked tri-sialylated triantennary glycan containing α1,3-linked fucose attached to the four-linked position of the three-arm mannose of N-linked core pentasaccharide. These preliminary findings suggest that the specific glycoform of Hp may be useful as a marker to monitor lung cancer progression.

Mass spectrometric assay for analysis of haptoglobin fucosylation in pancreatic cancer

A mass spectrometric method was developed to elucidate the N-glycan structures of serum glycoproteins and utilize fucosylated glycans as potential markers for pancreatic cancer. This assay was applied to haptoglobin in human serum where N-glycans derived from the serum of 16 pancreatic cancer patients were compared with those from 15 individuals with benign conditions (5 normals, 5 chronic pancreatitis, and 5 type II diabetes). This assay used only 10 μL of serum where haptoglobin was extracted using a monoclonal antibody and quantitative permethylation was performed on desialylated N-glycans followed by MALDI-QIT-TOF MS analysis. Eight desialylated N-glycan structures of haptoglobin were identified where a bifucosylated triantennary structure was reported for the first time in pancreatic cancer samples. Both core and antennary fucosylation were elevated in pancreatic cancer samples compared to samples from benign conditions. Fucosylation degree indices were calculated and show a significant difference between pancreatic cancer patients of all stages and the benign conditions analyzed. This study demonstrates that a serum assay based on haptoglobin fucosylation patterns using mass spectrometric analysis may serve as a novel method for the diagnosis of pancreatic cancer.

Prominent expression of sialyl Lewis X-capped core 2-branched O-glycans on high endothelial venule-like vessels in gastric MALT lymphoma

High endothelial venule (HEV)-like vessels have been observed in gastric B cell lymphoma of mucosa-associated lymphoid tissue type (MALT lymphoma), as well as in its preceding lesion, chronic Helicobacter pylori gastritis. Previously we reported that glycans on HEV-like vessels in the latter lesion served as L-selectin ligands, although their function is unclear. We have investigated sialyl Lewis X (sLeX)-related glycoepitopes and found that MECA-79(-) /HECA-452(+) /NCC-ST-439(+) HEV-like vessels preferentially mark gastric MALT lymphoma compared to chronic H. pylori gastritis. We then constructed CHO cell lines expressing potential MECA-79(-) /HECA-452(+) /NCC-ST-439(+) glycans, as well as other sLeX-type glycans, on CD34 and evaluated L-selectin binding to those cells, using L-selectin-IgM chimera binding and lymphocyte adhesion assays. L-selectin-IgM chimeras bound to CHO cells expressing 6-sulpho-sLeX attached to core 2-branched O-glycans with or without 6-sulpho-sLeX attached to extended core 1 O-glycans, but only marginally to other CHO cell lines. By contrast, CHO cells expressing 6-sulpho-sLeX attached to extended core 1 and/or core 2-branched O-glycans, as well as non-sulphated sLeX attached to core 2-branched O-glycans, showed substantial lymphocyte binding, while binding was negligible on lines expressing 6-sulpho- and non-sulphated sLeX attached to N-glycans and non-sulphated sLeX attached to extended core 1 O-glycans. These results indicate that MECA-79(-) /HECA-452(+) /NCC-ST-439(+) glycans, specifically, 6-sulpho- and non-sulphated sLeXs attached to core 2-branched O-glycans, expressed on HEV-like vessels in gastric MALT lymphoma function as L-selectin ligands and likely contribute to H. pylori-specific T cell recruitment in the progression of gastric MALT lymphoma.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for the period 2005-2006

This review is the fourth update of the original review, 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 2006. The review covers fundamental studies, fragmentation of carbohydrate ions, method developments, and applications of the technique to the analysis of different types of carbohydrate. Specific compound classes that are covered include carbohydrate polymers from plants, N- and O-linked glycans from glycoproteins, glycated proteins, glycolipids from bacteria, glycosides, and various other natural products. There is a short section on the use of MALDI-TOF mass spectrometry for the study of enzymes involved in glycan processing, a section on industrial processes, particularly the development of biopharmaceuticals and a section on the use of MALDI-MS to monitor products of chemical synthesis of carbohydrates. Large carbohydrate-protein complexes and glycodendrimers are highlighted in this final section.

Switching of the core structures of glycosphingolipids from globo- and lacto- to ganglio-series upon human embryonic stem cell differentiation

A systematic survey of expression profiles of glycosphingolipids (GSLs) in two hESC lines and their differentiated embryoid body (EB) outgrowth with three germ layers was carried out using immunofluorescence, flow cytometry, and MALDI-MS and MS/MS analyses. In addition to the well-known hESC-specific markers stage-specific embryonic antigen 3 (SSEA-3) and SSEA-4, we identified several globosides and lacto-series GSLs, previously unrevealed in hESCs, including Gb(4)Cer, Lc(4)Cer, fucosyl Lc(4)Cer, Globo H, and disialyl Gb(5)Cer. During hESC differentiation into EBs, MS analysis revealed a clear-cut switch in the core structures of GSLs from globo- and lacto- to ganglio-series, which was not as evident by immunostaining with antibodies against SSEA-3 and SSEA-4, owing to their cross-reactivities with various glycosphingolipids. Such a switch was attributable to altered expression of key glycosyltransferases (GTs) in the biosynthetic pathways by the up-regulation of ganglio-series-related GTs with simultaneous down-regulation of globo- and lacto-series-related GTs. Thus, these results provide insights into the unique stage-specific transition and mechanism for alterations of GSL core structures during hESC differentiation. In addition, unique glycan structures uncovered by MS analyses may serve as surface markers for further delineation of hESCs and help identify of their functional roles not only in hESCs but also in cancers.

Core2 O-glycan structure is essential for the cell surface expression of sucrase isomaltase and dipeptidyl peptidase-IV during intestinal cell differentiation

Alterations in glycosylation play an important role during intestinal cell differentiation. Here, we compared expression of mucin-type O-glycan synthases from proliferating and differentiated HT-29 and Caco-2 cells. Mucin-type O-glycan structures were analyzed at both stages by mass spectrometry. Core2 β1,6-N-acetylglucosaminyltransferase-2 (C2GnT-2) was markedly increased in differentiated HT-29 and Caco-2 cells, but the core3 structure was hardly detectable. To determine whether such differential expression of mucin-type O-glycan structures has physiological significance in intestinal cell differentiation, expression of sucrase isomaltase (SI) and dipeptidyl-peptidase IV (DPP-IV), two well known intestinal differentiation markers, was examined. Interestingly, the fully glycosylated mature form of SI was decreased in C2GnT-2 knock-out mice but not in core2 N-acetylglucosaminyltransferase-3 (C2GnT-3) nulls. In addition, expression of SI and DPP-IV was dramatically reduced in C2GnT-1-3 triple knock-out mice. These patterns were confirmed by RNAi analysis; C2GnT-2 knockdown significantly reduced cell surface expression of SI and DPP-IV in Caco-2 cells. Similarly, overexpression of the core3 structure in HT-29 cells attenuated cell surface expression of both enzymes. These findings indicate that core3 O-glycan structure regulates cell surface expression of SI and DPP-IV and that core2 O-glycan is presumably an essential mucin-type O-glycan structure found in both molecules in vivo. Finally, goblet cells in the upper part of the crypt showed impaired maturation in the core2 O-glycan-deficient mice. These studies are the first to clearly identify functional mucin-type O-glycan structures modulating cell surface expression of SI and DPP-IV during the intestinal cell differentiation.

Mass spectrometric analysis of mutant mice

Mass spectrometry (MS) has proven to be the preeminent tool for the rapid, high-sensitivity analysis of the primary structure of glycans derived from diverse biological sources including cells, fluids, secretions, tissues, and organs. These analyses are anchored by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) analysis of permethylated derivatives of glycan pools released from the samples, to produce glycomic mass fingerprints. The application of complimentary techniques, such as chemical and enzymatic digestions, GC-MS linkage analysis, and tandem mass spectrometry (MS/MS) utilizing both electrospray (ES) and MALDI-TOF/TOF, together with bioinformatic tools allows the elucidation of incrementally more detailed structural information from the sample(s) of interest. The mouse as a model organism offers many advantages in the study of human biology, health, and disease; it is a mammal, shares 99% genetic homology with humans and its genome supports targeted mutagenesis in specific genes to produce knockouts efficiently and precisely. Glycomic analyses of tissues and organs from mice genetically deficient in one or more glycosylation gene and comparison with data collected from wild-type samples enables the facile identification of changes and perturbations within the glycome. The Consortium for Functional Glycomics (CFG) has been applying such MS-based glycomic analyses to a range of murine tissues from both wild-type and glycosylation-knockout mice in order to provide a repository of structural data for the glycobiology community. In this chapter, we describe in detail the methodologies used to prepare, derivatize, purify, and analyze glycan pools from mouse organs and tissues by MS. We also present a summary of data produced from the CFG systematic structural analysis of wild-type and knockout mouse tissues, together with a detailed example of a glycomic analysis of the Mgat4a knockout mouse.

Mass spectrometric analysis of sulfated N- and O-glycans

Sulfated N- and O-glycans carried on a myriad of cell-surface adhesion molecules and receptors are often not detected by current approaches in mass spectrometry (MS)-based glycomic mapping of cells and tissues. This is in part due to a natural lower abundance, compounded further by their negatively charged nature, which adversely disfavors their ionization and detection amid a sea of often much more abundant, nonsulfated, sialylated glycans. However, this particular limitation can actually be taken advantage of to effect highly selective enrichment and sensitive MS screening in negative ion mode, provided the ubiquitous sialic acids can first be neutralized. It has been demonstrated that permethylation not only fulfills this role adequately but further confers better MS/MS fragmentation characteristics for more efficient structural mapping and sequencing. Protocols and general practical considerations are described here which would enable one to readily prepare permethylated sulfated glycans, fractionate them away from the more abundant nonsulfated ones in simple steps for high-sensitivity MS analysis, and sensibly interpret the initial sulfoglycomic screening data thus obtained.

Identification of blood group A/A-Leb/y and B/B-Leb/y active glycotopes co-expressed on the O-glycans isolated from two distinct human ovarian cyst fluids

Although the individual human blood group A and B determinants are well defined, their co-expression pattern on a particular glycan carrier in individuals of blood group AB status has not been delineated. To address this issue, complex O-glycans were isolated from two distinct sources of human ovarian cyst glycoproteins (HOC 89 and Cyst 19) and profiled by advanced MS analyses, in conjunction with defining their binding characteristics against a panel of lectins and monoclonal antibodies. The major O-glycans of HOC 89 were found to correspond to sialyl Tn, mono- and di-sialyl T structures, whereas those of Cyst 19 were apparently more heterogeneous and extended to larger sizes. A minimal structure that carries both A and B determinants on the same molecule was identified, in which the A epitope is attached directly to the core GalNAc, whereas the B epitope is preferentially located on the six arms of a core 2 structure. Both arms can be further extended with internal fucosylation that appears to be restricted to those non-sialylated chains already carrying the terminal ABH determinants, thus giving rise to rather prominent A/B-Le(b/y) glycotopes on larger O-glycans.

Determination of N-glycosylation site and glycan structures of pectin methylesterase in jelly fig (Ficus awkeotsang) Achenes

Pectin methylesterase (PME) in jelly fig (Ficus awkeotsang) achenes is an N-glycosylated enzyme responsible for the gelation of jelly curd. A recombinant jelly fig PME was overexpressed in Escherichia coli and confirmed by immunodetection and LC-nanoESI-MS/MS analysis. To identify the N-glycosylation site, native PME and its deglycosylated and recombinant forms, which lacked glycan, were purified and subjected to comparative MALDI-MS mapping of the corresponding tryptic fragments. The results showed that N-glycosylation occurred at Asn(153) of the mature jelly fig PME, the only glycosylation site predicted by its sequence analysis. The major N-glycans released from the native PME by PNGase F were identified by MS/MS analyses as xylosylated, noncore fucosylated pauci-mannose, and complex-type structures. Molecular modeling of the 3D structure of jelly fig PME indicated that the N-glycan was putatively attached to the back region of the active site of this enzyme.

Enabling techniques and strategic workflow for sulfoglycomics based on mass spectrometry mapping and sequencing of permethylated sulfated glycans

Sulfate modifications on terminal epitopes of N- and O-glycans have increasingly been implicated as critical determinants mediating a diverse range of biological recognition functions. To address these low abundance but important sulfated glycans, and the sulfoglycome in general, further development of enrichment strategies and enabling mass spectrometry (MS)-based mapping techniques are needed. In this report, we demonstrate that the sulfated glycans, with and without additional sialylation, can be successfully permethylated by the sodium hydroxide slurry method and be distinguished from phosphorylated glycans by virtue of this derivatization. In conjunction with simple microscale postderivatization fractionation steps, permethyl derivatives fully retaining the negatively charged sulfate moiety and separated from the nonsulfated ones, can be efficiently detected and sequenced de novo by advanced MS/MS in the positive-ion mode. In particular, we show that the highly sequence and linkage informative high energy collision induced dissociation (CID) MS/MS afforded by MALDI-TOF/TOF can be extended to sulfoglycomic applications. The sulfated parent ion selected for CID MS/MS was found to mostly retain the sulfate moiety and therefore allow efficient fragmentation via the usual array of glycosidic, cross ring, and concerted double cleavages. Collectively, the optimized strategy enables a high sensitivity detection and critical mapping of the sulfoglycome such as the one derived from lymph node tissues or cell lines in both negative and positive-ion modes. Novel sulfated epitopes were identified from a crude mouse lymph node preparation, which fully attested to the practical utility of the methodology developed.

Core3 O-glycan synthase suppresses tumor formation and metastasis of prostate carcinoma PC3 and LNCaP cells through down-regulation of alpha2beta1 integrin complex

Although there are numerous reports of carbohydrates enriched in cancer cells, very few studies have addressed the functions of carbohydrates present in normal cells that decrease in cancer cells. It has been reported that core3 O-glycans are synthesized in normal gastrointestinal cells but are down-regulated in cancer cells. To determine the roles of core3 O-glycans, we transfected PC3 and LNCaP prostate cancer cells with beta3-N-acetylglucosaminyltransferase-6 (core3 synthase) required to synthesize core3 O-glycans. Both engineered cell lines exhibited reduced migration and invasion through extracellular matrix components compared with mock-transfected cells. Moreover we found that alpha2beta1 integrin acquired core3 O-glycans in cells expressing core3 synthase with decreased maturation of beta1 integrin, leading to decreased levels of the alpha2beta1 integrin complex, decreased activation of focal adhesion kinase, and reduced lamellipodia formation. Upon inoculation into the prostate of nude mice, PC3 cells expressing core3 O-glycans produced much smaller tumors without metastasis to the surrounding lymph nodes in contrast to robust tumor formation and metastasis seen in mock-transfected PC3 cells. Similarly LNCaP cells expressing core3 O-glycans barely produced subcutaneous tumors in contrast to robust tumor formation by mock-transfected LNCaP cells. These findings indicate that addition of core3 O-glycans to beta1 and alpha2 integrin subunits in prostate cancer cells suppresses tumor formation and tumor metastasis.