Diversity Of Glycans Research Articles

GlycoSS: A DNA Glycosignal Sieve for Deciphering Spatially Resolved EpCAM-Specific Glycoforms.

Malignant transformation of cancer is often accompanied by aberrant glycopatterns. Epithelial-mesenchymal transition (EMT) is a crucial biological process in cancer migration and invasion, accelerating cancer deterioration. High-precision analysis of protein-glycan spatial profiling in the EMT process is essential for elucidating glycosylation functions and cancer progression. However, the diversity of glycans in composition and conformation complicates their spatial analysis. Here, we develop a DNA glycosignal sieve (GlycoSS) visualization platform for screening glycoform expression with a protein spatial dimension. GlycoSS utilizes protein-anchored DNA nanoscanners of distinct lengths to control glycosignal readout, enabling protein-glycan distance modulations, and simultaneously orthogonally amplify glycoform output through signal amplification by an exchange reaction. Using GlycoSS, we screened EpCAM-specific hypoglycosylated glycoform signals in different breast cancer cell subtypes, especially characterizing the spatial distribution of glycans on the MCF-7 cell surface. Considering that the EpCAM-specific N-glycan dysregulation in EMT is pivotal, GlycoSS revealed dynamic glycan fluctuations during IGF-1-induced EMT, revealing that the N-glycans were positively associated with tumor malignancy and metastasis. GlycoSS is anticipated to accelerate the identification of aberrant N-glycosylation in tumor progression, advancing systemic glycobiology insights. Notably, GlycoSS is capable of analyzing diverse glycoprotein profiles, offering additional dimensions into the role of glycoprotein nanoenvironments in regulating membrane protein function.

Sugar-binding Profiles of the Mesothelial Glycocalyx in Frozen Tissues of Mice Revealed by Lectin Staining

The mesothelium is a non-adhesive protective surface that lines the serosal cavities and organs within the body. The glycocalyx is a complex structure that coats the outer layer of the mesothelium. However, due to the limitations of conventional fixation techniques, studies on glycans are limited. In this study, lectin staining of frozen tissues was performed to investigate the diversity of glycans in the glycocalyx of mesothelial cells in mice. Datura stramonium lectin (DSL), which recognizes lactosamine and binds to Galectin-3 and -1, was broadly bound to the mesothelial cells of the visceral and parietal peritoneum but not to the pancreas, liver, intestine, or heart. Furthermore, human mesothelial cells in the omentum and parietal peritoneum were positive for DSL. Erythrina cristagalli lectin binding was specific to mesothelial cells in the parietal peritoneum, that is, the pleura, diaphragm, and peritoneum. Intriguingly, surface sialylation, the key element in reducing peritoneal dissemination and implantation, and promoting ascites formation by ovarian carcinoma cells, was much higher in the parietal peritoneum than in the omentum. These findings revealed slight differences in the glycans of mesothelial cells of different organs, which may be related to clinical diseases. These results also suggest that there may be differences in the functions of parietal and visceral mesothelial cells.

Galactosylation of glycoconjugates using Pacific oyster β-1,3-galactosyltransferases

The Pacific oyster (Magallana gigas) exhibits an extensive diversity of N- and O-linked glycoconjugates, offering significant potential for biotechnological applications. Through genomic data mining, we have identified and characterized a suite of β-1,3-galactosyltransferase enzymes, pivotal for the synthesis of glycan structures. Out of ten cloned gene candidates, six enzymes were successfully expressed recombinantly in Escherichia coli. Four of these enzymes exhibited measurable catalytic activity in the transfer of galactose to various acceptor substrates. Notably, MgB3GalT1 demonstrated the highest efficiency, achieving a 91.2 % conversion rate. This enzyme was proficient in glycosylating diverse glycan structures, including Core 2 O-glycans and several di-, tri-, and tetra-antennary complex N-glycan standards. Mass spectrometric analysis confirmed the successful modification of N-glycans. These findings open new approaches for utilizing oyster-derived enzymes in glycan-based therapeutics and molecular glycoengineering, highlighting their utility in synthetic applications and biotechnological advancements.

Single-Molecule Identification and Quantification of Steviol Glycosides with a Deep Learning-Powered Nanopore Sensor.

Steviol glycosides (SGs) are a class of high-potency noncalorie natural sweeteners made up of a common diterpenoid core and varying glycans. Thus, the diversity of glycans in composition, linkage, and isomerism results in the tremendous structural complexity of the SG family, which poses challenges for the precise identification and leads to the fact that SGs are frequently used in mixtures and their variances in biological activity remain largely unexplored. Here we show that a wild-type aerolysin nanopore can detect and discriminate diverse SG species through the modulable electro-osmotic flow effect at varied applied voltages. At low voltages, the neutral SG molecule was drawn and stuck in the pore entrance due to an energy barrier around R220 sites. The ensuing binding events enable the identification of the majority of SG species. Increasing the voltage can break the barrier and cause translocation events, allowing for the unambiguous identification of several pairs of SGs differing by only one hydroxyl group through recognition accumulation from multiple sensing regions and sites. Based on nanopore data of 15 SGs, a deep learning-based artificial intelligence (AI) model was created to process the individual blockage events, achieving the rapid, automated, and precise single-molecule identification and quantification of SGs in real samples. This work highlights the value of nanopore sensing for precise structural analysis of complex glycans-containing glycosides, as well as the potential for sensitive and rapid quality assurance analysis of glycoside products with the use of AI.

Synergistic pectin deconstruction is a prerequisite for mutualistic interactions between honeybee gut bacteria

The honeybee gut microbiome is crucial for degrading diverse pollen glycans. Yet it is unclear how this process shapes the interactions among bacteria. Here, we demonstrate a conditional mutualistic interaction between strains of two honeybee gut bacteria Bifidobacterium asteroides and Gilliamella apicola. When co-occurring in vitro and in vivo, Bifidobacterium provides complementary demethylation service to promote Gilliamella growth on methylated homogalacturonan, an enriched polysaccharide of pectin. In exchange, Gilliamella shares digestive products with Bifidobacterium, through which a positive interaction is established. This positive interaction vanishes when Bifidobacterium is not required on a non-methylated diet. Results from biochemical and gene expression analyses combined with model simulation further suggest that the ratio change of the two major homogalacturonan breakdown products, galacturonic acid (GalA) and di-GalA, determines the bacterial interaction. This study unravels how glycan metabolism may shape the interactions between honeybee gut bacteria.

Sweet Secrets: Exploring Novel Glycans and Glycoconjugates in the Extracellular Polymeric Substances of "Candidatus Accumulibacter".

Biological wastewater treatment relies on microorganisms that grow as flocs, biofilms, or granules for efficient separation of biomass from cleaned water. This biofilm structure emerges from the interactions between microbes that produce, and are embedded in, extracellular polymeric substances (EPS). The true composition and structure of the EPS responsible for dense biofilm formation are still obscure. We conducted a bottom-up approach utilizing advanced glycomic techniques to explore the glycan diversity in the EPS from a highly enriched "Candidatus Accumulibacter" granular sludge. Rare novel sugar monomers such as N-Acetylquinovosamine (QuiNAc) and 2-O-Methylrhamnose (2-OMe-Rha) were identified to be present in the EPS of both enrichments. Further, a high diversity in the glycoprotein structures of said EPS was identified by means of lectin based microarrays. We explored the genetic potential of "Ca. Accumulibacter" high quality metagenome assembled genomes (MAGs) to showcase the shortcoming of top-down bioinformatics based approaches at predicting EPS composition and structure, especially when dealing with glycans and glycoconjugates. This work suggests that more bottom-up research is necessary to understand the composition and complex structure of EPS in biofilms since genome based inference cannot directly predict glycan structures and glycoconjugate diversity.

Virus-encoded glycosyltransferases hypermodify DNA with diverse glycans

Enzymatic modification of DNA nucleobases can coordinate gene expression, nuclease protection, or mutagenesis. We recently discovered a clade of phage-specific cytosine methyltransferase (MT) and 5-methylpyrimidine dioxygenase (5mYOX) enzymes that produce 5-hydroxymethylcytosine (5hmC) as a precursor for enzymatic hypermodifications on viral genomes. Here, we identify phage MT- and 5mYOX-associated glycosyltransferases (GTs) that catalyze linkage of diverse sugars to 5hmC nucleobase substrates. Metavirome mining revealed thousands of biosynthetic gene clusters containing enzymes with predicted roles in cytosine sugar hypermodification. We developed a platform for high-throughput screening of GT-containing pathways, relying on the Escherichiacoli metabolome as a substrate pool. We successfully reconstituted several pathways and isolated diverse sugar modifications appended to cytosine, including mono-, di-, or tri-saccharides comprised of hexoses, N-acetylhexosamines, or heptose. These findings expand our knowledge of hypermodifications on nucleic acids and the origins of corresponding sugar-installing enzymes.

Integrated chemoenzymatic synthesis of a comprehensive sulfated ganglioside glycan library to decipher functional sulfoglycomics and sialoglycomics.

Ganglioside glycans are ubiquitous and complex biomolecules that are involved in a wide range of biological functions and disease processes. Variations in sialylation and sulfation render the structural complexity and diversity of ganglioside glycans, and influence protein-carbohydrate interactions. Structural and functional insights into the biological roles of these glycans are impeded due to the limited accessibility of well-defined structures. Here we report an integrated chemoenzymatic strategy for expeditious and systematic synthesis of a comprehensive 65-membered ganglioside glycan library covering all possible patterns of sulfation and sialylation. This strategy relies on the streamlined modular assembly of three common sialylated precursors by highly stereoselective iterative sialylation, modular site-specific sulfation through flexible orthogonal protecting-group manipulations and enzymatic-catalysed diversification using three sialyltransferase modules and a galactosidase module. These diverse ganglioside glycans enable exploration into their structure-function relationships using high-throughput glycan microarray technology, which reveals that different patterns of sulfation and sialylation on these glycans mediate their unique binding specificities.

LectoScape: A Highly Multiplexed Imaging Platform for Glycome Analysis and Biomedical Diagnosis.

Glycosylation, a fundamental biological process, involves the attachment of glycans to proteins, lipids, and RNA, and it plays a crucial role in various biological pathways. It is of great significance to obtain the precise spatial distribution of glycosylation modifications at the cellular and tissue levels. Here, we introduce LectoScape, an innovative method enabling detailed imaging of tissue glycomes with up to 1 μm resolution through image mass cytometry (IMC). This method utilizes 12 distinct, nonoverlapping lectins selected via microarray technology, enabling the multiplexed detection of a wide array of glycans. Furthermore, we developed an efficient labeling strategy for these lectins. Crucially, our approach facilitates the concurrent imaging of diverse glycan motifs, including N-glycan and O-glycan, surpassing the capabilities of existing technologies. Using LectoScape, we have successfully delineated unique glycan structures in various cell types, enhancing our understanding of the glycan distribution across human tissues. Our method has identified specific glycan markers, such as α2,3-sialylated Galβ1, 3GalNAc in O-glycan, and terminal GalNAc, as diagnostic indicators for cervical intraepithelial neoplasia. This highlights the potential of LectoScape in cancer diagnostics through the detection of abnormal glycosylation patterns.

Donor Preactivation-Based Glycan Assembly: from Manual to Automated Synthesis.

Carbohydrates are called the third chain of life. Carbohydrates participate in many important biochemical functions in living species, and the biological information carried by them is several orders of magnitude larger than that of nucleic acids and proteins. However, due to the intrinsic complexity and heterogeneity of carbohydrate structures, furnishing pure and structurally well-defined glycans for functional studies is a formidable task, especially for homogeneous large-size glycans. To address this issue, we have developed a donor preactivation-based one-pot glycosylation strategy enabling multiple sequential glycosylations in a single reaction vessel.The donor preactivation-based one-pot glycosylation refers to the strategy in which the glycosyl donor is activated in the absence of a glycosyl acceptor to generate a reactive intermediate. Subsequently, the glycosyl acceptor with the same anomeric leaving group is added, leading to a glycosyl coupling reaction, which is then iterated to rapidly achieve the desired glycan in the same reactor. The advantages of this strategy include the following: (1) unique chemoselectivity is obtained after preactivation; (2) it is independent of the reactivity of glycosyl donors; (3) multiple-step glycosylations are enabled without the need for intermediate purification; (4) only stoichiometric building blocks are required without complex protecting group manipulations. Using this protocol, a range of glycans including tumor-associated carbohydrate antigens, various glycosaminoglycans, complex N-glycans, and diverse bacterial glycans have been synthesized manually. Gratifyingly, the synthesis of mycobacterial arabinogalactan containing 92 monosaccharide units has been achieved, which created a precedent in the field of polysaccharide synthesis. Recently, the synthesis of a highly branched arabinogalactan from traditional Chinese medicine featuring 140 monosaccharide units has been also accomplished to evaluate its anti-pancreatic-cancer activity. In the spirit of green and sustainable chemistry, this strategy can also be applied to light-driven glycosylation reactions, where either UV or visible light can be used for the activation of glycosyl donors.Automated synthesis is an advanced approach to the construction of complex glycans. Based on the two preactivation modes (general promoter activation mode and light-induced activation mode), a universal and highly efficient automated solution-phase synthesizer was further developed to drive glycan assembly from manual to automated synthesis. Using this synthesizer, a library of oligosaccharides covering various glycoforms and glycosidic linkages was assembled rapidly, either in a general promoter-activation mode or in a light-induced-activation mode. The automated synthesis of a fully protected fondaparinux pentasaccharide was realized on a gram scale. Furthermore, the automated synthesis of large-size polysaccharides was performed, allowing the assembly of arabinans up to an astonishing 1080-mer using the automated multiplicative synthesis strategy, taking glycan synthesis to a new height far beyond the synthesis of nucleic acids (up to 200-mer) and proteins (up to 472-mer).

Abstract 1839: Proteomic and glycoproteomic differences associated with prostate cancer in urine

Abstract Background and Aims: Prostate cancer is one of the most common cancers affecting men in the United States, with ~288,300 new cases and 34,700 deaths in 2023 alone. Prostate-specific antigen (PSA), the most widely used prostate cancer biomarker, lacks specificity and sensitivity, leading to unnecessary biopsies, overdiagnosis, and overtreatment. There is an urgent unmet clinical need to find new biomarkers that can distinguish patients with benign disease from those with prostate cancer. Urine is an attractive source for these biomarkers as prostate-derived proteins are more highly concentrated in urine than in blood. To better understand both global proteomic and glycoproteomic molecular signatures that could lead to improved diagnostics for prostate cancer, we analyzed urine samples from unaffected men, men with benign prostatic hyperplasia (BPH), and men with prostate cancer. Methods: Urine samples (N = 58 total) were collected from unaffected men (N = 17), men with BPH (N = 24), and men with prostate cancer (N = 17). Samples were digested with trypsin and analyzed with high-resolution liquid chromatography-tandem mass spectrometry (LC-MS/MS) for shotgun proteomics analysis. Association with cancer was determined through supervised analysis using Pearson correlation. For glycoproteomics analysis, intact glycopeptides were enriched using strong anion exchange-electrostatic repulsion hydrophilic interaction chromatography, fractionated using high pH reversed-phase chromatography, and analyzed with LC-MS/MS. Association with the three conditions was determined through several rounds of supervised analysis using Pearson correlation. Results: In total, 3542 human proteins were identified, and 78 proteins (p < 0.01) were significantly associated with prostate cancer. The glycolysis pathway and lysosome pathway were enriched in samples from men with prostate cancer. In the glycoproteomics analysis, 36 proteins (p < 0.05) had altered glycan diversity in one of the three conditions, and the complement and coagulation cascade pathway and the lysosome pathway were highly enriched. Six proteins (p < 0.05) had significantly increased glycan diversity in the cancerous samples than in the BPH and normal samples. Conclusions: This study identifies a set of interesting proteomic and glycoproteomic differences in urine from men with prostate cancer compared to BPH and non-cancer samples, which warrant further investigation in additional sample cohorts as potential novel biomarkers. Citation Format: Nikhiya Shamsher, Fernando Garcia-Marques, Abel Bermudez, Mark R. Flory, Sharon J. Pitteri. Proteomic and glycoproteomic differences associated with prostate cancer in urine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1839.

Chemical Evolution of Enzyme-Catalyzed Glycosylation.

ConspectusThe limited availability of structurally well-defined diverse glycans remains a major obstacle for deciphering biological functions as well as biomedical applications of carbohydrates. Despite tremendous progress that has been made in past decades, the synthesis of structurally well-defined complex glycans still represents one of the most challenging topics in synthetic chemistry. Chemical synthesis of glycans is a time-consuming and labor-intensive process that requires elaborate planning and skilled personnel. In contrast, glycosyltransferase-catalyzed enzymatic synthesis provides a more efficient, convenient, low-cost, and sustainable alternative to affording diverse and complex glycans. However, the existing methods are still insufficient to fulfill the increasing demand for specific synthetic glycan libraries necessary for functional glycomics research. This is mainly attributed to the inherent character of the glycan biosynthetic pathway. In nature, there are too many glycosyltransferases involved in the in vivo glycan synthesis, but only a small number of them are available for in vitro enzymatic synthesis. For instance, humans have over 200 glycosyltransferases, but only a few of them could be produced from the conventional bacterial expression system, and most of these membrane-associated enzymes could be overexpressed only in eukaryotic cells. Moreover, the glycan biosynthetic pathway is a nontemplate-driven process, which eventually ends up with heterogeneous glycan product mixtures. Therefore, it is not a practical solution for the in vitro enzymatic synthesis of complex glycans by simply copying the glycan biosynthetic pathway.In the past decade, we have tried to develop a simplified and transformable approach to the enzymatic modular assembly of a human glycan library. Despite the structural complexity of human glycans, the glycoinformatic analysis based on the known glycan structure database and the human glycosyltransferase database indicates that there are approximately 56 disaccharide patterns present in the human glycome and only 16 disaccharide linkages are required to account for over 80% of the total disaccharide fragments, while 35 disaccharide linkages are sufficient to cover over 95% of all disaccharide fragments of human glycome. Regardless of the substrate specificity, if one glycosyltransferase could be used for the synthesis of all of the same glycosidic linkages in human glycome, it will require only a few dozen glycosyltransferases for the assembly of entire human glycans. According to the glycobioinformatics analysis results, we rationally designed about two dozen enzyme modules for the synthesis of over 20 common glycosidic linkages in human glycome, in which each enzyme module contains a glycosyltransferase and a group of enzymes for the in situ generation of a nucleotide-activated sugar donor. By sequential glycosylation using orchestrated enzyme modules, we have completed the synthesis of over 200 structurally well-defined complex human glycans including blood group antigens, O-mannosyl glycans, human milk oligosaccharides, and others. To overcome the product microheterogeneity problem of enzymatic synthesis in the nontemplate-driven glycan biosynthetic pathway, we developed several substrate engineering strategies to control or manipulate the outcome of glycosyltransferase-catalyzed reactions for the precise synthesis of structurally well-defined isomeric complex glycans.

Altered expression of Sialyl Lewis X in experimental models of Parkinson’s disease

The mechanisms underlying neurodegeneration in Parkinson’s disease (PD) are still not fully understood. Glycosylation is an important post-translational modification that affects protein function, cell-cell contacts and inflammation and can be modified in pathologic conditions. Although the involvement of aberrant glycosylation has been proposed for PD, the knowledge of the diversity of glycans and their role in PD is still minimal. Sialyl Lewis X (sLeX) is a sialylated and fucosylated tetrasaccharide with essential roles in cell-to-cell recognition processes. Pathological conditions and pro-inflammatory mediators can up-regulate sLeX expression on cell surfaces, which has important consequences in intracellular signalling and immune function. Here, we investigated the expression of this glycan using in vivo and in vitro models of PD. We show the activation of deleterious glycation-related pathways in mouse striatum upon treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a toxin-based model of PD. Importantly, our results show that MPTP triggers the presentation of more proteins decorated with sLeX in mouse cortex and striatum in a time-dependent manner, as well as increased mRNA expression of its rate-limiting enzyme fucosyltransferase 7. sLeX is expressed in neurons, including dopaminergic neurons, and microglia. Although the underlying mechanism that drives increased sLeX epitopes, the nature of the protein scaffolds and their functional importance in PD remain unknown, our data suggest for the first time that sLeX in the brain may have a role in neuronal signalling and immunomodulation in pathological conditions.Key messagesMPTP triggers the presentation of proteins decorated with sLeX in mouse brain.MPTP triggers the expression of sLeX rate-limiting enzyme FUT 7 in striatum.sLeX is expressed in neurons, including dopaminergic neurons, and microglia.sLeX in the brain may have a role in neuronal signalling and immunomodulation.

Sweet complexity: O-linked protein glycosylation in pathogenic Neisseria.

The genus Neisseria, which colonizes mucosal surfaces, includes both commensal and pathogenic species that are exclusive to humans. The two pathogenic Neisseria species are closely related but cause quite different diseases, meningococcal sepsis and meningitis (Neisseria meningitidis) and sexually transmitted gonorrhea (Neisseria gonorrhoeae). Although obvious differences in bacterial niches and mechanisms for transmission exists, pathogenic Neisseria have high levels of conservation at the levels of nucleotide sequences, gene content and synteny. Species of Neisseria express broad-spectrum O-linked protein glycosylation where the glycoproteins are largely transmembrane proteins or lipoproteins localized on the cell surface or in the periplasm. There are diverse functions among the identified glycoproteins, for example type IV biogenesis proteins, proteins involved in antimicrobial resistance, as well as surface proteins that have been suggested as vaccine candidates. The most abundant glycoprotein, PilE, is the major subunit of pili which are an important colonization factor. The glycans attached can vary extensively due to phase variation of protein glycosylation (pgl) genes and polymorphic pgl gene content. The exact roles of glycosylation in Neisseria remains to be determined, but increasing evidence suggests that glycan variability can be a strategy to evade the human immune system. In addition, pathogenic and commensal Neisseria appear to have significant glycosylation differences. Here, the current knowledge and implications of protein glycosylation genes, glycan diversity, glycoproteins and immunogenicity in pathogenic Neisseria are summarized and discussed.

Alterations of Glycan Composition in Aerobic Granular Sludge during the Adaptation to Seawater Conditions.

Bacteria can synthesize a diverse array of glycans, being found attached to proteins and lipids or as loosely associated polysaccharides to the cells. The major challenge in glycan analysis in environmental samples lies in developing high-throughput and comprehensive characterization methodologies to elucidate the structure and monitor the change of the glycan profile, especially in protein glycosylation. To this end, in the current research, the dynamic change of the glycan profile of a few extracellular polymeric substance (EPS) samples was investigated by high-throughput lectin microarray and mass spectrometry, as well as sialylation and sulfation analysis. Those EPS were extracted from aerobic granular sludge collected at different stages during its adaptation to the seawater condition. It was found that there were glycoproteins in all of the EPS samples. In response to the exposure to seawater, the amount of glycoproteins and their glycan diversity displayed an increase during adaptation, followed by a decrease once the granules reached a stable state of adaptation. Information generated sheds light on the approaches to identify and monitor the diversity and dynamic alteration of the glycan profile of the EPS in response to environmental stimuli.

Characterization of PglJ, a Glycosyltransferase in the Campylobacter concisus N-Linked Protein Glycosylation Pathway that Expands Glycan Diversity.

The Campylobacter genus of Gram-negative bacteria is characterized by the expression of N-linked protein glycosylation (pgl) pathways. As Campylobacter concisus is an emerging human pathogen, a better understanding of the variation of the biosynthetic pathways across the genus is necessary to identify the relationships between protein glycosylation and disease. The pgl pathways of C. concisus strains have been reported to diverge from other Campylobacter in steps after the biosynthesis of N-acetylgalactosamine-α1,3-N,N'-diacetylbacillosamine-α-1-diphosphate undecaprenyl (GalNAc-diNAcBac-PP-Und), which is catalyzed by PglC and PglA, a phosphoglycosyltransferase (PGT) and a glycosyltransferase (GT), respectively. Here we characterize the PglJ GTs from two strains of C. concisus. Chemical synthesis was employed to access the stereochemically defined glycan donor substrates, uridine diphosphate N-acetyl-d-galactosaminuronic acid (UDP-GalNAcA) and uridine diphosphate N-acetyl-d-glucosaminuronic acid (UDP-GlcNAcA), to allow biochemical investigation of PglJ. Evidence for the PglJ substrate specificity structural determinants for the C6″ carboxylate-containing sugar was obtained through variant-based biochemical assays. Additionally, characterization of a UDP-sugar dehydrogenase encoded in the pgl operon, which is similar to the Pseudomonas aeruginosa WbpO responsible for the oxidization of a UDP-HexNAc to UDP-HexNAcA, supports the availability of a UDP-HexNAcA substrate for a GT that incorporates the modified sugar and provides evidence for the presence of a HexNAcA in the N-linked glycan. Utilizing sequence similarity network (SSN) analysis, we identified conserved sequence motifs among PglJ glycosyltransferases, shedding light on substrate preferences and offering predictive insights into enzyme functions across the Campylobacter genus. These studies now allow detailed characterization of the later steps in the pgl pathway in C. concisus strains and provide insights into enzyme substrate specificity determinants for glycan assembly enzymes.

Synthesis and application of BODIPY-based fluorescent labeling tag for oligosaccharide and N-linked glycan analysis by high-performance liquid chromatography with fluorescence detection

BackgroundGlycosylation analysis is still challenging, not only because of the extreme structure complexity and conjugation diversity of glycans but also because of instrumental aspects such as the sensitivity limits of analyses. Therefore, glycan analysis by chromatographic methods is very often combined with fluorescence detection in addition to MS. The majority of fluorescent labeling employed before LC separation is based on 2-aminobenzamide, which has several disadvantages such as low labeling yield, poor fluorescence properties, and MS ionization efficiency. Therefore, even after several decades of development of new labels, there is still a need for new labeling tags with improved characteristics. ResultsWe present the application of a newly synthesized fluorescent label designed for oligosaccharide and glycan analysis by high-performance liquid chromatography with fluorescence detection (HPLC/FLD). The novel hydrazide derivative of dipyrrometheneboron difluoride (BODIPY) was synthesized from 2,4-dimethylpyrrole, methyl succinyl chloride, and boron trifluoride etherate followed by a reaction with hydrazine. The synthesized label was characterized by several analytical methods including NMR, UV/Vis and fluorescence spectroscopy, and mass spectrometry. The labeling reaction via hydrazone formation chemistry was optimized by labeling of maltooligosaccharide standards. The analysis of maltohexaose labeled by BODIPY-hydrazide followed by HPLC/FLD analysis provided the limit of detection in the low tens of femtomole. The presented method based on fluorescence detection is at least 30 times more sensitive than the standard approach employing labeling by 2-aminobenzamide. In addition, the labeling method by BODIPY-hydrazide was used for N-linked glycan profiling of several glycoproteins (ribonuclease B, immunoglobulin G) by RP-HPLC/FLD as well as HILIC/FLD analysis. SignificanceThis work represents the design, synthesis, and application of a new fluorescent label based on the BODIPY core and hydrazone formation chemistry for oligosaccharide and glycan analysis by HPLC/FLD. The proposed approach significantly improved the oligosaccharide and glycan analysis in comparison to the commonly used procedure employing 2-aminobenzamide.

B4galt1 Regulates the WNT-β-Catenin Axis to Control Hematopoietic Stem and Progenitor Cells (HSPCs) Fitness

In achieving the optimal numbers of fully functional blood cells across different lineages, intrinsic developmental programs within the cells and external guidance mechanisms are crucial. Glycans on the cell surface and extracellular environment are pivotal in regulating cell maintenance, differentiation, and function. We recently discovered that the glycosyltransferase β-1,4-galactosyltransferase 1 (B4galt1) leads to dysplastic megakaryocytes, impaired thrombopoiesis, and increased hematopoietic stem cells (HSC). To investigate the relationship between B4galt-dependent glycosylation and HSC function, we analyzed the glycan composition in control and B4galt1 null (B4 -/-) femurs by spatial mass spectrometry using matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI). In control femurs, we observed a distinct gradient of complex N-glycans, with higher expression at the distal ends and decreasing complexity towards the shaft, showcasing diverse glycan expression in the hematopoietic environment. However, this gradient was absent in B4 -/-femurs, where we detected an increase of immature N-glycans and a concurrent decrease in complex N-glycan structures (p<0.05). Additionally, we observed aberrant O-glycosylation in B4 -/- LT-HSCs, as determined using lectin arrays. The glycan composition in the absence of B4galt1-dependent glycosylation mirrors cancer-associated glycan patterns. To further understand the role of B4galt1 in steady-state hematopoiesis, we next examined the bone marrow (BM) immunophenotypic composition of B4 -/- mice. Flow cytometry analysis revealed a significant expansion of immunophenotypically defined long term (LT)-HSCs (p=0.0061) and multipotent progenitors (MPPs) (p<0.05) in B4 -/-BM. Additionally, B4 -/- LT-HSCs showed higher expression of the platelet marker CD41 (p=0.0171), suggesting the presence of an expanded megakaryocyte (MK) biased LT-HSCs population (LT-HSC CD41+ cells). This expansion occurred without pro-inflammatory cues, as determined through cytokine arrays. To investigate if the global transcriptional landscape in B4 -/- cells could explain the observed expansion phenotype, we conducted droplet-based single-cell RNA-seq. Transfer learning classification allowed us to identify an expansion of the transcriptional output associated with LT-HSC and MPP2 signatures in B4 -/- cells (p<0.05). Further transcriptional analysis revealed an increased number of B4 -/- cells expressing MKs specific markers (CD41, Pf4, GP9, Vwf, GP1ba), providing additional support for the expansion of B4 -/- MK-biased LT-HSCs. Gene Set Enrichment Analysis (GSEA) of B4 -/- LT-HSCs demonstrated enrichment in metabolism-associated pathways and cell cycle regulation (FDR<0.05). Conversely, critical differentiation processes at the stem cell level, such as cellular adhesion and lineage commitment, were downregulated (FDR<0.05). To investigate the role of B4galt1 in HSC expansion, we transcriptionally classified LT-HSCs based on their cell cycle status (G1, G2M, and S). Analysis of LT-HSC CD41+ cell cycle distribution revealed an increased in S phase in B4 -/- LT-HSC CD41+ cells. Additionally, B4 -/- LT-HSC CD41+ cells exhibited enrichment in cell cycle regulation pathways, including DNA replication, DNA strand elongation, and G1 to S cell cycle control (FDR<0.05). Conversely, critical pathways associated with HSC homeostasis and quiescence were depleted in the absence of B4galt1 (FDR<0.05). GSEA analysis unveiled upregulation of Wnt and Myc pathways in B4 -/- LT-HSC CD41+ cells. Immunofluorescence and immunoblot analysis demonstrated elevated total β-catenin levels in B4 -/- LSK cells and enhanced nuclear translocation of non-phosphorylated Ser33/37/Thr41 β-catenin. To confirm the functional significance, we treated B4 -/- LSK cells with the Wnt inhibitor XAV939 which normalized cell numbers to control levels and cause a reduction in the observed expansion at the stem and progenitor compartments. These findings suggest that B4galt1 is vital in regulating HSC expansion, likely through the Wnt/β-catenin signaling pathway. Our data provide compelling evidence that B4galt1 regulates steady-state hematopoiesis, through its influence on glycosylation in the bone marrow niche, highlighting the critical role of the B4galt1-Wnt-β-catenin axis in regulating LT-HSC fitness and expansion.

Innovative Chemical Tools to Address Analytical Challenges of Protein Phosphorylation and Glycosylation.

ConspectusProtein post-translational modifications (PTMs) modulate almost all cellular processes. Aberrant PTMs are closely bound to various human diseases, which greatly complicates the association of a specific disease with a genetic mutation and even renders genomics-driven personalized therapeutics ineffective. PTM proteomics has the potential to provide a more comprehensive understanding of disease biology and is emerging as one of the new breakthroughs of precision medicine in the postgenomics era. As two of the most prominent PTMs, phosphorylation and glycosylation have attracted broad research interest both in academia for the discovery of cancer pathogenesis, biomarkers, and therapeutic targets and in industry for the development of targeted drugs and vaccines. Despite the great rewards, current phosphorylation and glycosylation analyses are still faced with some considerable challenges due to the ultralow abundance of phosphorylation and glycosylation and the grand heterogeneity and structural complexity of glycosylation. To date, our laboratory has concentrated on protein phosphorylation and glycosylation and offered unique insights for the development of innovative separation and analytical tools. An overview of these chemical tools, together with our views on potential solutions to the challenges of protein phosphorylation and glycosylation analysis, is presented in this Account.The first part describes our efforts in phosphorylation enrichment and sensing. Given the excellent responsiveness and expandability of smart polymers, we designed a smart polymer material bearing affinity ligands that target the phosphate group and achieved efficient enrichment of multiply phosphorylated peptides through a tunable catch-and-release. Further, the combination of ligand-bearing smart polymers with solid-state nanochannels for the creation of functional nanofluidic devices is presented. The devices allow us to monitor the kinase reaction, thus providing a low-cost, label-free assay for kinase activity. In the next section, we discuss capture strategies for glycosylated species and glycan analysis methods. A Schiff base-containing material was revealed to achieve high-efficiency capture of sialylated glycopeptides through a hydrolysis reaction, demonstrating the power of dynamic covalent chemistry for enrichment. Then, a directed evolution strategy based on phage display was used to develop a lipopolysaccharide (LPS)-targeted ligand that, when incorporated into a polymer as an adsorbent, can efficiently clear the circulating LPS. Based on the distinction of simple glycan isomers with a nanofluidic device, we further explored the identification of diverse glycans with a protein nanopore through a derivatization strategy. The success of the exploration offers a solution to advance nanopore-based single-molecule glycan profiling and glycan sequencing. Although not comprehensive, this Account could provide new insight into the development of chemical tools to facilitate the analysis of phosphorylation and glycosylation as well as other PTMs.

Human milk oligosaccharides in milk of mothers with term and preterm delivery at different lactation stage

Human milk oligosaccharides (HMOs) are structurally diverse unconjugated glycans, and play crucial roles in protecting infants from infections. Preterm birth is one of the leading causes of neonatal mortality, and preterm infants are particularly vulnerable and are in need of improved outcomes from breast-feeding due to the presence of bioactive HMOs. However, studies on specific difference in HMOs as a function of gestation time have been very limited. We established an approach to extract and analyze HMOs based on 96-well plate extraction and mass spectrometry, and determined maternal phenotypes through distinctive fragments in product-ion spectra. We enrolled 85 women delivering at different gestation times (25–41 weeks), and observed different HMOs correlating with gestation time based on 233 samples from the 85 donors. With the increase of postpartum age, we observed a regular changing trajectory of HMOs in composition and relative abundance, and found significant differences in HMOs secreted at different postpartum times. Preterm delivery induced more variations between participants with different phenotypes compared with term delivery, and more HMOs varied with postpartum age in the population of secretors. The sialylation level in mature milk decreased for women delivering preterm while such decrease was not observed for women delivering on term.