Glycobiology最新文献

Fucosylated chondroitin sulfate (FCS) is a unique polysaccharide, first described nearly four decades ago, and found exclusively in sea cucumbers. It is a component of the extracellular matrix, possibly associated with peculiar properties of the invertebrate tissue. The carbohydrate features a chondroitin sulfate core with branches of sulfated α-Fuc linked to position 3 of the β-GlcA. FCSs from different species of sea cucumbers share a similar chondroitin sulfate core but the structure of the sulfated α-Fuc branches varies significantly. The predominant pattern consists of a single unit of sulfated α-Fuc, though some species exhibit branches with multiple α-Fuc units. This comprehensive review focuses on four major aspects of FCS. Firstly, we describe the initial approaches to elucidate the structure of FCS using classical methods of carbohydrate chemistry. Secondly, we highlight the impact of two-dimensional NMR methods in consolidating and revealing further details about the structure of FCS. These studies were conducted by various researchers across different countries and involving multiple species of sea cucumbers. Thirdly, we summarize the biological activities reported for FCS. Our survey identified 104 publications involving FCS from 42 species of sea cucumbers, reporting 10 types of biological activities. Most studies focused on anticoagulant and antithrombotic activities. Finally, we discuss future perspectives for studies related to FCS. These studies aim to clarify the evolutionary advantage for sea cucumbers in developing such a peculiar fucosylated glycosaminoglycan. Additionally, there is a need to identify the enzymes and genes involved in the metabolism of this unique carbohydrate.

Glycosylation is an important posttranslational modification in platelets, and the glycosylation pattern is critical for platelet function. To date, the exploration of the roles of various glycoforms in specific platelet functions is largely lacking. In this study, a global analysis of intact N-glycopeptides in human platelets was performed to map all the glycopeptides, glycosites and glycans of platelets. The glycopeptides were enriched by the ZIC- hydrophilic interaction chromatography method and then analyzed by Liquid Chromatography-Tandem Mass Spectrometry analysis. A total of 1,425 intact glycopeptides belonging to 190 N-glycoproteins from human platelets were identified. Moreover, 358 glycans modified 328 glycosites from those glycoproteins. Functional analysis revealed that these glycoproteins are involved mainly in processes and pathways related to platelet adhesion. Among the proteins in these adhesion-related annotations, von Willebrand factor, thrombospondin 1and glycoprotein V were found to contain a possible Lewis y structure, and this finding was further verified by immunoprecipitation assays. As a blood group-related antigen, Lewis y was previously reported to exist in human platelets, but its function remains unclear. Since the glycosylation of von Willebrand factor, thrombospondin 1 and glycoprotein V is involved in platelet-collagen adhesion, the importance of Lewis y on platelet function was evaluated by adhesion assays, which demonstrated that the blockade of Lewis y on platelets decreased the adhesion of platelets to collagen I under both static and flow conditions.

For studies involving glycosyltransferases and nucleotide sugar transporters, radioactive nucleotide sugars are critical reagents. Of these, GDP-L-[3H]Fucose is currently commercially unavailable. Here, we present a facile approach for the preparation of GDP-[3H]-L-Fucose, using the enzymatic machinery present in the cytosol of the non-infectious and easily cultivated protozoan, Crithidia fasciculata, and its purification by solid phase extraction ion exchange chromatography.

The O-glycan composition of jellyfish (JF) mucin (qniumucin: Q-mucin) extracted from three Cubozoan species was studied after the optimization of the purification protocol. Application of a stepwise gradient of ionic strength to anion exchange chromatography (AEXC) was effective for isolating Q-mucin from coexisting impurities. In the three species, the amino acid sequence of the tandem repeat (TR) region in Q-mucin in all three Cubozoans seemed to remain the same as that in all Scyphozoans, although their glycan chains seemed to exhibit clear diversity. In particular, the amounts of acidic moieties on the glycan chains of Q-mucin from the Cubozoans markedly varied even in these genetically close species. In two of the three Cubozoan species, the fraction of disaccharides was large, showing a sharp contrast to that of the glycans of Q-mucin in Scyphozoans. This study also indicates that the simple sequence of TR commonly inherited in all Cubozoan and Scyphozoan JF species after the long term of evolution over 500 M years. According to this research, the glycans and the TR of mucin-type glycoproteins (MTGPs), forming a hierarchical structure, appear to complement each other in the evolutionary changes because the time required for their hereditary conversion is considerably different. The cooperation of these mechanisms is a strategy to achieve the contradictory functions of biosystems, namely species conservation and diversity acquisition.

Aspergillus fumigatus, a filamentous fungus, is an opportunistic pathogen and the major causative agent of the often-fatal disease, invasive aspergillosis (IA). Current treatments for IA are limited due to their high toxicity and/or the emergence of drug resistance; therefore, a need exists for the development of new therapeutics to treat IA. The Kdnase produced by A. fumigatus plays a vital role in maintaining cell wall integrity. As there are no known Kdnases in humans, developing inhibitors of Kdnase from this fungal pathogen is a promising therapeutic approach. The rapid testing of enzymatic activity in a high-throughput screen of large chemical libraries can be an efficient way to find new small molecule lead compounds. Herein we show that a Kdn glycoside with a self-immolative cleavable aglycon is a practical and efficient substrate for a high throughput assay to identify Kdnase inhibitors. We optimized the activity assay and screened over 27,000 compounds from two bioactive chemical libraries as potential inhibitors, and we compared the hit compounds' potency towards Aspergillus terreus and Trichophyton rubrum Kdnases, two other fungal Kdnases. We validated a number of hits and these small molecules are potential leads for the development of novel therapeutics to treat invasive aspergillosis.

Protein-O-mannosylation (POM) is a form of O-glycosylation that is ubiquitous and has been studied extensively throughout in fungi and animals. The key glycosyltransferase, protein O-mannosyltransferase (PMT), a member of family GT-39, is also found in over 3,800 bacterial genomes but has only been minimally examined from prokaryotes. In prokaryotes POM has only been investigated in terms of pathogenicity (in Mycobacterium tuberculosis) even though there are far more non-pathogenic bacteria that appear to carry out POM. To date, there is no consensus on what benefit POM imparts to the non-pathogenic bacteria that can perform it. Through the generation of a POM deficient mutant of Corynebacterium glutamicum - a widely utilized and known protein O-mannosylating actinobacteria - this work shows that even closely related actinobacterial GT-39 s (the enzymes responsible for the initiation of POM) can have different substrate specificities for targets of POM. Moreover, presented here is evidence that POM does not only occur in a SEC-dependent manner; POM also occurs with TAT and non-SEC secreted substrates in a specific and likely tightly regulated manner. Together these results highlight the need for further biochemical characterization of POM in these and other bacterial species to help elucidate the true nature of its biological functions.

Abdala is a COVID-19 vaccine produced in Pichia pastoris and is based on the receptor-binding domain (RBD) of the SARS-CoV-2 spike. Abdala is currently approved for use in multiple countries with clinical trials confirming its safety and efficacy in preventing severe illness and death. Although P. pastoris is used as an expression system for protein-based vaccines, yeast glycosylation remains largely uncharacterised across immunogens. Here, we characterise N-glycan structures and their site of attachment on Abdala and show how yeast-specific glycosylation decreases binding to the ACE2 receptor and a receptor-binding motif (RBM) targeting antibody compared to the equivalent mammalian-derived RBD. Reduced receptor and antibody binding is attributed to changes in conformational dynamics resulting from N-glycosylation. These data highlight the critical importance of glycosylation in vaccine design and demonstrate how individual glycans can influence host interactions and immune recognition via protein structural dynamics.