Glycoconjugate Journal最新文献

Total plasma N-glycans alter in disease states, with few studies focused on COVID-19. A discovery cohort of 310 COVID-19 patients, replicated with 97 COVID-19 patients and tested with 100 COVID-19 patients, was used to unearth the N-glycans capable of distinguishing infection, as well as prognosis of intensive care unit (ICU) admission and mortality. All significant bisected glycans were decreased in patients compared to controls, whilst fucosylated tri-antennary glycans and sialylated tetra-antennary glycans were increased in patients. For both those admitted to the ICU and those who died, Peak 61 (A4G4S4F) was elevated in the more severe disease course, while Peak 29 (FA2G2S2) was lowered. Pinpointing specific glycosylation changes has alluded to a potential story of glycoprotein pathways in response to SARS-CoV-2 infection. This study could be further explored through deriving the glycoproteins associated with the glycans of interest and the glycosylation changes experienced on these proteins.

Six oligosaccharides with the degree of polymerization (DP) 2 to 7 were isolated from the active fraction of Trillium tschonoskii using a high-temperature semi-preparative porous graphitic carbon (PGC) column based on high-performance liquid chromatography coupled with a charged aerosol detector and vanquish fraction collector (HPLC-CAD-VFC) system. The structures of DP2 - 7 were determined as maltose, maltotriose, maltotetraose, maltopentaose, maltohexaose, and maltoheptaose with (1→4)-α-D-glucopyranose residues by relative quantitative ¹H nuclear magnetic resonance (qHNMR) spectroscopy with anomeric protons integration and NMR structural-reporter-group resonances. The immunomodulatory activities of this series of maltooligosaccharides (MOS) were tested on RAW264.7 cells. All samples on cells had no cytotoxicity, and the oligosaccharide fraction (TOS1) could increase the phagocytic capacity and production of nitric oxide (NO) and cytokines to a much higher level than monomers. In particular, maltopentaose (DP5) showed a relatively higher capacity for stimulating proliferation, NO, and cytokine production than other purified oligosaccharides. The immunomodulatory activity of MOS investigated in this study is beneficial for utilizing MOS as a functional ingredient in novel product development.

Glycosylation is a crucial post-translational modification, and numerous studies have reported its significant role in cancer progression. Nevertheless, no study has comprehensively analyzed the causal effect of glycosylation on the risk of cancer till now. Herein, we identified 32 SNPs of glycosylation-related genes (GRGs) that correlated with the risk of 8 kinds of cancer by summary-statistics-based mendelian randomization (SMR) analysis for genome-wide association study (GWAS) data. Next, the heterogeneity in dependent instrument (HEIDI) test and colocalisation analysis were utilized to verify the heterogeneity and consistency of SMR results. Further fine-mapping of causal gene set (FOCUS) analysis based on transcriptome-wide association study (TWAS) data showed that rs9810189 of ST6GAL1 and rs223489 of MANBA were negatively correlated with the risk of breast cancer and squamous cell carcinoma, respectively. Moreover, the MANBA protein in blood plasma also exhibited a probably negative causal effect on squamous cell carcinoma according to two-sample MR analyses for protein quantitative trait locus (pQTLs). In addition, single-cell RNA sequencing analysis and Kaplan-Meier plot analysis were performed to evaluate the potential role of GRGs in corresponding cancer prioritized by the above MR analysis. Finally, we attempted to illustrate the function of glycosyltransferases and investigate the druggable status of GRGs. Together, our study comprehensively analyzed the causal effect of glycosylation on cancer risk and identified potential strategies for cancer treatment.

Integrins are heterodimeric receptors involved in cell adhesion and bidirectional signaling. Ganglioside GM3 in the outer leaflet of cell membranes possibly regulates integrin activity via direct interactions; however, its specific binding mode with integrins remains unclear. Therefore, in this study, we focused on the GM3 glycan moiety, which encounters the integrin ectodomain on the cell surface, and synthesized a soluble GM3 probe without hydrocarbon chains using a chemoenzymatic approach. Binding analysis using surface plasmon resonance (SPR) indicated that the synthetic GM3 probe interacts with the integrin α5β1 ectodomain with a significantly higher affinity than the lactosylceramide probe. Saturation transfer difference (STD) NMR spectra suggested that the integrin α5β1 ectodomain interacts with N-acetylneuraminic acid (Neu5Ac) at the GM3 terminal and α2-3Gal linkage. Notably, RGD peptide, an integrin ligand interacting with the heterodimer interface, competed with GM3 to bind to integrin α5β1 on the SPR sensor chip. Consistent with these results, the GM3-binding site predicted by Chai-1 partially overlapped with the RGD peptide-binding groove on integrin α5β1; however, the binding mode was different. RGD peptide bridged the α and β subunits of the integrin head moiety, whereas the GM3 probe found at the cleft between the subunits. The Neu5Ac-Gal moiety primarily interacts with the metal ion-dependent adhesion site and nearby residues in the β1 subunit. Overall, our findings suggest that gangliosides directly interact with integrin α5β1 at a previously unknown binding site, revealing a novel regulatory mechanism for the integrin activity.

Tay-Sachs disease is a rare neurodegenerative disorder caused by mutations in the HEXA gene. The HEXA gene encodes the α-subunit of the enzyme β-hexosaminidase A, which degrades GM2 ganglioside. Previously, we identified impaired autophagy in the brains of a mouse model of Tay-Sachs disease, which exhibited neuropathological and clinical abnormalities. Moreover, we demonstrated autophagosome clearance in Tay-Sachs cells under lithium-induced conditions. Here, we further aimed to evaluate N- and O-glycan changes in these cells and examine whether glycan alterations are linked to ER stress. The profiles of N- and O-glycans were analyzed using LC-MS/MS in fibroblasts and neuroglial cells from 5-month-old Hexa-/-Neu3-/- mice and neuroglial cells from Tay-Sachs patients under lithium induction and nutrient deprivation. The expression levels of ER stress-related markers were assessed using qRT-PCR and Western blot analyses. We demonstrated higher levels of high mannose and lower levels of complex types of N-glycans, along with increased O-glycan levels in Tay-Sachs cells. Compared to control groups, we observed upregulated expression of endoplasmic reticulum (ER) stress-related markers, CHOP and ATF-6, in Tay-Sachs cells. Our study demonstrated that autophagy induction causes the degradation of accumulated high-mannose N-glycans and O-glycans, which is associated with the downregulation of ER stress-related genes in Tay-Sachs cells. Our study is the first to show this phenomenon in Tay-Sachs cells and suggests the presence of ER stress-mediated autophagy. Therefore, targeting glycans through autophagy induction could offer therapeutic benefits to patients with Tay-Sachs disease in future studies.

Native fucosylated glycosaminoglycan (FG), a structurally unique polysaccharide with chondroitin sulfate like backbone and sulfated fucose side chains, has multiple anticoagulant mechanisms. Analyzing the interaction between FG and coagulation proteins will help to further understand its pharmacological mechanisms. Previously, we have reported that high molecular weight depolymerized FG (dFG) and unfractionated heparin (UFH) exhibit different binding models for antithrombin (AT), which is a primary natural anticoagulant in plasma by inhibiting coagulation proteases including thrombin (FIIa). In this study, the effect of dFG or UFH on the interaction between AT and FIIa was detected by biolayer interferometry. The relative AT binding affinity and AT-dependent anti-FIIa activity of dFG derivatives were measured to elucidate the structure-activity relationship. The results demonstrate that high molecular weight dFG significantly promotes the irreversible binding of FIIa and AT by a template mechanism. As the molecular weight decreases, the relative AT binding affinity of dFG decreases and molecular weight above 8.55 kDa is required for their interaction in this study. Both the fucose side chains and carboxyl groups are indispensable for dFG to bind with AT and inhibit FIIa activity. This study clarifies the mechanism and structure-activity relationship of dFG inhibiting FIIa by AT, providing references for the development of novel anticoagulant drugs based on FG and its derivatives.

Sialic acids are a diverse family of acidic sugars typically found at the terminal positions of glycan chains, mediating key physiological and pathological processes across animals - particularly vertebrates - including cell signaling and host-pathogen interactions. The distribution of sialic acids in lower animals such as mollusks, however, remains largely unresolved. Here, we report the discovery of unconjugated 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (KDN), a deaminated analogue of N-acetylneuraminic acid, in the muscle tissue of Pacific oysters (Magallana gigas). Using UPLC-ESI-MS/MS fingerprinting, we identified naturally occurring free KDN at a concentration of 1.2 ± 0.1 nmol/100 mg of oyster muscle tissue. To investigate the biosynthetic pathway, four candidate genes were identified in the M. gigas genome, and the corresponding recombinant proteins were expressed and characterized. Enzymatic assays revealed that one putative sialic acid aldolase (MgNPL) specifically catalyzes the cleavage of KDN into mannose and pyruvate. To our knowledge, this represents the first molecular evidence of KDN metabolism in mollusks and highlights both the unexpected conservation of substrate-specific aldolase activity and distinct sialic acid utilization mechanisms compared to vertebrates.

Diabetes mellitus (DM) is marked by prolonged elevated blood glucose levels, which lead to the formation of covalent adducts between glucose and plasma proteins through a non-enzymatic reaction called glycation. This biochemical process plays a crucial role in the development of DM complications, including retinopathy, nephropathy, neuropathy, and cardiomyopathy, while also impacting conditions such as rheumatoid arthritis, osteoporosis, and aging. Glycation alters the molecular structure, enzymatic activity, and receptor interactions of proteins, affecting their normal functions. Advanced glycation end products (AGEs) arise from these modifications, forming cross-links within and between cells, which affect proteins and other vital biomolecules, such as lipids and nucleic acids. This contributes significantly to the complex complications associated with DM. Recent studies highlight the interaction between AGEs and their specific receptors, receptor for advanced glycation end products (RAGE), located on the plasma membrane. This involvement initiates changes in intracellular signaling, alters gene expression, and stimulates the release of pro-inflammatory cytokines and reactive oxygen species. This review examines the glycation of key plasma proteins albumin, fibrinogen, globulins, and collagen and discusses the various AGEs formed. Furthermore, it elucidates the role of AGEs in the exacerbation of DM complications, providing a comprehensive overview of the molecular pathways involved and the systemic impact of these glycation products.