Glycoconjugate Journal最新文献

The structure and properties of a group of gangliosides modified by mild alkaline treatment are discussed. We will present the occurrence and the structure of gangliosides carrying the N-acetyneuraminic acid O-acetylated in position 9, the Neu5,9Ac₂, and of gangliosides carrying a sialic acid that forms a lactone ring. Starting from biochemical data we will discuss the possible biochemical role played by these gangliosides in the processes of cell signaling and maintenance of brain functions.

After tissue damage, a series of molecular and cellular events are initiated to promote tissue repair and regeneration to restore its original structure and function. These events include inter-cell communication, cell proliferation, cell migration, extracellular matrix differentiation, and other critical biological processes. Glycosylation is the crucial conservative and universal post-translational modification in all eukaryotic cells [1], with influential roles in intercellular recognition, regulation, signaling, immune response, cellular transformation, and disease development. Studies have shown that abnormally glycosylation of proteins is a well-recognized feature of cancer cells, and specific glycan structures are considered markers of tumor development. There are many studies on gene expression and regulation during tissue repair and regeneration. Still, there needs to be more knowledge of complex carbohydrates' effects on tissue repair and regeneration, such as glycosylation. Here, we present a review of studies investigating protein glycosylation in the tissue repair and regeneration process.

CD22, one of the sialic acid-binding immunoglobulin-like lectins (Siglecs), regulates B lymphocyte signaling via its interaction with glycan ligands bearing the sequence Neu5Ac/Gcα(2→6)Gal. We have developed the synthetic sialoside GSC-718 as a ligand mimic for CD22 and identified it as a potent CD22 inhibitor. Although the synthesis of CD22-binding sialosides including GSC-718 has been reported by our group, the synthetic route was unfortunately not suitable for large-scale synthesis. In this study, we developed an improved scalable synthetic procedure for sialosides which utilized 1,5-lactam formation as a key step. The improved procedure yielded sialosides incorporating a series of aglycones at the C2 position. Several derivatives with substituted benzyl residues as aglycones were found to bind to mouse CD22 with affinity comparable to that of GSC-718. The new procedure developed in this study affords sialosides in sufficient quantities for cell-based assays, and will facilitate the search for promising CD22 inhibitors that have therapeutic potential.

Changes in protein glycosylation are clinically used as biomarkers. In the present study, we employed a twin cohort to investigate the contributions of genetic and environmental factors to glycan modifications of glycoproteins. Mac-2 binding protein (Mac-2 bp), haptoglobin (Hp), and their glycosylated forms are liver fibrosis and cancer biomarkers. Sera from 107 twin pairs without clinical information were used as a training cohort for the Mac-2 bp and Mac-2 bp glycosylation isomer (M2BPGi) assay. As a validation cohort, 22 twin pairs were enrolled in the study. For each twin pair, one twin was diagnosed with liver or pancreatic disease. For the training cohort, the correlation ratios of serum Mac-2 bp and M2BPGi levels in twin sera with random sequences were 0.30 and 0.018, respectively. The correlation ratios between twin pairs in the validation cohort for serum Mac-2 bp and M2BPGi levels were 0.75 and 0.35, respectively. In contrast, correlation ratios of serum Hp and fucosylated haptoglobin (Fuc-Hp) levels between twin sera with liver and pancreatic disease were 0.49 and 0.16, respectively. Although serum protein levels of glycoproteins are susceptible to genetic factors, characteristic glycan changes of these glycoproteins are more susceptible to environmental factors, including liver and pancreatic disease.

Sugar-stabilised nanomaterials have received a lot of attention in cancer therapy in recent years due to their pronounced application as specific targeting agents and maximizing their therapeutic potential while bypassing off-target effects. Lectins, the carbohydrate-binding proteins, are capable of binding to receptors present on the target cell/tissue and interact with transformed glycans better than normal cells. Besides some of the lectins exhibit anticancer activity. Conjugating sugar-stabilised NPs with lectins there for is expected to multiply the potential for the early diagnosis of cancer cells and the specific release of drugs into the tumor site. Because of the prospective applications of lectin-sugar-stabilised nanoparticle conjugates, it is important to understand their molecular interaction and physicochemical properties. Momordica charantia Seed Lectin (MCL) is a type II RIP and has been known as an anti-tumor agent. Investigation of the interaction between sugar-stabilised silver nanoparticles and MCL has been performed by fluorescence spectroscopy to explore the possibility of creating an effective biocompatible drug delivery system against cancer cells. In this regard interaction between lectin and NPs should be well-preserved, while recognizing the specific cell surface sugar. Therefore experiments were carried out in the presence and absence of specific sugar galactose. Protein intrinsic fluorescence emission is quenched at ~ 20% at saturation during the interaction without any significant shift in fluorescence emission maximum. Binding experiments reveal a good affinity. Tetrameric MCL binds to a single nanoparticle. Stern-Volmer analysis of the quenching data suggests that the interaction is via static quenching leading to complex formation. Hemagglutination experiments together with interaction studies in the presence of specific sugar show that the sugar-binding site of the lectin is distinct from the nanoparticle-binding site and cell recognition is very much intact even after binding to AgNPs. Our results propose the possibility of developing MCL-silver nanoparticle conjugate with high stability and multiple properties in the diagnosis and treatment of cancer.

Vascular calcification is an abnormal process in which bone specific hydroxyapatite crystals are actively deposited on the vascular wall mediated by phenotypic differentiated smooth muscle cells and other mesenchymal cells under various pathological conditions. It is one of the important characteristics in the occurrence and development of atherosclerosis, prevalent in patients with type 2 diabetes and advanced chronic kidney disease, especially those requiring maintenance hemodialysis, with severely threatening human health. Previous studies have shown that the early diagnosis and control of vascular calcification is of great significance for cardiovascular risk stratification, prevention of acute cardiovascular events, which can greatly improve the prognosis and quality of life of patients. Galectins are a family of lectin superfamily. It is widely distributed in various animals and plays an important role in many physiological and pathological processes, such as cell adhesion, apoptosis, inflammatory response, tumor metastasis and so on. Many biomarker-and association-related studies and Preclinical-mechanistic studies have suggested that galactose-specific lectin-3 (galectin-3) plays an important role in vascular calcification and vascular intimal calcification (VIC) calcification induced by Wnt/βcatenin signaling pathway, NF-κB signaling pathway and ERK1/2 signaling pathway. This paper mainly expounds the role and mechanism of galectin-3 in vascular calcification under different pathological conditions including atherosclerosis, diabetes and chronic kidney disease.

The structure of a sialoglycan can be translated into to a biological response when it binds to a specific endogenous lectin. Among endogenous sialic acid-binding lectins in humans are those comprising the 15-member Siglec family, most of which are expressed on overlapping sets of immune cells. Endogenous Siglec ligands are sialoglycolipids (gangliosides) and/or sialoglycoproteins, on cell surfaces or in the extracellular milieu, that bind to and initiate signaling by cell surface Siglecs. In the nervous system, where gangliosides are the predominant sialoglycans, Siglec-4 (myelin-associated glycoprotein) on myelinating cells binds to gangliosides GD1a and GT1b on nerve cell axons to ensure stable and productive axon-myelin interactions. In the immune system, Siglec-7 on natural killer cells binds to gangliosides GD3 and GD2 to inhibit immune signaling. Expression of GD3 and GD2 on cancer cells can lead to tumor immune evasion. Siglec-1 (sialoadhesin, CD169) on macrophages binds to gangliosides on tumors and enveloped viruses. This may enhance antigen presentation in some cases, or increase viral distribution in others. Several other Siglecs bind to gangliosides in vitro, the biological significance of which has yet to be fully established. Gangliosides, which are found on all human cells and tissues in cell-specific distributions, are functional Siglec ligands with varied roles driving Siglec-mediated signaling.

Ganglioside GD2 is associated with the proliferation and migration of breast cancer cells. However, the precise role of GD2 is unclear because its tendency to form dynamic and transient domains in cell plasma membranes (PMs), called lipid rafts, makes it difficult to observe. Previously, we developed fluorescent analogs of gangliosides (e.g., GM3 and GM1), which enabled the observation of lipid raft formation for the first time using single-molecule imaging. In this report, we describe the first chemical synthesis of a fluorescent ganglioside, GD2. A biophysical analysis of the synthesized analog revealed its raft-philic character, suggesting its potential to aid single-molecule imaging-based investigations into raft-associated interactions.

A low-oxygen (hypoxia) tumor microenvironment can facilitate chemotherapy and radiation therapy resistance in tumors and is associated with a poor prognosis. Hypoxia also affects PCa (prostate cancer) phenotype transformation and causes therapeutic resistance. Although O-glycans are known to be involved in the malignancy of various cancers under hypoxia, the expression and function of O-glycans in PCa are not well understood. In this study, the saccharide primer method was employed to analyze O-glycan expression in PCa cells. Results showed that the expression of sTn antigens was increased in PCa cells under hypoxia. Furthermore, it was found that ST6GalNAc1, the sTn antigen synthase gene, was involved in the migration-proliferation dichotomy and drug resistance in PCa cells under hypoxia. The results of this study will contribute to the development of novel diagnostic markers and drug targets for PCa under hypoxia.

Characterization of O-glycans linked to serine or threonine residues in glycoproteins has mostly been achieved using chemical reaction approaches because there are no known O-glycan-specific endoglycosidases. Most O-glycans are modified with sialic acid residues at the non-reducing termini through various linkages. In this study, we developed a novel approach for sialic acid linkage-specific O-linked glycan analysis through lactone-driven ester-to-amide derivatization combined with non-reductive β-elimination in the presence of hydroxylamine. O-glycans released by non-reductive β-elimination were efficiently purified using glycoblotting via chemoselective ligation between carbohydrates and a hydrazide-functionalized polymer, followed by modification of methyl or ethyl ester groups of sialic acid residues on solid-phase. In-solution lactone-driven ester-to-amide derivatization of ethyl-esterified O-glycans was performed, and the resulting sialylated glycan isomers were discriminated by mass spectrometry. In combination with PNGase F digestion, we carried out simultaneous, quantitative, and sialic acid linkage-specific N- and O-linked glycan analyses of a model glycoprotein and human cartilage tissue. This novel glycomic approach will facilitate detailed characterization of biologically relevant sialylated N- and O-glycans on glycoproteins.