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Diagnosis and Pathobiology
Published in Franklyn De Silva, Jane Alcorn, The Elusive Road Towards Effective Cancer Prevention and Treatment, 2023
Franklyn De Silva, Jane Alcorn
The covalent linking of a carbohydrate to another molecule is known as glycation (nonenzymatic glycosylation, which is a process of joining glycans to proteins, lipids, or other organic molecules via catalysis) [368]. Over 50% of proteins undergo this type of PTM and influence multiple activities involving cellular adhesion, proliferation, inflammation, oncogenesis, immunological responses, and viral replication [368]. While histones can be O-GlcNAc-modified proteins, the joining of O-linked β-N-acetylglucosamine (O-GlcNAc) moieties to serine and threonine residues of nuclear, mitochondrial, and cytoplasmic proteins (histone and nonhistone) is termed ‘O-GlcNAcylation' [387, 419–423]. This is a noncanonical glycosylation and is linked to metabolic disorders because of its sensitivity to cellular stress (e.g., nutrient deprivation, heat shock, hypoxia) [421, 424–426]. O-GlcNAcylation is the hexosamine biosynthetic pathway (HBP) nutrient flux product [421]. HBP combines amino acid, glucose, nucleotide, and fatty acid metabolism to produce the O-GlcNAcylation donor substrate [421]. The transfer of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc: donor substrate), to the target protein is catalyzed by O-GlcNAc transferase (OGT) and the removal of the sugar is performed by β-N-acetylglucosaminidase (O-GlcNAcase or OGA) [387, 419, 421].
What are the diagnostic capabilities of glycans for breast cancer?
Published in Expert Review of Molecular Diagnostics, 2023
N-1 glycans are glycosylated forms consisting of an N-acetylglucosamine (GlcNAc) linked to the amide group of asparagine (Asn). N-glycan structures can be annotated into three groups, depending on the glycan residues outside the core pentasaccharide: high-mannose type, complex type, and hybrid type [9]. O-glycosylation on serine (Ser) or threonine (Thr) residues often refers to O-linked GlcNAc (O-GlcNAc) and O-linked N-acetylgalactosamine (O-GalNAc) glycosylations. O-GlcNAc is a dynamic and reversible glycosylation which involves the addition or removal of GlcNAc to Ser or Thr residues of proteins by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively [10,11]. O-GalNAc glycans are initiated by the transfer of GalNAc onto Ser or Thr residues on proteins. This initial GalNAcα1-Ser/Thr (called Tn antigen) can then be elongated to four core structures. Since O-GalNAc is most commonly found in mucins, it is often referred to mucin-type O-glycans [12,13]. N-glycans and O-glycans structures are also often sialylated and fucosylated. Examples of terminal glycan epitopes commonly found on transformed cells include sialyl T(sT), sialyl Tn (sTn), and sialyl Lewis x (sLex) [14,15].
Relevance of glycans in the interaction between T lymphocyte and the antigen presenting cell
Published in International Reviews of Immunology, 2021
Wilton Gómez-Henao, Eda Patricia Tenorio, Francisco Raúl Chávez Sanchez, Miguel Cuéllar Mendoza, Ricardo Lascurain Ledezma, Edgar Zenteno
O-GlcNAcylation (O-GlcNAc) is a type of dynamic glycosylation found in cytosolic, nuclear, and mitochondrial proteins, involved in biological processes such as cell metabolism, cell differentiation, development of neurodegenerative diseases, among others [20, 122, 123]. O-GlcNAc consists of the addition of a GlcNAc molecule to a Ser/Thr residue, its synthesis is regulated by the substrate donor UDP-GlcNAc and by the O-GlcNAc transferase (OGT) and the O-GlcNAcase (OGA) enzymes that, respectively, add and remove glycans from the target protein [115]. O-GlcNAc along with phosphorylation regulates protein functions acting as a “switch” to activate and inhibit signals in cascades that lead to the development of cellular responses, maintaining the homeostasis of the communication systems of the cell with its environment [19, 124].
O-GlcNAc Signaling Augmentation Protects Human Corneal Endothelial Cells from Oxidative Stress via AKT Pathway Activation
Published in Current Eye Research, 2020
Chang Ki Yoon, Sam Young Yoon, Jin Sun Hwang, Young Joo Shin
O-linked β-N-acetylglucosamine (O-GlcNAc) is a post-translational modification on serine or threonine residues of nucleocytoplasmic and mitochondrial proteins.21 Interestingly, the novel post-translational sugar modification, O-GlcNAc has been shown in numerous studies and in different cell types to act as an inducible, cytoprotective stress response.21–23 PUGNAc ((phenylcarbamoyl)oxime analog of GlcNAc; Molecular Weight, 353.3) is a drug, which acts as an inhibitor of N-acetylglucosaminidase. PUGNAc inhibits O-GlcNAcase (OGA), a beta-exo-N-acetylhexosaminidase, which results in increasing O-GlcNAc levels in cells. The solubility of PUGNAc is approximately 1 mg/ml in PBS, pH 7.2 and 100 mM in DMSO. In this study, we investigated the effect of O-GlcNAc augmentation on CECs against oxidative stress.