Expression, Purification, and Applications of the Recombinant Lectin PVL from Psathyrella velutina Specific for Terminal N-Acetyl-Glucosamine

An overview of tools to decipher O-GlcNAcylation from historical approaches to new insights

O-GlcNAcylation is a post-translational modification which affects approximately 5000 human proteins. Its involvement has been shown in many if not all biological processes. Variations in O-GlcNAcylation levels can be associated with the development of diseases. Deciphering the role of O-GlcNAcylation is an important issue to (i) understand its involvement in pathophysiological development and (ii) develop new therapeutic strategies to modulate O-GlcNAc levels. Over the past 30 years, despite the development of several approaches, knowledge of its role and regulation have remained limited. This review proposes an overview of the currently available tools to study O-GlcNAcylation and identify O-GlcNAcylated proteins. Briefly, we discuss pharmacological modulators, methods to study O-GlcNAcylation levels and approaches for O-GlcNAcylomic profiling. This review aims to contribute to a better understanding of the methods used to study O-GlcNAcylation and to promote efforts in the development of new strategies to explore this promising modification.

O-GlcNAcylation Quantification of Certain Protein by the Proximity Ligation Assay and Clostridium perfringen OGAD298N(CpOGAD298N)

O-GlcNAcylation is an O-linked β-N-acetyl-glucosamine (O-GlcNAc)-monosaccharide modification of serine or threonine in proteins that plays a vital role in many critical cellular processes. Owing to its low molecular weight, uncharged property, and difficulty in distinguishing from β-N-acetyl-galactosamine (GalNAc), the lack of high specificity and avidity tools and sophisticated quantification methods have always been the bottleneck in analyzing O-GlcNAc functions. Here, we compared glycan array data of the mutant of Clostridium perfringen OGA (CpOGA^D298N), O-GlcNAc antibody CTD110.6, and several lectins. We found that CpOGA^D298N can effectively distinguish GlcNAc from GalNAc. Glycan array analysis and isothermal titration calorimetry (ITC) show that CpOGA^D298N has a GlcNAc specific binding characteristic. CpOGA^D298N could be used in far-western, flow cytometry analysis, and confocal imaging to demonstrate the existence of O-GlcNAc proteins. Using the CpOGA^D298N affinity column, we identified 84 highly confident O-GlcNAc modified peptides from 82 proteins in the MCF-7 cell line and 33 highly confident peptides in 33 proteins from mouse liver tissue; most of them are novel O-GlcNAc proteins and could not bind with wheat germ agglutinin (WGA). Besides being used as a facile enrichment tool, a combination of CpOGA^D298N with the proximity ligation assay (PLA) is successfully used to quantify O-GlcNAc modified histone H2B, which is as low as femtomoles in MCF-7 cell lysate. These results suggest that CpOGA^D298N is a specific tool for detection (far-western, flow cytometry analysis, and confocal imaging) and enrichment of O-GlcNAcylated proteins and peptides, and the CpOGA^D298N-PLA method is useful for quantifying certain O-GlcNAc protein.