O-linked N-acetylglucosamine transferase (OGT), a key protein in O-linked N-acetylglucosamine (O-GlcNAc) post-translational modification, catalyzes O-GlcNAcylation by linking GlcNAc from glycosyl ...donors to protein Ser/Thr residues to regulate multiple biological processes. OGT has become a popular research topic in the field of glycobiology as a potential target. This report consists of three parts, namely: the basic information of OGT, the relationship between OGT and diseases, and the research progress of OGT inhibitors. This report aims to improve the understanding of OGT-related fields from the perspective of its structure. OGT inhibitors could aid the effective and efficient investigation of the O-GlcNAcylation mechanism, and provide new ideas and methods for the treatment of related diseases.
•Structure and function of OGT protein.•Relationship between OGT protein and diseases.•A comprehensive summary of the reported OGT inhibitors.•Design ideas and directions of OGT inhibitors.
A reversible post-translational protein modification which involves addition of N-acetylglucosamine (GlcNAc) onto hydroxyl groups of serine and/or threonine residues which is known as ...O-GlcNAcylation, has emerged as a potent competitor of phosphorylation. This glycosyltransfer reaction is catalyzed by the enzyme O-linked β-N-acetylglucosamine transferase (OGT). This enzyme uses uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), the end product of hexosamine biosynthetic pathway, to modify numerous nuclear and cytosolic proteins. O-GlcNAcylation influences cancer cell metabolism in such a way that hyper-O-GlcNAcylation is considered as a prominent trait of many cancers, and is proposed as a major factor enabling cancer cell proliferation and progression. Growing evidence supports a connection between O-GlcNAcylation and major oncogenic factors, including for example, c-MYC, HIF-1α, and NF-κB. A comprehensive study of the roles of O-GlcNAc modification of oncogenic factors is warranted as a thorough understanding may help drive advances in cancer diagnosis and therapy. The focus of this article is to highlight the interplay between oncogenic factors and O-GlcNAcylation along with OGT in cancer cell proliferation and survival. The prospects for OGT inhibitors will also be discussed.
•Aberrant O-GlcNAcylation is considered as hallmark of cancer.•Hyper O-GlcNAcylation favours stabilization of oncogenic factors.•Transcription of oncogenic factors lead to uncontrolled cell division, invasion and metastasis of cancer cells.•Development of a potent, selective and cell permeable inhibitors of OGT enzyme is required.
-GlcNAcylation is an essential post-translational modification installed by the enzyme
-β-
-acetyl-d-glucosaminyl transferase (OGT). Modulating this enzyme would be extremely valuable to better ...understand its role in the development of serious human pathologies, such as diabetes and cancer. However, the limited availability of potent and selective inhibitors hinders the validation of this potential therapeutic target. To explore new chemotypes that target the active site of OGT, we performed virtual screening of a large library of commercially available compounds with drug-like properties. We purchased samples of the most promising virtual hits and used enzyme assays to identify authentic leads. Structure-activity relationships of the best identified OGT inhibitor were explored by generating a small library of derivatives. Our best hit displays a novel uridine mimetic scaffold and inhibited the recombinant enzyme with an IC
value of 7 µM. The current hit represents an excellent starting point for designing and developing a new set of OGT inhibitors that may prove useful for exploring the biology of OGT.
Accumulated data indicated that many types of cancers have increased protein O-GlcNAcylation at cell surface and inside cells. The aberrant O-GlcNAcylation is considered a potential therapeutic ...target. Although several types of compounds capable of inhibiting O-GlcNAcylation have been developed, their low solubility, poor permeability and delivery efficiency have impeded the application for in vivo and pre-clinical studies. Nanocarriers have the advantages of controllable drug release and active cancer-targeting capability. Moreover, nanoparticles can improve drug delivery efficiency and reduce the non-specific distribution in normal tissues by the enhanced permeability and retention (EPR) effect in cancer. Taking the advantage of O-GlcNAc-specific antibodies or lectins, nanoparticles could further improve their cancer-targeting capability. Although nanocarriers targeting the canonical N- and O-linked glycosylation have been extensively investigated for cancer detection and therapy, application of nanotechniques for the specific targeting of O-GlcNAcylation has not been actively pursued. This review summarizes the general features of GlcNAcylation and its alterations in cancers. Analyses are focused on the following areas: How the nanocarriers may improve the solubility and/or cell permeability of O-GlcNAc transferase (OGT) inhibitors; The modification of nanocarriers with lectins or antibodies for active targeting of O-GlcNAc; The nanocarriers-mediated co-delivery of OGT inhibitors and conventional drugs, which may lead to synergistic effects. Unsolved issues impeding the research progression on O-GlcNAcylation-targeting scheme are also discussed.
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•Bioisosteric replacement of pyrophosphate moiety represents novel approach for OGT inhibitor design.•This is the first examples of N-terminally tethered hOGT bisubstrate ...inhibitors.•OGT inhibition activity rationalised using in silico study provides insight into inhibitor design.
Protein O-linked β-D-N-acetylglucosamine (O-GlcNAc) modification (O-GlcNAcylation), an essential post-translational as well as cotranslational modification, is the attachment of β-D-N-acetylglucosamine to serine and threonine residues of nucleocytoplasmic proteins. An aberrant O-GlcNAc profile on certain proteins has been implicated in metabolic diseases such as diabetes and cancer. Inhibitors of O-GlcNAc transferase (OGT) are valuable tools to study the cell biology of protein O-GlcNAc modification. In this study we report novel uridine-peptide conjugate molecules composed of an acceptor peptide covalently linked to a catalytically inactive donor substrate analogue that bears a pyrophosphate bioisostere and explore their inhibitory activities against OGT by a radioactive hOGT assay. Further, we investigate the structural basis of their activities via molecular modelling, explaining their lack of potency towards OGT inhibition.
-GlcNAcylation is a posttranslational modification that occurs at serine and threonine residues of protein substrates by the addition of
-linked β-d-
-acetylglucosamine (GlcNAc) moiety. Two enzymes ...are involved in this modification:
-GlcNac transferase (OGT), which attaches the GlcNAc residue to the protein substrate, and
-GlcNAcase (OGA), which removes it. This biological balance is important for many biological processes, such as protein expression, cell apoptosis, and regulation of enzyme activity. The extent of this modification has sparked interest in the medical community to explore OGA and OGT as therapeutic targets, particularly in degenerative diseases. While some OGA inhibitors are already in phase 1 clinical trials for the treatment of Alzheimer's disease, OGT inhibitors still have a long way to go. Due to complex expression and instability, the discovery of potent OGT inhibitors is challenging. Over the years, the field has grappled with this problem, and scientists have developed a number of techniques and assays. In this review, we aim to highlight assays and techniques for OGT inhibitor discovery, evaluate their strength for the field, and give us direction for future bioassay methods.
-GlcNAcylation is an essential post-translational modification that occurs on nuclear and cytoplasmic proteins, regulating their function in response to cellular stress and altered nutrient ...availability.
-GlcNAc transferase (OGT) is the enzyme that catalyzes this reaction and represents a potential therapeutic target, whose biological role is still not fully understood. To support this research field, a series of cell-permeable, low-nanomolar OGT inhibitors were recently reported. In this study, we resynthesized the most potent OGT inhibitor of the library, OSMI-4, and we used it to investigate OGT inhibition in different human cell lines. The compound features an ethyl ester moiety that is supposed to be cleaved by carboxylesterases to generate its active metabolite. Our LC-HRMS analysis of the cell lysates shows that this is not always the case and that, even in the cell lines where hydrolysis does not occur, OGT activity is inhibited.
Abstract
Posttranslational modifications (PTM) including glycosylation, phosphorylation, acetylation, methylation and ubiquitination dynamically alter the proteome. The evolutionarily conserved ...enzymes O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) and O-GlcNAcase are responsible for the addition and removal, respectively, of the nutrient-sensitive PTM of protein serine and threonine residues with O-GlcNAc. Indeed, the O-GlcNAc modification acts at every step in the "central dogma" of molecular biology and alters signaling pathways leading to amplified or blunted biological responses. The cellular roles of OGT and the dynamic PTM O-GlcNAc have been clarified with recently developed chemical tools including high-throughput assays, structural and mechanistic studies and potent enzyme inhibitors. These evolving chemical tools complement genetic and biochemical approaches for exposing the underlying biological information conferred by O-GlcNAc cycling.
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