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Physiological Reviews Apr 2021In the mid-1980s, the identification of serine and threonine residues on nuclear and cytoplasmic proteins modified by a -acetylglucosamine moiety (-GlcNAc) via an... (Review)
Review
In the mid-1980s, the identification of serine and threonine residues on nuclear and cytoplasmic proteins modified by a -acetylglucosamine moiety (-GlcNAc) via an -linkage overturned the widely held assumption that glycosylation only occurred in the endoplasmic reticulum, Golgi apparatus, and secretory pathways. In contrast to traditional glycosylation, the -GlcNAc modification does not lead to complex, branched glycan structures and is rapidly cycled on and off proteins by -GlcNAc transferase (OGT) and -GlcNAcase (OGA), respectively. Since its discovery, -GlcNAcylation has been shown to contribute to numerous cellular functions, including signaling, protein localization and stability, transcription, chromatin remodeling, mitochondrial function, and cell survival. Dysregulation in -GlcNAc cycling has been implicated in the progression of a wide range of diseases, such as diabetes, diabetic complications, cancer, cardiovascular, and neurodegenerative diseases. This review will outline our current understanding of the processes involved in regulating -GlcNAc turnover, the role of -GlcNAcylation in regulating cellular physiology, and how dysregulation in -GlcNAc cycling contributes to pathophysiological processes.
Topics: Acetylglucosamine; Animals; Cell Physiological Phenomena; Glycosylation; Humans; N-Acetylglucosaminyltransferases; Protein Processing, Post-Translational
PubMed: 32730113
DOI: 10.1152/physrev.00043.2019 -
International Journal of Molecular... Sep 2020Mucolipidosis II and III (ML II/III) are caused by a deficiency of uridine-diphosphate -acetylglucosamine: lysosomal-enzyme--acetylglucosamine-1-phosphotransferase... (Review)
Review
Mucolipidosis II and III (ML II/III) are caused by a deficiency of uridine-diphosphate -acetylglucosamine: lysosomal-enzyme--acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase, EC2.7.8.17), which tags lysosomal enzymes with a mannose 6-phosphate (M6P) marker for transport to the lysosome. The process is performed by a sequential two-step process: first, GlcNAc-1-phosphotransferase catalyzes the transfer of GlcNAc-1-phosphate to the selected mannose residues on lysosomal enzymes in the cis-Golgi network. The second step removes GlcNAc from lysosomal enzymes by -acetylglucosamine-1-phosphodiester α--acetylglucosaminidase (uncovering enzyme) and exposes the mannose 6-phosphate (M6P) residues in the trans-Golgi network, in which the enzymes are targeted to the lysosomes by M6Preceptors. A deficiency of GlcNAc-1-phosphotransferase causes the hypersecretion of lysosomal enzymes out of cells, resulting in a shortage of multiple lysosomal enzymes within lysosomes. Due to a lack of GlcNAc-1-phosphotransferase, the accumulation of cholesterol, phospholipids, glycosaminoglycans (GAGs), and other undegraded substrates occurs in the lysosomes. Clinically, ML II and ML III exhibit quite similar manifestations to mucopolysaccharidoses (MPSs), including specific skeletal deformities known as dysostosis multiplex and gingival hyperplasia. The life expectancy is less than 10 years in the severe type, and there is no definitive treatment for this disease. In this review, we have described the updated diagnosis and therapy on ML II/III.
Topics: Animals; Biological Transport, Active; Disease Models, Animal; Enzyme Replacement Therapy; Genetic Therapy; Glycosaminoglycans; Hematopoietic Stem Cell Transplantation; Humans; Lysosomes; Mannosephosphates; Mucolipidoses
PubMed: 32957425
DOI: 10.3390/ijms21186812 -
The Journal of Clinical Investigation Apr 2023Major depressive disorder is a common and devastating psychiatric disease, and the prevalence and burden are substantially increasing worldwide. Multiple studies of...
Major depressive disorder is a common and devastating psychiatric disease, and the prevalence and burden are substantially increasing worldwide. Multiple studies of depression patients have implicated glucose metabolic dysfunction in the pathophysiology of depression. However, the molecular mechanisms by which glucose and related metabolic pathways modulate depressive-like behaviors are largely uncharacterized. Uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) is a glucose metabolite with pivotal functions as a donor molecule for O-GlcNAcylation. O-GlcNAc transferase (OGT), a key enzyme in protein O-GlcNAcylation, catalyzes protein posttranslational modification by O-GlcNAc and acts as a stress sensor. Here, we show that Ogt mRNA was increased in depression patients and that astroglial OGT expression was specifically upregulated in the medial prefrontal cortex (mPFC) of susceptible mice after chronic social-defeat stress. The selective deletion of astrocytic OGT resulted in antidepressant-like effects, and moreover, astrocytic OGT in the mPFC bidirectionally regulated vulnerability to social stress. Furthermore, OGT modulated glutamatergic synaptic transmission through O-GlcNAcylation of glutamate transporter-1 (GLT-1) in astrocytes. OGT astrocyte-specific knockout preserved the neuronal morphology atrophy and Ca2+ activity deficits caused by chronic stress and resulted in antidepressant effects. Our study reveals that astrocytic OGT in the mPFC regulates depressive-like behaviors through the O-GlcNAcylation of GLT-1 and could be a potential target for antidepressants.
Topics: Mice; Animals; Astrocytes; Depressive Disorder, Major; Depression; Synaptic Transmission; N-Acetylglucosaminyltransferases; Antidepressive Agents; Glucose; Acetylglucosamine
PubMed: 36757814
DOI: 10.1172/JCI160016 -
Nature Communications Jan 2020Many cancer cells display enhanced glycolysis and suppressed mitochondrial metabolism. This phenomenon, known as the Warburg effect, is critical for tumor development....
Many cancer cells display enhanced glycolysis and suppressed mitochondrial metabolism. This phenomenon, known as the Warburg effect, is critical for tumor development. However, how cancer cells coordinate glucose metabolism through glycolysis and the mitochondrial tricarboxylic acid (TCA) cycle is largely unknown. We demonstrate here that phosphoglycerate kinase 1 (PGK1), the first ATP-producing enzyme in glycolysis, is reversibly and dynamically modified with O-linked N-acetylglucosamine (O-GlcNAc) at threonine 255 (T255). O-GlcNAcylation activates PGK1 activity to enhance lactate production, and simultaneously induces PGK1 translocation into mitochondria. Inside mitochondria, PGK1 acts as a kinase to inhibit pyruvate dehydrogenase (PDH) complex to reduce oxidative phosphorylation. Blocking T255 O-GlcNAcylation of PGK1 decreases colon cancer cell proliferation, suppresses glycolysis, enhances the TCA cycle, and inhibits tumor growth in xenograft models. Furthermore, PGK1 O-GlcNAcylation levels are elevated in human colon cancers. This study highlights O-GlcNAcylation as an important signal for coordinating glycolysis and the TCA cycle to promote tumorigenesis.
Topics: Acetylglucosamine; Amino Acid Motifs; Animals; Cell Line, Tumor; Citric Acid Cycle; Colonic Neoplasms; Glycolysis; Humans; Male; Mice; Mice, Nude; Mitochondria; Phosphoglycerate Kinase; Pyruvate Dehydrogenase Complex
PubMed: 31911580
DOI: 10.1038/s41467-019-13601-8 -
Nature Cell Biology May 2022A decline in skeletal muscle mass and low muscular strength are prognostic factors in advanced human cancers. Here we found that breast cancer suppressed O-linked...
A decline in skeletal muscle mass and low muscular strength are prognostic factors in advanced human cancers. Here we found that breast cancer suppressed O-linked N-acetylglucosamine (O-GlcNAc) protein modification in muscle through extracellular-vesicle-encapsulated miR-122, which targets O-GlcNAc transferase (OGT). Mechanistically, O-GlcNAcylation of ryanodine receptor 1 (RYR1) competed with NEK10-mediated phosphorylation and increased K48-linked ubiquitination and proteasomal degradation; the miR-122-mediated decrease in OGT resulted in increased RYR1 abundance. We further found that muscular protein O-GlcNAcylation was regulated by hypoxia and lactate through HIF1A-dependent OGT promoter activation and was elevated after exercise. Suppressed O-GlcNAcylation in the setting of cancer, through increasing RYR1, led to higher cytosolic Ca and calpain protease activation, which triggered cleavage of desmin filaments and myofibrillar destruction. This was associated with reduced skeletal muscle mass and contractility in tumour-bearing mice. Our findings link O-GlcNAcylation to muscular protein homoeostasis and contractility and reveal a mechanism of cancer-associated muscle dysregulation.
Topics: Acetylglucosamine; Animals; Humans; Mice; MicroRNAs; Muscle, Skeletal; N-Acetylglucosaminyltransferases; Neoplasms; Protein Processing, Post-Translational; Proteolysis; Ryanodine Receptor Calcium Release Channel
PubMed: 35469018
DOI: 10.1038/s41556-022-00893-0 -
Cell Metabolism Feb 2020While obesity and associated metabolic complications are linked to inflammation of white adipose tissue (WAT), the causal factors remain unclear. We hypothesized that...
While obesity and associated metabolic complications are linked to inflammation of white adipose tissue (WAT), the causal factors remain unclear. We hypothesized that the local metabolic environment could be an important determinant. To this end, we compared metabolites released from WAT of 81 obese and non-obese women. This identified glutamine to be downregulated in obesity and inversely associated with a pernicious WAT phenotype. Glutamine administration in vitro and in vivo attenuated both pro-inflammatory gene and protein levels in adipocytes and WAT and macrophage infiltration in WAT. Metabolomic and bioenergetic analyses in human adipocytes suggested that glutamine attenuated glycolysis and reduced uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) levels. UDP-GlcNAc is the substrate for the post-translational modification O-linked β-N-acetylglucosamine (O-GlcNAc) mediated by the enzyme O-GlcNAc transferase. Functional studies in human adipocytes established a mechanistic link between reduced glutamine, O-GlcNAcylation of nuclear proteins, and a pro-inflammatory transcriptional response. Altogether, glutamine metabolism is linked to WAT inflammation in obesity.
Topics: Acetylglucosamine; Adipocytes; Adipose Tissue, White; Adult; Animals; Cells, Cultured; Cohort Studies; Female; Glucose; Glutamine; Glycosylation; Humans; Inflammation; Male; Mice, Inbred C57BL; Middle Aged; N-Acetylglucosaminyltransferases; Obesity
PubMed: 31866443
DOI: 10.1016/j.cmet.2019.11.019 -
Chemical Society Reviews Sep 2021The addition of -linked-β-D--acetylglucosamine (-GlcNAc) onto serine and threonine residues of nuclear and cytoplasmic proteins is an abundant, unique... (Review)
Review
The addition of -linked-β-D--acetylglucosamine (-GlcNAc) onto serine and threonine residues of nuclear and cytoplasmic proteins is an abundant, unique post-translational modification governing important biological processes. -GlcNAc dysregulation underlies several metabolic disorders leading to human diseases, including cancer, neurodegeneration and diabetes. This review provides an extensive summary of the recent progress in probing -GlcNAcylation using mainly chemical methods, with a special focus on discussing mechanistic insights and the structural role of -GlcNAc at the molecular level. We highlight key aspects of the -GlcNAc enzymes, including development of OGT and OGA small-molecule inhibitors, and describe a variety of chemoenzymatic and chemical biology approaches for the study of -GlcNAcylation. Special emphasis is placed on the power of chemistry in the form of synthetic glycopeptide and glycoprotein tools for investigating the site-specific functional consequences of the modification. Finally, we discuss in detail the conformational effects of -GlcNAc glycosylation on protein structure and stability, relevant -GlcNAc-mediated protein interactions and its molecular recognition features by biological receptors. Future research in this field will provide novel, more effective chemical strategies and probes for the molecular interrogation of -GlcNAcylation, elucidating new mechanisms and functional roles of -GlcNAc with potential therapeutic applications in human health.
Topics: Acetylglucosamine; Glycosylation; Humans; N-Acetylglucosaminyltransferases; Protein Processing, Post-Translational; Proteins
PubMed: 34338261
DOI: 10.1039/d0cs01275k -
Gastroenterology Jan 2023Weight loss and exercise intervention have been reported to increase the interaction between Bacteroides spp and Akkermansiamuciniphila (Am), although the underlying...
BACKGROUND & AIMS
Weight loss and exercise intervention have been reported to increase the interaction between Bacteroides spp and Akkermansiamuciniphila (Am), although the underlying mechanisms and consequences of the interaction remain unknown.
METHODS
Using a healthy Korean twin cohort (n = 582), we analyzed taxonomic associations with host body mass index. B vulgatus strains were isolated from mice and human subjects to investigate the strain-specific effect of B vulgatus SNUG 40005 (Bvul) on obesity. The mechanisms underlying Am enrichment by Bvul administration were investigated by multiple experiments: (1) in vitro cross-feeding experiments, (2) construction of Bvul mutants with the N-acetylglucosaminidase gene knocked out, and (3) in vivo validation cohorts with different metabolites. Finally, metabolite profiling in mouse and human fecal samples was performed.
RESULTS
An interaction between Bvul and Am was observed in lean subjects but was disrupted in obese subjects. The administration of Bvul to mice fed a high-fat diet decreased body weight, insulin resistance, and gut permeability. In particular, Bvul restored the abundance of Am, which decreased significantly after a long-term high-fat diet. A cross-feeding analysis of Am with cecal contents or Bvul revealed that Am enrichment was attributed to metabolites produced during mucus degradation by Bvul. The metabolome profile of mouse fecal samples identified N-acetylglucosamine as contributing to Am enrichment, which was confirmed by in vitro and in vivo experiments. Metabolite network analysis of the twin cohort found that lysine serves as a bridge between N-acetylglucosamine, Bvul, and Am.
CONCLUSIONS
Strain-specific microbe-microbe interactions modulate the mucosal environment via metabolites produced during mucin degradation in the gut.
Topics: Humans; Mice; Animals; Akkermansia; Acetylglucosamine; Bacteroides; Obesity; Diet, High-Fat
PubMed: 36240952
DOI: 10.1053/j.gastro.2022.09.040 -
Cell Jan 2023O-GlcNAc is a dynamic post-translational modification (PTM) that regulates protein functions. In studying the regulatory roles of O-GlcNAc, a major roadblock is the...
O-GlcNAc is a dynamic post-translational modification (PTM) that regulates protein functions. In studying the regulatory roles of O-GlcNAc, a major roadblock is the inability to change O-GlcNAcylation on a single protein at a time. Herein, we developed a dual RNA-aptamer-based approach that simultaneously targeted O-GlcNAc transferase (OGT) and β-catenin, the key transcription factor of the Wnt signaling pathway, to selectively increase O-GlcNAcylation of the latter without affecting other OGT substrates. Using the OGT/β-catenin dual-specificity aptamers, we found that O-GlcNAcylation of β-catenin stabilizes the protein by inhibiting its interaction with β-TrCP. O-GlcNAc also increases β-catenin's interaction with EZH2, recruits EZH2 to promoters, and dramatically alters the transcriptome. Further, by coupling riboswitches or an inducible expression system to aptamers, we enabled inducible regulation of protein-specific O-GlcNAcylation. Together, our findings demonstrate the efficacy and versatility of dual-specificity aptamers for regulating O-GlcNAcylation on individual proteins.
Topics: Aptamers, Nucleotide; beta Catenin; Protein Processing, Post-Translational; Wnt Signaling Pathway; N-Acetylglucosaminyltransferases; Acetylglucosamine
PubMed: 36626902
DOI: 10.1016/j.cell.2022.12.016 -
Proceedings of the National Academy of... Jan 2023-GlcNAc transferase (OGT) modifies serine and threonine residues on nuclear and cytosolic proteins with -linked N-acetylglucosamine (GlcNAc). OGT is essential for...
-GlcNAc transferase (OGT) modifies serine and threonine residues on nuclear and cytosolic proteins with -linked N-acetylglucosamine (GlcNAc). OGT is essential for mammalian cell viability, but the underlying mechanisms are still enigmatic. We performed a genome-wide CRISPR-Cas9 screen in mouse embryonic stem cells (mESCs) to identify candidates whose depletion rescued the block in cell proliferation induced by OGT deficiency. We show that the block in cell proliferation in OGT-deficient cells stems from mitochondrial dysfunction secondary to mTOR (mechanistic target of rapamycin) hyperactivation. In normal cells, OGT maintains low mTOR activity and mitochondrial fitness through suppression of proteasome activity; in the absence of OGT, increased proteasome activity results in increased steady-state amino acid levels, which in turn promote mTOR lysosomal translocation and activation, and increased oxidative phosphorylation. mTOR activation in OGT-deficient mESCs was confirmed by an independent phospho-proteomic screen. Our study highlights a unique series of events whereby OGT regulates the proteasome/ mTOR/ mitochondrial axis in a manner that maintains homeostasis of intracellular amino acid levels, mitochondrial fitness, and cell viability. A similar mechanism operates in CD8 T cells, indicating its generality across mammalian cell types. Manipulating OGT activity may have therapeutic potential in diseases in which this signaling pathway is impaired.
Topics: Animals; Mice; Acetylglucosamine; CD8-Positive T-Lymphocytes; Cell Survival; Mitochondria; N-Acetylglucosaminyltransferases; Proteasome Endopeptidase Complex; Proteomics; TOR Serine-Threonine Kinases
PubMed: 36626549
DOI: 10.1073/pnas.2218332120