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Gut Microbes Dec 2023subsp. utilizes oligosaccharides secreted in human milk as a carbohydrate source. These human milk oligosaccharides (HMOs) integrate the nitrogenous residue...
subsp. utilizes oligosaccharides secreted in human milk as a carbohydrate source. These human milk oligosaccharides (HMOs) integrate the nitrogenous residue N-acetylglucosamine (NAG), although HMO nitrogen utilization has not been described to date. Herein, we characterize the nitrogen utilization phenotype on two NAG-containing HMO species, LNT and LNnT. This was characterized through growth kinetics, incorporation of isotopically labeled NAG nitrogen into the proteome, as well as modulation of intracellular 2-oxoglutarate levels while utilizing HMO nitrogen. Further support is provided by comparative transcriptomics and proteomics that identified global regulatory networks deployed during HMO nitrogen utilization. The aggregate data demonstrate that strains utilize HMO nitrogen with the potential to significantly impact fundamental and clinical studies, as well as enable applications.
Topics: Humans; Bifidobacterium longum subspecies infantis; Acetylglucosamine; Milk, Human; Gastrointestinal Microbiome; Oligosaccharides; Nitrogen
PubMed: 37609905
DOI: 10.1080/19490976.2023.2244721 -
Cells Nov 2022The modification of nuclear, mitochondrial, and cytosolic proteins by O-linked βN-acetylglucosamine (O-GlcNAc) has emerged as a dynamic and essential post-translational... (Review)
Review
The modification of nuclear, mitochondrial, and cytosolic proteins by O-linked βN-acetylglucosamine (O-GlcNAc) has emerged as a dynamic and essential post-translational modification of mammalian proteins. O-GlcNAc is cycled on and off over 5000 proteins in response to diverse stimuli impacting protein function and, in turn, epigenetics and transcription, translation and proteostasis, metabolism, cell structure, and signal transduction. Environmental and physiological injury lead to complex changes in O-GlcNAcylation that impact cell and tissue survival in models of heat shock, osmotic stress, oxidative stress, and hypoxia/reoxygenation injury, as well as ischemic reperfusion injury. Numerous mechanisms that appear to underpin O-GlcNAc-mediated survival include changes in chaperone levels, impacts on the unfolded protein response and integrated stress response, improvements in mitochondrial function, and reduced protein aggregation. Here, we discuss the points at which O-GlcNAc is integrated into the cellular stress response, focusing on the roles it plays in the cardiovascular system and in neurodegeneration.
Topics: Animals; Acetylglucosamine; Protein Processing, Post-Translational; Glycosylation; Oxidative Stress; Signal Transduction; Proteins; Mammals
PubMed: 36359905
DOI: 10.3390/cells11213509 -
Orphanet Journal of Rare Diseases Dec 2016Aspartylglucosaminuria (AGU), a recessively inherited lysosomal storage disease, is the most common disorder of glycoprotein degradation with a high prevalence in the... (Review)
Review
Aspartylglucosaminuria (AGU), a recessively inherited lysosomal storage disease, is the most common disorder of glycoprotein degradation with a high prevalence in the Finnish population. It is a lifelong condition affecting on the patient's appearance, cognition, adaptive skills, physical growth, personality, body structure, and health. An infantile growth spurt and development of macrocephalia associated to hernias and respiratory infections are the key signs to an early identification of AGU. Progressive intellectual and physical disability is the main symptom leading to death usually before the age of 50 years.The disease is caused by the deficient activity of the lysosomal enzyme glycosylasparaginase (aspartylglucosaminidase, AGA), which leads to a disorder in the degradation of glycoasparagines - aspartylglucosamine or other glycoconjugates with an aspartylglucosamine moiety at their reducing end - and accumulation of these undegraded glycoasparagines in tissues and body fluids. A single nucleotide change in the AGA gene resulting in a cysteine to serine substitution (C163S) in the AGA enzyme protein causes the deficiency of the glycosylasparaginase activity in the Finnish population. Homozygosity for the single nucleotide change causing the C163S mutation is responsible for 98% of the AGU cases in Finland simplifying the carrier detection and prenatal diagnosis of the disorder in the Finnish population. A mouse strain, which completely lacks the Aga activity has been generated through targeted disruption of the Aga gene in embryonic stem cells. These Aga-deficient mice share most of the clinical, histopathologic and biochemical characteristics of human AGU disease. Treatment of AGU mice with recombinant AGA resulted in rapid correction of the pathophysiologic characteristics of AGU in non-neuronal tissues of the animals. The accumulation of aspartylglucosamine was reduced by up to 40% in the brain tissue of the animals depending on the age of the animals and the therapeutic protocol. Enzyme replacement trials on human AGU patients have not been reported so far. Allogenic stem cell transplantation has not proved effective in curing AGU.
Topics: Acetylglucosamine; Animals; Aspartylglucosaminuria; Aspartylglucosylaminase; Glycoproteins; Humans; Lysosomal Storage Diseases; Mutation
PubMed: 27906067
DOI: 10.1186/s13023-016-0544-6 -
Developmental Cell Dec 2014The addition of the monosaccharide O-GlcNAc is one of the most mysterious posttranslational modifications. In this issue of Developmental Cell, Gambetta and Müller...
The addition of the monosaccharide O-GlcNAc is one of the most mysterious posttranslational modifications. In this issue of Developmental Cell, Gambetta and Müller (2014) show that O-GlcNAcylation of the Drosophila Polycomb group (PcG) protein Polyhomeotic (PH) is essential for homeotic gene silencing. O-GlcNAcylation counteracts nonproductive aggregation of PH, allowing transcriptional repression.
Topics: Acetylglucosamine; Animals; DNA-Binding Proteins; Drosophila Proteins; Drosophila melanogaster; Humans; Polycomb Repressive Complex 1; Repressor Proteins
PubMed: 25490262
DOI: 10.1016/j.devcel.2014.11.027 -
Current Opinion in Structural Biology Jun 2019Glycosylation, or the addition of sugars to proteins, is a highly conserved protein modification defined by both the monosaccharide initially added as well as the amino... (Review)
Review
Glycosylation, or the addition of sugars to proteins, is a highly conserved protein modification defined by both the monosaccharide initially added as well as the amino acid to which it is attached. O-Linked glycosylation represents a diverse group of protein modifications occurring on the hydroxyl groups of serine and/or threonine residues. O-Glycosylation can have wide-ranging effects on protein stability and function, which translate into crucial consequences at the organismal level. This review will summarize structural and biological insights into the major O-glycans formed within the secretory apparatus (O-GalNAc, O-Man, O-Fuc, O-Glc and extracellular O-GlcNAc) from studies in the fruit fly Drosophila melanogaster. Drosophila has many advantages for investigating these complex modifications, boasting reduced functional redundancy within gene families, reduced length/complexity of glycan chains and sophisticated genetic tools. Gaining an understanding of the normal cellular and developmental roles of these conserved modifications in Drosophila will provide insight into how changes in O-glycans are involved in human disease and disease susceptibilities.
Topics: Acetylglucosamine; Animals; Drosophila melanogaster; Extracellular Space; Glycosylation; Humans; Oxygen
PubMed: 30852302
DOI: 10.1016/j.sbi.2019.01.014 -
Nature Communications Jul 2023The unique dumbbell-shape of grass guard cells (GCs) is controlled by their cell walls which enable their rapid responses to the environment. The molecular mechanisms...
The unique dumbbell-shape of grass guard cells (GCs) is controlled by their cell walls which enable their rapid responses to the environment. The molecular mechanisms regulating the synthesis and assembly of GC walls are as yet unknown. Here we have identified BZU3, a maize gene encoding UDP-glucose 4-epimerase that regulates the supply of UDP-glucose during GC wall synthesis. The BZU3 mutation leads to significant decreases in cellular UDP-glucose levels. Immunofluorescence intensities reporting levels of cellulose and mixed-linkage glucans are reduced in the GCs, resulting in impaired local wall thickening. BZU3 also catalyzes the epimerization of UDP-N-acetylgalactosamine to UDP-N-acetylglucosamine, and the BZU3 mutation affects N-glycosylation of proteins that may be involved in cell wall synthesis and signaling. Our results suggest that the spatiotemporal modulation of BZU3 plays a dual role in controlling cell wall synthesis and glycosylation via controlling UDP-glucose/N-acetylglucosamine homeostasis during stomatal morphogenesis. These findings provide insights into the mechanisms controlling formation of the unique morphology of grass stomata.
Topics: Zea mays; Racemases and Epimerases; Glycosylation; Acetylglucosamine; Poaceae; Cell Wall; Uridine Diphosphate
PubMed: 37474494
DOI: 10.1038/s41467-023-40013-6 -
Biochemical Society Transactions Apr 2017The post-translational modification of serine and threonine residues of proteins found in numerous subcellular locations by -linked -acetylglucosamine (-GlcNAc) is... (Review)
Review
The post-translational modification of serine and threonine residues of proteins found in numerous subcellular locations by -linked -acetylglucosamine (-GlcNAc) is emerging as a key mediator of many cardiovascular pathophysiological processes. Early studies implicated increased protein O-GlcNAcylation as contributing to the cardiovascular complications associated with diabetes, whereas subsequent studies demonstrated that acute increases in -GlcNAc levels were protective against ischemia/reperfusion injury. There is now a growing understanding that -GlcNAc modification of proteins influences numerous cellular functions, including transcription, protein turnover, calcium handling, and bioenergetics. As a result, a more nuanced view of the role of protein O-GlcNAcylation in the cardiovascular system is emerging along with the recognition that it is required for normal cellular function and homeostasis. Consequently, the impact of changes in -GlcNAc cycling due to stress or disease on the heart is complex and highly dependent on the specific context of these events. The goal of this review is to provide an overview of some of the more recent advances in our understanding of the role O-GlcNAcylation plays in mediating cardiovascular function and disease.
Topics: Acetylglucosamine; Animals; Cardiovascular Diseases; Diabetes Mellitus; Gene Expression Regulation; Glycosylation; Humans; Protein Processing, Post-Translational; Proteins; Signal Transduction
PubMed: 28408494
DOI: 10.1042/BST20160164 -
Journal of Neuroinflammation Sep 2023In the demyelinating disease multiple sclerosis (MS), chronic-active brain inflammation, remyelination failure and neurodegeneration remain major issues despite...
BACKGROUND
In the demyelinating disease multiple sclerosis (MS), chronic-active brain inflammation, remyelination failure and neurodegeneration remain major issues despite immunotherapy. While B cell depletion and blockade/sequestration of T and B cells potently reduces episodic relapses, they act peripherally to allow persistence of chronic-active brain inflammation and progressive neurological dysfunction. N-acetyglucosamine (GlcNAc) is a triple modulator of inflammation, myelination and neurodegeneration. GlcNAc promotes biosynthesis of Asn (N)-linked-glycans, which interact with galectins to co-regulate the clustering/signaling/endocytosis of multiple glycoproteins simultaneously. In mice, GlcNAc crosses the blood brain barrier to raise N-glycan branching, suppress inflammatory demyelination by T and B cells and trigger stem/progenitor cell mediated myelin repair. MS clinical severity, demyelination lesion size and neurodegeneration inversely associate with a marker of endogenous GlcNAc, while in healthy humans, age-associated increases in endogenous GlcNAc promote T cell senescence.
OBJECTIVES AND METHODS
An open label dose-escalation mechanistic trial of oral GlcNAc at 6 g (n = 18) and 12 g (n = 16) for 4 weeks was performed in MS patients on glatiramer acetate and not in relapse from March 2016 to December 2019 to assess changes in serum GlcNAc, lymphocyte N-glycosylation and inflammatory markers. Post-hoc analysis examined changes in serum neurofilament light chain (sNfL) as well as neurological disability via the Expanded Disability Status Scale (EDSS).
RESULTS
Prior to GlcNAc therapy, high serum levels of the inflammatory cytokines IFNγ, IL-17 and IL-6 associated with reduced baseline levels of a marker of endogenous serum GlcNAc. Oral GlcNAc therapy was safe, raised serum levels and modulated N-glycan branching in lymphocytes. Glatiramer acetate reduces T1, T17 and B cell activity as well as sNfL, yet the addition of oral GlcNAc dose-dependently lowered serum IFNγ, IL-17, IL-6 and NfL. Oral GlcANc also dose-dependently reduced serum levels of the anti-inflammatory cytokine IL-10, which is increased in the brain of MS patients. 30% of treated patients displayed confirmed improvement in neurological disability, with an average EDSS score decrease of 0.52 points.
CONCLUSIONS
Oral GlcNAc inhibits inflammation and neurodegeneration markers in MS patients despite concurrent immunomodulation by glatiramer acetate. Blinded studies are required to investigate GlcNAc's potential to control residual brain inflammation, myelin repair and neurodegeneration in MS.
Topics: Humans; Animals; Mice; Acetylglucosamine; Interleukin-17; Glatiramer Acetate; Interleukin-6; Multiple Sclerosis; Inflammation; Encephalitis; Cytokines
PubMed: 37705084
DOI: 10.1186/s12974-023-02893-9 -
Nature Communications Oct 2023O-GlcNAcylation is a conserved post-translational modification that attaches N-acetyl glucosamine (GlcNAc) to myriad cellular proteins. In response to nutritional and...
O-GlcNAcylation is a conserved post-translational modification that attaches N-acetyl glucosamine (GlcNAc) to myriad cellular proteins. In response to nutritional and hormonal signals, O-GlcNAcylation regulates diverse cellular processes by modulating the stability, structure, and function of target proteins. Dysregulation of O-GlcNAcylation has been implicated in the pathogenesis of cancer, diabetes, and neurodegeneration. A single pair of enzymes, the O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), catalyzes the addition and removal of O-GlcNAc on over 3,000 proteins in the human proteome. However, how OGT selects its native substrates and maintains the homeostatic control of O-GlcNAcylation of so many substrates against OGA is not fully understood. Here, we present the cryo-electron microscopy (cryo-EM) structures of human OGT and the OGT-OGA complex. Our studies reveal that OGT forms a functionally important scissor-shaped dimer. Within the OGT-OGA complex structure, a long flexible OGA segment occupies the extended substrate-binding groove of OGT and positions a serine for O-GlcNAcylation, thus preventing OGT from modifying other substrates. Conversely, OGT disrupts the functional dimerization of OGA and occludes its active site, resulting in the blocking of access by other substrates. This mutual inhibition between OGT and OGA may limit the futile O-GlcNAcylation cycles and help to maintain O-GlcNAc homeostasis.
Topics: Humans; Acetylglucosamine; Acetylglucosaminidase; Cryoelectron Microscopy; N-Acetylglucosaminyltransferases; Protein Processing, Post-Translational; Proteins
PubMed: 37907462
DOI: 10.1038/s41467-023-42427-8 -
Journal of Bioenergetics and... Jun 2018The rapidly expanding field of immunometabolism focuses on how metabolism controls the function of immune cells. CD4 T cells are essential for the adaptive immune... (Review)
Review
The rapidly expanding field of immunometabolism focuses on how metabolism controls the function of immune cells. CD4 T cells are essential for the adaptive immune response leading to the eradication of specific pathogens. However, when T cells are inappropriately over-active, they can drive autoimmunity, allergic disease, and chronic inflammation. The mechanisms by which metabolic changes influence function in CD4 T cells are not fully understood. The post-translational protein modification, O-GlcNAc (O-linked β-N-acetylglucosamine), dynamically cycles on and off of intracellular proteins as cells respond to their environment and flux through metabolic pathways changes. As the rate of O-GlcNAc cycling fluctuates, protein function, stability, and/or localization can be affected. Thus, O-GlcNAc is critically poised at the nexus of cellular metabolism and function. This review highlights the intra- and extracellular metabolic factors that influence CD4 T cell activation and differentiation and how O-GlcNAc regulates these processes. We also propose areas of future research that may illuminate O-GlcNAc's role in the plasticity and pathogenicity of CD4 T cells and uncover new potential therapeutic targets.
Topics: Acetylglucosamine; Animals; CD4-Positive T-Lymphocytes; Humans; Lymphocyte Activation; Protein Processing, Post-Translational
PubMed: 29404877
DOI: 10.1007/s10863-018-9744-1