Microglial pyroptosis and neuroinflammation have been implicated in the pathogenesis of sepsis-associated encephalopathy (SAE). OGT-mediated O-GlcNAcylation is involved in neurodevelopment and injury. However, its regulatory function in microglial pyroptosis and involvement in SAE remains unclear. In this study, we demonstrated that OGT deficiency augmented microglial pyroptosis and exacerbated secondary neuronal injury. Furthermore, OGT inhibition impaired cognitive function in healthy mice and accelerated the progression in SAE mice. Mechanistically, OGT-mediated O-GlcNAcylation of ATF2 at Ser44 inhibited its phosphorylation and nuclear translocation, thereby amplifying NLRP3 inflammasome activation and promoting inflammatory cytokine production in microglia in response to LPS/Nigericin stimulation. In conclusion, this study uncovers the critical role of OGT-mediated O-GlcNAcylation in modulating microglial activity through the regulation of ATF2 and thus protects against SAE progression.
Animals ; Microglia/metabolism* ; Pyroptosis/physiology* ; Mice ; Sepsis-Associated Encephalopathy/prevention & control* ; Activating Transcription Factor 2/metabolism* ; N-Acetylglucosaminyltransferases/genetics* ; Mice, Inbred C57BL ; Male ; Mice, Knockout

Glycosylation modification is an important post-translational modification of proteins, which participates in regulating protein half-life, biological activity, and immunogenicity, thereby affecting their functions. Glycoproteins expressed in Pichia pastoris predominantly carry high-mannose type glycans, primarily composed of mannose residues, which starkly contrasts with the complex-type glycans synthesized by mammalian cells. This study aims to transform the high mannose glycosylation modification of P. pastoris into a hybrid glycosylation modification similar to that of mammalian cells through genetic engineering technology. We introduced the mannosidase Ⅰ gene (MDSⅠ) from Trichoderma viride and the human β-1,2-N-acetylglucosaminyltransferase I gene (GnTⅠ) into a previously constructed P. pastoris strain (∆och1) capable of producing Man₈GlcNAc₂ glycans. To precisely regulate the expression of MDSⅠ and GnTⅠ, we designed various promoter combinations, including the strong inducible AOX promoter and the constitutive GAP promoter. The receptor-binding domain (RBD, residues 377-588) of the spike protein from the Middle East respiratory syndrome coronavirus (MERS-CoV) was selected as the reporter protein for this investigation (MERS-RBD). The N-glycosylation profile of MERS-RBD was systematically analyzed using PNGase F digestion coupled with mass spectrometry. The results showed that after the knockout of och1 and the introduction of MDSⅠ and GnTⅠ genes with different promoter combinations, P. pastoris strains capable of producing GlcNAcMan₅GlcNAc₂ glycans were successfully generated. When the AOX promoter was used to control the MDSⅠ gene and the GAP promoter was used to control the GnTⅠ gene, the engineered strain exhibited the highest proportion of hybrid-type GlcNAcMan₅GlcNAc₂ glycans, which accounted for 68.38% of the total N-glycosylation. In conclusion, we successfully engineered a P. pastoris strain capable of synthesizing hybrid-type GlcNAcMan₅GlcNAc₂ glycans, establishing a foundation for subsequent research on the biosynthesis of complex-type N-glycans in P. pastoris.
Glycosylation ; Glycoproteins/genetics* ; Polysaccharides/metabolism* ; N-Acetylglucosaminyltransferases/metabolism* ; Pichia/metabolism* ; Humans ; Mannosidases/metabolism* ; Genetic Engineering ; Trichoderma/genetics* ; Recombinant Proteins/genetics* ; Saccharomycetales

Animals ; Biological Transport, Active/physiology* ; Centrioles/metabolism* ; Cilia/metabolism* ; Mice ; Mice, Mutant Strains ; N-Acetylglucosaminyltransferases/metabolism*

Dynamic changes of the post-translational O-GlcNAc modification (O-GlcNAcylation) are controlled by O-linked β-N-acetylglucosamine (O-GlcNAc) transferase (OGT) and the glycoside hydrolase O-GlcNAcase (OGA) in cells. O-GlcNAcylation often occurs on serine (Ser) and threonine (Thr) residues of the specific substrate proteins via the addition of O-GlcNAc group by OGT. It has been known that O-GlcNAcylation is not only involved in many fundamental cellular processes, but also plays an important role in cancer development through various mechanisms. Recently, accumulating data reveal that O-GlcNAcylation at histones or non-histone proteins can lead to the start of the subsequent biological processes, suggesting that O-GlcNAcylation as 'protein code' or 'histone code' may provide recognition platforms or executive instructions for subsequent recruitment of proteins to carry out the specific functions. In this review, we summarize the interaction of O-GlcNAcylation and epigenetic changes, introduce recent research findings that link crosstalk between O-GlcNAcylation and epigenetic changes, and speculate on the potential coordination role of O-GlcNAcylation with epigenetic changes in intracellular biological processes.
Acetylglucosamine ; metabolism ; Animals ; Epigenesis, Genetic ; Glycoside Hydrolases ; metabolism ; Humans ; N-Acetylglucosaminyltransferases ; metabolism ; Neoplasms ; genetics ; metabolism ; Protein Processing, Post-Translational

OBJECTIVETo study the effects of Xixin decoction (XXD) on O-GlcNAc transferase (OGT) and O-GlcNAc glycosidase in O-GlcNAc glycosylation of tau proteins in the brain of rats with sporadic Alzheimer's disease (SAD) and explore the possible mechanism.

METHODSMale SD rats were randomly divided into sham-operated group, model group, donepezil group, and low-, moderate-, and high-dose XXD groups. After treatment and behavioral test, the rats were sacrificed for detecting the expressions of OGT and O-GlcNAc glycosidase in the brain using immunohistochemistry and Western blotting.

RESULTSXXD significantly enhanced the expressions of OGT in the hippocampus of SAD rats and lowered the expression of O-GlcNAc glycosidase (P<0.05 or 0.01). OGT and O-GlcNAc glycosidase expressions showed no significant differences between the model group and donepezil group (P>0.05).

CONCLUSIONXXD can regulate the expression of OGT and O-GlcNAc glycosidase to enhance O-GlcNAc glycosylation of tau proteins in the hippocampus of SAD rats.

Acetylglucosaminidase ; metabolism ; Alzheimer Disease ; chemically induced ; enzymology ; metabolism ; Animals ; Dose-Response Relationship, Drug ; Drugs, Chinese Herbal ; administration & dosage ; pharmacology ; Glycosylation ; Hippocampus ; enzymology ; metabolism ; Male ; N-Acetylglucosaminyltransferases ; metabolism ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Streptozocin ; tau Proteins ; metabolism

Glycosaminoglycans are important structural components in the skin and exist as various proteoglycan forms, except hyaluronic acid. Heparan sulfate (HS), one of the glycosaminoglycans, is composed of repeated disaccharide units, which are glucuronic acids linked to an N-acetyl-glucosamine or its sulfated forms. To investigate acute ultraviolet (UV)-induced changes of HS and HS proteoglycans (HSPGs), changes in levels of HS and several HSPGs in male human buttock skin were examined by immunohistochemistry and real-time quantitative polymerase chain reaction (qPCR) after 2 minimal erythema doses (MED) of UV irradiation (each n = 4-7). HS staining revealed that 2 MED of UV irradiation increased its expression, and staining for perlecan, syndecan-1, syndecan-4, CD44v3, and CD44 showed that UV irradiation increased their protein levels. However, analysis by real-time qPCR showed that UV irradiation did not change mRNA levels of CD44 and agrin, and decreased perlecan and syndecan-4 mRNA levels, while increased syndecan-1 mRNA level. As HS-synthesizing or -degrading enzymes, exostosin-1 and heparanase mRNA levels were increased, but exostosin-2 was decreased by UV irradiation. UV-induced matrix metalloproteinase-1 expression was confirmed for proper experimental conditions. Acute UV irradiation increases HS and HSPG levels in human skin, but their increase may not be mediated through their transcriptional regulation.
Adult ; Agrin/genetics ; Antigens, CD44/genetics ; Base Sequence ; DNA Primers/genetics ; Gene Expression/radiation effects ; Glucuronidase/genetics ; Heparan Sulfate Proteoglycans/genetics/*metabolism ; Heparitin Sulfate/metabolism ; Humans ; Male ; Matrix Metalloproteinase 1/genetics ; N-Acetylglucosaminyltransferases/genetics ; RNA, Messenger/genetics/metabolism ; Skin/*metabolism/*radiation effects ; Skin Aging/genetics/physiology ; Syndecan-1/genetics ; Syndecan-4/genetics ; Ultraviolet Rays/*adverse effects ; Young Adult

Acetyl-N-glucosaminyltransferase gene (nodC) was successfully cloned to Escherichia coli from Mesorhizobium loti. The recombinant E. coli harboring nodC gene was able to synthesize chitooligosaccharides (COs) in MMYNG medium. In optimized condition, a yield of 526 mg/L was obtained after 26 h cultivation in 10 L bioreactor. COs concentration reached up to 4.5% of the cell dry weight. The COs products were purified by charcoal adsorption and Bio-gel P4 chromatography, penta-N-acetylchitopentaose (m/z, 1034[M + H]+) and tetra-N-acetylchitopentaose (m/z, 831 [M + H]+) were identified as the dominating COs product using the method of liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS).
Bacterial Proteins ; genetics ; metabolism ; Chitosan ; isolation & purification ; metabolism ; Chromatography, Gel ; Chromatography, High Pressure Liquid ; Escherichia coli ; genetics ; metabolism ; N-Acetylglucosaminyltransferases ; genetics ; metabolism ; Oligosaccharides ; biosynthesis ; isolation & purification ; Recombinant Proteins ; metabolism ; Spectrometry, Mass, Electrospray Ionization