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Nature Communications Oct 2023The neurofilament (NF) cytoskeleton is critical for neuronal morphology and function. In particular, the neurofilament-light (NF-L) subunit is required for NF assembly...
The neurofilament (NF) cytoskeleton is critical for neuronal morphology and function. In particular, the neurofilament-light (NF-L) subunit is required for NF assembly in vivo and is mutated in subtypes of Charcot-Marie-Tooth (CMT) disease. NFs are highly dynamic, and the regulation of NF assembly state is incompletely understood. Here, we demonstrate that human NF-L is modified in a nutrient-sensitive manner by O-linked-β-N-acetylglucosamine (O-GlcNAc), a ubiquitous form of intracellular glycosylation. We identify five NF-L O-GlcNAc sites and show that they regulate NF assembly state. NF-L engages in O-GlcNAc-mediated protein-protein interactions with itself and with the NF component α-internexin, implying that O-GlcNAc may be a general regulator of NF architecture. We further show that NF-L O-GlcNAcylation is required for normal organelle trafficking in primary neurons. Finally, several CMT-causative NF-L mutants exhibit perturbed O-GlcNAc levels and resist the effects of O-GlcNAcylation on NF assembly state, suggesting a potential link between dysregulated O-GlcNAcylation and pathological NF aggregation. Our results demonstrate that site-specific glycosylation regulates NF-L assembly and function, and aberrant NF O-GlcNAcylation may contribute to CMT and other neurodegenerative disorders.
Topics: Humans; Charcot-Marie-Tooth Disease; Intermediate Filaments; Mutation; Glycosylation; Acetylglucosamine; Protein Processing, Post-Translational
PubMed: 37848414
DOI: 10.1038/s41467-023-42227-0 -
CNS Neuroscience & Therapeutics Nov 2023This metabolomic study aimed to evaluate the role of N-acetylneuraminic acid (Neu5Ac) in the neurological deficits of normal pressure hydrocephalus (NPH) and its...
AIMS
This metabolomic study aimed to evaluate the role of N-acetylneuraminic acid (Neu5Ac) in the neurological deficits of normal pressure hydrocephalus (NPH) and its potential therapeutic effect.
METHODS
We analyzed the metabolic profiles of NPH using cerebrospinal fluid with multivariate and univariate statistical analyses in a set of 42 NPH patients and 38 controls. We further correlated the levels of differential metabolites with severity-related clinical parameters, including the normal pressure hydrocephalus grading scale (NPHGS). We then established kaolin-induced hydrocephalus in mice and treated them using N-acetylmannosamine (ManNAc), a precursor of Neu5Ac. We examined brain Neu5Ac, astrocyte polarization, demyelination, and neurobehavioral outcomes to explore its therapeutic effect.
RESULTS
Three metabolites were significantly altered in NPH patients. Only decreased Neu5Ac levels were correlated with NPHGS scores. Decreased brain Neu5Ac levels have been observed in hydrocephalic mice. Increasing brain Neu5Ac by ManNAc suppressed the activation of astrocytes and promoted their transition from A1 to A2 polarization. ManNAc also attenuated the periventricular white matter demyelination and improved neurobehavioral outcomes in hydrocephalic mice.
CONCLUSION
Increasing brain Neu5Ac improved the neurological outcomes associated with the regulation of astrocyte polarization and the suppression of demyelination in hydrocephalic mice, which may be a potential therapeutic strategy for NPH.
Topics: Humans; Mice; Animals; N-Acetylneuraminic Acid; Hydrocephalus, Normal Pressure; Brain; Metabolomics; Demyelinating Diseases
PubMed: 37222223
DOI: 10.1111/cns.14253 -
Genes Dec 2023is an important woody edible oil tree species in southern China that is characterized by large fruits and seed kernels with high oil contents. Increasing soil...
is an important woody edible oil tree species in southern China that is characterized by large fruits and seed kernels with high oil contents. Increasing soil acidification due to increased use of fossil fuels, misuse of acidic fertilizers, and irrational farming practices has led to leaching of aluminum (Al) in the form of free Al, Al(OH), and Al(OH), which inhibits the growth and development of in South China. To investigate the mechanism underlying responses to Al stress, we determined the changes in photosynthetic parameters, antioxidant enzyme activities, and osmoregulatory substance contents of leaves under different concentrations of Al stress treatments (0, 1, 2, 3, and 4 mmol/L Alcl) using a combination of physiological and proteomics approaches. In addition, we identified the differentially expressed proteins (DEPs) under 0 (CK or GNR0), 2 mmol/L (GNR2), and 4 mmol/L (GNR4) Al stress using a 4D-label-free technique. With increasing stress concentration, the photosynthetic indexes of leaves, peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), soluble protein (SP), and soluble sugar (SS) showed an overall trend of increasing and then decreasing, and proline (Pro) and malondialdehyde (MDA) contents tended to continuously increase overall. Compared with the control group, we identified 124 and 192 DEPs in GNR2 and GNR4, respectively, which were mainly involved in metabolic processes such as photosynthesis, flavonoid metabolism, oxidative stress response, energy and carbohydrate metabolism, and signal transduction. At 2 mmol/L Al stress, carbon metabolism, amino sugar and nucleotide sugar metabolism, and flavonoid metabolism-related proteins were significantly changed, and when the stress was increased to 4 mmol/L Al, the cells accumulated reactive oxygen species (ROS) at a rate exceeding the antioxidant system scavenging capacity. To deal with this change, leaves enhanced their glutathione metabolism, drug metabolism-cytochrome P450, metabolism of xenobiotics by cytochrome P450, and other metabolic processes to counteract peroxidative damage to the cytoplasmic membrane caused by stress. In addition, we found that resisted aluminum toxicity mainly by synthesizing anthocyanidins under 2 mmol/L stress, whereas proanthocyanidins were alleviated by the generation of proanthocyanidins under 4 mmol/L stress, which may be a special mechanism by which responds to different concentrations of aluminum stress.
Topics: Camellia; Aluminum; Antioxidants; Proanthocyanidins; Proteomics; Cytochrome P-450 Enzyme System; Sugars
PubMed: 38254944
DOI: 10.3390/genes15010055 -
Nucleic Acids Research May 2024RNA interference (RNAi) is an endogenous process that can be harnessed using chemically modified small interfering RNAs (siRNAs) to potently modulate gene expression in...
RNA interference (RNAi) is an endogenous process that can be harnessed using chemically modified small interfering RNAs (siRNAs) to potently modulate gene expression in many tissues. The route of administration and chemical architecture are the primary drivers of oligonucleotide tissue distribution, including siRNAs. Independently of the nature and type, oligonucleotides are eliminated from the body through clearance tissues, where their unintended accumulation may result in undesired gene modulation. Divalent siRNAs (di-siRNAs) administered into the CSF induce robust gene silencing throughout the central nervous system (CNS). Upon clearance from the CSF, they are mainly filtered by the kidneys and liver, with the most functionally significant accumulation occurring in the liver. siRNA- and miRNA-induced silencing can be blocked through substrate inhibition using single-stranded, stabilized oligonucleotides called antagomirs or anti-siRNAs. Using APOE as a model target, we show that undesired di-siRNA-induced silencing in the liver can be mitigated through administration of liver targeting GalNAc-conjugated anti-siRNAs, without impacting CNS activity. Blocking unwanted hepatic APOE silencing achieves fully CNS-selective silencing, essential for potential clinical translation. While we focus on CNS/liver selectivity, coadministration of differentially targeting siRNA and anti-siRNAs can be adapted as a strategy to achieve tissue selectivity in different organ combinations.
Topics: Animals; Humans; Male; Mice; Acetylgalactosamine; Antagomirs; Apolipoproteins E; Central Nervous System; Gene Silencing; Liver; Mice, Inbred C57BL; MicroRNAs; RNA Interference; RNA, Small Interfering
PubMed: 38348876
DOI: 10.1093/nar/gkae100 -
Plants (Basel, Switzerland) Dec 2023Floral nectar contains sugars and numerous other compounds, including amino acids, but little is known about their function and origin in nectar. Therefore, the amino...
Floral nectar contains sugars and numerous other compounds, including amino acids, but little is known about their function and origin in nectar. Therefore, the amino acid, sugar, and inorganic ion concentrations, as well as the activity of alanine aminotransferase (AlaAT) and glutamine synthetase (GS) in nectar, nectaries, and leaves were analyzed in 30 species. These data were compared with various floral traits, the pollinator type, and the phylogenetic relationships of the species to find possible causes for the high amino acid concentrations in the nectar of some species. The highest concentrations of amino acids (especially alanine) in nectar were found in species with reddish flowers. Furthermore, the concentration of amino acids in nectar and nectaries is determined through analyzing flower color/pollination type rather than phylogenetic relations. This study provides new insights into the origin of amino acids in nectar. The presence of almost all amino acids in nectar is mainly due to their transport in the phloem to the nectaries, with the exception of alanine, which is partially produced in nectaries. In addition, active regulatory mechanisms are required in nectaries that retain most of the amino acids and allow the selective secretion of specific amino acids, such as alanine.
PubMed: 38202331
DOI: 10.3390/plants13010023 -
Glycoconjugate Journal Aug 2023Every eukaryotic cell is covered with a thick layer of complex carbohydrates with essential roles in their social life. In Deuterostoma, sialic acids present at the... (Review)
Review
Every eukaryotic cell is covered with a thick layer of complex carbohydrates with essential roles in their social life. In Deuterostoma, sialic acids present at the outermost positions of glycans of glycoconjugates are known to be key players in cellular interactions including host-pathogen interactions. Their negative charge and hydrophilic properties enable their roles in various normal and pathological states and their expression is altered in many diseases including cancers. Sialylation of glycoproteins and glycolipids is orchestrated by the regulated expression of twenty sialyltransferases in human tissues with distinct enzymatic characteristics and preferences for substrates and linkages formed. However, still very little is known on the functional organization of sialyltransferases in the Golgi apparatus and how the sialylation machinery is finely regulated to provide the ad hoc sialome to the cell. This review summarizes current knowledge on sialyltransferases, their structure-function relationships, molecular evolution, and their implications in human biology.
Topics: Animals; Humans; Sialyltransferases; Sialic Acids; Vertebrates; Glycoproteins; Evolution, Molecular
PubMed: 37247156
DOI: 10.1007/s10719-023-10123-w -
The Journal of Biological Chemistry Jul 2023A primary pathology of Alzheimer's disease (AD) is amyloid β (Aβ) deposition in brain parenchyma and blood vessels, the latter being called cerebral amyloid angiopathy...
A primary pathology of Alzheimer's disease (AD) is amyloid β (Aβ) deposition in brain parenchyma and blood vessels, the latter being called cerebral amyloid angiopathy (CAA). Parenchymal amyloid plaques presumably originate from neuronal Aβ precursor protein (APP). Although vascular amyloid deposits' origins remain unclear, endothelial APP expression in APP knock-in mice was recently shown to expand CAA pathology, highlighting endothelial APP's importance. Furthermore, two types of endothelial APP-highly O-glycosylated APP and hypo-O-glycosylated APP-have been biochemically identified, but only the former is cleaved for Aβ production, indicating the critical relationship between APP O-glycosylation and processing. Here, we analyzed APP glycosylation and its intracellular trafficking in neurons and endothelial cells. Although protein glycosylation is generally believed to precede cell surface trafficking, which was true for neuronal APP, we unexpectedly observed that hypo-O-glycosylated APP is externalized to the endothelial cell surface and transported back to the Golgi apparatus, where it then acquires additional O-glycans. Knockdown of genes encoding enzymes initiating APP O-glycosylation significantly reduced Aβ production, suggesting this non-classical glycosylation pathway contributes to CAA pathology and is a novel therapeutic target.
Topics: Animals; Mice; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Cerebral Amyloid Angiopathy; Endothelial Cells; Glycosylation; Protein Transport; Neurons; Golgi Apparatus; Acetylgalactosamine
PubMed: 37302553
DOI: 10.1016/j.jbc.2023.104905 -
Frontiers in Plant Science 2023
PubMed: 38250444
DOI: 10.3389/fpls.2023.1261186 -
Carbohydrate Research May 2024Sialic acid, the terminal structure of cell surface glycans, has essential functions in regulating immune response, cell-to-cell communication, and cell adhesion. More... (Review)
Review
Sialic acid, the terminal structure of cell surface glycans, has essential functions in regulating immune response, cell-to-cell communication, and cell adhesion. More importantly, an increased level of sialic acid, termed hypersialylation, has emerged as a commonly observed phenotype in cancer. Therefore, targeting sialic acid ligands (sialoglycans) and their receptors (Siglecs) may provide a new therapeutic approach for cancer immunotherapy. We highlight the complexity of the sialic acid metabolism and its involvement in malignant transformation within individual cancer subtypes. In this review, we focus on the dysregulation of sialylation, the intricate nature of sialic acid synthesis, and clinical perspective. We aim to provide a brief insight into the mechanism of hypersialylation and how our understanding of these processes can be leveraged for the development of novel therapeutics.
Topics: Humans; Neoplasms; N-Acetylneuraminic Acid; Animals
PubMed: 38669826
DOI: 10.1016/j.carres.2024.109123 -
Biosensors Jan 2024Chiral sensing is crucial in the fields of biology and the pharmaceutical industry. Many naturally occurring biomolecules, i.e., amino acids, sugars, and nucleotides,... (Review)
Review
Chiral sensing is crucial in the fields of biology and the pharmaceutical industry. Many naturally occurring biomolecules, i.e., amino acids, sugars, and nucleotides, are inherently chiral. Their enantiomers are strongly associated with the pharmacological effects of chiral drugs. Owing to the extremely weak chiral light-matter interactions, chiral sensing at an optical frequency is challenging, especially when trace amounts of molecules are involved. The nanophotonic platform allows for a stronger interaction between the chiral molecules and light to enhance chiral sensing. Here, we review the recent progress in nanophotonic-enhanced chiral sensing, with a focus on the superchiral near-field and enhanced circular dichroism (CD) spectroscopy generated in both the dielectric and in plasmonic structures. In addition, the recent applications of chiral sensing in biomedical fields are discussed, including the detection and treatment of difficult diseases, i.e., Alzheimer's disease, diabetes, and cancer.
Topics: Humans; Alzheimer Disease; Amino Acids; Medicine; Nucleotides
PubMed: 38248416
DOI: 10.3390/bios14010039