Glycomic profiling and the mammalian brain

The importance of protein glycosylation in the biomedical field requires methods that not only quantitate structures by their monosaccharide composition, but also resolve and identify the many isomers expressed by mammalian cells. The art of unambiguous identification of isomeric structures in complex mixtures, however, did not yet catch up with the fast pace of advance of high-throughput glycomics. Here, we present a strategy for deducing structures with the help of a deci-minute accurate retention time library for porous graphitic carbon chromatography with mass spectrometric detection. We implemented the concept for the fundamental N-glycan type consisting of five hexoses, four Nacetylhexosamines and one fucose residue. Nearly all of the 40 biosynthetized isomers occupied unique elution positions. This result demonstrates the unique isomer selectivity of porous graphitic carbon. With the help of a rather tightly spaced grid of isotope-labeled internal N-glycan, standard retention times were transposed to a standard chromatogram. Application of this approach to animal and human brain N-glycans immediately identified the majority of structures as being of the bisected type. Most notably, it exposed hybrid-type glycans with galactosylated and even Lewis X containing bisected N-acetylglucosamine, which have not yet been discovered in a natural source. Thus, the time grid approach implemented herein facilitated discovery of the still missing pieces of the N-glycome in our most noble organ and suggests itselfin conjunction with collision induced dissociationas a starting point for the overdue development of isomer-specific deep structural glycomics.

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“… 55 Therefore, interest in this element and other glyco-features experiences a renaissance. 22 , 56 , 57 …”

Section: Discussionmentioning

confidence: 99%

“…The decoration of the bisecting GlcNAc in human brain glycans may be of particular significance because GnT-III, which produces the bisecting structures, shows altered expression levels in Alzheimer’s disease patients , and other diseases . Therefore, interest in this element and other glyco-features experiences a renaissance. ,, …”

Section: Discussionmentioning

confidence: 99%

Bisecting Lewis X in Hybrid-Type N-Glycans of Human Brain Revealed by Deep Structural Glycomics

et al. 2021

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“…About 70% of brain proteins are present as glycoproteins. They mainly contain a higher number of high-mannose, hexose, and N-acetyl hexosamine (HexNAc) with fucose and sialic acid ( Lee et al, 2020 ; Tena and Lebrilla, 2021 ). Many brain lipids also present as glycoconjugates that play various biological functions in the brain ( Tena and Lebrilla, 2021 ).…”

Section: Role Of Glycosylation In the Brainmentioning

confidence: 99%

Mass Spectrometry Imaging for Glycome in the Brain

et al. 2021

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Glycans are diverse structured biomolecules that play crucial roles in various biological processes. Glycosylation, an enzymatic system through which various glycans are bound to proteins and lipids, is the most common and functionally crucial post-translational modification process. It is known to be associated with brain development, signal transduction, molecular trafficking, neurodegenerative disorders, psychopathologies, and brain cancers. Glycans in glycoproteins and glycolipids expressed in brain cells are involved in neuronal development, biological processes, and central nervous system maintenance. The composition and expression of glycans are known to change during those physiological processes. Therefore, imaging of glycans and the glycoconjugates in the brain regions has become a “hot” topic nowadays. Imaging techniques using lectins, antibodies, and chemical reporters are traditionally used for glycan detection. However, those techniques offer limited glycome detection. Mass spectrometry imaging (MSI) is an evolving field that combines mass spectrometry with histology allowing spatial and label-free visualization of molecules in the brain. In the last decades, several studies have employed MSI for glycome imaging in brain tissues. The current state of MSI uses on-tissue enzymatic digestion or chemical reaction to facilitate successful glycome imaging. Here, we reviewed the available literature that applied MSI techniques for glycome visualization and characterization in the brain. We also described the general methodologies for glycome MSI and discussed its potential use in the three-dimensional MSI in the brain.

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“…In the brain, over 70% of proteins and a large fraction of the lipids are glycosylated (Tena & Lebrilla, 2021). These common structure modifications are considered to mediate cell-cell communication via interacting with glycan-binding proteins or other signaling processes.…”

Section: Introductionmentioning

confidence: 99%

The role of FUT8‐catalyzed core fucosylation in Alzheimer's amyloid‐β oligomer‐induced activation of human microglia

Jin

Lucente

Mendiola

et al. 2023

Glia

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Fucosylation, especially core fucosylation of N‐glycans catalyzed by α1‐6 fucosyltransferase (fucosyltransferase 8 or FUT8), plays an important role in regulating the peripheral immune system and inflammation. However, its role in microglial activation is poorly understood. Here we used human induced pluripotent stem cells‐derived microglia (hiMG) as a model to study the role of FUT8‐catalyzed core fucosylation in amyloid‐β oligomer (AβO)‐induced microglial activation, in view of its significant relevance to the pathogenesis of Alzheimer's disease (AD). HiMG responded to AβO and lipopolysaccharides (LPS) with a pattern of pro‐inflammatory activation as well as enhanced core fucosylation and FUT8 expression within 24 h. Furthermore, we found increased FUT8 expression in both human AD brains and microglia isolated from 5xFAD mice, a model of AD‐like cerebral amyloidosis. Inhibition of fucosylation in AβO‐stimulated hiMG reduced the induction of pro‐inflammatory cytokines, suppressed the activation of p38MAPK, and rectified phagocytic deficits. Specific inhibition of FUT8 by siRNA‐mediated knockdown also reduced AβO‐induced pro‐inflammatory cytokines. We further showed that p53 binds to the two consensus binding sites in the Fut8 promoter, and that p53 knockdown abolished FUT8 overexpression in AβO‐activated hiMG. Taken together, our evidence supports that FUT8‐catalyzed core fucosylation is a signaling pathway required for AβO‐induced microglia activation and that FUT8 is a component of the p53 signaling cascade regulating microglial behavior. Because microglia are a key driver of AD pathogenesis, our results suggest that microglial FUT8 could be an anti‐inflammatory therapeutic target for AD.

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Glycomic profiling and the mammalian brain

Cited by 11 publications

References 22 publications

Bisecting Lewis X in Hybrid-Type N-Glycans of Human Brain Revealed by Deep Structural Glycomics

Bisecting Lewis X in Hybrid-Type N-Glycans of Human Brain Revealed by Deep Structural Glycomics

Mass Spectrometry Imaging for Glycome in the Brain

The role of FUT8‐catalyzed core fucosylation in Alzheimer's amyloid‐β oligomer‐induced activation of human microglia

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