Sialic Acid is strong on Exosomes, but Why?

Glycans are said to be the face of cells, and the glycosylation on the cell surface changes depending on the tissue and desease state.
As a result, the glycosylation of exosomes released from cells drags the glycosylation of the cell surface, but for some reason, expression of sialic acid tends to be very strong.
For example, there is a paper written by Shimoda and Akiyoshi at. al., Kyoto University (see below).
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6687741/
Why is this?
There is a paper that says it may be aimed at masking the immune system (in Japanese), but is that true?
for example,
https://www.jstage.jst.go.jp/article/dds/38/4/38_270/_pdf
In contrast, the authors cited above suggest that it is involved in the uptake of exosomes via Siglecs on the cell surface.
https://www.sciencedirect.com/science/article/abs/pii/S0006291X17314845?via%3Dihub


(cited from the above listed paper)

Behind the “Cry for Help” response caused by plant pathogen infection

A group from State Key Laboratory of Efficient Utilization of Arid and Semi-arid Arable Land in Northern China, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China, etc. has reported about how to induce “cry for help” response to assemble disease suppressing and growth promoting rhizomicrobiome.
https://www.nature.com/articles/s41467-024-46254-3

The well-studied model pathogen Pseudomonas syringae pv. tomato (Pst) DC3000 and its nonpathogenic derivatives (D36E, D36EFLC and D36EHPM) were used in this experiment using Arabidopsis as a model plant.

Treatment with either DC3000 or the derivatives increased the relative contents of long chain organic acids (LCOAs) and amino acids in root exudates. The bacterial phyla Proteobacteria (32.1%–38.3%) and Actinobacteria (15.4%–20.7%) were the most abundant groups in the rhizosphere, and the genus Devosia (belonging to phylum Proteobacteria) was enriched in the D36E and D36EFLC treatments. Interestingly, the abundance of genus Devosia was negatively correlated with L-malic acid and myristic acid in root exudates but positively correlated with 4-hydroxypyridine.

Finally, it was shown that the metabolites of D36E and D36EFLC alone are sufficient to induce a “cry for help” response. So, this study demonstrates the ability of nonpathogenic strains and their MAMPs to act as elicitors to induce the formation of a disease-suppressive soil legacy, which can potentially support agricultural applications.

DC-SIGN recognizes the outer core oligosaccharide of LPS expressed on Gram-negative bacteria

Department of Chemical Science, University of Naples Federico II Via Cinthia 4, Naples, Italy, etc. has reported about molecular recognition of LPS by DC-SIGN.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10828809/

Lipopolysaccharides (LPS) are peculiar glycolipids which represent the major components of the external leaflet of the gram-negative bacteria outer membrane. They consist of three structurally and genetically distinct domains: the lipid A, integrated in the outer membrane; the core oligosaccharide (OS), in turn composed of inner and outer core regions; and the distal O-specific polysaccharide (O-PS) chain, that extends outwards the bacterial surface

Structurally speaking, it is a dodecasaccharide composed of two residues of galactose and three glucose units in the outer core region and three L-glycero-D-manno-heptoses and two 3-deoxy-D-manno-oct-2-ulosonic acids (Kdo), in the inner core portion; the two glucosamine residues at reducing end belong to the lipid A moiety.

One of the main representatives of transmembrane C-type lectins is DC-SIGN also known as CD209. This lectin is found on macrophages, monocytes, and is mainly expressed by dendritic cells which act as potent phagocytic cells, and it is know that DC-SIGN belongs to the mannose receptor family. On the other hand, it has been shown that the DC-SIGN induced phagocytosis of E. coli occurs in the absence of O-antigen polysaccharides, and in the presence of a complete core OS.

In this study, it was found that DC-SIGN binds to the outer core pentasaccharide (composed of two residues of galactose and three glucose units), which acts as a crosslinker between two different tetrameric units of DC-SIGN.

VVA Lectin characteristically binds to invasive urothelial carcinomas

A group from Department of Urology, Gifu University Graduate School of Medicine, Gifu, Japan, etc. has reported about characteristic glycan marker in invasive urothelial carcinomas.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10806140/

The study found that a specific lectin, VVL, was present in cases of invasive urothelial carcinoma and its variant components. More intense VVL staining was observed with invasive or muscle invasive urothelial carcinomas and urothelial carcinomas with variant components than that in non-invasive urothelial carcinomas

VVL recognizes the GalNAc residue linked to serine or threonine in a polypeptide Tn antigen. Other glycan structures, such as Galβ1,3GalNAc-α-Ser/Thr (T antigen) and GlcNAcα1,6-GalNAc-α-Ser/Thr, including terminal α1,4- and β1,4-linked GalNAc, were also recognized by VVL, but with a weaker affinity.

VVA will have the potential to serve as a promising target for drug delivery in future clinical studies.

Changes in glycan composition of EPS produced by bacteria in aerobic granular sludge used in wastewater treatment processes

A group from Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands, etc. has reported about changes of glycan composition in aerobic granular sludge by using lectin microarray and GC-MS etc.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10788855/

Aerobic granular sludge is a community of microbial organisms that remove carbon, nitrogen, phosphorus and other pollutants in a single sludge system used for wastewater treatments. In this research, the dynamic changes of the glycan profile of a few extracellular polymeric substance (EPS) samples extracted from aerobic granular sludge were monitored by GC-MS and lectin microarray.

EPSs were collected at different stages during its adaptation to the seawater condition on the initial day, 18th, and 30th days after the start of the reactor (denoted as EPSt0, EPSt18, and EPSt30 hereafter).

The application of the lectin microarray confirmed the presence of glycoproteins and effectively monitored its alteration along the adaptation to the seawater condition. Additionally, the result of lectin microarray is in line with the results of other analyses performed by GC-MS etc. This suggests that the lectin microarray is a successful platform for high-throughput glycan profiling of glycoproteins in microbial aggregates such as granular sludge.

Interestingly, there were more glycoproteins in EPSt18 than EPSt0 and EPSt30, and the glycosylation pattern of EPSt18 is significantly diverse. This indicates that, in response to the environmental change, i.e., exposure to the increased salt condition, one of the adaptation strategies of the microorganisms can be altering the glycosylation of proteins in quantity and diversity.

p.s., Her collaborator, Dr. Tateno in AIST, is also our collaborator regarding a glycan profiling system using lectin microarrays and an evanescent-filed fluorescence excitation scanner, GlycoStation.

Pregnancy diagnosis targeting to changes in urinary glycopatterns

A group from Shaanxi Key Laboratory for Animal Conservation, College of Life Sciences, Northwest University, China, etc. has reported about a possibility of pregnancy diagnosis targeting changes in urinary glycopatterns.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10783609/

This study investigates the urinary glycopatterns of golden snub-nosed monkeys (GSM) with using lectin microarrays. It was shown that the types, amounts and structure of N-glycans and the proportion of sialylation and fucoslation of N-glycans are different between pregnant and non-pregnant females, and between (non-pregnant) females and males. This method will provide reference information for pregnancy diagnosis and sex identification, which will benefit the management of the animals.

where, pregnant (P) and non-pregnant (NP) females, and females (F) and males (M)

Bacillus, Ensifer, and Pseudomonas are dominant in the rhizosphere of salt-tolerant alfalfa varieties

A group from Key Laboratory of Grassland Resources of the Ministry of Education and Key Laboratory of Forage Cultivation, Inner Mongolia Agricultural University, Hohhot, China, etc. has reported about rhizosphere microbiome responsible for salt tolerance to alfalfa.
https://www.frontiersin.org/articles/10.3389/fpls.2023.1324333/full

They reported that the higher abundance of Bacillus, Ensifer, and Pseudomonas in the rhizosphere of salt-tolerant alfalfa varieties is crucial in determining their elevated salt tolerance.

Differences in maize rhizosphere microbiome due to drought and flooding stress

A group from Nanjing Agricultural University, China, etc. has reported about differences in maize rhizosphere microbiome due to drought and flooding stress.
https://www.frontiersin.org/articles/10.3389/fmicb.2023.1295376/full

The results showed that
(1) the sum of the two phylums, Actinobacteria and Proteobacteri, accounted for nearly 50% existance, and
(2) Actinobacteria was the most dominant phylum in the two drought-flood abrupt alternation (DFAA) groups during the drought period and the rewatering period, and Proteobacteria was the most dominant phylum during the flooding period and the harvest period.
For your info., DFAA1 group means a trace rainfall to heavy rain condition and DFAA2 means a continuous drought to flooding condition.

where, A: during the drought period, and B:flooding period

Structure and Characteristics of a Lectin named ”Cvill” isolated from Canavalia villosa seeds

A group from Laboratory of Biochemistry and Glycobiology, Department of Biotechnology, Ghent University, Belgium, etc. has reported about a ConA-like mannose-specific lectin, Cvill, isolated from Canavalia villosa seeds.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10649158/

Cvill is a ConA-like mannose-specific lectin isolated from Canavalia villosa seeds.

The lectin structure is composed of 237 amino acid residues, similar to other ConA-like lectins .

Cvill exhibits the typical legume lectin fold, also known as a β-sandwich, characterized by the presence of two superimposed beta sheets, resembling a sandwich. These beta sheets consist of antiparallel strands, with one beta sheet formed by six long, flat beta strands and the other by seven curved strands.The arrangement of dimers and tetramers in the quaternary structure was predicted.

Glycan array experiments indicated that Cvill exhibits affinity for terminal α-mannosyl residues and the tri-mannosidic core of N-glycans.

Cvill demonstrated dose-dependent cytotoxicity against all tested cell lines and this toxicity was carbohydrate-mediated. Cvill presented IC50 values of 97.0 μg/mL after 48 h incubation period for HeLa ells. Cvill also affected the viability of the fibrosarcoma (HT1080 cells) and the NHDF cells with IC50 values of 116.08 μg/mL and 108.34 μg/mL after a 48 h incubation period.

Gal modification of laminin receptor integrin α6β1 is reduced in hepatocellular carcinoma, and thereby accelerates cancer cell invasion

A group from Graduate Institute of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, Taiwan, etc. has reported that Beta1,4-galactosyltransferases (B4GALTs) downregulation upregurates agalacto N-glycans and enhances the laminin-binding activity of integrin α6 and integrin β1 to promote invasiveness of Hepatocellular carcinoma (HCC) cells.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10618527/