Identification of N-acetylneuraminyl alpha 2-->3 poly-N-acetyllactosamine glycans as the receptors of sialic acid-binding Streptococcus suis strains (original) (raw)
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Microbiology and Immunology, 2008
Bacterial recognition of host sialic acid-containing receptors plays an important role in microbial colonization of the human oral cavity. The aggregation of human platelets by Streptococcus gordonii DL1 is implicated in the pathogenesis of infective endocarditis. In addition, we consider that hemagglutination of this organism may act as an additive factor to increase the severity of this disease. We previously reported that this interaction requires the bacterial expression of a 203-kDa protein (Hsa), which has sialic acid-binding activity. In the present study, we confirmed that erythrocyte surface sialoglycoproteins are the receptors for Hsa. We examined the effects of proteinase K, chymotrypsin, phospholipase C, and α(2-3) or α(2-3, 6, 8) neuraminidase on hemagglutination activity and found that the interaction occurs between Hsa and α2-3-linked sialic acid-containing proteins of erythrocytes. We expressed recombinant NR2, which is the putative binding domain of Hsa, fused with GST in Escherichia coli BL21. Dot-blot analysis demonstrated that GST-HsaNR2 binds both glycophorin A (GPA) and band 3. Moreover, GPA and a small amount of band 3 were detected by GST pull-down assays. These findings indicate that S. gordonii Hsa specifically binds to GPA and band 3, α2-3-linked sialic acid membrane glycoproteins.
Interactions of mitis group streptococci with sialic acid receptors
International Congress Series, 2006
The serine-rich repeat glycoprotein Hsa in Streptococcus gordonii Challis mediates bacterial cell interactions with fetuin, glycocalicin, fibronectin and human platelets. Different strains of S. gordonii vary markedly in their adhesion levels to sialylated proteins, while other mitis group streptococci have distinct patterns of recognition of sialylated or desialylated receptor oligosaccharides.
FEMS Immunology & Medical Microbiology, 1996
Streptococcus suis capsular type 2 has a capsule rich in sialic acid (NANA). Sialic acid, known to be an antiphagocytic factor for many bacterial species, inhibits the activation of the alternative complement pathway. The role of capsular NANA in virulence, resistance to phagocytosis and intracellular survival of S. suis capsular type 2 was evaluated. In general, a low concentration of NANA 'was observed for all the S. suis strains tested. In addition, no difference could be found in NANA concentrations between lstrains of different virulence degrees. Sialic acid concentration increased in the virulent strain 89-1591 and the avirulent strain 90-1330 after in vivo growth with an increased capsular material thickness compared to growth in vitro. No significant difference could be found in the phagocytosis rate by porcine blood monocytes of either strain and strain 89-1591 treated with sialidase or the sialic acid-binding lectin from Sambucus nigra (SNA I). Intracellular survival of strain 89-1591 decreased after treatments with sialidase or lectin, becoming comparable to that of strain 90-1330. Finally, no difference could be seen in virulence using a murine model, even if strain 89-1591 was treated with the enzyme or the lectin. Thus, NANA does not seem to be a critical virulence factor for S. suis capsular type 2.
Infection and Immunity
The erythrocyte receptors for S-fimbriated Escherichia coli, which causes sepsis and meningitis in newborn infants, were investigated. Neuraminidase and trypsin treatments of erythrocytes abolished the hemagglutination ability of the bacteria. To identify the receptor glycoproteins, we separated erythrocyte membrane proteins by gel electrophoresis, blotted them to nitrocellulose, and incubated them with 125I-labeled bacteria. The only bacterium-binding bands identified corresponded to glycophorin A dimer and monomer, and the binding was abolished by neuraminidase treatment of the blot. Radiolabeled bacteria also bound to purified glycophorin A adsorbed to polyvinyl chloride microwells, and the binding was inhibited by other sialoglycoproteins and isolated sialyloligosaccharides containing the NeuAc alpha 2-3Gal sequence. Oligosaccharides which contain the NeuAc alpha 2-3Gal beta 1-3GalNAc and NeuAc alpha 2-3Gal beta 1-3(NeuAc alpha 2-6)GalNAc sequence and which are identical to the ...
Glycobiology, 2009
NeuA O-acetylesterase on specific glycosylation phenotypes of GBS, pinpointing an isogenic strain pair that differs dramatically in the degree of the O-acetyl modification (80% versus 5%) while still expressing comparable levels of overall sialylation. Using these strains, higher levels of O-acetylation were found to protect GBS CPS Sia against enzymatic removal by microbial sialidases and to impede engagement of human Siglec-9, but not to significantly alter the ability of GBS to restrict complement C3b deposition on its surface. Additional experiments demonstrated that pH-induced migration of the O-acetyl modification from the 7-to 9-carbon position had a substantial impact on GBS-Siglec-9 interactions, with 7-O-acetylation exhibiting the strongest interference. These studies show that both the degree and position of the GBS O-acetyl modification influence Sia-specific interactions relevant to the host-pathogen relationship. We conclude that native GBS likely expresses a phenotype of intermediate Sia O-acetylation to strike a balance between competing selective pressures present in the host environment.
Evolutionary inactivation of a sialidase in group B Streptococcus
Scientific Reports, 2016
Group B Streptococcus (GBS) is a leading cause of bacterial sepsis and meningitis in newborns. GBS possesses a protein with homology to the pneumococcal virulence factor, NanA, which has neuraminidase (sialidase) activity and promotes blood-brain barrier penetration. However, phylogenetic sequence and enzymatic analyses indicate the GBS NanA ortholog has lost sialidase function-and for this distinction we designate the gene and encoded protein nonA/NonA. Here we analyze NonA function in GBS pathogenesis, and through heterologous expression of active pneumococcal NanA in GBS, potential costs of maintaining sialidase function. GBS wild-type and ΔnonA strains lack sialidase activity, but forced expression of pneumococcal NanA in GBS induced degradation of the terminal sialic acid on its exopolysaccharide capsule. Deletion of nonA did not change GBS-whole blood survival or brain microvascular cell invasion. However, forced expression of pneumococcal NanA in GBS removed terminal sialic acid residues from the bacterial capsule, restricting bacterial proliferation in human blood and in vivo upon mouse infection. GBS expressing pneumococcal NanA had increased invasion of human brain microvascular endothelial cells. Thus, we hypothesize that nonA lost enzyme activity allowing the preservation of an effective survival factor, the sialylated exopolysaccharide capsule. Streptococcus agalactiae (Group B Streptococcus, GBS) is a Gram-positive bacterial pathogen that is a leading cause of sepsis, pneumonia, and meningitis during neonatal period and up to the first 90 days of life 1,2. Each of the 10 different GBS capsular polysaccharide types 1 , though possessing different repeating subunits, share a terminal α-2-3-linked sialic acid (N-acetylneuraminic acid, Neu5Ac motif), which is identical to a sugar epitope capping many surface glycans on all mammalian cells 3. Humans in particular express just the terminal α-2-3-linked Neu5Ac since they have lost the gene required to synthesize the alternative sialic acid, N-glycolylneuraminic acid (Neu5Gc) present in other mammals including primates 3. The GBS sialylated capsule mimics a common presentation of Neu5Ac in the α-2-3-linkage, which contributes to evasion of the host immune system and promoting bacterial survival in vivo 4. GBS capsular sialylation interferes with the host complement system to block C3b deposition and limit C5a deposition 5,6 , and inhibits neutrophil activation through interaction with inhibitory sialic acid-binding immunoglobulin-like lectin-9 (Siglec-9) 7. The in vivo significance of these findings was corroborated in mice with and without Siglec-E, the closest homolog of human Siglec-9, which interacts with GBS in a sialic acid-dependent manner, triggering protein tyrosine phosphatase, SHP-1, recruitment to its intracellular domain and suppressing myeloid cell inflammatory responses 8. Streptococcus pneumoniae (pneumococcus) is a related Gram-positive pathogen and a major cause of pneumonia, sepsis, and meningitis 9,10. Most severe S. pneumoniae diseases occur in children younger than 2 years and adults older than 65 years. The polysaccharide capsule of S. pneumoniae confers the antigenicity utilized to classify S. pneumoniae into at least 97 serotypes 11. In contrast to GBS, no S. pneumoniae strains express sialic acid in its capsular polysaccharide. Instead, the bacterium expresses three sialic acid-cleaving enzymes or sialidases, NanA, NanB, and NanC 11,12. The nanA and nanB genes are located in the same operon and detected in almost all clinical isolates, whereas the nanC gene is present in approximately half (51%) of isolates 12. While the
Infection and Immunity
A total of 378 streptococcal isolates of Lancefield groups B, C, D and G were tested for their ability to hemagglutinate untreated, sialidase-treated, and endo-beta-galactosidase-treated human erythrocytes. Of the 43 strains showing positive hemagglutination, 9 were inhibitable with neutral monosaccharides. Four strains were inhibited with galactose and N-acetylgalactosamine, whereas five were inhibited with galactose only. A third, sialic acid-specific adhesion activity was suggested for two additional strains on the basis of their agglutination of native and endo-beta-galactosidase-treated but not sialidase-treated erythrocytes. All the sugar-specific agglutination activities detected were confined to Streptococcus suis strains of group D streptococci, whereas streptococci of other groups did not exhibit these types of hemagglutination activities. The adhesins were sensitive to proteases and heat treatment, which indicates that they were proteins. The hemagglutinating isolates of ...
Infection and Immunity, 2002
Oral colonization by Streptococcus gordonii , an important cause of subacute bacterial endocarditis, involves bacterial recognition of sialic acid-containing host receptors. The sialic acid-binding activity of this microorganism was previously detected by bacterium-mediated hemagglutination and associated with a streptococcal surface component identified as the Hs antigen. The gene for this antigen ( hsa ) has now been cloned in Escherichia coli , and its expression has been detected by colony immunoblotting with anti-Hs serum. Mutants of S. gordonii containing hsa inactivated by the insertion of an erythromycin resistance gene or deletion from the chromosome were negative for Hs-immunoreactivity, bacterium-mediated hemagglutinating activity, and adhesion to α2-3-linked sialoglycoconjugates. The deletion in the latter mutants was complemented by plasmid-borne hsa , resulting in Hs antigen production and the restoration of cell surface sialic acid-binding activity. The hsa gene encod...
Infection and Immunity, 1989
A total of 378 streptococcal isolates of Lancefield groups B, C, D and G were tested for their ability to hemagglutinate untreated, sialidase-treated, and endo-beta-galactosidase-treated human erythrocytes. Of the 43 strains showing positive hemagglutination, 9 were inhibitable with neutral monosaccharides. Four strains were inhibited with galactose and N-acetylgalactosamine, whereas five were inhibited with galactose only. A third, sialic acid-specific adhesion activity was suggested for two additional strains on the basis of their agglutination of native and endo-beta-galactosidase-treated but not sialidase-treated erythrocytes. All the sugar-specific agglutination activities detected were confined to Streptococcus suis strains of group D streptococci, whereas streptococci of other groups did not exhibit these types of hemagglutination activities. The adhesins were sensitive to proteases and heat treatment, which indicates that they were proteins. The hemagglutinating isolates of ...
Infection and Immunity, 2014
Leukotoxin (LtxA) from Aggregatibacter actinomycetemcomitans is known to target and lyse  2 -integrin-expressing cells such as polymorphonuclear leukocytes and macrophages. LtxA is an important virulence factor that facilitates chronic inflammation and is strongly associated with a fast-progressing form of periodontitis caused by the JP2 clone of the bacterium. Here, we show that sialic acid residues are important for LtxA-induced cell lysis, regardless of whether the cell express  2 -integrin or not. Clearly, removal of sialic acid groups significantly reduces a  2 -integrin-specific LtxA-induced lysis. Moreover, sialic acid presented on alternative proteins, such as, for instance, on erythrocytes that do not express  2 -integrin, also makes the cells more sensitive to LtxA. The data also illustrate the importance of the negative charge in order for the sialic acid to associate LtxA with the membrane. Removal of sialic acid is in itself sufficient to significantly reduce the negative charge on the erythrocytes. Moreover, we found that on human erythrocytes there is a positive association between the sensitivity to LtxA and the amount of negative charge caused by sialic acid. Interestingly, these features are not shared by all RTX toxins, since ␣-hemolysin from Escherichia coli induced cell lysis of both  2 -integrin-expressing and nonexpressing cells and this lysis is independent of the presence of sialic acid residues. In conclusion, LtxA not only is cytotoxic to  2 -integrin-expressing cells but can potentially initiate cell lysis in all cells that present a sufficient density of sialic acid groups on their plasma membrane.