Factors affecting binding of galacto ligands to Actinomyces viscosus lectin

Actinomyces tissue specificity may depend on differences in receptor specificity for GalNAc beta-containing glycoconjugates

Actinomyces naeslundii 12104 and A. viscosus LY7 were compared for receptor specificities and adherence properties because these relate to their oral colonization sites. Both strains bind GalNAc beta-containing glycosphingolipids (GSLs) in a GalNAc beta 1-3Gal alpha Oethyl-sensitive fashion but differ with respect to the number of cells bound to GSLs and the effect of neighboring sugar groups on the binding. Their hemagglutination and saccharide inhibition profiles confirms the existence of two receptor specificities (for example, when GalNAc beta 1-3Gal alpha Oethyl is multivalently conjugated to albumin, its inhibitory activity increases fourfold toward strain 12104 but decreases fourfold toward strain LY7). Trypsin or chymotrypsin treatment of human erythrocytes, which possess receptor GSLs, improves their hemagglutination with strain 12104. In contrast, the same treatment of chicken erythrocytes, which lack receptor GSLs, abolishes their hemagglutination. These findings suggest that both GSLs and glycoproteins act as functional receptors on eukaryotic cells. The strains also differ with respect to the following GalNAc beta 1-3Gal alpha Oethyl-sensitive adherence properties: (i) strain LY7 adheres somewhat better than does strain 12104 to buccal epithelial cells; (ii) in spite of their similar overall coaggregation patterns with streptococci, strain 12104 coaggregates with Streptococcus oralis MPB1 but strain LY7 does not; (iii) strain 12104 alone shows GalNAc beta-sensitive saliva aggregation and adherence to saliva-coated hydroxyapatite. The GSL binding patterns of fresh Actinomyces isolates reveal a high prevalence of LY7-like specificities among buccal isolates, whereas 12104-like specificities are most prevalent among plaque isolates. These findings strongly suggest that fresh Actinomyces isolates use fine specificity for GalNAc beta-containing glycoconjugates in recognition and subsequent colonization of specific oral surfaces.

Salivary receptors for GalNAc beta-sensitive adherence of Actinomyces spp.: evidence for heterogeneous GalNAc beta and proline-rich protein receptor properties

The receptors for GalNAc beta 1-3Gal alpha Oethyl (GalNAc beta)-sensitive adherence of Actinomyces strains to salivary pellicles were investigated. Parotid and submaxillary saliva from one individual was size fractionated and utilized in hydroxyapatite adherence assays with Actinomyces naeslundii 12104 and A. viscosus 19246 and LY7 with and without GalNAc beta. Three parotid salivary fractions, the high-molecular-weight, acidic proline-rich protein (PRP), and statherin fractions, promote GalNAc beta-sensitive adherence of strain 12104, whereas only the high-molecular-weight fraction of submaxillary saliva promotes such adherence. In contrast, strain LY7, possessing a variant GalNAc beta specificity, shows GalNAc beta-sensitive adherence to the leading and trailing regions of the submaxillary PRP fractions but less distinct adherence to the parotid and submaxillary high-molecular-weight fractions. In addition, the PRP and statherin fractions promote adherence of strains LY7 and 19246 that is not inhibited by GalNAc beta. However, whereas strain LY7 binds more strongly to the PRP fraction than to the statherin fraction, strain 19246 binds preferentially to the statherin fractions of parotid and submaxillary saliva. These salivary protein fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunostained to detect glycosylated proteins. The different salivary receptor properties are paralleled by different glycosylation patterns. The variable GalNAc beta specificities may have evolved to match different salivary glycosylation patterns, and PRP and statherin binding properties seem to be heterogeneous among the Actinomyces strains.

Specificity of Amaranthus leucocarpus lectin

We have demonstrated that Amaranthus leucocarpus lectin hemagglutinating activity was powerfully inhibited by the T-antigen, containing Gal(beta 1-3)GalNAc(alpha 1-3)Ser/Thr, and the Tn-antigen, which contains GalNAc(alpha 1-3)Ser/Thr. This suggests that the acetamido group at C-2 and the axial -OH at C-4 of the N-acetyl-D-galactopyranosylamine ring are important for lectin binding. The hemagglutination assays also established that desialylated and Pronase-treated human type O erythrocytes with an M phenotype were better recognized than erythrocytes from all other blood groups. The recognition was dependent on pH and ionic strength.

Specific and nonspecific inhibition of adhesion of oral actinomyces and streptococci to erythrocytes and polystyrene by caseinoglycopeptide derivatives

Various caseinoglycopeptide derivatives prepared from mammalian milk were evaluated as inhibitors of hemagglutinations mediated by Actinomyces viscosus Ny1, Streptococcus sanguis OMZ9, and, for comparative purposes, plant lectins from Arachis hypogaea and Bauhinia purpurea. It was found that recognition of the beta-D-galactose-(1----3)-2-acetamido-2-deoxy-D-galactose carbohydrate chain by Actinomyces viscosus Ny1 organisms and Arachis hypogaea and B. purpurea agglutinins had similar structural requirements; in all cases, the desialylated bovine caseinoglycomacropeptide, on which several units of the above mentioned disaccharide are clustered, behaved as the most potent hemagglutination inhibitor. By contrast, none of the preparations tested inhibited erythrocyte agglutination by S. sanguis OMZ9. Thus, the desialylated bovine caseinoglycomacropeptide acts as a potent and specific inhibitor of oral Actinomyces adhesion to cell membranes (a soft surface) and could be used as a probe for the study of recognition mechanisms mediated by Actinomyces galactose-binding lectins. During the present study, both native and desialylated variants of the same bovine glycomacropeptide also totally prevented the adhesion of Actinomyces viscosus Ny1, S. sanguis OMZ9, and S. mutans OMZ176 to polystyrene surfaces. Comparative evaluations of various structurally different compounds gave the following results. Neither mono- nor disaccharides related to caseinoglycopeptide carbohydrates prevented adhesion; highly positively or negatively charged polypeptides and polysaccharides were either not or only moderately active. Besides these glycomacropeptides, an inhibitory activity was also exhibited by other mucin-type glycoproteins carrying short O-linked carbohydrate chains (including bovine submaxillary mucin), polyethylene glycol, and bovine serum albumin. Consequently, caseinoglycopeptide prevention of oral bacterial adhesion to polystyrene tubes (a hard surface) takes place with no species specificity and can be compared to nonspecific inhibition exhibited by various polymers with very different structural characteristics.

A polysaccharide from Streptococcus sanguis 34 that inhibits coaggregation of S. sanguis 34 with Actinomyces viscosus T14V

Coaggregation between Actinomyces viscosus T14V and Streptococcus sanguis 34 depends on interaction of a lectin on A. viscosus T14V with a cell surface carbohydrate on S. sanguis 34. This carbohydrate was isolated, and its chemical makeup was established. The carbohydrate remained attached to S. sanguis 34 cells through extraction with Triton X-100 and treatment with pronase. It was cleaved from the cell residue by autoclaving and purified by differential centrifugation and column chromatography on DEAE-Sephacel and Sephadex G-75. The polysaccharide contained phosphate which was neither inorganic nor monoester. Treatment with NaOH-NaBH4, followed by Escherichia coli alkaline phosphatase, or with 48% HF at 4 degrees C, followed by NaBH4, yielded inorganic phosphate and oligosaccharide alditols. Therefore, the polysaccharide is composed of oligosaccharide units joined together by phosphodiester bridges. The structure and stereochemistry of the main oligosaccharide alditol was established previously (F. C. McIntire, C. A. Bush, S.-S. Wu, S.-C. Li, Y.-T. Li, M. McNeil, S. Tjoa, and P. V. Fennessey, Carbohydr. Res. 166:133-143). Permethylation analysis, 1H and 31P nuclear magnetic resonance studies on the whole polysaccharide revealed the position of the phosphodiester linkages. The polysaccharide is mainly a polymer of (6) GalNAc(alpha 1-3)Rha(beta 1-4)Glc(beta 1-6)Galf(beta 1-6)GalNAc(beta 1- 3)Gal(alpha 1)-OPO3. It reacted as a single antigen with antiserum to S. sanguis 34 cells and was a potent inhibitor of coaggregation between A. viscosus T14V and S. sanguis 34. Quantitative inhibition of precipitation assays with oligosaccharides, O-allyl N-acetylgalactosaminides, and simple sugars indicated that specific antibodies were directed to the GalNAc end of the hexasaccharide unit. In contrast, coaggregation was inhibited much more effectively by saccharides containing betaGalNAc. Thus, the specificity of the A. viscosus T14V lectin is strikingly different from that of antibodies directed against the S. sanguis 34 polysaccharide.

A 160-kilodalton epithelial cell surface glycoprotein recognized by plant lectins that inhibit the adherence of Actinomyces naeslundii

The adherence of Actinomyces naeslundii to human epithelial (KB) cells is mediated by the interaction of a fimbrial lectin on this oral bacterium with epithelial cell receptors exposed by sialidase. The D-galactose- and N-acetyl-D-galactosamine-reactive plant lectins from peanut and from Bauhinia purpurea inhibit this interaction. This report describes the partial purification and characterization of a 160-kilodalton (kDa) cell surface glycoprotein which is the principal receptor for these lectins. Radioiodinated lectins detected a band of 160 kDa on sialidase-treated Western blots of epithelial cell extracts but did not detect bands on nontreated filters. However, wheat germ agglutinin was reactive with the 160-kDa band on filters that were not treated with sialidase, suggesting that this lectin recognizes the sialic acid residues of this molecule. The 160-kDa component was partially purified from n-octylglucoside extracts of the epithelial cells by wheat germ agglutinin affinity chromatography. This molecule was metabolically labeled with D-[14C]glucosamine and labeled at the cell surface by lactoperoxidase-catalyzed iodination or periodate oxidation followed by sodium borotritide reduction. Incubation of epithelial cells with sialidase before extraction resulted in the loss of the 160-kDa band and the appearance of a band at 200 kDa which was directly reactive with 125I-labeled peanut agglutinin. These results indicate that the 160-kDa glycoprotein on the surface of the epithelial cell serves as a receptor for the agglutinins from the peanut and B. purpurea and presumably the fimbrial lectin of actinomyces.