Identification of sialic acids on the cell surface of Candida albicans

The cell-surface expression of sialic acids in two isolates of Candida albicans was analyzed by thin-layer and gas chromatography, binding of lectins, colorimetry, sialidase treatment and flow cytofluorimetry with fluorescein-labeled lectins. N-acetylneuraminic acid (NANA) was the only derivative found in both strains of C. albicans grown in a chemically defined medium. Its identification was confirmed by mass spectrometry in comparison with an authentic standard. the density of sialic acid residues per cell ranged from 1.6x10(6) to 2.8x10(6). the surface distribution of sialic acids over the entire C. albicans was inferred from labeling with fluorescein-Limulus polyphemus and Limax flavus agglutinins and directly observed by optical microscopy with (FITC)-Sambucus nigra agglutinin (SNA), abrogated by previous treatment of yeasts with bacterial sialidase. Sialidase-treated yeasts generated beta-galactopyranosyl terminal residues that reacted with peanut agglutinin. in C. albicans N-acetyl-neuraminic acids are alpha 2,6- and alpha 2,3-linked as indicated by yeast binding to SNA and Maackia amurensis agglutinin. the alpha 2,6-linkage clearly predominated in both strains. We also investigated the contribution of sialic acids to the electronegativity of C. albicans, an important factor determining fungal interactions in vivo. Adhesion of yeast cells to a cationic solid phase substrate (poly-L-lysine) was mediated in part by sialic acids, since the number of adherent cells was significantly reduced after treatment with bacterial sialidase. the present evidence adds C. albicans to the list of pathogenic Fungi that synthesize sialic acids, which contribute to the negative charge of fungal cells and have a role in their specific interaction with the host tissue. (C) 2000 Elsevier Science B.V. All rights reserved.Univ Fed Rio de Janeiro, Inst Microbiol Prof Paulo Goes, Dept Microbiol Geral, BR-21941590 Rio de Janeiro, BrazilUniversidade Federal de São Paulo, Disciplina Biol Celular, BR-04023062 São Paulo, BrazilUniversidade Federal de São Paulo, Disciplina Biol Celular, BR-04023062 São Paulo, BrazilWeb of Scienc

Changes of sialomolecules during the dimethylsulfoxide-induced differentiation of Herpetomonas samuelpessoai

The expression of sialoglycoconjugates during the dimethylsulfoxide (DMSO)-induced differentiation of Herpetomonas samuelpessotti was analyzed by flow cytometry and Western blotting using sialic acid-specific lectins. Parasites reacted strongly with Limax flavus (LFA) and Sambucus nigra (SNA) agglutinins, and only weakly with Maackia amurensis (MAA) lectin. However, analysis of crude protein extracts by Western blotting revealed that bands with molecular masses corresponding to 15 and 40 kDa are recognized by MAA, and that treatment with DMSO induced the expression of two additional polypeptides with molecular masses of 65 and 90 kDa. Profiles of binding to LFA were indistinguishable when protein extracts from control or differentiated cells were analyzed. SNA recognized a major molecule with 25 kDa in extracts from non-differentiate forms and two low-molecular-weight bands from differentiated cells. These results indicate that molecules containing alpha2,6 and alpha2,3 sialyl-galactosyl sequences are present in H. samuelpessoai, and that their biosynthesis and expression are influenced by DMSO-induced differentiation.Univ Fed Rio de Janeiro, Univ Brasil, Dept Microbiol Geral, IMPPG,CCS, BR-21941590 Rio de Janeiro, BrazilUniversidade Federal de São Paulo, UNIFESP, Disciplina Biol Celular, São Paulo, BrazilUniversidade Federal de São Paulo, UNIFESP, Disciplina Biol Celular, São Paulo, BrazilWeb of Scienc