A comparative study of the incorporation of a 1,6-ss-glucan and an O-glycosylated protein epitope into the cell wall of Candida albicans

Abstract

B u rjassot (Va lenci a), 5 pa i nThe topological distribution of two epitopes in the cell wall of Candida albicans, the kinetics of their incorporation into the regenerating protoplast wall, and the effect of different antibiotics upon their incorporation and localization have been studied. To do so, two monoclonal antibodies that react against an 0-glycosylated mannoprotein (1 B12) and against a 1,6-P-glucan epitope (JRR1) were used. The results show that the JRRl epitope is localized in an internal layer o f the cell wall, in contrast to the 1B12 epitope, which is superficial, and that the incorporation o f the JRRl epitope into walls of regenerating protoplasts precedes that of the 1 B12 epitope. The JRRl epitope is normally found in the culture medium of control cells, but not in that of papulacandin-B-treated cells, and tunicamycin interferes with the incorporation of the 1B12 epitope into the cell walls. Finally, the results support the hypothesis that mannoproteins are not 1,6-/?-glycosylated before their secret ion.

Genomic response programs of Saccharomyces cerevisiae following protoplasting and regeneration

“…On the other hand, in hypertonic liquid medium they synthesize b-1,3-glucans, chitin and a number of cell wall proteins, that form a loosely-bound coat surrounding the protoplasts and that may trap several protoplasts together, but do not organize into a normal cell wall (Svoboda et al, 2001). These results contrast with Candida albicans protoplasts that synthesize a rather normal cell wall when incubated in hypertonic liquid medium (Elorza et al, 1994;Sanjuan et al, 1996). The reasons for this different behaviour are not known, but it is likely that the difference must depend on some key processes involved in the organization of the structure of the wall.…”

Cell Wall and Secreted Proteins ofCandida albicans: Identification, Function, and Expression

“…Proteins covalently attached to glucan are postulated to represent species contributing to cell wall structure (59,122,123,125,482). Covalent attachment of mannoprotein to glucan, perhaps through phosphodiester linkages, has been suggested, as noted below (237,238,462,463).…”

“…Surarit et al (527) reported the presence of glycosidic linkages between glucan and chitin in the nascent wall of C. albicans. Recent evidence indicates that mannoproteins may also establish covalent associations with ␤-glucans (237,238,462,463). It is suggested that ␤-1,3-and ␤-1,6-glucans are linked to proteins by phosphodiester linkages, a process that may involve the participation of a GPI (glycosyl phosphatidylinositol) anchor (238) (see below).…”

“…Cell wall architecture has been studied most extensively in S. cerevisiae and is likely to be a model for C. albicans since there are some similar observations, in particular sensitivity to enzymatic digestion, glucan-mannoprotein linkages, and candidate proteins, that fit the same model (237,238,246,247,268,462,463). In a very recent study, Kollár et al (268) detected the presence of material containing all four major cell wall components, ␤-1,3-glucan, ␤-1,6-glucan, chitin, and mannoprotein.…”

Candida albicanscell wall antigens for serological diagnosis of candidemia

“…Since b(1-3)(1-6) glucan alone induces high antibody levels in immunized rabbits (unpublished data) our results are in agreement with the suggestion that glucan is located relatively deep in the cell wall of C. albicans and is thereby poorly immunogenic [43]. In addition, the anti-Glu antibodies were highly specific for b(1-3)(1-6) linkages, since no inhibitory activity was observed with b(1-4)(1-6) or b(1-3) glucan.…”