Glucosylation of cell wall proteins in regenerating spheroplasts of Candida albicans

Abstract

The cell wall of Candida albicans contains mannoproteins that are covalently associated with beta-1,6-glucan. When spheroplasts were allowed to regenerate a new cell wall, initially non-glucosylated cell wall proteins accumulated in the medium. While the spheroplasts became osmotically stable, beta-1,6-glucosylated proteins could be identified in their cell wall by SDS-extraction or beta-1,3-glucanase digestion. At later stages of regeneration, beta-1,3-glucosylated proteins were also found. Hence, incorporation of proteins into the cell wall is accompanied by extracellular coupling to beta-1,6-/beta-1,3-glucan. The SDS-extractable glucosylated proteins probably represent degradation products of wall proteins rather than their precursors. Tunicamycin delayed, but did not prevent the formation of beta-1,6-glucosylated proteins, demonstrating that beta-1,6-glucan is not attached to N-glycosidic side-chains of wall proteins.

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“…Kapteyn et al, (1996) believe that the ethanolamine remains, which is consistent with the fact that proteins can be removed from the cell wall by aqueous HF treatment (which cleaves phosphodiester bonds). Similar results have been obtained with the fungal pathogen Candida albicans (Kapteyn et al, 1994(Kapteyn et al, , 1995a. Figure 2 summarizes the proposed processing events of the glucanase extractable yeast wall mannoproteins.…”

“…Kapteyn et al, (1995a) used regenerating protoplasts to show that a class of cell wall proteins is secreted in the early stages of wall regeneration, due to the absence of glucan to which they are attached normally. Simi- lar experiments were carried out with P. variotii and A. niger to test which proteins are secreted and thus are candidate cell wall proteins.…”

β-1,2 Oligomannose Adhesin Epitopes Are Widely Distributed over the Different Families of Candida albicans Cell Wall Mannoproteins and Are Associated through both N- and O-Glycosylation Processes

“…To map ␤-Man epitopes for the different CWMP families, we slightly modified the protocols generally used (10,48) to sequentially release CWMPs. ConA, a lectin specific for terminal ␣-D-mannosyl and ␣-D-glucosyl residues and widely used to detect CWMPs (1,26,39), served as a systematic control in this study. As one of the aims of this study was to compare the well-defined PPM to other CWMPs, it was important to release noncovalently bound proteins, like PPM, without detergents, even at a low concentration, to avoid any contamination with covalently bound mannoproteins.…”

β‐1,6‐Glucan synthesis in Saccharomyces cerevisiae

“…It therefore appeared that β‐1,6‐glucan serves to attach at least some mannoproteins to the cell wall via their GPI moiety. Similar experiments have identified β‐1,6‐glucan‐anchored cell wall proteins in other fungi such as Candida albicans (Kapteyn et al ., 1994, 1995a,b), Exophilia (Wangiella) dermatidis (Montijn et al ., 1997) as well as filamentous fungi involved in food spoilage (Brul et al ., 1997).…”