CELL-WALL AND SECRETED PROTEINS OF CANDIDA-ALBICANS - IDENTIFICATION,FUNCTION, AND EXPRESSION

The cell wall is essential to nearly every aspect of the biology and p athogenicity of Candida albicans. Although it was intially considered an almost inert cellular structure that protected the protoplast again st osmotic offense, more recent studies have demonstrated that it is a dynamic organelle. The major components of the cell wall are glucan a nd chitin, which are associated with structural rigidity, and mannopro teins. The protein component, including both mannoprotein and nonmanno proteins, comprises some 40 or more moieties. Wall proteins may differ in their expression, secretion, ol topological location within the wa ll structure. Proteins may be modified by glycosylation (primarily add ition of mannose residues), phosphorylation, and ubiquitination. Among the secreted enzymes are those that are postulated to have substrates within the cell wall and those that find substrates in the extracellu lar environment. Cell wall proteins have been implicated in adhesion t o host tissues and ligands. Fibrinogen, complement fragments, and seve ral extracellular matrix components are among the host proteins bound by cell wall proteins. Proteins related to the hsp70 and hsp90 familie s of conserved stress proteins and some glycolytic enzyme proteins are also found in the cell wall apparently as bona fide components. In ad dition, the expression of some proteins is associated with the morphol ogical growth form of the fungus and may play a role in morphogenesis. Finally, surface mannoproteins are strong immunogens that trigger and modulate the host immune response during candidiasis.