The cell wall is essential to nearly every aspect of the biology and pathogenicity of Candida albicans. Although it was initially considered an almost inert cellular structure that protected the protoplast against osmotic offense, more recent studies have demonstrated that it is a dynamic organelle. The major components of the cell wall are
glucan and
chitin, which are associated with structural rigidity, and
mannoproteins. The
protein component, including both mannoprotein and nonmannoproteins, comprises some 40 or more moieties. Wall
proteins may differ in their expression, secretion, or topological location within the wall structure.
Proteins may be modified by glycosylation (primarily addition 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 extracellular environment. Cell wall
proteins have been implicated in adhesion to host tissues and
ligands.
Fibrinogen,
complement fragments, and several extracellular matrix components are among the host
proteins bound by cell wall
proteins.
Proteins related to the hsp70 and hsp90 families of conserved
stress proteins and some glycolytic
enzyme proteins are also found in the cell wall, apparently as bona fide components. In addition, the expression of some
proteins is associated with the morphological 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.