Candida albicans Ssa: An Hsp70 Homologue and Virulence Factor
Candida albicans is a member of the normal oral and gut microbiota and is also an opportunistic pathogen causing oral and genital infections in humans. Two of the Hsp70 proteins of this organism, Ssa 1 and Ssa 2, show unusual biological actions, presumably moonlighting actions, which contribute to the interaction of this yeast with its host. Both Ssa 1/2 are found on the outer surface of the fungus and this location provides novel functions for these proteins. It also appears to be an Achilles heel of this fungus. The Hsp70 proteins are highly immunogenic and so the surface location of Ssa 1/2 makes a good immunological target for innate and adaptive immune responses to this organism and also suggests these proteins could be vaccine candidates. Surprisingly, Ssa 1/2 binds to the antifungal peptide Histatin (Hst) 5 and enables this toxic molecule to be taken up by the yeast causing cell death. In spite of these findings, C. albicans lacking Ssa 1, but not Ssa 2, were significantly less virulent in infected mice and this was related to the loss of invasiveness of this fungus. Thus these Hsp70 proteins play unexpected roles in the lifestyle of C. albicans.
KeywordsHeat Shock Protein Hsp70 Protein Heat Shock Response Client Protein Oral Candidiasis
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