The Marine Sponge-Derived Polyketide Endoperoxide Plakortide F Acid Mediates Its Antifungal Activity by Interfering with Calcium Homeostasis

Abstract

ABSTRACT Plakortide F acid (PFA), a marine-derived polyketide endoperoxide, exhibits strong inhibitory activity against the opportunistic fungal pathogens Candida albicans , Cryptococcus neoformans , and Aspergillus fumigatus . In the present study, transcriptional profiling coupled with mutant and biochemical analyses were conducted using the model organism Saccharomyces cerevisiae to investigate the mechanism of action of this compound. PFA elicited a transcriptome response indicative of a Ca 2+ imbalance, affecting the expression of genes known to be responsive to altered cellular calcium levels. Several additional lines of evidence obtained supported a role for Ca 2+ in PFA's activity. First, mutants lacking calcineurin and various Ca 2+ transporters, including pumps (Pmr1 and Pmc1) and channels (Cch1 and Mid1), showed increased sensitivity to PFA. In addition, the calcineurin inhibitors FK506 and cyclosporine strongly enhanced PFA activity in wild-type cells. Furthermore, PFA activated the transcription of a lacZ reporter gene driven by the calcineurin-dependent response element. Finally, elemental analysis indicated a significant increase in intracellular calcium levels in PFA-treated cells. Collectively, our results demonstrate that PFA mediates its antifungal activity by perturbing Ca 2+ homeostasis, thus representing a potentially novel mechanism distinct from that of currently used antifungal agents.