Inhibition of heat-shock protein 90 enhances the susceptibility to antifungals and reduces the virulence of Cryptococcus neoformans/Cryptococcus gattii species complex

Abstract

Heat-shock proteins (Hsps) are chaperones required for the maintenance of cellular homeostasis in different fungal pathogens, playing an important role in the infectious process. This study investigated the effect of pharmacological inhibition of Hsp90 by radicicol on the Cryptococcus neoformans/Cryptococcus gattii species complex -agents of the most common life-threatening fungal infection amongst immunocompromised patients. The influence of Hsp90 inhibition was investigated regarding in vitro susceptibility to antifungal agents of planktonic and sessile cells, ergosterol concentration, cell membrane integrity, growth at 37 8C, production of virulence factors in vitro, and experimental infection in Caenorhabditis elegans. Hsp90 inhibition inhibited the in vitro growth of planktonic cells of Cryptococcus spp. at concentrations ranging from 0.5 to 2 mg ml 21 and increased the in vitro inhibitory effect of azoles, especially fluconazole (FLC) (P,0.05). Inhibition of Hsp90 also increased the antifungal activity of azoles against biofilm formation and mature biofilms of Cryptococcus spp., notably for Cryptococcus gattii. Furthermore, Hsp90 inhibition compromised the permeability of the cell membrane, and reduced planktonic growth at 37 8C and the capsular size of Cryptococcus spp. In addition, Hsp90 inhibition enhanced the antifungal activity of FLC during experimental infection using Caenorhabditis elegans. Therefore, our results indicate that Hsp90 inhibition can be an important strategy in the development of new antifungal drugs.

Identification of cyclosporin C from Amphichorda felina using a Cryptococcus neoformans differential temperature sensitivity assay

“…However, application of temperature sensitivity screening for antibiotics that interfere with thermal adaption is a relatively newly recognized possibility (Cordeiro et al 2016; Cowen et al 2009; Steinbach et al 2007). We have shown that a simple two-plate temperature sensitivity assay detected cyclosporins in crude extracts from fungal fermentations.…”

Environmental Factors That Contribute to the Maintenance of Cryptococcus neoformans Pathogenesis

“…For example, cells can deploy heat shock protein 90 (hsp90) that is critical in thermotolerance [83]. Hsp90 is a molecular chaperone that is universal in all eukaryotic organisms and is responsible for regulating the morphology of C. neoformans at high temperatures [84,85]. This protein is documented to be expressed at low levels at 25 • C to suppress the expression of heat shock transcriptional factor (HSF) [86].…”

Combinatorial strategies for combating invasive fungal infections

“…[98][99][100] In S. cerevisiae, C. albicans, C. neoformans and C. gattii pharmacological inhibition of Hsp90 impairs the evolution of azole resistance and potentiates azole activity in vitro. [101][102][103] Moreover, in C. albicans, C. glabrata and A. fumigatus, Hsp90 enables basal tolerance and resistance to the echinocandins. [104][105][106][107] In Caenorhabditis elegans and murine models of fungal pathogenesis, combination therapy with Hsp90 inhibitors with caspofungin or fluconazole improves survival upon infection with A. fumigatus or C. albicans and C. neoformans, respectively.…”