Echinocandin Drugs Induce Differential Effects in Cytokinesis Progression and Cell Integrity

Abstract

Fission yeast contains three essential β(1,3)-D-glucan synthases (GSs), Bgs1, Bgs3, and Bgs4, with non-overlapping roles in cell integrity and morphogenesis. Only the bgs4+ mutants pbr1-8 and pbr1-6 exhibit resistance to GS inhibitors, even in the presence of the wild-type (WT) sequences of bgs1+ and bgs3+. Thus, Bgs1 and Bgs3 functions seem to be unaffected by those GS inhibitors. To learn more about echinocandins’ mechanism of action and resistance, cytokinesis progression and cell death were examined by time-lapse fluorescence microscopy in WT and pbr1-8 cells at the start of treatment with sublethal and lethal concentrations of anidulafungin, caspofungin, and micafungin. In WT, sublethal concentrations of the three drugs caused abundant cell death that was either suppressed (anidulafungin and micafungin) or greatly reduced (caspofungin) in pbr1-8 cells. Interestingly, the lethal concentrations induced differential phenotypes depending on the echinocandin used. Anidulafungin and caspofungin were mostly fungistatic, heavily impairing cytokinesis progression in both WT and pbr1-8. As with sublethal concentrations, lethal concentrations of micafungin were primarily fungicidal in WT cells, causing cell lysis without impairing cytokinesis. The lytic phenotype was suppressed again in pbr1-8 cells. Our results suggest that micafungin always exerts its fungicidal effect by solely inhibiting Bgs4. In contrast, lethal concentrations of anidulafungin and caspofungin cause an early cytokinesis arrest, probably by the combined inhibition of several GSs.

Analysis of the Localization of Schizosaccharomyces pombe Glucan Synthases in the Presence of the Antifungal Agent Caspofungin

“…In S. pombe, the fact that the bgs4 + mutant strains pbr1-8 and pbr1-6 exhibit resistance to echinocandins and other classes of βGS antifungals, even in the presence of the wild-type (WT) sequences of bgs1 + and bgs3 + , suggests that the two encoding synthases, Bgs1 and Bgs3, might be naturally resistant to the currently available βGS inhibitors [30]. However, recent findings show that lethal concentrations of anidulafungin and caspofungin produce early cytokinesis arrest in S. pombe WT and pbr1-8 mutant cells, suggesting at least a partial combined inhibition of several βGSs [50].…”

“…Both the conservation of β(1-3)glucan synthesis and the corresponding βGS enzymes across the fungi kingdom and the presence of three essential βGS catalytic subunits exhibiting both differential antifungal susceptibility and non-redundant essential roles in β(1-3)glucan synthesis, together with the absence of cell wall chitin and, therefore, chitinderived compensatory mechanisms, make S. pombe an ideal tool for studying resistance and the mechanism of action of echinocandins despite its lack of pathogenicity [30,50]. The GS subunits Bgs1, Bgs3, Bgs4, and Ags1 are each essential for cell viability as a result of their different impacts on cytokinesis and cell integrity.…”

“…Other studies with echinocandins analyzed the long-term effect of antifungals. However, in this study, in order to diminish the consequences of cell wall compensatory mechanisms that might alter the caspofungin-derived phenotypes [50][51][52], microscopy fluorescence imaging was performed during the first 3 h of treatment with both sublethal (non-inhibitory) and lethal (inhibitory) concentrations of caspofungin. Surprisingly, we observed a fungicidal effect and cell death at sublethal concentrations and a fungistatic effect of cell growth arrest and an absence of cell death at lethal concentrations.…”

Photonic Si microwell architectures for rapid antifungal susceptibility determination of Candida auris

“…2B-ii) appear round and swollen – characteristic of morphological changes induced by this type of antifungal agent. 29 In the case of amphotericin B, cells exhibit a deformed appearance, which is ascribed to cell membrane damage (Fig. 2B-iii).…”

Advances in Antifungal Development: Discovery of New Drugs and Drug Repurposing

“…Using the fission yeast Schizosaccharomyces pombe (a model fungal system), Yagüe et al [ 22 ] determined that various echinocandin drugs induce differential effects in cytokinesis progression and cell integrity in fungi. S. pombe contains three β(1,3)-D-glucan synthases (GSs), Bgs1, Bgs3, and Bgs4, which exert essential functions with non-overlapping roles involved in maintaining cell integrity and morphogenesis.…”