Abstract
The echinocandins (e.g., caspofungin) are a relatively new class of antifungal drugs that function by inhibiting the synthesis of β-1,3-glucan in the cell wall and thus lead to lysis of the cell. In this work the effect of caspofungin on the release of peptides from non-growing cells of the yeast Candida albicans that had been exposed to the drug was monitored. Exposure to 0.19 μg/ml caspofungin resulted in the release of amino acids from cells and of both small and large molecular weight proteins as demonstrated by 1- and 2-dimensional gel electrophoresis. Matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-ToF) mass spectrometry was employed to identify a number of escaped peptides that were found to have increased in intensity upon exposure to the drug. A number of wall-associated proteins (e.g., phosphoglycerate kinase) and a number of glycolytic enzymes (phosphoglycerate mutase 1, fructose-bisphosphate aldolase) were identified. Importantly, several released proteins (e.g., pyruvate kinase, enolase 1, phosphoglycerate mutase, glyceraldehydes 3-phosphate dehydrogenase, fructose bisphosphate aldolase and alcohol dehydrogenase 1) are highly immunogenic in nature. The results presented here demonstrate that non-growing C. albicans cells are susceptible to the effect of caspofungin and that the caspofungin-mediated release of proteins from such cells could lead to a stronger immune response in vivo. This report illustrates that, in addition to hampering cell wall synthesis, caspofungin may also interfere with the permeability of the fungal cell wall.
Acknowledgements
This work was supported by funding from the Higher Education Authority of Ireland through the Programmes for Research in Third Level Institutes 3 and 4.
Declaration of interest: The authors have no conflicts of interest to disclose.
This paper was first published online on Early Online on 15 April 2010.