Background: The echinocandin micafungin (MFG) inhibits the activity of glucan synthase (GS), thus damaging the fungal cell wall. Transcriptome analysis identified genes that are differentially expressed upon exposure to MFG in a wild type A.fumigatus strain (WT, MEC 0.01Âµg/ml), and a strain with reduced susceptibility to echinocandins (S678Y, MEC 1-2Âµg/ml). Strain S678Y contains a target site mutation within the AfFKS1 gene, encoding the putative catalytic subunit of GS. Methods: To identify MFG-responsive genes in A.fumigatus, we determined the transcriptome profiles of strains which were exposed to varying levels of drug for 4 hours at 37ºC. Results: Exposure of WT A. fumigatus to MFG induced the expression of genes encoding proteins which are involved in the structure and maintenance of the cell wall, such as glucan synthases, GPI proteins and cell wall processing enzymes. Increased expression of genes involved in cell stress response, transcriptional regulation and transport was also observed. Further indication of cell stress response was shown by down regulation of genes involved in ribosomal protein synthesis and RNA metabolism. The transcriptome profile of strain S678Y upon exposure to 4Âµg/ml MFG was comparable to that of the WT strain, indicating a similar physiological response. However, an altered expression profile of cell wall-related and stress response genes was observed at 0.5Âµg/ml MFG for strain S678Y, suggesting a drug tolerance mechanism in this strain is dose dependent. Conclusion: Modulation of cell wall architecture is known to occur in response to changing environmental conditions. Our results have indicated that exposure of A. fumigatus to MFG leads to cell wall remodeling and a general stress response, which is consistent with comparable studies of Saccharomyces cerevisiae and Candida albicans. Further investigation is underway to identify additional genes implicated in MFG tolerance in strain S678Y.
Full conference title:
46th Interscience Conference on Antimicrobial Agents and Chemotherapy
- ICAAC 46th