Proteomic Evaluation of Aspergillus fumigatus in Response to Caspofungin

CAGAS, STEVEN E.; RAJA JAIN, M.; GARCIA-EFFRON, GUILLERMO; PARK, STEVEN; PERLIN, DAVID S.

San Francisco (EEUU)

Congreso; 49 th Interscience Conference on Antimicrobial Agents and Chemotherapy; 2009

American Society for Microbiology

Background: Aspergillus fumigatus is the most common filamentous fungal pathogen.  Echinocandin drugs are fungistatic against A. fumigatus causing changes in morphology. One member of the class, caspofungin (CSF), was initially approved for salvage therapy against invasive aspergillosis.  Limited data is available on the affect of CSF on A. fumigatus at the molecular level.  To better understand the response of A. fumigatus to CSF, a global proteomic approach was used to assess protein changes. Methods:  Isogenic CSF-susceptible (S) and -resistant (R) A. fumigatus strains were grown for 48 hours in the presence of a sub-inhibitory concentration of CSF (0.12 µg/ml).  Mycelia were separated into soluble and membrane fractions by differential centrifugation.  Each fraction was subjected to 2D gel electrophoresis with a pI range of 5-8 and >1000 proteins were easily distinguished on gels.  Results:  A total of 66 differentially or highly expressed proteins were identified by Mass Spectrometry and another 36 were identified as markers in multiple gels. Changes in the protein profile were seen for both the CSF-R and CSF-S strains with more changes observed in the CSF-S strain.  Cytoplasmic proteins like allergen Asp F3 were highly abundant in both strains. Some proteins changed only in the CSF-S when CSF was present.  Pathways affected included stress response (e.g. Hsp), metabolism (e.g. transaldolase), electron transport (e.g. cytochrome C complex) and translation (e.g. EF-Tu).  Conclusion: Although RNA expression profiling has been widely used for studying A. fumigatus, proteomic techniques provide a more detailed view of the expressed protein profile of the pathogen.  Proteins from different cellular compartments and fractions show differential expression indicating that global changes are occurring after CSF treatment.  These proteins may show compensatory mechanisms or novel proteins involved in CSF resistance which could be used as potential biomarkers or drug targets.