Phospholipases are assumed to weaken the membrane stability of mammalian cells by releasing fatty acids from the phospholipid layer. It has been shown that phospholipase activity contributes to virulence of different Candida species. However, although phospholipase activity was also detected in supernatants of Aspergillus fumigatus isolates, neither one of the responsible proteins has been purified nor has their impact on virulence been studied. Since the genome of A. fumigatus contains several genes coding for secreted phospholipases, a deletion strategy for all coding genes is not recommended. Therefore, we used phospholipid-containing media to screen the supernatants for putative phospholipases by 2-D-gel electrophoresis. Interestingly, although more than 100 protein spots were analysed, none of them coded for one of the annotated phospholipases. In contrast, two extracellular lipases were found, which may contribute to the phospholipase activities detected in former studies. Since both proteins were absent from medium of glucose grown cells, both lipases are specifically induced in the presence of, at least, phospholipids. Currently, we are overproducing the enzymes in A. fumigatus to study their substrate specificity and to use the purified proteins to investigate them for their ability to cause membrane destruction of different mammalian cell lines. Additionally, gene deletions will reveal, whether these lipases contribute to virulence of A. fumigatus.
Full conference title:
9th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 9th (2008)