The influence of Aspergillus fumigatus fatty acid oxygenases PpoA and PpoC on caspofungin susceptibility

<i>Aspergillus fumigatus</i> can cause Invasive Pulmonary Aspergillosis (IPA). Fungicidal azoles and fungistatic caspofungin (CAS) are the first- and second-line therapies, respectively, used to treat IPA. Treatment of <i>A. fumigatus</i> with CAS or micafungin induces production of the oxylipin 5,8-diHODE by the fungal oxygenase PpoA. Here we investigated the influence of ppo genes, that encode fatty acid oxygenases responsible for oxylipin biosynthesis, on CAS tolerance. PpoA and PpoC influence on CAS tolerance is mediated by MpkA phosphorylation and protein kinase A (PKA) activity. RNAseq transcriptional profiling and label-free quantitative proteomics of the ppoA and ppoC mutants showed that differentially expressed genes and proteins are related to secondary metabolites and carbohydrate metabolism. We also characterized two clinical isolates, CM7555 and IFM61407, that have decreased and increased susceptibility to CAS, respectively. CM7555 does not have increased oxylipin production in the presence of CAS while the oxylipin induction upon CAS exposure is increased in the IFM61407, suggesting oxylipins are not the single mechanism involved in CAS tolerance in these isolates. Upon CAS exposure, CM7555 has higher MpkA phosphorylation and PKA activity than IFM61407. Our results reveal different aspects and genetic determinants involved in <i>A. fumigatus</i> CAS tolerance.