Functional characterization of genes encoding cadmium pumping P 1B -type ATPases in Aspergillus fumigatus and Aspergillus nidulans .

Several P _1B -type ATPases are important Cd ²⁺ /Cu ²⁺ pumps in Aspergillus species, and they are tightly associated with the heavy metal stress tolerance of these ascomycetous fungi. To better understand the roles of the two P _1B -type ATPases, Aspergillus nidulans CrpA Cd ²⁺ /Cu ²⁺ pump (orthologue of the Candida albicans Crp1 Cd ²⁺ /Cu ²⁺ pump) and Aspergillus fumigatus PcaA Cd ²⁺ pump (orthologue of the Saccharomyces cerevisiae Pca1 Cd ²⁺ pump), we have generated individual mutants and characterized their heavy metal susceptibilities. The deletion of CrpA in A. nidulans has led to the increased sensitivity of the fungus to stresses induced by Zn ²⁺ , Fe ²⁺ , or the combination of oxidative-stress-inducing menadione sodium bisulfite and Fe ³⁺ . Heterologous expression of A. fumigatus PcaA in the S. cerevisiae pca1 deletion mutant has resulted in enhanced tolerance of the yeast to stresses elicited by Cd ²⁺ or Zn ²⁺ but not by Fe ²⁺ /Fe ³⁺ or Cu ²⁺ . Mammalian host immune defense can attack microbes by secreting Zn ²⁺ or Cu ²⁺ , and the oxidative stress induced by host immune systems can also disturb metal (Cu ²⁺ , Fe ²⁺ , and Zn ²⁺ ) homeostasis in microbes. In summary, PcaA and CrpA can protect fungal cells from these complex stresses that contribute to the virulence of the pathogenic Aspergillus species. Moreover, due to their presence on the fungal cell surface, these P _1B -type ATPases may serve as a novel drug target in the future. IMPORTANCE Mammalian host immune defense disrupts heavy metal homeostasis of fungal pathogens. P1B-type ATPase of Aspergillus fumigatus and Aspergillus nidulans may help to cope with this stress and serve as virulence traits. In our experiments, both A. nidulans Cd2+/Cu2+ pump CrpA and A. fumigatus Cd2+ pump PcaA protected fungal cells from toxic Zn2+, and CrpA also decreased Fe2+ susceptibility most likely indirectly. In addition, CrpA protected cells against the combined stress induced by the oxidative stressor menadione and Fe3+. Since P1B-type ATPases are present on the fungal cell surface, these proteins may serve as a novel drug target in the future.