Thioredoxin-dependent peroxidase as cytoplasmatic redox-sensor in Neospora caninum

The apicomplexan protozoan Neospora caninum, the etiological agent of neosporosis, is associated with neurological symptoms in dogs and abortion in cattle. This disease is worldwide spread and has no efficient treatment(1). The survival and replication of the parasite depend on an enzymatic antioxidant system defense for evading the oxidative stress inside the host cell(2). We investigated the localization and role of Thioredoxin-dependent peroxidase (NcPrx) in the antioxidant system of N. caninum. Flow cytometry analyses demonstrated that H2O2 treatment (1mM and 500uM) increased significantly ROS production in N. caninum tachyzoite. Further, NcPrx showed a significant increase of dimerization/hyperoxidation in N. caninum tachyzoites treated with H2O2 for 1h15min, detected by western blot analyses. Finally, NcPrx was found in the cytoplasmatic compartment by confocal analysis. These results suggest that NcPrx is a cytoplasmatic redox sensor in N. caninum and its oxidative state provide insight into disturbances of tachyzoite redox homeostasis over drug treatments.