Characterization of a cDNA of peroxiredoxin II responding to hydrogen peroxide and phagocytosis in Amoeba proteus.

Phagocytic cells have defense systems against reactive oxygen species generated as the first non-specific defense mechanism against invading pathogens or microorganisms. We cloned a cDNA encoding a 21.69-kDa protein in Amoeba proteus homologous to 2-Cys peroxiredoxin (Prx-Ap). In the disk inhibition assay using H2O2 as an oxidizing agent, Escherichia coli overproducing Prx-Ap showed better viability than did E. coli transformed with pBluescript II SK for control. Monoclonal antibodies (mAb) produced against Prx-Ap reacted with a 22.5-kDa protein and several minor proteins. In Western blot analysis, levels of the 22.5-kDa protein in amoebae treated with 2-mM H2O2 for 1 h increased about 2-fold over those in control cells. Immunofluorescence scattered throughout the cytoplasm also increased after H2O2 treatment. In Northern blot analysis using the cDNA as a probe, the level of transcripts also changed with H2O2 treatment. When amoebae were fed with Tetrahymena, the intensity of immunofluorescence increased from 15 min and persisted until 2 h after phagocytosis. These results suggest that the 22.5-kDa protein of A. proteus is a Prx protein and that it has an antioxidant property responding to phagocytosis.