Figure 4.

PfArf1 and PfRab1b regulated the export of PEXEL-positive Rifin to the erythrocyte cytoplasm. Parasites expressing Rifin-RFP and PfArf1-YFP-DD (A, B) or DD-YFP-PfRab1b (C, D) were examined via the immunofluorescence assay. Fluorescence signals from RFP (red), YFP (green), and DAPI (blue) are shown. Wild-type PfArf1 or PfRab1b (upper panels), active mutant PfArf1^Q71L or PfRab1b^Q67L (middle panels), and the inactive mutant PfArf1^T31N or PfRab1b^S22N (lower panels) are shown. White dotted lines indicate the parasite plasma membrane. The arrowheads indicate dot-like exported Rifin-RFP signals. The bars indicate 2 µm. The rate of parasites that showed a Rifin-RFP signal was detected in the erythrocyte cytoplasm in PfArf1-RFP (B) and RFP-PfRab1b (D) expressing cells are shown in graphs. Thirty individual early trophozoites and early schizonts were counted from three independent experiments. Infected RBCs, recognized by the DAPI and YFP signals under the microscope, were imaged by the laser microcopy, and then analyzed for the localization of RFP and whether Rifin-RFP was exported to the iRBC. The statistical significance was determined using the Student’s t-test.