Stage-specific expression and localization of ETRAMP4 during gametocyte development in the malaria parasite Plasmodium falciparum.

The early transcribed membrane protein 4 (ETRAMP4) is one of 14 predicted members of the ETRAMP family in the malaria parasite Plasmodium. All characterized ETRAMP proteins localize to the parasitophorous vacuole membrane (PVM) and associated membranous structures during the early stages of parasite infection of erythrocytes; and are thought to participate in host-parasite material transport, which is critical for parasite development. In this study, we investigated the stage-specific expression and subcellular localization of ETRAMP4 during the asexual and gametocyte intraerythrocytic stages. Indirect immunofluorescence assays revealed that ETRAMP4 is prominently detected in immature stage I and II gametocytes; whereas no detectable signal was observed in stage III to V gametocytes or in asexual blood-stage parasites under our experimental conditions. Immunoelectron microscopy demonstrated that ETRAMP4 predominantly localizes to the PVM and PVM-derived membranous structures extending into the host erythrocyte cytoplasm, suggesting a potential role in membrane dynamics during early gametocyte development.