Abstract text

Introduction: During their development within the vertebrate host, Plasmodium parasites invade and proliferate in hepatocytes and red blood cells. Within these cells, parasites are surrounded by a parasitophorous vacuole membrane (PVM). Consequently, for their release from host cells and to propagate the infection, parasites have to disrupt the PVM and the host cell membrane in the process of egress. Despite its importance, only a few parasite proteins have been identified so far to be involved in host cell egress and the underlying molecular mechanism is not well understood. An important regulator of egress is the subtilisin-like serine protease 1 (SUB1), which localizes to specialized secretory organelles. SUB1 is released into the parasitophorous vacuole, where it activates other proteins involved in egress.

Objectives: In this study, we aimed to identify novel proteins that might be processed by SUB1 and that might exert important functions for parasite release from host cells.

Materials & methods: To probe into the pool of SUB1 substrates, we generated parasites conditionally expressing SUB1 fused to the ascorbate peroxidase APEX2 and used these for proximity-dependent biotinylation.

Results: Mass spectrometry-based analysis of SUB1-APEX2 parasites after proximity-dependent biotinylation resulted in 24 putative SUB1 interactors, including 13 known or predicted SUB1 substrates. To understand their function, especially in light of parasite egress from its host cell, we are currently characterizing four of these potential SUB1 interactors using reverse genetics.

Conclusion: Parasites conditionally expressing SUB1 fused to the ascorbate peroxidase APEX2 might be a powerful tool to screen for novel SUB1 substrates.