An Exported Protein-Interacting Complex involved in the trafficking of virulence determinants in Plasmodium-infected erythrocytes

The human malaria parasite, P. falciparum, generates virulence complexes on the surface of infected red blood cells (RBCs), which include the major virulence antigen Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). The trafficking of PfEMP1 from the parasite to the host cell and its correct display on the RBC surface involves a complement of host and parasite-derived trafficking machineries. In this work we examine the physical organisation of PfEMP1 trafficking intermediates in infected RBCs and determine interacting partners using an epitope-tagged minimal construct (PfEMP1B). We show that PV-located PfEMP1B interacts with components of the Plasmodium Translocon of EXported proteins (PTEX) as well as a novel protein complex we refer to as the Exported Protein-Interacting Complex (EPIC). Within the RBC cytoplasm PfEMP1B interacts with components of the Maurer’s clefts and the RBC chaperonin complex. We define the EPIC interactome and, using an inducible knockdown approach, show that depletion of one of its components, the parasitophorous vacuolar protein-1 (PV1), results in altered knob morphology, reduced cell rigidity and decreased binding of infected RBCs to CD36. Accordingly, we show that deletion of the P. berghei homologue of PV1 is associated with attenuation of parasite virulence in vivo.