Interaction of Plasmodium falciparum Casein kinase 1 (PfCK1) with components of host cell protein trafficking machinery.

Abstract

During infection, the Plasmodium falciparum casein kinase 1 (PfCK1) is secreted to the extracellular medium and appears on the RBC membrane during trophozoite stage of development. We attempted to identify a mechanism that describes the secretion of PfCK1 and its appearance on the RBC membrane and suspected a mechanism involving multiple host proteins may be utilised. Indeed, we found that the host proteins GTPase-activating protein and Vps9 domain-containing protein (GAPVD1) and Sorting nexin 22 (SNX22), which have described functions in membrane trafficking in higher eukaryotes, consistently co-purify with PfCK1 suggesting the parasite utilises trafficking pathways previously thought to be inactive in RBCs. Further, reciprocal immunoprecipitation experiments with GAPVD1 identified parasite proteins suggestive of a recycling pathway hitherto only described in higher eukaryotes to recycle membrane proteins. Thus, we have identified components of a trafficking pathway involving parasite proteins that act in concert with host proteins which we hypothesise coordinate the trafficking of PfCK1 during infection.