A pool of Plasmodium falciparum casein kinase 1 (PfCK1) has been shown to localize to the host red blood cell (RBC) membrane and be secreted to the extracellular medium during trophozoite stage of development. We attempted to identify mechanisms for secretion of PfCK1 and its appearance on the RBC membrane. We found that two host proteins with established functions in membrane trafficking in higher eukaryotes, GTPase‐activating protein and Vps9 domain‐containing protein 1 (GAPVD1), and Sorting nexin 22, consistently co‐purify with PfCK1, suggesting that the parasite utilizes trafficking pathways previously thought to be inactive in RBCs. Furthermore, reciprocal immunoprecipitation experiments with GAPVD1 identified parasite proteins suggestive of a protein recycling pathway hitherto only described in higher eukaryotes. Thus, we have identified components of a trafficking pathway involving parasite proteins that act in concert with host proteins, and which we hypothesize mediates trafficking of PfCK1 to the RBC during infection.

中文翻译：

---

恶性疟原虫酪蛋白激酶 1 与宿主细胞蛋白运输机制成分的相互作用

已显示恶性疟原虫酪蛋白激酶 1 (PfCK1) 池定位于宿主红细胞 (RBC) 膜，并在滋养体发育阶段分泌到细胞外培养基中。我们试图确定 PfCK1 的分泌机制及其在 RBC 膜上的出现。我们发现两种在高等真核生物中具有确定的膜运输功能的宿主蛋白，即 GTPase 激活蛋白和含有 Vps9 结构域的蛋白 1 (GAPVD1) 和 Sorting nexin 22，始终与 PfCK1 共同纯化，表明寄生虫利用运输途径以前认为在红细胞中不活跃。此外，GAPVD1 的相互免疫沉淀实验确定了寄生虫蛋白质，暗示了迄今为止仅在高等真核生物中描述的蛋白质回收途径。因此，