Toxoplasma gondii is a master manipulator capable of exploiting the resources from the host cell for its intracellular subsistence. However, the extent to which the parasite-host interactions influence the parasite’s nutrient acquisition remains to be elucidated. Residing within a non-fusogenic vacuole, the parasite encounters a barrier when it scavenges food that needs to cross the parasitophorous vacuole (PV) membrane. We discovered a potential role for the Endosomal Sorting Complex Required for Transport (ESCRT) machinery in host cytosolic protein uptake by T. gondii after disruption of host ESCRT function. Dense granule (GRA) secretory proteins are important for remodeling and maintenance of the PV to support intracellular replication and for mediating host-microbe interactions. We have identified the transmembrane dense granule protein GRA14, that contains cytosolically exposed motifs homologous to the late domain motifs of the HIV Gag, as a candidate for the recruitment of the host ESCRT machinery to the PV membrane. Using an HIV virus-like particle (VLP) release assay, we found that the motif-containing portion of GRA14 is sufficient to substitute for HIV Gag late domain to mediate ESCRT-dependent VLP budding. Furthermore, proximity ligation assay and co-immunoprecipitation data support our working hypothesis for an interaction between GRA14 and host ESCRT components during infection. Lastly, analysis of GRA14-deficient parasites revealed a marked reduction in ingestion of a host cytosolic protein compared to WT parasites. Thus, as a working model we propose that host ESCRT components interact with GRA14 at the PV membrane to trigger the formation of vesicles containing host cytosolic material that further bud into the PV lumen and are endocytosed by the parasite. Future studies are expected to provide insight on a novel mechanism of how T. gondii acquires host-derived resources to support its replication and development of infection.
