TgSEC14-LTP1 is a vacuole-secreted SEC14/CRAL-TRIO-like protein required for host DAG flux and PC homeostasis in T. gondii.

Intracellular apicomplexan parasites depend on host-derived lipids to expand the parasitophorous vacuole (PV) and replicate. Toxoplasma gondii secretes numerous dense granule proteins (GRAs) for PV remodeling, but PV lumen factors that selectively bind host lipids and shape host-to-parasite lipid flux remain poorly defined. Here, we identify TgSEC14-LTP1, a previously uncharacterized GRA with a divergent SEC14/CRAL-TRIO domain. Structural and genetic analyses show that TgSEC14-LTP1 is secreted into the PV lumen and is essential for parasite replication. Lipidomic profiling, protein-lipid pulldown assays, 13C-labeling-based lipid flux analysis, and fluorescent lipid uptake assays show that TgSEC14-LTP1 binds phosphatidylcholine (PC) and diacylglycerol (DAG) and is required for efficient host-to-parasite PC and DAG flux and parasite lipid homeostasis. TgSEC14-LTP1 depletion reduces parasite PC and DAG pools, disrupts bulk PC synthesis and parasite biogenesis, delays egress, and ultimately impairs growth. These findings identify TgSEC14-LTP1 as a key Sec14-like PV lumen factor that links lipid binding to host lipid acquisition and PC homeostasis, underscoring the importance of host lipid scavenging for parasite survival.