APEX2 proximity labeling maps the mGBP2-proximal proteome at the Toxoplasma gondii parasitophorous vacuole

Interferon-inducible guanylate binding proteins (GBPs) are large GTPases crucial for the host immune response against Toxoplasma gondii , a globally prevalent intracellular apicomplexan parasite. Upon infection, T. gondii forms a parasitophorous vacuole (PV) that protects the parasite from host intracellular defense mechanisms. Murine GBPs (mGBPs) can recognize these PVs and assemble into supramolecular homo- and heterocomplexes, which is an essential step for PV membrane disruption, ultimately enabling cell-autonomous immune control of vacuole-resident pathogens. Our previous work has shown that mGBP2 is an important factor in the immune control of T. gondii . To further elucidate the functions of mGBP2, we employed an APEX2-based proximity labeling strategy to biotinylate proteins in the vicinity of mGBP2 during T. gondii infection. Mass spectrometry analysis of the biotinylated proteins revealed several novel PV-associated proteins such as Cyclooxygenase 2 (COX2/ Ptgs2), Caspase 12 (Cas12), Annexin 11 (Anxa11), Calnexin (Canx), Galectin 3 (Gal3), and Transgelin (Tagln) and valosin-containing protein (VCP) that co-recruit with mGBP2 at T. gondii PVs. In addition, we investigated their regulation by IFN-γ and determined that inhibition of COX2 severely impairs T. gondii growth, highlighting a critical role for COX2 for parasite survival.