LC-MS of interacting partners Toxoplasma gondii GRA57

We identified GRA57 as a Toxoplasma gondii secreted effector required for parasite survival of interferon gamma in HFFs. To identify interaction partners of GRA57 during infection of HFFs, which could indicate how GRA57 functions to protect the parasite, we performed co-immunoprecipitation (IP) experiments with an endogenously tagged RHGRA57-HA strain.To enable detection of protein-protein interactions specific to activated cells, HFFs were pre-stimulated before infection with 2.5 U/ml IFN for 6 h, which we found was sufficient to induce IFN responses while retaining host cell viability. HFFs were infected for 24 h with either RH∆Ku80 or RHGRA57-HA parasites prior to lysis. GRA57-HA was immunoprecipitated from lysates, then co-immunoprecipitated proteins were identified by liquid chromatography (LC)-tandem mass spectrometry (MS/MS).