Trem2 negatively regulates the MTOR-PKCα axis to protect against Toxoplasma gondii-induced adverse pregnancy outcomes.

BACKGROUND: Triggering receptor expressed on myeloid cells 2 (Trem2) deficiency aggravated adverse pregnancy outcomes caused by Toxoplasma gondii (T. gondii) infection during pregnancy; however, the precise molecular mechanisms involved remain to be fully elucidated. METHODS: Molecular docking, co-immunoprecipitation, and alanine scanning mutagenesis were employed to identify the interaction between Trem2 and mammalian target of rapamycin (MTOR). In vivo experiments utilized a T. gondii-infected pregnant mouse model with wild-type and Trem2-knockout mice, while in vitro studies were performed using Raw264.7 macrophages and bone marrow-derived macrophages (BMDMs) with T. gondii antigen stimulation, Trem2 overexpression, and siRNA-mediated MTOR knockdown. RESULTS: A direct high-affinity interaction between Trem2 and MTOR was identified, with GLN-198, ARG-195, and LYS-199 as critical binding residues. T. gondii infection significantly downregulated Trem2 expression while upregulating MTOR and its downstream effector protein kinase C alpha (PKCα). Trem2 deficiency exacerbated MTOR-PKCα hyperactivation upon infection and aggravated placental hemorrhage, necrosis, and fetal growth restriction. Conversely, Trem2 overexpression suppressed MTOR and PKCα expression, and MTOR knockdown confirmed that PKCα acts downstream of MTOR. CONCLUSION: Trem2 negatively regulates the MTOR-PKCα axis through direct interaction, and T. gondii infection downregulates Trem2 to relieve this inhibition, leading to MTOR-PKCα hyperactivation and adverse pregnancy complications.