Toxoplasma gondii effector GRA35 mediates neuronal damage via ER stress and mitochondria-associated apoptosis

Encephalitis resulting from acute reactivation of chronic Toxoplasma gondii infection in the central nervous system poses a significant mortality risk in immunodeficient individuals. However, the specific molecular mechanisms underlying this process remain elusive. We constructed the GRA35 gene knockout ME49 strain and compared the differences with wild type ME49 strain. We used the GST-pull down experiment to explore the mechanism of GRA35 promoting neuronal cell apoptosis. We used immunofluorescence, flow cytometry and CCK8 experiments to verify the pathway of GRA35 promoting neuronal cell apoptosis. Our study reveals that wild type ME49 strain promotes neuronal apoptosis in brain following chronic infection activation. Conversely, infection with the ME49Δgra35 strain leads to a reduced apoptotic response in brain neurons. Furthermore, we demonstrate that GRA35 interacts with RTN1-c, thereby promoting mitochondrial pathway-mediated apoptosis in neurons. Additionally, GRA35 can trigger host cell ER stress-associated apoptosis through the PERK signaling pathway. GRA35 serves as a crucial virulence factor in the pathogenesis of Toxoplasmic encephalitis (TE), which offers potential new therapeutic target and theoretical insights for TE.