TAF15 mediates ROP16-induced apoptosis and cell cycle arrest in lung cancer

This study aimed to investigate the effects of the interaction between ROP16 and TAF15 on apoptosis and cell cycle regulation in A549 lung adenocarcinoma cells.

Lentivirus-infected A549 cells which could overexpress type I, II, and III ROP16, along with an empty vector control group, were established. Potential interacting proteins with ROP16 were identified by using co-immunoprecipitation (Co-IP) and liquid chromatography-mass spectrometry (LC-MS). High-scoring interacting proteins were selected for verification through Venn diagram analysis, scoring, and intensity evaluation. The interaction between ROP16 and TAF15 was confirmed by using co-immunoprecipitation. Moreover, TAF15-specific siRNA was synthesized and transfected into A549 cells overexpressing ROP16 types I, II, and III. The levels of apoptosis and cell cycle were detected by flow cytometry (FCM), and the expression levels of apoptosis-related proteins and cell cycle-related proteins were detected by real-time fluorescence quantitative PCR (RT-qPCR) and western blotting.

Three stable A549 cell lines overexpressing type I, II, and III ROP16 were successfully established. IP-LC/MS identified 29 potential ROP16-interacting proteins, among which 13 had a score greater than 100. Subsequent bioinformatic analysis and co-immunoprecipitation confirmed the interaction between ROP16 and TAF15. Flow cytometry analysis revealed that type I and III ROP16 promoted A549 cell apoptosis and induced cell cycle arrest. Furthermore, western blotting and RT-qPCR demonstrated their modulation of the expression of cell cycle regulators (p21, CDK6, Cyclin D1) and apoptosis-related proteins (Bax, BCL-2, p53, Caspase-9). In contrast, type II ROP16 exhibited none of these effects. However, upon TAF15 silencing, the pro-apoptotic effects of type I and III ROP16 were attenuated, no significant cell cycle arrest was observed, and their regulatory effects on the expression of cell cycle- and apoptosis-related proteins were also significantly diminished.

Our study demonstrates that type I/III ROP16 induce apoptosis and cell cycle arrest in A549 cells through interactions with the host RNA-binding protein TAF15. These findings not only provide compelling evidence for the oncosuppressive potential of Toxoplasma gondii-derived secretory proteins but also uncover a previously unrecognized mechanism by which parasite effectors hijack host transcriptional regulators to subvert cancer cell survival pathways.