USP9X deubiquitinates TRRAP to promote glioblastoma cell proliferation and migration and M2 macrophage polarization.

Glioblastoma (GBM) is the most aggressive form of brain cancer, characterized by rapid growth and invasion into surrounding brain tissue. Ubiquitin-specific protease 9X (USP9X) has emerged as a key regulator in various cancers, but its role in GBM pathogenesis remains unclear. Understanding the molecular mechanisms underlying USP9X modulation of GBM progression could unveil potential therapeutic targets for this deadly disease. The mRNA and protein levels were determined in GBM tissues and/or cells using quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting assays, respectively. Cell migration was evaluated through wound-healing assay, while cell proliferation was measured using colony formation and CCK-8 assays. Flow cytometry analysis was performed to quantify the CD206-positive macrophages to assess M2 polarization. Co-immunoprecipitation (Co-IP) assays were conducted to elucidate the association between USP9X and transformation/transcription domain-associated protein (TRRAP). Cycloheximide (CHX) treatment was used to determine the impact of USP9X on TRRAP protein stabilization. Furthermore, the effect of USP9X depletion on GBM cell malignancy was validated using a xenograft mouse model. We found that USP9X expression was elevated in GBM tissues and cells. Depletion of USP9X suppressed GBM cell migration, proliferation, and M2 macrophage polarization. Mechanistically, USP9X stabilized TRRAP through the deubiquitination pathway in GBM cells, and TRRAP mitigated the effects of USP9X silencing on GBM cell malignant phenotypes and M2 macrophage polarization. Moreover, silencing of USP9X inhibited tumor formation in vivo. Together, USP9X deubiquitinated TRRAP, thereby promoting glioblastoma cell proliferation, migration, and M2 macrophage polarization. These results highlight the potential of targeting the USP9X-TRRAP axis as a therapeutic strategy for GBM.