BRSK2 accumulation mediated by TRIM28 accelerates hepatocellular carcinoma progression via activating the PI3K/AKT/mTOR signaling pathway.

BR serine/threonine kinase 2 (BRSK2) plays critical roles in neuronal polarization, cell cycle progression, and glucose-stimulated insulin secretion. However, its function in HCC remains unknown. Through bioinformatics analysis of public databases, we identified BRSK2 as a PCD-related gene with potential clinical diagnostic value in HCC. Functionally, BRSK2 knockdown significantly suppressed the proliferation, migration, and invasion of HCC cells and promoted apoptosis in vitro, as well as inhibited tumor growth in a xenograft mouse model in vivo. Mechanistically, we found that BRSK2 is associated with the PI3K/AKT signaling pathway, and western blot analysis confirmed that BRSK2 silencing attenuates PI3K/AKT activation in HCC cells. Furthermore, immunoprecipitation-mass spectrometry (IP-MS) analysis revealed that the elevated expression of BRSK2 in HCC is associated with post-translational regulation. Tripartite Motif Containing 28 (TRIM28) was identified as a BRSK2-interacting protein that upregulates BRSK2 protein levels. In vitro ubiquitination assays demonstrated that TRIM28 suppresses BRSK2 ubiquitination, leading to its accumulation in HCC cells. Finally, rescue experiments showed that BRSK2 silencing abrogates TRIM28 overexpression-induced enhancement of HCC cell proliferation, PI3K/AKT/mTOR activation, and resistance to apoptosis. Collectively, these findings uncover that TRIM28 prevents ubiquitin-proteasomal degradation of BRSK2, thereby enhancing its protein stability and activating the PI3K/AKT/mTOR signaling pathway to promote HCC progression.