LYN-mediated phosphorylation promotes TJP1 deubiquitination via USP8 to drive neovascularization and tumorigenesis in bladder cancer

As a highly vascularized tumor, the recurrence and metastasis of bladder cancer (BLCA) are closely related to tumor angiogenesis. We previously identified that TJP1 as an important target in the regulation of BLCA vasculogenesis regulation. However, the molecular mechanisms and related signaling pathways still require characterization. In this study, we reported that the overexpression of deubiquitinase-USP8 obviously increased the expression and stability of TJP1, thereby promoting BLCA neovascularization. Mechanistically, USP8 competitively bound to TJP1, preventing the ubiquitin-mediated degradation of TJP1 by the E3 ligase TRIM21 through the TJP1 K695 site. Furthermore, LYN kinase-mediated phosphorylation of TJP1 played a key role in the ubiquitination regulation by USP8 and TRIM21, improving TJP1 stability. In addition, phosphorylated TJP1 significantly increased binding to TWIST1, thereby increasing the nuclear localization of TJP1/TWIST1 complex and thus promoting transcriptional activation of CCL2, ultimately leading to BLCA vascular remodeling. Moreover, the LYN inhibitor combined with the USP8 inhibitor obviously decreased the lung metastasis of BLCA cells in murine tumor models. In conclusion, our findings shed new light on the function of TJP1 function in BLCA and provide favorable evidence that TJP1 and its upstream molecules might be new targets for BLCA treatment.