UNC5B activates hepatic stellate cells and promotes liver fibrosis via FAK.

BACKGROUND: Liver fibrosis represents a critical stage in the progression of chronic liver diseases toward cirrhosis and hepatocellular carcinoma. However, there are no targeted therapies specifically designed for the treatment of liver fibrosis. This research aims to identify novel targets for anti-hepatic fibrosis and to provide new insights into therapeutic strategies for addressing this condition. METHODS: Dual-luciferase reporter assays and chromatin immunoprecipitation (ChIP) analyses were conducted to assess the modulation of UNC5B gene transcription. Co-immunoprecipitation experiments were performed to investigate the interactions between UNC5B and Src homology phosphotyrosyl phosphatase 2 (SHP2) or Focal adhesion kinase (FAK) proteins. Virtual screening was utilized to identify small-molecule inhibitors of UNC5B. The in vivo effects of Unc5b knockdown in liver fibrosis mouse models were evaluated using an Unc5b inhibitor (D359-0264) and an adeno-associated virus vector of serotype 6 (AAV6) containing short hairpin RNA targeting Unc5b. RESULTS: This study demonstrates that the pro-fibrotic pathway TGF-β1/SMAD3 transcriptionally regulates UNC5B expression. Unc5b expression was significantly upregulated in liver fibrosis mouse models. Knocking down Unc5b resulted in reduced hepatocyte damage and decreased fibrosis in these models. Additionally, UNC5B was shown to interact with the PTP domain of SHP2 and the Y397 site of FAK, indicating that UNC5B competitively binds to the Y397 site of FAK, thereby inhibiting FAK dephosphorylation by SHP2 and promoting liver fibrosis. CONCLUSION: This study identifies a novel regulatory axis in liver fibrosis models involving UNC5B, which is regulated by the TGF-β/SMAD signaling pathway. UNC5B facilitates liver fibrosis by competitively binding to the Y397 site of FAK with SHP2, thus enhancing its phosphorylation and activating FAK. Furthermore, the UNC5B inhibitor has demonstrated the therapeutic potential of targeting this molecule for the treatment of liver fibrosis.