Btg2 Inhibits the UFMylation of Fmo1 thus Restricting Taurine Synthesis and Exacerbating Ferroptosis in Hepatic Ischemia-Reperfusion Injury in Mice

Hepatic ischemia‒reperfusion (I/R) injury (HIRI) represents a frequently occurring pathological phenomenon during liver surgery, yet the mechanisms governing HIRI remain inadequately comprehended. This study intends to explore the role of B-cell translocation gene 2 (Btg2) in HIRI. We find that Btg2 expression is up-regulated following HIRI. We subsequently develop an HIRl model utilizing hepatocyte-specific Btg2 transgenic over-expression and systemic Btg2 knockout male mice, discovering that Btg2 deletion mitigates inflammation and apoptosis. Furthermore, cellular experiments confirm that Btg2 knockdown alleviates inflammation and mitochondrial stress generated by hypoxia/reoxygenation (H/R). Metabolomics reveals enrichment of taurine metabolism pathway in the Btg2-/- mice. Mechanistically, we demonstrate that Btg2 restricts the UFMylation of flavin-containing monooxygenase 1 (Fmo1), the essential enzyme for taurine synthesis, by the E3 ligase UFM1-specific ligase 1 (Ufl1), consequently facilitating the K48 ubiquitination-mediated degradation of Fmo1. Adeno-associated virus-mediated Fmo1 over-expression inhibits ferroptosis and HIRI significantly in vivo, while adenovirus-mediated Btg2 over-expression mitigates ferroptosis and hypoxia/reoxygenation damage in vitro. Moreover, virtual screening of natural compounds reveals that Daturataturin A inhibits Btg2 and attenuates ferroptosis and HIRI sufficiently. These results propose that Btg2 may constitute a promising therapeutics target for HIRI.

肝缺血再灌注（ischemia-reperfusion, I/R）损伤（hepatic ischemia-reperfusion injury, HIRI）是肝脏外科手术中常见的病理现象，但其具体发病机制尚未得到充分阐明。本研究旨在探讨B细胞易位基因2（B-cell translocation gene 2, Btg2）在HIRI中的作用。研究发现，HIRI发生后Btg2的表达显著上调。本研究随后构建了肝细胞特异性Btg2转基因过表达及全身性Btg2敲除的雄性小鼠HIRI模型，结果显示敲除Btg2可减轻炎症反应与细胞凋亡。此外，细胞实验证实，敲低Btg2可缓解缺氧复氧（hypoxia/reoxygenation, H/R）诱导的炎症反应与线粒体应激。代谢组学分析显示，Btg2基因敲除（Btg2-/-）小鼠的牛磺酸代谢通路存在显著富集。从机制层面来看，本研究证实Btg2可通过E3泛素连接酶UFM1特异性连接酶1（UFM1-specific ligase 1, Ufl1）抑制牛磺酸合成关键酶黄素单加氧酶1（flavin-containing monooxygenase 1, Fmo1）的UFM1化修饰，进而促进Fmo1经K48泛素化介导的蛋白质降解。体内实验表明，腺相关病毒介导的Fmo1过表达可显著抑制铁死亡（ferroptosis）与HIRI；而体外实验中，腺病毒介导的Btg2过表达可有效缓解铁死亡及缺氧复氧损伤。此外，天然化合物虚拟筛选结果显示，曼陀罗萜素A（Daturataturin A）可靶向抑制Btg2，并有效缓解铁死亡与HIRI。综上，本研究结果提示Btg2有望成为治疗HIRI的潜在治疗靶点。