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Abstract：
Hepatitis C virus (HCV) infection causes abnormal lipid metabolism in hepatocytes, which leads to hepatic steatosis and even hepatocellular carcinoma. HCV nonstructural protein 4B (NS4B) has been reported to induce lipogenesis, but the underlying mechanism is unclear. In this study, western blots were performed to investigate the effect of NS4B protein levels on key effectors of the Hippo and AKT signaling pathways. Yes-associated protein (YAP) and moesin-ezrin-radixin-like protein (Merlin) are effectors of the Hippo pathway. NS4B downregulated Merlin and phosphorylated YAP (p-YAP) protein expression while increasing the expression of the key AKT pathway proteins p-AKT and NF-κB. By observing the levels of AKT pathway proteins when Merlin was overexpressed or silenced, it was determined that Merlin mediates the AKT pathway. We suggest that HCV NS4B may mediate the AKT signaling pathway by inhibiting the Hippo pathway. Lipid droplets were observed in Huh7.5 cells overexpressing NS4B, and they increased significantly in number when Merlin was silenced. Overexpression of NS4B and Merlin silencing enhanced the expression of sterol regulatory element binding proteins (SREBPs), which have been demonstrated to be key regulatory factors controlling fatty acid synthesis. NS4B and Merlin silencing also enhanced the in vitro proliferative capacity of hepatocellular carcinoma cells. In conclusion, NS4B induces lipogenesis via the effect of the Hippo-YAP pathway on the AKT signaling pathway and thereby plays a significant role in the pathogenesis of HCV-associated diseases.
摘要：
丙型肝炎病毒（HCV）感染导致肝细胞脂质代谢异常，导致肝脏脂肪变性甚至肝细胞癌。HCV非结构蛋白4B（NS4B）已被报道诱导脂肪生成，但潜在的机制尚不清楚。在这项研究中,进行蛋白质印迹以研究NS4B蛋白水平对Hippo和AKT信号通路的关键效应子的影响。Yes相关蛋白（YAP）和膜蛋白-ezrin-radixin样蛋白（Merlin）是Hippo途径的效应子。NS4B下调Merlin和磷酸化YAP（p-YAP）蛋白的表达，同时增加关键AKT途径蛋白p-AKT和NF-κB的表达。通过观察Merlin过表达或沉默时AKT通路蛋白的水平,已确定Merlin介导AKT途径。我们认为HCVNS4B可能通过抑制Hippo途径介导AKT信号通路。在过表达NS4B的Huh7.5细胞中观察到脂滴，当梅林沉默时，它们的数量显著增加。NS4B的过表达和Merlin沉默增强了固醇调节元件结合蛋白（SREBPs）的表达，已被证明是控制脂肪酸合成的关键调节因素。NS4B和Merlin沉默也增强了肝癌细胞的体外增殖能力。总之,NS4B通过Hippo-YAP途径对AKT信号传导途径的作用诱导脂肪生成，从而在HCV相关疾病的发病机理中发挥重要作用。
