Zhou Peng, Chang Wen-Yi, Gong De-Ao, Huang Lu-Yi, Liu Rui, Liu Yi, Xia Jie, Wang Kai, Tang Ni, Huang Ai-Long
Key Laboratory of Molecular Biology for Diseases (Ministry of Education), Institute for Viral Hepatitis, Department of Infectious Diseases, The Second Affiliated Hospital, Chongqing Medical University, Chongqing, China.
Oncogene. 2023 Mar;42(10):725-736. doi: 10.1038/s41388-022-02589-z. Epub 2023 Jan 5.
Aberrantly elevated O-GlcNAcylation level is commonly observed in human cancer patients, and has been proposed as a potential therapeutic target. Speckle-type POZ protein (SPOP), an important substrate adaptor of cullin3-RING ubiquitin ligase, plays a key role in the initiation and development of various cancers. However, the regulatory mechanisms governing SPOP and its function during hepatocellular carcinoma (HCC) progression remain unclear. Here, we show that, in HCC, SPOP is highly O-GlcNAcylated by O-GlcNAc transferase (OGT) at Ser96. In normal liver cells, the SPOP protein mainly localizes in the cytoplasm and mediates the ubiquitination of the oncoprotein neurite outgrowth inhibitor-B (Nogo-B) (also known as reticulon 4 B) by recognizing its N-terminal SPOP-binding consensus (SBC) motifs. However, O-GlcNAcylation of SPOP at Ser96 increases the nuclear positioning of SPOP in hepatoma cells, alleviating the ubiquitination of the Nogo-B protein, thereby promoting HCC progression in vitro and in vivo. In addition, ablation of O-GlcNAcylation by an S96A mutation increased the cytoplasmic localization of SPOP, thereby inhibiting the Nogo-B/c-FLIP cascade and HCC progression. Our findings reveal a novel post-translational modification of SPOP and identify a novel SPOP substrate, Nogo-B, in HCC. Intervention with the hyper O-GlcNAcylation of SPOP may provide a novel strategy for HCC treatment.
在人类癌症患者中普遍观察到异常升高的O-连接N-乙酰葡糖胺化（O-GlcNAcylation）水平，并且它已被提议作为一个潜在的治疗靶点。斑点型POZ蛋白（SPOP）是cullin3-RING泛素连接酶的一种重要底物衔接蛋白，在各种癌症的发生和发展中起关键作用。然而，在肝细胞癌（HCC）进展过程中调控SPOP及其功能的机制仍不清楚。在此，我们表明，在HCC中，SPOP在Ser96位点被O-GlcNAc转移酶（OGT）高度O-GlcNAc化。在正常肝细胞中，SPOP蛋白主要定位于细胞质，并通过识别其N端的SPOP结合共有序列（SBC）基序介导癌蛋白神经突生长抑制因子-B（Nogo-B，也称为网蛋白4B）的泛素化。然而，SPOP在Ser96位点的O-GlcNAc化增加了其在肝癌细胞中的核定位，减轻了Nogo-B蛋白的泛素化，从而在体外和体内促进HCC进展。此外，通过S96A突变消除O-GlcNAc化增加了SPOP的细胞质定位，从而抑制Nogo-B/c-FLIP级联反应和HCC进展。我们的研究结果揭示了SPOP一种新的翻译后修饰，并在HCC中鉴定出一种新的SPOP底物Nogo-B。干预SPOP的高O-GlcNAc化可能为HCC治疗提供一种新策略。
