Purpose

Deubiquitination, the inverse process of ubiquitination, is catalyzed by deubiquitinases (DUBs) that remove ubiquitin from target proteins and subsequently prevent their degradation by proteasomes. Previously, deubiquitination has been found to be involved in hepatocellular carcinoma (HCC) progression. As yet, however, little is known about the exact role of deubiquitination in the development and/or progression of this type of cancer.

Methods

HCC tissues and tissue microarrays were used to detect expression of the DUB ubiquitin-specific protease 2a (USP2a). The critical role of USP2a in HCC development and progression was assessed in both in vitro cell and in vivo animal models. LC-MS/MS analyses were performed to identify potential targets of USP2a in HCC cells, after which regulation of target protein stability and ubiquitin status by USP2a were investigated.

Results

We found that USP2a was significantly upregulated in HCC tissues, and that a high expression was positively associated with a poor prognosis. Subsequently, we found that USP2a silencing resulted in inhibition of HCC cell proliferation, migration and invasion, whereas exogenous USP2a overexpression resulted in the opposite effects, both in vitro and in vivo. Mechanistically, LC-MS/MS analysis revealed that RAB1A, a key regulator of the ER and Golgi vesicular transport system, serves as a potential target of USP2a in HCC cells. In addition, we found that USP2a can deubiquitinate and stabilize RAB1A and prevent its degradation, and that this process is required for inducing HCC progression by USP2a.

Conclusions

Our data indicate that USP2a can promote HCC progression via deubiquitination and stabilization of RAB1A. This observation indicates that DUB targeting may serve as a novel approach to improve the treatment of HCC.

中文翻译：

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泛素特异性蛋白酶 2a 通过 RAB1A 的去泛素化和稳定化促进肝细胞癌进展

 目的

去泛素化是泛素化的逆过程，由去泛素酶 (DUB) 催化，从目标蛋白中去除泛素，随后防止其被蛋白酶体降解。此前，已发现去泛素化与肝细胞癌（HCC）进展有关。然而，迄今为止，人们对去泛素化在此类癌症的发生和/或进展中的确切作用知之甚少。

 方法

使用 HCC 组织和组织微阵列检测 DUB 泛素特异性蛋白酶 2a (USP2a) 的表达。在体外细胞和体内动物模型中评估了 USP2a 在 HCC 发生和进展中的关键作用。进行 LC-MS/MS 分析以确定 HCC 细胞中 USP2a 的潜在靶标，然后研究 USP2a 对靶蛋白稳定性和泛素状态的调节。

 结果

我们发现USP2a在HCC组织中显着上调，并且高表达与不良预后呈正相关。随后，我们发现USP2a沉默导致HCC细胞增殖、迁移和侵袭受到抑制，而外源性USP2a过表达在体外和体内均导致相反的效果。从机制上讲，LC-MS/MS 分析表明，RAB1A（ER 和高尔基体囊泡运输系统的关键调节因子）是 HCC 细胞中 USP2a 的潜在靶标。此外，我们发现USP2a可以去泛素化和稳定RAB1A并防止其降解，并且该过程是USP2a诱导HCC进展所必需的。

 结论

我们的数据表明，USP2a 可以通过 RAB1A 的去泛素化和稳定化促进 HCC 进展。这一观察结果表明 DUB 靶向可能作为改善 HCC 治疗的新方法。