Impaired Phosphorylation and Ubiquitination by p70 S6 Kinase (p70S6K) and Smad Ubiquitination Regulatory Factor 1 (Smurf1) Promote Tribbles Homolog 2 (TRIB2) Stability and Carcinogenic Property in Liver Cancer
Impaired Phosphorylation and Ubiquitination by p70 S6 Kinase (p70S6K) and Smad Ubiquitination Regulatory Factor 1 (Smurf1) Promote Tribbles Homolog 2 (TRIB2) Stability and Carcinogenic Property in Liver Cancer
复制标题
p70 S6 激酶 (p70S6K) 和 Smad 泛素化调节因子 1 (Smurf1) 的磷酸化和泛素化受损可促进 Tribbles 同源物 2 (TRIB2) 在肝癌中的稳定性和致癌性。
DOI：
10.1074/jbc.m113.503292
复制
发表时间：
2013-11-22
影响因子：
4.8
通讯作者：
Sun, Fenyong
中科院分区：
文献类型：
--
作者：
Wang, Jiayi;Zhang, Yue;Sun, Fenyong
tribles同源物2 （TRIB2）对实性和非实性恶性肿瘤都至关重要。最近，TRIB2被确定为肝癌特异性Wnt/-catenin信号下游靶点，对肝癌细胞的存活和转化具有重要的功能。TRIB2是一种与E3泛素连接酶相互作用的蛋白质，从而调节下游效应物的蛋白质稳定性。然而，TRIB2蛋白稳定性的调控本身尚未被报道。在本研究中，我们发现TRIB2在肝癌细胞中与其他细胞相比表达上调，并表现出较高的稳定性。我们对TRIB2进行了结构-功能分析，并在N端发现了一个结构域（氨基酸1-5），该结构域与E3泛素连接酶Smurf1相互作用，对蛋白质稳定性至关重要。与野生型TRIB2相比，该结构域的缺失延长了TRIB2的半衰期，并伴有更显著的恶性性质。此外，smurf1介导的泛素化需要p70S6激酶（p70S6K）通过另一个结构域（氨基酸69-85）磷酸化TRIB2，这也是正确的TRIB2亚细胞定位所必需的。Ser-83突变减少了p70s6k诱导的TRIB2磷酸化。此外，TRIB2的高稳定性可能是由于p70S6K和Smurf1在肝癌组织和已建立的肝癌细胞系中均下调并与TRIB2表达负相关。综上所述，p70S6K和Smurf1磷酸化和泛素化受损增加了肝癌中TRIB2蛋白的稳定性，因此可能有助于制定针对这种恶性疾病的诊断和治疗策略。
Tribbles homolog 2 (TRIB2) is critical for both solid and non-solid malignancies. Recently, TRIB2 was identified as a liver cancer-specific Wnt/-catenin signaling downstream target and is functionally important for liver cancer cell survival and transformation. TRIB2 functions as a protein that interacts with E3 ubiquitin ligases and thereby modulates protein stability of downstream effectors. However, the regulation underlying TRIB2 protein stability per se has not yet been reported. In this study, we found that TRIB2 was up-regulated and exhibited high stability in liver cancer cells compared with other cells. We performed a structure-function analysis of TRIB2 and identified a domain (amino acids 1-5) at the N terminus that interacted with the E3 ubiquitin ligase Smurf1 and was critical for protein stability. Deletion of this domain extended TRIB2 half-life time accompanied with a more significant malignant property compared with wild type TRIB2. Furthermore, Smurf1-mediated ubiquitination required phosphorylation of TRIB2 by p70 S6 kinase (p70S6K) via another domain (amino acids 69-85) that is also essential for correct TRIB2 subcellular localization. Mutation of Ser-83 diminished p70S6K-induced phosphorylation of TRIB2. Moreover, the high stability of TRIB2 may be due to the fact that both p70S6K and Smurf1 were down-regulated and negatively correlated with TRIB2 expression in both liver cancer tissues and established liver cancer cell lines. Taken together, impaired phosphorylation and ubiquitination by p70S6K and Smurf1 increase the protein stability of TRIB2 in liver cancer and thus may be helpful in the development of diagnosis and treatment strategies against this malignant disease.