The E3 ubiquitin protein ligase MDM2 dictates all-trans retinoic acid-induced osteoblastic differentiation of osteosarcoma cells by modulating the degradation of RARα
The E3 ubiquitin protein ligase MDM2 dictates all-trans retinoic acid-induced osteoblastic differentiation of osteosarcoma cells by modulating the degradation of RARα
复制标题
E3 泛素蛋白连接酶 MDM2 通过调节 RARα 的降解来控制全反式视黄酸诱导骨肉瘤细胞的成骨细胞分化
DOI：
10.1038/onc.2015.503
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发表时间：
2016-08-01
期刊：
影响因子：
8
通讯作者：
He, Q.
中科院分区：
文献类型：
--
作者：
Ying, M.;Zhang, L.;He, Q.
视黄酸受体α（RAR α）在全反式视黄酸（ATRA）诱导骨肉瘤细胞分化过程中起重要作用。然而，RAR α通过泛素蛋白酶体途径降解，削弱了骨肉瘤细胞的分化效率。在这项研究中，我们发现小鼠双分钟-2（MDM 2）作为E3泛素连接酶靶向RAR α降解。我们观察到MDM 2是RAR α多聚泛素化和蛋白酶体降解所必需的，因为短发夹RNA下调MDM 2导致RAR α的积累，而MDM 2过表达促进RAR α的降解。我们还证明了MDM 2的N-末端结构域（氨基酸1-109）是主要的RAR α结合位点。重要的是，内源性MDM 2水平不仅在人原发性骨肉瘤母细胞中上调，而且还与骨桥蛋白（骨分化的标志物）的水平负相关。此外，MDM 2损害ATRA诱导的骨肉瘤细胞的成骨细胞分化，而MDM 2泛素连接酶的抑制剂与ATRA协同增强骨肉瘤细胞和原代骨肉瘤母细胞的分化。因此，我们的研究表明MDM 2作为E3泛素连接酶调节RAR α的降解，并表明MDM 2是骨肉瘤中基于ATRA的分化治疗方法的新治疗靶点。
Retinoic acid receptor alpha (RAR alpha) has a critical role in the differentiation process of osteosarcoma cells induced by all-trans retinoic acid (ATRA). However, degradation of RAR alpha through ubiquitin proteasome pathway weakens the differentiation efficiency of osteosarcoma cells. In this study, we discover that murine double minute-2 (MDM2) acts as an E3 ubiquitin ligase to target RAR alpha for degradation. We observe that MDM2 is required for RAR alpha polyubiquitination and proteasomal degradation because downregulation of MDM2 by short hairpin RNA results in the accumulation of RAR alpha, and MDM2 overexpression promotes the degradation of RAR alpha. We also demonstrate that the N-terminal domain of MDM2 (amino acids 1-109) is the major RAR alpha-binding site. Importantly, endogenous MDM2 levels are not only upregulated in human primary osteosarcoma blasts but are also inversely correlated with the level of osteopontin, which is a marker of bone differentiation. Moreover, MDM2 impairs the ATRA-induced osteoblastic differentiation of osteosarcoma cells, whereas an inhibitor of the MDM2 ubiquitin ligase synergizes with ATRA to enhance the differentiation of osteosarcoma cells and primary osteosarcoma blasts. Therefore, our study indicates that MDM2 serves as an E3 ubiquitin ligase to regulate the degradation of RARa and suggests that MDM2 is a novel therapeutic target for ATRA-based differentiation therapeutic approaches in osteosarcoma.