Cbl-c suppresses v-Src-induced transformation through ubiquitin-dependent protein degradation
Cbl-c suppresses v-Src-induced transformation through ubiquitin-dependent protein degradation
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DOI：
10.1038/sj.onc.1207298
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发表时间：
2004-03-04
期刊：
影响因子：
8
通讯作者：
Yamamoto, T
中科院分区：
文献类型：
--
作者：
Kim, M;Tezuka, T;Yamamoto, T
Cbl家族蛋白Cbl、Cbl- B和Cbl-c/Cbl-3被认为通过蛋白酪氨酸激酶调节信号传导，作为支架蛋白是积极的，作为泛素连接酶是消极的。然而，每个Cbl家族成员的精确信号通路和靶蛋白还没有很好地理解。在这里，我们表明Src是Cbl- c降解的优先目标。虽然所有Cbl家族蛋白的外源性表达抑制了v-Src转化的NIH 3 T3细胞的锚定非依赖性生长，但只有Cbl- c引起了可触形态的逆转。Cbl- c可能通过溶酶体依赖性途径降低v-Src蛋白水平。Cbl- c的TKB结构域和RING指是其抗肿瘤活性的重要组成部分.野生型Cbl- c促进293 T细胞中Src的泛素化，而RING指突变体则没有。Cbl- c特异性结合于Tyr 419处磷酸化的Src。Cbl- c与UbcH 5共同诱导Src的泛素化.重要的是，Src的Tyr 419非磷酸化形式不被Cbl- c泛素化.因此，激活的Src可能是Cbl- c在体内的直接靶点.我们的研究结果表明，Cbl和Cbl- B通过与Cbl- c不同的机制抑制v-Src诱导的转化。
The Cbl family proteins Cbl, Cbl- b, and Cbl-c/Cbl-3 are thought to regulate signaling through protein-tyrosine kinases, positively as scaffold proteins and negatively as ubiquitin ligases. However, the precise signaling pathways and target proteins for each Cbl family member are not well understood. Here we show that Src is a preferential target of Cbl- c for degradation. Although exogenous expression of all Cbl family proteins suppressed the anchorage-independent growth of v-Src-transformed NIH3T3 cells, only Cbl- c caused reversion of the refractile morphology. The level of v-Src protein was reduced by Cbl- c, possibly through a lysosome-dependent pathway. The TKB domain and RING finger of Cbl- c were important for its antioncogenic activity. Wild-type Cbl- c promoted ubiquitination of Src in 293T cells, whereas a RING finger mutant did not. Cbl- c bound specifically to Src phosphorylated at Tyr419. Furthermore, Cbl- c together with UbcH5 induced ubiquitination of Src in vitro. Importantly, the Tyr419 nonphosphorylated form of Src was not ubiquitinated by Cbl- c. Therefore, activated Src may be a direct target of Cbl- c in vivo. Our results suggest that Cbl and Cbl- b suppress v-Src-induced transformation through mechanisms distinct from that of Cbl- c.