Distinct turnover of alternatively spliced isoforms of the RET kinase receptor mediated by differential recruitment of the Cbl ubiquitin ligase
Distinct turnover of alternatively spliced isoforms of the RET kinase receptor mediated by differential recruitment of the Cbl ubiquitin ligase
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DOI：
10.1074/jbc.m500507200
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发表时间：
2005-04-08
影响因子：
4.8
通讯作者：
Ibáñez, CF
中科院分区：
文献类型：
--
作者：
Scott, RP;Eketjäll, S;Ibáñez, CF
编码RET激酶受体的转录本的选择性剪接导致其胞质尾区不同的同种型。尽管体外研究已经证明了长RET同种型（RET 51）的更高转化活性，但只有短同种型（RET 9）可以挽救RET无效突变在肠神经系统和肾脏发育中的作用。两种RET亚型不同功能的分子基础尚不清楚。在这里，我们证明了激活的RET 51与泛素连接酶Cbl的关联比RET 9更强，导致RET 51的泛素化增加和更快的周转。Cbl与RET的关联是间接的，并通过Grb 2介导。Grb 2和Cbl的组成型复合物可以通过Shc与RET中磷酸化Tyr-1062的对接而被招募到两种受体亚型。不能募集Grb2.Cbl复合物的突变Shc蛋白降低了RET 9的周转率并延长了其半衰期，因此将先前未知的负作用归因于Shc衔接分子。此外，Tyr-1096的磷酸化（其存在于RET 51中但不存在于RET 9中）赋予较长的同种型第二途径来募集Grb2.Cbl复合物。这些发现建立了RET 9和RET 51信号传导差异下调的机制，可以解释这两种RET亚型的明显自相矛盾的活性。更一般地说，这些结果说明了选择性剪接如何调节生长因子受体的半衰期和功能。
Alternative splicing of transcripts encoding the RET kinase receptor leads to isoforms differing in their cytoplasmic tail. Although in vitro studies have demonstrated a higher transforming activity of the long RET isoform (RET51), only the short isoform (RET9) can rescue the effects of a RET null mutation in the enteric nervous system and kidney development. The molecular basis underlying the distinct functions of the two RET isoforms is not understood. Here we demonstrated that activated RET51 associated more strongly with the ubiquitin ligase Cbl than did RET9, leading to increased ubiquitylation and faster turnover of RET51. The association of Cbl with RET was indirect and was mediated through Grb2. A constitutive complex of Grb2 and Cbl could be recruited to both receptor isoforms via docking of Shc to phosphorylated Tyr-1062 in RET. A mutant Shc protein unable to recruit the Grb2.Cbl complex decreased the turnover and prolonged the half-life of RET9, thus ascribing a previously unknown negative role to the Shc adaptor molecule. In addition, phosphorylation of Tyr-1096, which is present in RET51 but absent in RET9, endowed the longer isoform with a second route to recruit the Grb2.Cbl complex. These findings establish a mechanism for the differential down-regulation of RET9 and RET51 signaling that could explain the apparently paradoxical activities of these two RET isoforms. More generally, these results illustrate how alternative splicing can regulate the half-life and function of a growth factor receptor.