The Hedgehog-induced Smoothened conformational switch assembles a signaling complex that activates Fused by promoting its dimerization and phosphorylation
The Hedgehog-induced Smoothened conformational switch assembles a signaling complex that activates Fused by promoting its dimerization and phosphorylation
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DOI：
10.1242/dev.067959
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发表时间：
2011-10-01
期刊：
影响因子：
4.6
通讯作者：
Jiang, Jin
中科院分区：
文献类型：
--
作者：
Shi, Qing;Li, Shuang;Jiang, Jin
Hedgehog（Hh）通过调节GPCR样蛋白Smoothened（Smo）的亚细胞定位和构象状态来传递信号，但Smo如何将信号传递给细胞质信号传导组分仍然知之甚少。在这里，我们表明，Hh诱导的Smo构象变化招募Costal 2（Cos 2）/融合（Fu）和促进Fu激酶结构域二聚化。我们发现，诱导二聚化通过Fu激酶结构域激活Fu通过诱导其激活环（AL）的多位点磷酸化和AL的磷酸模拟突变激活Hh途径。有趣的是，我们观察到分级Hh信号逐渐增加Fu激酶结构域二聚化和AL磷酸化，表明Hh以剂量依赖性方式激活Fu。此外，我们发现，激活Fu调节Cubitus interruptus（Ci），既促进其转录激活因子的活性，抑制其蛋白水解成阻遏物的形式。我们提供的证据表明，激活Fu发挥这些规定，通过干扰形成的Ci-Sufu和Ci-Cos 2-激酶复合物，通常抑制Ci的活动，并促进其加工。两者合计，我们的研究结果表明，Hh诱导的Smo构象变化促进组装的活性Smo-Cos 2-Fu信号复合物，促进Fu激酶结构域二聚化，磷酸化和激活，和Fu调节激活剂和抑制剂形式的Ci。
Hedgehog (Hh) transduces signal by regulating the subcellular localization and conformational state of the GPCR-like protein Smoothened (Smo) but how Smo relays the signal to cytoplasmic signaling components remains poorly understood. Here, we show that Hh-induced Smo conformational change recruits Costal2 (Cos2)/Fused (Fu) and promotes Fu kinase domain dimerization. We find that induced dimerization through the Fu kinase domain activates Fu by inducing multi-site phosphorylation of its activation loop (AL) and phospho-mimetic mutations of AL activate the Hh pathway. Interestingly, we observe that graded Hh signals progressively increase Fu kinase domain dimerization and AL phosphorylation, suggesting that Hh activates Fu in a dose-dependent manner. Moreover, we find that activated Fu regulates Cubitus interruptus (Ci) by both promoting its transcriptional activator activity and inhibiting its proteolysis into a repressor form. We provide evidence that activated Fu exerts these regulations by interfering with the formation of Ci-Sufu and Ci-Cos2-kinase complexes that normally inhibit Ci activity and promote its processing. Taken together, our results suggest that Hh-induced Smo conformational change facilitates the assembly of active Smo-Cos2-Fu signaling complexes that promote Fu kinase domain dimerization, phosphorylation and activation, and that Fu regulates both the activator and repressor forms of Ci.