Protein kinase B/Akt-dependent phosphorylation of glycogen synthase kinase-3β in irradiated vascular endothelium
Protein kinase B/Akt-dependent phosphorylation of glycogen synthase kinase-3β in irradiated vascular endothelium
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DOI：
10.1158/0008-5472.can-05-2700
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发表时间：
2006-02-15
期刊：
影响因子：
11.2
通讯作者：
Hallahan, DE
中科院分区：
文献类型：
--
作者：
Tan, JH;Geng, L;Hallahan, DE
血管内皮在癌症对电离辐射的反应中起关键作用。磷酸肌醇-3-激酶/Akt通路的激活是辐照内皮细胞中的一个初始信号传导事件。具体而言，低剂量电离辐射（3戈伊）在辐射的几分钟内诱导血管内皮中Ser（473）处Akt的磷酸化。然而，Akt下游的信号传导事件尚未得到很好的定义。在这里，我们发现Akt下游靶糖原合成酶激酶-3（GSK-3 β）在Ser（9）的磷酸化也发生在电离辐射暴露的几分钟内。此外，电离辐射导致GSK-3 β从细胞膜上解离，与GSK-3 β酶活性失活一致。显性失活突变体Alit的过表达减弱了GSK-3 β在Ser（9）的磷酸化，并增强了辐射诱导的细胞凋亡。在体外和体内模型中，X射线照射的内皮细胞形成毛细血管，而显性阴性突变体Akt的过表达抑制了毛细血管小管的形成。使用GSK-3 β拮抗剂的研究表明，GSK-3 β活性是同时用Akt拮抗剂和辐射处理的内皮细胞凋亡所必需的。在小鼠血管模型中，Akt拮抗剂引起的辐射诱导的微血管破坏也需要GSK 3 β功能。这些数据表明，在血管内皮暴露于电离辐射时，Akt信号传导的激活有助于GSK-3 β抑制，这反过来促进内皮细胞存活和毛细血管形成。因此，Akt/GSK-3 β信号的药理学调节可能为肿瘤微血管系统的辐射反应提供新的途径。
The vascular endothelium plays a critical role in the response of cancer to ionizing radiation. Activation of the phosphoinositide-3-kinase/Akt pathway is one initial signaling event in irradiated endothelial cells. Specifically, a low dose of ionizing radiation (3 Gy) induces phosphorylation of Akt at Ser(473) in the vascular endothelium within minutes of irradiation. However, signaling events that are downstream of Akt have not been well defined. Here, we show that phosphorylation of the Akt downstream target glycogen synthase kinase-3 (GSK-3 beta) at Ser(9) also occurred within minutes of exposure to ionizing radiation. In addition, ionizing radiation caused the dissociation of GSK-3 beta from the cell membrane, consistent with the inactivation of GSK-3 beta enzyme activity. Overexpression of the dominant negative mutant Alit attenuated GSK-3 beta phosphorylation at Ser(9) and enhanced radiation-induced apoptosis. X-irradiated endothelial cells formed capillaries in both in vitro and in vivo models, whereas overexpression of the dominant negative mutant Akt inhibited capillary tubule formation. Studies using GSK-3 beta antagonists showed that GSK-3 beta activity was required for apoptosis in endothelial cells treated simultaneously with Akt antagonists and radiation. In mouse vascular models, radiation-induced microvascular destruction in response to Akt antagonists also required GSK3 beta function. These data indicate that on exposure of vascular endothelium to ionizing radiation, activation of Akt signaling contributes to GSK-3 beta inhibition, which in turn promotes endothelial cell survival and capillary formation. Thus, pharmacologic regulation of Akt/GSK-3 beta signaling may present a new approach to the radiation response in the tumor microvasculature.