Functional studies of Shaggy/glycogen synthase kinase 3 phosphorylation sites in Drosophila melanogaster
Functional studies of Shaggy/glycogen synthase kinase 3 phosphorylation sites in Drosophila melanogaster
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DOI：
10.1128/mcb.24.11.4909-4919.2004
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发表时间：
2004-06-01
影响因子：
5.3
通讯作者：
Bourouis, M
中科院分区：
文献类型：
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作者：
Papadopoulou, D;Bianchi, MW;Bourouis, M
糖原合成酶激酶3（GSK-3）在哺乳动物系统中的早期研究集中在其在糖原代谢和胰岛素介导的信号传导中的关键作用。现在认识到GSK-3是许多不同信号系统的核心。在这里，我们表明，激酶Shaggy（Sgg）的主要形式，GSK-3的苍蝇直系同源物，在体内胰岛素样/磷脂酰肌醇3-激酶（PI 3 K）信号转导过程中受到负调控。由于果蝇的遗传学研究表明，Wingless（Wg）信号也起到拮抗Sgg，我们调查激酶如何整合，否则歧视，信号输入Wg和胰岛素。使用果蝇细胞系测定，我们发现，与以前的报告相反，Wg诱导积累其换能器Armadillo（臂）/β-连环蛋白没有显着改变的全球Sgg特异性活性。与先前使用人GSK-3 β的研究一致，Wg没有引起Sgg的Ser 9或Tyr 214调节磷酸化位点的磷酸化变化。相反，如在哺乳动物系统中所示，通过N-末端假底物位点（Ser 9）的磷酸化，胰岛素诱导的Sgg特异性活性抑制不会诱导Arm/β-连环蛋白蓄积，显示出对不同信号传导途径的选择性响应。有趣的是，一个小基因轴承Ser 9-丙氨酸的变化拯救突变体sgg不引起异常的发展，这表明通过抑制性假底物结构域的调节Sgg是不确定的，其功能的许多方面。我们对果蝇的研究表明，Wg和胰岛素或PI 3 K通路不收敛于Sgg，但它们表现出交叉调节相互作用。
Early studies of glycogen synthase kinase 3 (GSK-3) in mammalian systems focused on its pivotal role in glycogen metabolism and insulin-mediated signaling. It is now recognized that GSK-3 is central to a number of diverse signaling systems. Here, we show that the major form of the kinase Shaggy (Sgg), the GSK-3 fly ortholog, is negatively regulated during insulin-like/phosphatidylinositol 3-kinase (PI3K) signaling in vivo. Since genetic studies of Drosophila melanogaster had previously shown that Wingless (Wg) signaling also acts to antagonize Sgg, we investigate how the kinase might integrate, or else discriminate, signaling inputs by Wg and insulin. Using Drosophila cell line assays, we found, in contrast to previous reports, that Wg induces accumulation of its transducer Armadillo (Arm)/beta-catenin without significant alteration of global Sgg-specific activity. In agreement with a previous study using human GSK-3beta, Wg did not cause phosphorylation changes of the Ser9 or Tyr214 regulatory phosphorylated sites of Sgg. Conversely, as shown in mammalian systems, insulin-induced inhibition of Sgg-specific activity by phosphorylation at the N-terminal pseudosubstrate site (Ser9) did not induce Arm/beta-catenin accumulation, showing selectivity in response to the different signaling pathways. Interestingly, a minigene bearing a Ser9-to-Ala change rescued mutant sgg without causing abnormal development, suggesting that the regulation of Sgg via the inhibitory pseudosubstrate domain is dispensable for many aspects of its function. Our studies of Drosophila show that Wg and insulin or PI3K pathways do not converge on Sgg but that they exhibit cross-regulatory interactions.