Zhou Guo-Lei, Tucker David F, Bae Sun Sik, Bhatheja Kanav, Birnbaum Morris J, Field Jeffrey
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
J Biol Chem. 2006 Nov 24;281(47):36443-53. doi: 10.1074/jbc.M600788200. Epub 2006 Oct 1.
The Akt/PKB isoforms have different roles in animals, with Akt2 primarily regulating metabolic signaling and Akt1 regulating growth and survival. Here we show distinct roles for Akt1 and Akt2 in mouse embryo fibroblast cell migration and regulation of the cytoskeleton. Akt1-deficient cells responded poorly to platelet-derived growth factor while Akt2-deficient cells had a dramatically enhanced response, resulting in a substantial increase in dorsal ruffling. Swapping domains between Akt1 and Akt2 demonstrated that the N-terminal region containing the pleckstrin homology domain and a linker region distinguishes the two isoforms, while the catalytic domains are interchangeable. Akt2 knock-out cells also migrated faster than wild-type cells, especially through extracellular matrix (ECM), while Akt1 knock-out cells migrated more slowly than wild-type cells. Consistently, Akt2 knock-out cells had elevated Pak1 and Rac activities, suggesting that Akt2 inhibits Rac and Pak1. Both Akt2 and Akt1 associated in complexes with Pak1, but only Akt2 inhibited Pak1 in kinase assays, suggesting an underlying molecular basis for the different cellular phenotypes. Together these data provide evidence for an unexpected functional link between Akt2 and Pak1 that opposes the actions of Akt1 on cell migration.
Akt/PKB亚型在动物体内具有不同作用，其中Akt2主要调节代谢信号，而Akt1调节生长和存活。在此，我们展示了Akt1和Akt2在小鼠胚胎成纤维细胞迁移及细胞骨架调节中的不同作用。Akt1缺陷型细胞对血小板衍生生长因子反应不佳，而Akt2缺陷型细胞反应显著增强，导致背侧褶皱大幅增加。在Akt1和Akt2之间交换结构域表明，包含普列克底物蛋白同源结构域的N端区域和一个连接区域区分了这两种亚型，而催化结构域是可互换的。Akt2基因敲除细胞也比野生型细胞迁移得更快，尤其是通过细胞外基质（ECM）时，而Akt1基因敲除细胞比野生型细胞迁移得更慢。一致地，Akt2基因敲除细胞的Pak1和Rac活性升高，表明Akt2抑制Rac和Pak1。Akt2和Akt1都与Pak1形成复合物，但在激酶分析中只有Akt2抑制Pak1，这表明了不同细胞表型的潜在分子基础。这些数据共同为Akt2和Pak1之间意想不到的功能联系提供了证据，这种联系与Akt1对细胞迁移的作用相反。
