Center for Cancer Research and Therapeutic Development, Clark Atlanta University, Atlanta, Georgia.
Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee.
J Cell Physiol. 2018 Jan;234(1):802-815. doi: 10.1002/jcp.26894. Epub 2018 Aug 4.
Tumor cell motility is the essential step in cancer metastasis. Previously, we showed that oxytocin and epidermal growth factor (EGF) effects on cell migration in prostate cancer cells require Giα2 protein. In the current study, we investigated the interactions among G-protein coupled receptor (GPCR), Giα2, PI3-kinase, and Rac1 activation in the induction of migratory and invasive behavior by diverse stimuli. Knockdown and knockout of endogenous Giα2 in PC3 cells resulted in attenuation of transforming growth factor β1 (TGFβ1), oxytocin, SDF-1α, and EGF effects on cell migration and invasion. In addition, knockdown of Giα2 in E006AA cells attenuated cell migration and overexpression of Giα2 in LNCaP cells caused significant increase in basal and EGF-stimulated cell migration. Pretreatment of PC3 cells with Pertussis toxin resulted in attenuation of TGFβ1- and oxytocin-induced migratory behavior and PI3-kinase activation without affecting EGF-induced PI3-kinase activation and cell migration. Basal- and EGF-induced activation of Rac1 in PC3 and DU145 cells were not affected in cells after Giα2 knockdown. On the other hand, Giα2 knockdown abolished the migratory capability of PC3 cells overexpressing constitutively active Rac1. The knockdown or knockout of Giα2 resulted in impaired formation of lamellipodia at the leading edge of the migrating cells. We conclude that Giα2 protein acts at two different levels which are both dependent and independent of GPCR signaling to induce cell migration and invasion in prostate cancer cells and its action is downstream of PI3-kinase-AKT-Rac1 axis.
肿瘤细胞的迁移运动是癌症转移的关键步骤。之前，我们已经证明，催产素和表皮生长因子（EGF）对前列腺癌细胞迁移的影响需要 Giα2 蛋白。在本研究中，我们研究了 G 蛋白偶联受体（GPCR）、Giα2、PI3-激酶和 Rac1 激活之间的相互作用，这些作用在不同刺激物诱导迁移和侵袭行为中的作用。在 PC3 细胞中敲低和敲除内源性 Giα2，会减弱转化生长因子β1（TGFβ1）、催产素、SDF-1α 和 EGF 对细胞迁移和侵袭的作用。此外，在 E006AA 细胞中敲低 Giα2 会减弱细胞迁移，在 LNCaP 细胞中过表达 Giα2 会导致基础和 EGF 刺激的细胞迁移显著增加。PC3 细胞用百日咳毒素预处理会减弱 TGFβ1 和催产素诱导的迁移行为和 PI3-激酶激活，而不影响 EGF 诱导的 PI3-激酶激活和细胞迁移。在 Giα2 敲低的细胞中，基础和 EGF 诱导的 Rac1 激活在 PC3 和 DU145 细胞中不受影响。另一方面，Giα2 敲低会破坏过表达组成性激活 Rac1 的 PC3 细胞的迁移能力。Giα2 的敲低或敲除会导致迁移细胞前缘的片状伪足形成受损。我们得出结论，Giα2 蛋白在两个不同的水平上发挥作用，这两个水平既依赖于 GPCR 信号，又独立于 GPCR 信号，以诱导前列腺癌细胞的迁移和侵袭，其作用位于 PI3-激酶-AKT-Rac1 轴的下游。
