Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, Chapel Hill, NC 27599, USA.
Mol Biol Cell. 2010 May 1;21(9):1629-42. doi: 10.1091/mbc.e09-09-0809. Epub 2010 Mar 17.
RhoG is a member of the Rac-like subgroup of Rho GTPases and has been linked to a variety of different cellular functions. Nevertheless, many aspects of RhoG upstream and downstream signaling remain unclear; in particular, few extracellular stimuli that modulate RhoG activity have been identified. Here, we describe that stimulation of epithelial cells with epidermal growth factor leads to strong and rapid activation of RhoG. Importantly, this rapid activation was not observed with other growth factors tested. The kinetics of RhoG activation after epidermal growth factor (EGF) stimulation parallel the previously described Rac1 activation. However, we show that both GTPases are activated independently of one another. Kinase inhibition studies indicate that the rapid activation of RhoG and Rac1 after EGF treatment requires the activity of the EGF receptor kinase, but neither phosphatidylinositol 3-kinase nor Src kinases. By using nucleotide-free RhoG pull-down assays and small interfering RNA-mediated knockdown studies, we further show that guanine-nucleotide exchange factors (GEFs) of the Vav family mediate EGF-induced rapid activation of RhoG. In addition, we found that in certain cell types the recently described RhoG GEF PLEKHG6 can also contribute to the rapid activation of RhoG after EGF stimulation. Finally, we present results that show that RhoG has functions in EGF-stimulated cell migration and in regulating EGF receptor internalization.
RhoG 是 Rac 样 Rho GTPases 亚群的成员，与多种不同的细胞功能有关。然而，RhoG 上下游信号的许多方面仍不清楚；特别是，很少有调节 RhoG 活性的细胞外刺激被识别。在这里，我们描述了表皮生长因子刺激上皮细胞导致 RhoG 的强烈和快速激活。重要的是，这种快速激活在测试的其他生长因子中没有观察到。表皮生长因子（EGF）刺激后 RhoG 激活的动力学与先前描述的 Rac1 激活平行。然而，我们表明这两种 GTPases彼此独立激活。激酶抑制研究表明，EGF 处理后 RhoG 和 Rac1 的快速激活需要 EGF 受体激酶的活性，但不需要磷脂酰肌醇 3-激酶或Src 激酶。通过使用无核苷酸 RhoG 下拉测定和小干扰 RNA 介导的敲低研究，我们进一步表明 Vav 家族的鸟嘌呤核苷酸交换因子（GEF）介导 EGF 诱导的 RhoG 快速激活。此外，我们发现某些细胞类型中，最近描述的 RhoG GEF PLEKHG6 也可以促进 EGF 刺激后 RhoG 的快速激活。最后，我们提出的结果表明 RhoG 在 EGF 刺激的细胞迁移和调节 EGF 受体内化中具有功能。
