Institute of Pharmacology, University of Heidelberg, Heidelberg, Germany.
Oncogene. 2010 Apr 22;29(16):2441-8. doi: 10.1038/onc.2009.515. Epub 2010 Jan 25.
Invasive cell migration is a key step for cancer metastasis and involves Rho GTPase-controlled reorganization of the actin cytoskeleton. Altered Rho GTPase expression is found in various malignancies. Particularly, the closely related GTPases RhoA and RhoC are upregulated in many aggressive tumours, but specific effectors that distinguish between these two GTPases to explain mechanistic differences have not been identified. The formins are by far the largest family of Rho GTPase effectors and are characterized by the actin-nucleating formin homology 2 domain. Using siRNA-based screening against all 15 human formins, we systematically analysed their functions in 3D cell motility using three different cancer cell lines. These results reveal distinct requirements for specific formins in amoeboid versus mesenchymal invasive cell migration. Importantly, by knocking down all Rho proteins, we identified formin-like 2 (FMNL2) as a specific RhoC effector, showing selective interaction of FMNL2 with active RhoC, but not RhoA or RhoB. Functional analysis shows that RhoC regulates autoinhibition of FMNL2, whereas suppression of FMNL2 inhibits RhoC-, but not RhoA-dependent, rounded invasive cell migration. Thus, our data uncover a novel regulatory and functional interaction between RhoC and FMNL2 for modulating cell shape and invasiveness and provide mechanistic insight into RhoC-specific signalling events.
侵袭性细胞迁移是癌症转移的关键步骤，涉及 Rho GTPase 控制的肌动蛋白细胞骨架重组。各种恶性肿瘤中存在改变的 Rho GTPase 表达。特别是，密切相关的 GTPases RhoA 和 RhoC 在许多侵袭性肿瘤中上调，但尚未确定区分这两种 GTPases 的特定效应物来解释机制差异。迄今为止，formin 是 Rho GTPase 效应物中最大的家族，其特征是肌动蛋白成核 formin 同源结构域 2。我们使用针对所有 15 个人类 formin 的 siRNA 进行基于筛选的方法，使用三种不同的癌细胞系系统地分析了它们在 3D 细胞迁移中的功能。这些结果揭示了特定 formin 在变形虫样与间质侵袭性细胞迁移中的不同需求。重要的是，通过敲低所有 Rho 蛋白，我们鉴定出 formin-like 2（FMNL2）是 RhoC 的特定效应物，显示出 FMNL2 与活性 RhoC 的选择性相互作用，但与 RhoA 或 RhoB 没有相互作用。功能分析表明，RhoC 调节 FMNL2 的自动抑制，而抑制 FMNL2 则抑制 RhoC 依赖性但不依赖 RhoA 的圆形侵袭性细胞迁移。因此，我们的数据揭示了 RhoC 和 FMNL2 之间调节细胞形状和侵袭性的新型调节和功能相互作用，并为 RhoC 特异性信号事件提供了机制见解。
