Institute of Pharmacology and Toxicology, University of Ulm, D-89070 Ulm, Germany.
Biol Chem. 2009 Oct;390(10):1063-77. doi: 10.1515/BC.2009.110.
RhoA and RhoC are highly related Rho GTPases, but differentially control cellular behaviour. We combined molecular, cellular, and biochemical experiments to characterise differences between these highly similar GTPases. Our findings demonstrate that enhanced expression of RhoC results in a striking increase in the migration and invasion of pancreatic carcinoma cells, whereas forced expression of RhoA decreases these actions. These isoform-specific functions correlate with differences in the cellular activity of RhoA and RhoC in human cells, with RhoC being more active than RhoA in activity assays and serum-response factor-dependent gene transcription. Subcellular localisation studies revealed that RhoC is predominantly localised in the membrane-containing fraction, whereas RhoA is mainly localised in the cytoplasmic fraction. These differences are not mediated by a different interaction with RhoGDIs. In vitro GTP/GDP binding analyses demonstrate different affinity of RhoC for GTP[S] and faster intrinsic and guanine nucleotide exchange factor (GEF)-stimulated GDP/GTP exchange rates compared to RhoA. Moreover, the catalytic domains of SopE and Dbs are efficacious GEFs for RhoC. mRNA expression of RhoC is markedly enhanced in advanced pancreatic cancer stages, and thus the differences discovered between RhoA and RhoC might provide explanations for their different influences on cell migration and tumour invasion.
RhoA 和 RhoC 是高度相关的 Rho GTPases，但它们对细胞行为的控制方式存在差异。我们结合了分子、细胞和生化实验，以描述这些高度相似的 GTPases 之间的差异。我们的研究结果表明，RhoC 的过度表达会导致胰腺癌细胞的迁移和侵袭显著增加，而 RhoA 的强制表达则会降低这些作用。这些同工型特异性功能与 RhoA 和 RhoC 在人类细胞中的细胞活性差异相关联，在活性测定和血清反应因子依赖性基因转录中，RhoC 比 RhoA 更活跃。亚细胞定位研究表明，RhoC 主要定位于含有膜的部分，而 RhoA 主要定位于细胞质部分。这些差异不是由与 RhoGDIs 的不同相互作用介导的。体外 GTP/GDP 结合分析表明，与 RhoA 相比，RhoC 对 GTP[S]具有不同的亲和力，并且具有更快的内在和鸟嘌呤核苷酸交换因子（GEF）刺激的 GDP/GTP 交换率。此外，SopE 和 Dbs 的催化结构域是 RhoC 的有效 GEF。RhoC 的 mRNA 表达在晚期胰腺癌中显著增强，因此在 RhoA 和 RhoC 之间发现的差异可能为它们对细胞迁移和肿瘤侵袭的不同影响提供了解释。
