Cannet Aude, Schmidt Susanne, Delaval Bénédicte, Debant Anne
Signaling and Cytoskeleton Dynamics Group, University of Montpellier, 34293 Montpellier, France.
Centrosome, Cilia and Pathology Group, CRBM-CNRS, University of Montpellier, 34293 Montpellier, France
Mol Biol Cell. 2014 Dec 15;25(25):4063-71. doi: 10.1091/mbc.E14-06-1153. Epub 2014 Oct 29.
The Rho GTPases RhoA and Rac1 function as master regulators of cytokinesis by controlling the actomyosin cytoskeleton. RhoA and Rac1 have to be respectively activated and inactivated at the division plane for cytokinesis to occur properly. The inactivation of Rac1 at the cleavage furrow is controlled by MgcRacGAP. However, the guanine-nucleotide exchange factor (GEF) that activates Rac1 during cell division remains unknown. Here, using a siRNA screening approach in HeLa cells, we identify Trio as a mitotic GEF of Rac1. We demonstrate that Trio controls Rac1 activation and subsequent F-actin remodeling in dividing cells. Moreover, Trio depletion specifically rescues the cytokinesis failure induced by MgcRacGAP depletion. Of importance, we demonstrate that this rescue is mediated by the Trio-Rac1 pathway, using GEF-dead mutants of Trio and a specific inhibitor of Rac1 activation by Trio. Overall this work identifies for the first time a GEF controlling Rac1 activation in dividing cells that counteracts MgcRacGAP function in cytokinesis.
Rho GTP酶RhoA和Rac1通过控制肌动球蛋白细胞骨架，作为胞质分裂的主要调节因子发挥作用。为使胞质分裂正常发生，RhoA和Rac1必须分别在分裂平面被激活和失活。Rac1在分裂沟处的失活由MgcRacGAP控制。然而，在细胞分裂过程中激活Rac1的鸟嘌呤核苷酸交换因子（GEF）仍然未知。在这里，我们使用HeLa细胞中的siRNA筛选方法，鉴定出Trio是Rac1的有丝分裂GEF。我们证明Trio控制分裂细胞中Rac1的激活以及随后的F-肌动蛋白重塑。此外，Trio的缺失特异性地挽救了由MgcRacGAP缺失诱导的胞质分裂失败。重要的是，我们使用Trio的GEF失活突变体和Trio激活Rac1的特异性抑制剂，证明这种挽救是由Trio-Rac1途径介导的。总体而言，这项工作首次鉴定出一种在分裂细胞中控制Rac1激活的GEF，它在胞质分裂中抵消了MgcRacGAP的功能。
