Dao Vi Thuy, Dupuy Aurélien Guy, Gavet Olivier, Caron Emmanuelle, de Gunzburg Jean
Institut Curie, Centre de Recherche, Inserm U528, 26 rue d'Ulm, 75248 Paris, France.
J Cell Sci. 2009 Aug 15;122(Pt 16):2996-3004. doi: 10.1242/jcs.041301. Epub 2009 Jul 28.
At the onset of mitosis, most adherent cells undergo cell retraction characterised by the disassembly of focal adhesions and actin stress fibres. Mitosis takes place in rounded cells, and the two daughter cells spread again after cytokinesis. Because of the well-documented ability of the small GTPase Rap1 to stimulate integrin-dependent adhesion and spreading, we assessed its role during mitosis. We show that Rap1 activity is regulated during this process. Changes in Rap1 activity play an essential role in regulating cell retraction and spreading, respectively, before and after mitosis of HeLa cells. Indeed, endogenous Rap1 is inhibited at the onset of mitosis; conversely, constitutive activation of Rap1 inhibits the disassembly of premitotic focal adhesions and of the actin cytoskeleton, leading to delayed mitosis and to cytokinesis defects. Rap1 activity slowly increases after mitosis ends; inhibition of Rap1 activation by the ectopic expression of the dominant-negative Rap1[S17A] mutant prevents the rounded cells from spreading after mitosis. For the first time, we provide evidence for the direct regulation of adhesion processes during mitosis via the activity of the Rap1 GTPase.
在有丝分裂开始时，大多数贴壁细胞会经历细胞收缩，其特征是粘着斑和肌动蛋白应力纤维的解体。有丝分裂发生在圆形细胞中，两个子细胞在胞质分裂后再次铺展。由于小GTP酶Rap1具有刺激整合素依赖性粘附和铺展的能力，我们评估了它在有丝分裂过程中的作用。我们发现Rap1活性在此过程中受到调节。Rap1活性的变化分别在HeLa细胞有丝分裂之前和之后调节细胞收缩和铺展中起重要作用。实际上，内源性Rap1在有丝分裂开始时被抑制；相反，Rap1的组成型激活会抑制有丝分裂前粘着斑和肌动蛋白细胞骨架的解体，导致有丝分裂延迟和胞质分裂缺陷。有丝分裂结束后，Rap1活性缓慢增加；通过显性负性Rap1[S17A]突变体的异位表达抑制Rap1激活可防止圆形细胞在有丝分裂后铺展。我们首次提供了通过Rap1 GTP酶的活性在有丝分裂期间直接调节粘附过程的证据。
