Bellanger J-M, Estrach S, Schmidt S, Briançon-Marjollet A, Zugasti O, Fromont S, Debant A
CRBM-CNRS, FRE 2593 1919, route de Mende, 34293 Montpellier Cédex 5, France.
Biol Cell. 2003 Dec;95(9):625-34. doi: 10.1016/j.biolcel.2003.10.002.
Guanine nucleotide exchange factors for Rho-GTPases (Rho-GEFs) invariably share a catalytic Dbl-Homology (DH) domain associated with a Pleckstrin Homology (PH) domain, whose function in Rho-GEF activation is not well understood. Trio is the first member of an emerging family of Dbl proteins containing two Rho-GEF domains (GEFD1 and GEFD2). TrioGEFD1 activates the GTPases RhoG and Rac1, while TrioGEFD2 acts on RhoA. In this study, we have investigated the roles of the two PH domains of Trio in Rho-GEF activity. We show that TrioPH1 is required for GEFD1-mediated induction of actin cytoskeleton remodeling and JNK activation. TrioPH1 is involved both in the catalytic activity and in the subcellular localization of its associated DH domain, by acting as a cytoskeletal targeting signal. Moreover, TrioPH1 in association with DH2 activates the JNK pathway, by an unknown mechanism independent of DH2 catalytic activity. TrioPH2 does not behave as a targeting module in intact cells. TrioPH2 inhibits DH2-dependent stress fiber formation, which correlates with the TrioPH2-mediated inhibition of DH2 GEF activity. In addition, expression in the neuron-like PC12 cell line of the intact Trio protein deleted of each PH domain shows that only TrioPH1 is required for Trio-induced neurite outgrowth. Taken together, these data demonstrate that the two PH domains play a different role in the control of Trio Rho-GEF function.
Rho鸟苷三磷酸酶（Rho-GTPases）的鸟苷酸交换因子（Rho-GEFs）总是共享一个与普列克底物蛋白同源结构域（PH结构域）相关的催化性双同源结构域（DH结构域），其在Rho-GEF激活中的功能尚未完全明确。Trio是包含两个Rho-GEF结构域（GEFD1和GEFD2）的新兴Dbl蛋白家族的首个成员。TrioGEFD1激活鸟苷三磷酸酶RhoG和Rac1，而TrioGEFD2作用于RhoA。在本研究中，我们探究了Trio的两个PH结构域在Rho-GEF活性中的作用。我们发现，GEFD1介导的肌动蛋白细胞骨架重塑和JNK激活需要TrioPH1。TrioPH1通过作为细胞骨架靶向信号，参与其相关DH结构域的催化活性和亚细胞定位。此外，TrioPH1与DH2结合，通过一种独立于DH2催化活性的未知机制激活JNK通路。在完整细胞中，TrioPH2并非作为靶向模块发挥作用。TrioPH2抑制依赖于DH2的应力纤维形成，这与TrioPH2介导的DH2 GEF活性抑制相关。此外，在神经元样PC12细胞系中表达缺失每个PH结构域的完整Trio蛋白表明，只有TrioPH1是Trio诱导神经突生长所必需的。综上所述，这些数据表明这两个PH结构域在控制Trio Rho-GEF功能中发挥不同作用。
