Lavaur Jérémie, Bernard Frédéric, Trifilieff Pierre, Pascoli Vincent, Kappes Vincent, Pagès Christiane, Vanhoutte Peter, Caboche Jocelyne
Signalisation Neuronale et Régulations Géniques, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7102, 75005 Paris, France.
J Neurosci. 2007 Dec 26;27(52):14448-58. doi: 10.1523/JNEUROSCI.2279-07.2007.
The transcription factor Elk-1 plays a key role in cell differentiation, proliferation and apoptosis. This role is thought to arise from its phosphorylation by activated extracellular signal-regulated kinases (ERKs), a critical posttranslational event for the transcriptional activity of the ternary complex composed of Elk-1 and a dimer of serum response factor (SRF) at the serum response element (SRE) regulatory site of transcription. In addition to its nuclear localization, Elk-1 is found in the dendrites and soma of neuronal cells and recent evidence implicate a cytoplasmic proapoptotic function of Elk-1, via its association with the mitochondrial permeability transition pore complex. Thus, the nuclear versus cytoplasmic localization of Elk-1 seems to be crucial for its biological function. In this study we show that the excitatory neurotransmitter, glutamate, induces an ERK-dependent Elk-1 activation and nuclear relocalization. We demonstrate that Elk-1 phosphorylation on Ser383/389 has a dual function and triggers both Elk-1 nuclear translocation and SRE-dependent gene expression. Mutating these sites into inactive residues or using a synthetic penetrating peptide (TAT-DEF-Elk-1), which specifically interferes with the DEF docking domain of Elk-1, prevents Elk-1 nuclear translocation without interfering with ERK nor MSK1 (mitogen- and stress-activated protein kinase 1), a CREB kinase downstream from ERK- activation. This results in a differential regulation of glutamate-induced IEG regulation when compared with classical inhibitors of the ERK pathway. Using the TAT-DEF-Elk-1 peptide or the dominant-negative version of Elk-1, we show that Elk-1 phosphorylation controls dendritic elongation, SRF and Actin expression levels as well as cytoskeleton dynamics.
转录因子Elk-1在细胞分化、增殖和凋亡过程中发挥关键作用。人们认为这一作用源于其被激活的细胞外信号调节激酶（ERK）磷酸化，这是由Elk-1与血清反应因子（SRF）二聚体在转录的血清反应元件（SRE）调控位点组成的三元复合物转录活性的关键翻译后事件。除了其核定位外，Elk-1还存在于神经元细胞的树突和胞体中，最近的证据表明Elk-1通过与线粒体通透性转换孔复合物结合而具有细胞质促凋亡功能。因此，Elk-1的核定位与细胞质定位似乎对其生物学功能至关重要。在本研究中，我们表明兴奋性神经递质谷氨酸可诱导ERK依赖的Elk-1激活和核重新定位。我们证明，Ser383/Ser389位点的Elk-1磷酸化具有双重功能，可触发Elk-1核转位和SRE依赖的基因表达。将这些位点突变为无活性残基或使用特异性干扰Elk-1的DEF对接结构域的合成穿透肽（TAT-DEF-Elk-1），可阻止Elk-1核转位，而不干扰ERK或MSK1（丝裂原和应激激活蛋白激酶1，ERK激活下游的CREB激酶）。与ERK途径的经典抑制剂相比，这导致了谷氨酸诱导的即刻早期基因（IEG）调控的差异调节。使用TAT-DEF-Elk-1肽或Elk-1的显性负性形式，我们表明Elk-1磷酸化控制树突伸长、SRF和肌动蛋白表达水平以及细胞骨架动力学。
