Sgambato V, Pagès C, Rogard M, Besson M J, Caboche J
Laboratoire Neurochimie-Anatomie, Institut des Neurosciences, Unité Mixte de Recherche 7624, Université Pierre et Marie Curie, 75005 Paris, France.
J Neurosci. 1998 Nov 1;18(21):8814-25. doi: 10.1523/JNEUROSCI.18-21-08814.1998.
Activity-dependent changes in neuronal structure and synaptic remodeling depend critically on gene regulation. In an attempt to understand how glutamate receptor stimulation at the membrane leads to gene regulation in the nucleus, we traced intracellular signaling pathways targeting DNA regulatory elements of immediate early genes (IEGs). For this purpose we used an in vivo electrical stimulation of the glutamatergic corticostriatal pathway. We show that a transient activation of extracellular signal-regulated kinase (ERK) proteins (detected by immunocytochemistry with an anti-active antibody) is spatially coincident with the onset of IEG induction [c-fos, zif 268, and map kinase phosphatase-1 (MKP-1) detected by in situ hybridization] in the striatum, bilaterally. Both Elk-1 and CREB transcription factors (targeting SRE and CRE DNA regulatory elements, respectively) were hyperphosphorylated in register with ERK activation and IEG mRNA induction. However, their hyperphosphorylation occurred in different subcellular compartments: the cytoplasm and the nucleus for Elk-1 and the nucleus for CREB. The role of the ERK signaling cascade in gene regulation was confirmed after intrastriatal and unilateral injection of the specific ERK inhibitor PD 98059, which completely abolished c-fos, zif 268, and MKP-1 mRNA induction in the injected side. Of interest, both Elk-1 and CREB hyperphosphorylation also was impaired after PD 98059 injection. Thus two different ERK modules, one depending on the cytoplasmic activation of Elk-1 and the other one depending on the nuclear activation of CREB, control IEG transcriptional regulation in our model. Our findings provide significant insights into intracellular mechanisms underlying synaptic plasticity in the striatum.
神经元结构的活动依赖性变化和突触重塑关键取决于基因调控。为了理解膜上的谷氨酸受体刺激如何导致细胞核中的基因调控，我们追踪了靶向即刻早期基因（IEGs）DNA调控元件的细胞内信号通路。为此，我们对谷氨酸能皮质纹状体通路进行了体内电刺激。我们发现，细胞外信号调节激酶（ERK）蛋白的短暂激活（通过抗活性抗体免疫细胞化学检测）在空间上与纹状体中IEG诱导的起始（通过原位杂交检测c-fos、zif 268和丝裂原活化蛋白激酶磷酸酶-1（MKP-1））双侧一致。Elk-1和CREB转录因子（分别靶向SRE和CRE DNA调控元件）均与ERK激活和IEG mRNA诱导同步发生超磷酸化。然而，它们的超磷酸化发生在不同的亚细胞区室：Elk-1在细胞质和细胞核中，CREB在细胞核中。在纹状体内单侧注射特异性ERK抑制剂PD 98059后，ERK信号级联在基因调控中的作用得到证实，该抑制剂完全消除了注射侧c-fos、zif 268和MKP-1 mRNA的诱导。有趣的是，注射PD 98059后Elk-1和CREB的超磷酸化也受到损害。因此，在我们的模型中，两个不同的ERK模块，一个依赖于Elk-1的细胞质激活，另一个依赖于CREB的细胞核激活，控制IEG的转录调控。我们的发现为纹状体突触可塑性的细胞内机制提供了重要见解。
