Brain Health Research Centre, University of Otago Dunedin, New Zealand ; Department of Anatomy, Otago School of Medical Sciences, University of Otago Dunedin, New Zealand.
Queensland Brain Institute, The University of Queensland Brisbane, QLD, Australia.
Front Mol Neurosci. 2014 Dec 9;7:98. doi: 10.3389/fnmol.2014.00098. eCollection 2014.
Coordinated regulation of gene expression is essential for consolidation of the memory mechanism, long-term potentiation (LTP). Triggering of LTP by N-methyl-D-aspartate receptor (NMDAR) activation rapidly activates constitutive and inducible transcription factors, which promote expression of genes responsible for LTP maintenance. As microRNA (miRNA) coordinate expression of genes related through seed sites, we hypothesize that miRNA contribute to the regulation of the LTP-induced gene response. MiRNA function primarily as negative regulators of gene expression. As LTP induction promotes a generalized rapid up-regulation of gene expression, we predicted a complementary rapid down-regulation of miRNA levels. Accordingly, we carried out global miRNA expression profiling in the rat dentate gyrus 20 min post-LTP induction in vivo. Consistent with our hypothesis, we found a large number of differentially expressed miRNA, the majority down-regulated. Detailed analysis of miR-34a-5p and miR-132-3p revealed this down-regulation was transient and NMDAR-dependent, whereby block of NMDARs released an activity-associated inhibitory mechanism. Furthermore, down-regulation of mature miR-34a-5p and miR-132-3p occurred solely by post-transcriptional mechanisms, occurring despite an associated up-regulation of the pri-miR-132 transcript. To understand how down-regulation of miR-34a-5p and miR-132-3p intersects with the molecular events occurring following LTP, we used bioinformatics to identify potential targets. Previously validated targets included the key LTP-regulated genes Arc and glutamate receptor subunits. Predicted targets included the LTP-linked kinase, Mapk1, and neuropil-associated transcripts Hn1 and Klhl11, which were validated using luciferase reporter assays. Furthermore, we found that the level of p42-Mapk1, the protein encoded by the Mapk1 transcript, was up-regulated following LTP. Together, these data support the interpretation that miRNA, in particular miR-34a-5p and miR-132-3p, make a surprisingly rapid contribution to synaptic plasticity via dis-inhibition of translation of key plasticity-related molecules.
基因表达的协调调控对于巩固记忆机制——长时程增强（LTP）是必不可少的。N-甲基-D-天冬氨酸受体（NMDAR）的激活触发 LTP，迅速激活组成型和诱导型转录因子，促进负责 LTP 维持的基因表达。由于 microRNA（miRNA）通过种子位点协调相关基因的表达，我们假设 miRNA 有助于调节 LTP 诱导的基因反应。miRNA 主要作为基因表达的负调控因子。由于 LTP 诱导促进基因表达的广泛快速上调，我们预测 miRNA 水平会相应地快速下调。因此，我们在体内诱导 LTP 后 20 分钟对大鼠齿状回进行了全局 miRNA 表达谱分析。与我们的假设一致，我们发现大量差异表达的 miRNA，大多数下调。对 miR-34a-5p 和 miR-132-3p 的详细分析表明，这种下调是短暂的且依赖于 NMDAR，其中阻断 NMDAR 会释放出一种与活动相关的抑制机制。此外，成熟的 miR-34a-5p 和 miR-132-3p 的下调仅通过转录后机制发生，尽管与之相关的 pri-miR-132 转录物上调。为了了解 miR-34a-5p 和 miR-132-3p 的下调如何与 LTP 后发生的分子事件交叉，我们使用生物信息学来识别潜在的靶标。以前验证的靶标包括关键的 LTP 调节基因 Arc 和谷氨酸受体亚基。预测的靶标包括 LTP 相关激酶 Mapk1 和神经突相关转录物 Hn1 和 Klhl11，使用荧光素酶报告基因测定进行了验证。此外，我们发现 LTP 后 Mapk1 转录物编码的蛋白质 p42-Mapk1 的水平上调。总的来说，这些数据支持以下解释：miRNA，特别是 miR-34a-5p 和 miR-132-3p，通过解除关键可塑性相关分子翻译的抑制作用，对突触可塑性做出了惊人的快速贡献。
