Genetic Control of Glutamate Receptor Function

描述(由申请人提供)：相对于其他AMPA受体亚单位mRNAs而言，GluR2 mRNA的丰度在许多GABA能中间神经元中是高度可变的，这使得它们具有广泛的AMPA受体特性。在某些脆弱的神经元群体中，在强烈的癫痫发作活动或短暂的缺血后，GluR2的mRNA和蛋白水平在明显的组织学损伤迹象之前下降，这增加了更大的突触电流或通过新合成的缺乏GluR2的AMPA突触受体过量的钙内流导致神经元损伤的后期阶段的可能性。有证据表明，在LTP刺激后，GluR2 mRNA的局部树突状翻译和突触后的GluR2翻译是活性相关的。所有这些发现表明，导致GluR2表达适度变化的机制--发育中、突触可塑性期间以及成人癫痫发作或创伤性伤害后--是控制突触表型的重要神经调控因素。目前项目期的工作已经确定了作用于AMPA受体基因的特定转录和翻译调控机制。在拟议的工作中，我们打算检验以下假设：i)GluR2 mRNA的翻译调控需要位于3‘UTR的一个或多个保守的细胞质多聚腺苷化元件(CPE)或多聚腺苷反应元件(Pre)；ii)MAP激酶通路对GluR2转录本的翻译实施双重控制；iii)神经元依赖的转录起始位置的选择影响5’和3‘UTR对翻译控制的形式和程度；以及iv)癫痫发作抑制GluR2的表达需要GluR2启动子中的Re1沉默。在翻译和转录水平上调节谷氨酸受体通道的生理特性应该与LTP的晚期、学习和对癫痫的反应以及受体表型重塑的其他情况有关。

DESCRIPTION (provided by applicant): The abundance of GluR2 mRNA relative to other AMPA receptor subunit mRNAs is highly variable in many GABAergic interneurons, which endows them with a wide spectrum of AMPA receptor properties. GluR2 mRNA and protein levels decline following intense seizure activity or transient ischemia in certain vulnerable neuron populations before clear histological signs of cell damage, raising the possibility that larger synaptic currents or excess calcium entry through newly synthesized GluR2-deficient AMPA synaptic receptors contributes to the later phase of neuron damage. There is evidence for activity-dependent local dendritic translation of GluR2 mRNA, and for postsynaptic GluR2 translation following LTP stimuli. All of these findings indicate that the mechanisms responsible for moderate changes in GluR2 expression - developmentally, during synaptic plasticity, and after seizures or traumatic insult in the adult - are important neuronal regulatory controls governing synaptic phenotype. Work in the current project period has identified specific transcriptional and translational regulatory mechanisms operating on AMPA receptor genes. In the proposed work we intend to test the following hypotheses: i) that translational regulation of GluR2 mRNA requires one or more of the multiple conserved cytoplasmic polyadenylation elements (CPE) or polyadenylation response elements (PRE) resident in the 3'UTR; ii) that MAP kinase pathways exert dual control over translation of GluR2 transcripts; iii) that neuron-dependent transcriptional start site selection influences the form and extent of translational control by 5' and 3'UTR; and iv) that repression of GluR2 expression by seizures requires the RE1 silencer in the GluR2 promoter. Regulation of the physiological properties of glutamate receptor channels at the translational and transcriptional levels should be relevant to the late phase of LTP, learning, and the response to seizures, as well as other situations in which receptor phenotype is remodeled .