Genetic Control of Glutamate Receptor Function

描述（由申请人提供）：在许多gaba能中间神经元中，相对于其他AMPA受体亚基mRNA， GluR2 mRNA的丰度是高度可变的，这赋予了它们广泛的AMPA受体特性。在某些脆弱的神经元群体中，GluR2 mRNA和蛋白水平在剧烈发作活动或短暂缺血后下降，然后出现明确的细胞损伤组织学迹象，这提高了通过新合成的GluR2缺陷AMPA突触受体的更大突触电流或过量钙进入的可能性，有助于神经元损伤的后期。有证据表明GluR2 mRNA的局部树突翻译活动依赖，以及LTP刺激后的突触后GluR2翻译。所有这些发现表明，GluR2表达适度变化的机制——在发育过程中，在突触可塑性期间，以及在成人癫痫发作或创伤性损伤后——是控制突触表型的重要神经调节控制。当前项目期间的工作已经确定了AMPA受体基因的特定转录和翻译调控机制。在我们提出的工作中，我们打算测试以下假设：1)GluR2 mRNA的翻译调节需要一个或多个位于3'UTR中的保守胞质多聚腺苷化元件（CPE）或多聚腺苷化反应元件（PRE）；ii) MAP激酶通路对GluR2转录物的翻译具有双重调控作用；iii)神经元依赖性转录起始位点选择影响5‘和3’UTR对翻译控制的形式和程度；iv)癫痫发作对GluR2表达的抑制需要GluR2启动子中的RE1沉默子。谷氨酸受体通道的生理特性在翻译和转录水平上的调控应该与LTP的晚期、学习、对癫痫发作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 .