Departments of Pediatrics and Pharmacology, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA 19104, USA.
J Neurochem. 2011 Jun;117(5):812-23. doi: 10.1111/j.1471-4159.2011.07233.x. Epub 2011 Apr 11.
Recently, we demonstrated that mRNA for the neuronal glutamate transporter, excitatory amino acid carrier 1 (EAAC1), is found in dendrites of hippocampal neurons in culture and in dendrites of hippocampal pyramidal cells after pilocarpine-induced status epilepticus (SE). We also showed that SE increased the levels of EAAC1 mRNA 15-fold in synaptoneurosomes. In this study, the effects of SE on the distribution EAAC1 protein in hippocampus were examined. In addition, the effects of Group 1 mGluR receptor activation on the levels of EAAC1 protein were examined in synaptoneurosomes prepared from sham control animals and from animals that experience pilocarpine-induced SE. We find that EAAC1 immunoreactivity increases in pyramidal cells of the hippocampus after 3 h of SE. In addition, the group I mGluR agonist, (S)-3,5-dihydroxyphenylglycine (DHPG), caused an increase in EAAC1 protein levels in hippocampal synaptoneurosomes; this effect of DHPG was much larger (3- to 5-fold) after 3 h of SE. The DHPG-induced increases in EAAC1 protein were blocked by two different inhibitors of translation but not by inhibitors of transcription. mGluR1 or mGluR5 antagonists completely blocked the DHPG-induced increases in EAAC1 protein. DHPG also increased the levels of glutamate receptor 2/3 protein, but this effect was not altered by SE. The DHPG-induced increase in EAAC1 protein was blocked by an inhibitor of the mammalian target of rapamycin or an inhibitor of extracellular signal-regulated kinase. These studies provide the first evidence EAAC1 translation can be regulated, and they show that regulated translation of EAAC1 is up-regulated after SE.
最近，我们证明了神经元谷氨酸转运体、兴奋性氨基酸载体 1（EAAC1）的 mRNA 存在于培养的海马神经元树突中和匹罗卡品诱导的癫痫持续状态（SE）后的海马锥体神经元树突中。我们还表明，SE 使突触小体中的 EAAC1 mRNA 水平增加了约 15 倍。在这项研究中，我们研究了 SE 对海马 EAAC1 蛋白分布的影响。此外，还研究了 SE 后，在来自匹罗卡品诱导 SE 动物和假手术对照动物的突触小体中，1 型 mGluR 受体激活对 EAAC1 蛋白水平的影响。我们发现，SE 后 3 小时，海马锥体细胞中 EAAC1 免疫反应性增加。此外，I 组 mGluR 激动剂（S）-3,5-二羟苯甘氨酸（DHPG）使海马突触小体中的 EAAC1 蛋白水平增加；这种 DHPG 的作用在 SE 后 3 小时更大（约 3-5 倍）。DHPG 诱导的 EAAC1 蛋白增加被两种不同的翻译抑制剂阻断，但不被转录抑制剂阻断。mGluR1 或 mGluR5 拮抗剂完全阻断了 DHPG 诱导的 EAAC1 蛋白增加。DHPG 还增加了谷氨酸受体 2/3 蛋白的水平，但 SE 并没有改变这种作用。mTOR 或细胞外信号调节激酶抑制剂阻断了 DHPG 诱导的 EAAC1 蛋白增加。这些研究首次提供了 EAAC1 翻译可以被调节的证据，并且表明 SE 后 EAAC1 的调节翻译被上调。
