Institut für Pharmakologie und Toxikologie der Technischen Universität München, Biedersteiner Strasse 29, 80802 München, Germany.
Neurosci Lett. 2010 Apr 5;473(2):82-6. doi: 10.1016/j.neulet.2010.02.020. Epub 2010 Feb 18.
The process transforming newly learned information into stable long-term memory is called memory consolidation and, like the underlying long-term synaptic plasticity, critically depends on de novo RNA and protein synthesis. We have shown recently that the cGMP-dependent protein kinase Type I (cGKI) plays an important role for the consolidation of amygdala-dependent fear memory and long-term potentiation (LTP) in the lateral amygdala. Signalling downstream of cGKI at the level of transcriptional regulation remained unclear. A transcription factor of major importance for learning and memory is the cAMP-response element binding protein (CREB). The representation of fear memory in the lateral amygdala strikingly depends on the activity of CREB in individual neurons. Moreover, findings from in vitro experiments demonstrate CREB phosphorylation by cGK. In the hippocampus, CREB phosphorylation increases following activation of NO/cGMP signalling contributing to the late phase of LTP. To demonstrate a link from cGKI to activation of CREB and CREB-dependent transcription in neurons of the lateral amygdala as a possible mechanism for cGKI-mediated fear memory consolidation, we examined the effect of cGMP on activation of CREB/CRE using immunohistochemical staining specific for phospho-CREB and a reporter gene in control and cGKI-deficient mice, respectively. Supporting our hypothesis, marked CREB phosphorylation and CRE-mediated transcription was induced by cGMP in the lateral amygdala of control mice, but not in cGKI-deficient mice. It has been proposed that activation of cGKI is followed by its nuclear translocation that would allow direct phosphorylation of CREB. Therefore, we examined the cellular localisation of cGKI in neurons of the lateral amygdala in the presence of cGMP by double staining for cGKI and a nuclear marker in sections from areas showing prominent CREB phosphorylation, and did not observe prominent nuclear translocation of the enzyme. In summary, we provide evidence that cytosolic cGKI can support fear memory consolidation and LTP in neurons of the lateral amygdala via activation of CREB and CRE-dependent transcription.
将新学到的信息转化为稳定的长期记忆的过程称为记忆巩固，与潜在的长期突触可塑性一样，它严重依赖于新的 RNA 和蛋白质合成。我们最近表明，环鸟苷酸依赖性蛋白激酶 I（cGKI）在杏仁核依赖性恐惧记忆和外侧杏仁核中的长时程增强（LTP）的巩固中起着重要作用。cGKI 在转录调节水平上的信号转导仍不清楚。对于学习和记忆非常重要的转录因子是 cAMP 反应元件结合蛋白（CREB）。外侧杏仁核中恐惧记忆的表达强烈依赖于单个神经元中 CREB 的活性。此外，体外实验的结果表明 cGK 可使 CREB 磷酸化。在海马体中，NO/cGMP 信号的激活会导致 CREB 磷酸化增加，从而促进 LTP 的后期阶段。为了证明 cGKI 可激活 CREB 并在外侧杏仁核神经元中引发 CREB 依赖性转录，作为 cGKI 介导的恐惧记忆巩固的可能机制，我们使用磷酸化 CREB 的免疫组织化学染色和报告基因分别在对照和 cGKI 缺陷型小鼠中检测 cGMP 对 CREB/CRE 的激活作用。支持我们的假设，cGMP 可在对照小鼠的外侧杏仁核中诱导明显的 CREB 磷酸化和 CRE 介导的转录，但在 cGKI 缺陷型小鼠中则不能。已经提出，cGKI 的激活会导致其核转位，从而允许直接磷酸化 CREB。因此，我们通过在具有明显 CREB 磷酸化的区域的切片中对 cGKI 和核标记物进行双重染色，研究了 cGMP 存在时外侧杏仁核神经元中 cGKI 的细胞定位，并未观察到酶的明显核转位。总之，我们提供的证据表明，细胞质 cGKI 可以通过激活 CREB 和 CRE 依赖性转录来支持外侧杏仁核神经元中的恐惧记忆巩固和 LTP。
