Dubey D, Porter B E
Department of Neurology, School of Medicine, Stanford University, 1201 Welch Road, P211 MSLS, Stanford, CA 94305, United States.
Stanford University Medical School, P211 MSLS, 1201 Welch Road, Stanford, CA 94305, United States.
Neuroscience. 2016 Apr 21;320:57-68. doi: 10.1016/j.neuroscience.2016.01.059. Epub 2016 Feb 1.
cAMP response-element binding protein (CREB)-dependent genes are differentially expressed in brains of temporal lobe epilepsy (TLE) patients and also in animal models of TLE. Previous studies have demonstrated the importance of CREB regulated transcription in TLE. However, the role of the key regulator of CREB activity, CREB-regulated transcription coactivator 1 (CRTC1), has not been explored in epilepsy. In the present study the pilocarpine-induced status epilepticus (SE) model of TLE was used to study the regulation of CRTC1 during and following SE. Nuclear translocation of CRTC1 is critical for its transcriptional activity, and dephosphorylation at serine 151 residue via calcineurin phosphatase regulates cytoplasmic to nuclear transit of CRTC1. Here, we examined the localization and phosphorylation (Ser151) of CRTC1 in SE-induced rat hippocampus at two different time points after SE onset. One hour after SE onset, we found that CRTC1 translocates to the nucleus of CA1 neurons but not CA3 or dentate granule neurons. We further found that this CRTC1 nuclear localization is independent of Ser151 dephosphorylation since we did not detect any difference in dephosphorylation of Ser151 between control and SE animals at this time point. In contrast, 48 h after SE CRTC1 shows increased nuclear localization in the dentate gyrus (DG) of the SE-induced rats. At 48 h after SE, FK506 treatment blocked CRTC1 nuclear localization and dephosphorylation of Ser151. Our results provide evidence that CREB cofactor CRTC1 translocates into the nucleus of a distinct subset of hippocampal neurons during and following SE and this translocalization is regulated by calcineurin at a later time point following SE. Nuclear CRTC1 can bind to CREB possibly altering transcription during epileptogenesis.
环磷酸腺苷反应元件结合蛋白（CREB）依赖性基因在颞叶癫痫（TLE）患者的大脑以及TLE动物模型中存在差异表达。先前的研究已经证明CREB调节的转录在TLE中的重要性。然而，CREB活性的关键调节因子——CREB调节的转录共激活因子1（CRTC1）在癫痫中的作用尚未得到研究。在本研究中，采用毛果芸香碱诱导的TLE癫痫持续状态（SE）模型来研究SE期间及之后CRTC1的调节情况。CRTC1的核转位对其转录活性至关重要，通过钙调神经磷酸酶对丝氨酸151残基的去磷酸化作用调节CRTC1从细胞质到细胞核的转运。在此，我们在SE发作后的两个不同时间点检查了SE诱导的大鼠海马中CRTC1的定位和磷酸化（丝氨酸151）情况。SE发作后1小时，我们发现CRTC1转位至CA1神经元的细胞核，但未转位至CA3或齿状颗粒神经元的细胞核。我们进一步发现，这种CRTC1的核定位与丝氨酸151的去磷酸化无关，因为在这个时间点我们未检测到对照动物和SE动物之间丝氨酸151去磷酸化的任何差异。相反，SE发作后48小时，CRTC1在SE诱导的大鼠齿状回（DG）中的核定位增加。SE发作后48小时，FK506处理阻断了CRTC1的核定位以及丝氨酸151的去磷酸化。我们的结果提供了证据，表明CREB辅因子CRTC1在SE期间及之后转位至海马神经元不同亚群的细胞核中，并且这种转位在SE后的较晚时间点受钙调神经磷酸酶调节。细胞核中的CRTC1可能与CREB结合，从而在癫痫发生过程中改变转录。
