Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 501260, China; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China.
Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 501260, China; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China.
Biochim Biophys Acta Mol Basis Dis. 2017 Jun;1863(6):1492-1499. doi: 10.1016/j.bbadis.2017.04.018. Epub 2017 Apr 19.
Voltage-gated sodium channel α-subunit type I (Na1.1, encoded by SCN1A gene) plays a critical role in the excitability of brain. Downregulation of SCN1A expression is associated with epilepsy, a common neurological disorder characterized by recurrent seizures. Here we reveal a novel role of malate dehydrogenase 2 (MDH2) in the posttranscriptional regulation of SCN1A expression under seizure condition. We identified that MDH2 was an RNA binding protein that could bind two of the four conserved regions in the 3' UTRs of SCN1A. We further showed that knockdown of MDH2 or inactivation of MDH2 activity in HEK-293 cells increased the reporter gene expression through the 3' UTR of SCN1A, and MDH2 overexpression decreased gene expression by affecting mRNA stability. In the hippocampus of seizure mice, the upregulation of MDH2 expression contributed to the decrease of the Na1.1 levels at posttranscriptional level. In addition, we showed that the HO levels increased in the hippocampus of the seizure mice, and HO could promote the binding of MDH2 to the binding sites of Scn1a gene, whereas β-mercaptoethanol decreased the binding capability, indicating an important effect of the seizure-induced oxidation on the MDH2-mediated downregulation of Scn1a expression. Taken together, these data suggest that MDH2, functioning as an RNA-binding protein, is involved in the posttranscriptional downregulation of SCN1A expression under seizure condition.
电压门控钠离子通道 α 亚基型 I（Na1.1，由 SCN1A 基因编码）在大脑兴奋性中发挥关键作用。SCN1A 表达下调与癫痫有关，癫痫是一种常见的神经系统疾病，其特征是反复发作。在这里，我们揭示了苹果酸脱氢酶 2（MDH2）在癫痫状态下 SCN1A 表达的转录后调控中的新作用。我们确定 MDH2 是一种 RNA 结合蛋白，可以结合 SCN1A 的 3'UTR 中四个保守区域中的两个。我们进一步表明，在 HEK-293 细胞中敲低 MDH2 或失活 MDH2 活性会通过 SCN1A 的 3'UTR 增加报告基因的表达，而 MDH2 过表达会通过影响 mRNA 稳定性降低基因表达。在癫痫小鼠的海马体中，MDH2 表达的上调导致 Na1.1 水平在转录后水平下降。此外，我们表明，HO 水平在癫痫小鼠的海马体中增加，HO 可以促进 MDH2 与 Scn1a 基因结合位点的结合，而β-巯基乙醇降低了结合能力，表明氧化应激对 MDH2 介导的 Scn1a 表达下调的重要影响。总之，这些数据表明，MDH2 作为一种 RNA 结合蛋白，参与了癫痫状态下 SCN1A 表达的转录后下调。
