Functional analysis of phospholipid metabolizing enzymes during cell death after ischemia

在以往的研究中，我们证实了在大鼠大脑中动脉梗死后，在正常海马神经元中分布于胞核的二酰基甘油激酶(DGK)z被从胞核移位到胞浆。但目前尚不清楚缺血诱导DGKz易位的机制以及DGKz定位于细胞质后的生理功能。在本研究中，我们证实DGKz核输出受缺血后钙内流信号的调节。此外，胞浆中的DGKz在体外和体内的海马神经元中被泛素化和降解。通过DGKz基因缺陷小鼠脑缺血后细胞周期蛋白D和细胞周期蛋白E的表达，以及体内和体外siRNA敲除实验，这种下调导致内质网应激诱导的细胞死亡。这些数据表明，DGKz通过抑制细胞周期蛋白的表达和神经元的细胞周期重入而下调缺血钙信号。

In previous study, we demonstrated that diacylglycerol kinase (DGK)z which is distributed at nucleus in normal hippocampal neuron in vivo, is translocated to cytoplasm from nucleus by middle cerebral artery infarction in rat. But it is unclear that the mechanisms of ischemia induced translocation of DGKz and the physiological functions after localization in cytoplasm of DGKz. In this study, we demonstrated that DGKz nuclear export is regulated that calcium influx signaling after ischemia. Moreover, cytoplasmic DGKz is poly-ubiquitinated and degradated in hippocampal neuron in vitro and in vivo. This downregulation causes ER stress induced cell death following expression of cyclin D and cyclin E in neurons after ischema using DGKz deficient mice and siRNA knocdown study in vivo and in vitro. These datas suggest that DGKz is a downregulator of ischemic calcium signaling by inhibiting cyclin expression and cell cycle re-entry of neurons.