Chang Raymond Chuen-Chung, Suen Ka-Chun, Ma Chi-Him, Elyaman Wassim, Ng Ho-Keung, Hugon Jacques
Department of Anatomy, Faculty of Medicine, and Central Laboratory of the Institute of Molecular Technology for Drug Discovery and Synthesis, The University of Hong Kong, Hong Kong.
J Neurochem. 2002 Dec;83(5):1215-25. doi: 10.1046/j.1471-4159.2002.01237.x.
Inhibition of protein translation plays an important role in apoptosis. While double-stranded RNA-dependent protein kinase (PKR) is named as it is activated by double-stranded RNA produced by virus, its activation induces an inhibition of protein translation and apoptosis via the phosphorylation of the eukaryotic initiation factor 2alpha (eIF2alpha). PKR is also a stress kinase and its levels increase during ageing. Here we show that PKR activation and eIF2alpha phosphorylation play a significant role in apoptosis of neuroblastoma cells and primary neuronal cultures induced by the beta-amyloid (Abeta) peptides, the calcium ionophore A23187 and flavonoids. The phosphorylation of eIF2alpha and the number of apoptotic cells were enhanced in over-expressed wild-type PKR neuroblastoma cells exposed to Abeta peptide, while dominant-negative PKR reduced eIF2alpha phosphorylation and apoptosis induced by Abeta peptide. Primary cultured neurons from PKR knockout mice were also less sensitive to Abeta peptide toxicity. Activation of PKR and eIF2alpha pathway by Abeta peptide are triggered by an increase in intracellular calcium because the intracellular calcium chelator BAPTA-AM significantly reduced PKR phosphorylation. Taken together, these results reveal that PKR and eIF2alpha phosphorylation could be involved in the molecular signalling events leading to neuronal apoptosis and death and could be a new target in neuroprotection.
蛋白质翻译的抑制在细胞凋亡中起重要作用。双链RNA依赖性蛋白激酶(PKR)因其被病毒产生的双链RNA激活而得名,其激活通过真核起始因子2α(eIF2α)的磷酸化诱导蛋白质翻译抑制和细胞凋亡。PKR也是一种应激激酶,其水平在衰老过程中升高。在此我们表明,PKR激活和eIF2α磷酸化在由β-淀粉样蛋白(Aβ)肽、钙离子载体A23187和类黄酮诱导的神经母细胞瘤细胞凋亡及原代神经元培养中起重要作用。在暴露于Aβ肽的过表达野生型PKR神经母细胞瘤细胞中,eIF2α的磷酸化和凋亡细胞数量增加,而显性负性PKR降低了Aβ肽诱导的eIF2α磷酸化和细胞凋亡。来自PKR基因敲除小鼠的原代培养神经元对Aβ肽毒性也较不敏感。Aβ肽对PKR和eIF2α途径的激活是由细胞内钙增加触发的,因为细胞内钙螯合剂BAPTA-AM显著降低了PKR磷酸化。综上所述,这些结果表明PKR和eIF2α磷酸化可能参与导致神经元凋亡和死亡的分子信号事件,并且可能是神经保护的新靶点。