Li Y, Pei L, Zhang G Y
Research Center of Biochemistry and Molecular Biology, Xuzhou Medical College, Xuzhou 221002, China.
Sheng Li Xue Bao. 2000 Apr;52(2):137-42.
The effects of ischemia/reperfusion on the levels of protein tyrosine phosphorylation in the synaptosome of gerbil hippocampus and the effects of three drugs, ketamine (KT), a noncompetitive antagonist of NMDA receptor, nifedipine (ND), a voltage gated calcium channel (VGCC) antagonist and 6,7-dinitroquinoxaline-2,3-dione (DNQX), a non-NMDA receptor antagonist, on the phosphorylation were studied. The results showed that (1) 15 min of transient forebrain ischemia caused a marked decrease in the level of tyrosine phosphorylation of many protein bands, but, if followed by 15 min to 48 h of reperfusion, many protein bands including the 180 kD protein appeared to be increased; (2) the degree of tyrosine phosphorylation of the protein bands was higher than that of the sham-operated control, e.g. that of 180 kD protein was 1.8 fold of control; (3) administration of KT and ND before ischemia attenuated the increase of 180 kD protein tyrosine phosphorylation, while DNQX had no effect; and (4) immunoprecipitation and Western blot confirmed that the NR2B subunits of the NMDA receptors were among the phosphorylated 180 kD protein and ischemia /reperfusion did not affect the level of protein expression of NR2B. The above results suggest that the increase of tyrosine phosphorylation of NR2B induced by ischemia/reperfusion may further activate NR channels and aggravate neuronal injury, and that NR channels and other protein can be regulated by tyrosine phosphorylation not only through NR channels themselves but also via L-type VGCCs. Consequently, antagonists of both NR channels and L-type VGCCs may play a certain role in prevention and cure of ischemic brain injury.
研究了缺血/再灌注对沙土鼠海马突触体中蛋白质酪氨酸磷酸化水平的影响，以及三种药物（氯胺酮（KT），一种NMDA受体非竞争性拮抗剂；硝苯地平（ND），一种电压门控钙通道（VGCC）拮抗剂；6,7-二硝基喹喔啉-2,3-二酮（DNQX），一种非NMDA受体拮抗剂）对磷酸化的影响。结果表明：（1）15分钟短暂性前脑缺血导致许多蛋白条带的酪氨酸磷酸化水平显著降低，但如果随后进行15分钟至48小时的再灌注，包括180kD蛋白在内的许多蛋白条带似乎会增加；（2）蛋白条带的酪氨酸磷酸化程度高于假手术对照组，例如180kD蛋白的磷酸化程度是对照组的1.8倍；（3）缺血前给予KT和ND可减弱180kD蛋白酪氨酸磷酸化的增加，而DNQX则无作用；（4）免疫沉淀和蛋白质印迹证实，NMDA受体的NR2B亚基是磷酸化的180kD蛋白之一，缺血/再灌注不影响NR2B的蛋白表达水平。上述结果表明，缺血/再灌注诱导的NR2B酪氨酸磷酸化增加可能会进一步激活NR通道并加重神经元损伤，并且NR通道和其他蛋白质不仅可以通过NR通道自身，还可以通过L型VGCCs受到酪氨酸磷酸化的调节。因此，NR通道拮抗剂和L型VGCCs拮抗剂可能在缺血性脑损伤的防治中发挥一定作用。
