视神经损伤后脑衰反应调节蛋白-2表达及其磷酸化修饰的变化及意义

Changes of collapsin response mediator protein-2 and its phosphorylated protein levels following optic nerve injury

背景 脑衰反应调节蛋白-2（CRMP-2）具有促进中枢神经轴突生长的作用,但中枢神经损伤后在细胞周期素依赖蛋白激酶5（CDK5）诱导下CRMP-2会发生过度磷酸化修饰,从而导致生长锥塌陷,阻碍神经系统的修复.视神经作为一种特殊的中枢神经组织,其损伤后是否发生CRMP-2表达的变化和磷酸化修饰鲜见研究报道. 目的 探讨视神经钳夹伤小鼠模型视神经组织中CRMP-2表达及其磷酸化修饰水平的动态变化及意义.方法 选取8～9周龄健康BALB/c小鼠48只,雌雄不限.采用随机数字表法将小鼠随机分为假手术组和损伤后3、7、14 d组,每组12只.各损伤组小鼠右眼术中暴露视神经,用小号动脉夹于球后2 mm处夹持视神经10s,假手术组小鼠手术操作同各损伤组,但不钳夹视神经.分别于术后3、7、14 d获取小鼠视神经组织,采用实时荧光定量PCR法检测各组小鼠视神经组织中CRMP-2 mRNA的相对表达量;采用Western blot法检测各组小鼠视神经组织中CRMP-2蛋白、磷酸化CRMP-2（p-CRMP-2）及CDK5的表达变化,检测结果进行组间比较.结果 假手术组及损伤后3、7、14d组小鼠视神经组织中CRMP-2 mRNA及蛋白相对表达量的总体比较差异均无统计学意义（CRMP-2 mRNA：F=2.971,P=0.097;CRMP4蛋白：F=1.202,P=0.370）.假手术组及损伤后3、7、14 d组小鼠视神经组织中p-CRMP-2蛋白的相对表达量分别为0.001±0.000、0.064±0.003、0.136±0.005和0.346±0.012,CDK5蛋白的相对表达量分别为0.440±0.009、0.723±0.011、0.874±0.015和0.952±0.019,总体比较差异均有统计学意义（p-CRMP-2：F=445.600,P＜0.001;CDK5：F=186.600,P＜0.001）,其中损伤后3、7、14 d组小鼠视神经组织中p-CRMP-2和CDK5蛋白的相对表达量均明显高于假手术组,差异均有统计学意义（均P＜0.01）.结论 小鼠视神经钳夹伤后视神经组织中CRMP-2的表达无明显变化,但视神经组织中CDK5和p-CRMP-2蛋白表达均明显上调,且随着损伤后时间的延长上调更为明显.

Background Collapsin response mediator protein-2 （CRMP-2） can promote the growth of axons,but CRMP-2 occurs hyperphosphorylation under the induction of cyclin-dependent kinase-5 （CDK5） after central nervous system injury,which leads to the collapse of the growth cone and hinders the repair of nervous system.Being a central nervous system tissue,whether the expressions of CRMP-2 and its phosphorylated protein （p-CRMP-2） change after optic nerve injury are rarely studied.Objective This study was to investigate the dynamic changes of CRMP-2 and p-CRMP-2 expressions in injured optic nerve tissue.Methods Forty-eight 8-or 9-week-old BALB/c mice were randomly divided into the sham operation group and postoperative 3-,7-and 14-day group.Optic nerves were exposed and clamped at retrobulbar 2 mm for 10 seconds in the right eyes during the surgery in the postoperative 3-,7-and 14-day groups,and the same operation was performed except the clamp of optic nerve in the sham operation group.The optic nerve tissue was obtained from the eyes 3,7 and 14 days after surgery.The relative expression levels of CRMP-2 mRNA and CRMP-2,p-CRMP-2 and CDK5 proteins in the tissue were detected by real-time fluorescence quantitative PCR and Western blot,respectively.The use and care of the experimental animals complied with the Regulation for the Administration of Affair Concerning Experimental Animals of Third Military Medical University.Results No significant differences were found in the expression levels of CRMP-2 mRNA and CRMP-2 protein among the sham operation group and postoperative 3-,7-and 14-day groups （CRMP-2 mRNA：F =2.971,P =0.097;C RMP-2 protein：F=1.202,P =0.370）.The relative expression levels of p-CRMP-2 protein in the optical nerve were 0.001±0.000,0.064±0.003,0.136±0.005 and 0.346±0.012,and those of CDK5 protein were 0.440±0.009,0.723±0.011,0.874±0.015 and 0.952±0.019 in the sham operation group and postoperative 3-,7-and 14-day groups respectively,showing statistically significant differences among them （p-CRMP-2：F=445.600,P 〈 0.001;CDK5：F=186.600,P〈0.001）,and the relative expression levels of p-CRMP-2 and CDK5 protein were evidently higher in the optical nerve tissue in the postoperative 3-,7-and 14-day groups than those in the sham operation group （all at P〈0.01）.Conclusions There are not significant changes in the expression level of CRMP-2 in the BALB/c mice after optic nerve injury.However,the expression levels of p-CRMP-2 and CDK5 proteins are gradually upregulated as the extending of injured time.