蛋白酶体抑制剂对神经细胞前咽缺陷蛋白-1表达的影响

The effect of proteasomal inhibitors on anterior pharynx decfective-1 expression in neuronal cells

目的 探讨神经细胞内前咽缺陷蛋白-1（Aph-1）的蛋白降解是经蛋白酶体途径还是经溶酶体途径介导.方法 在人神经母细胞瘤细胞（SH-SY5Y）建立稳定表达Aph-1细胞株的基础上,应用蛋白酶体和溶酶体酶抑制剂分别处理Aph-1细胞株,并结合Western blotting、放射性同位素脉冲示踪技术（Pulse-chase）、免疫荧光双标等技术,检测细胞内Aph-1的蛋白表达变化.结果 Western blotting结果显示,特异性蛋白酶体抑制剂能显著提高神经细胞内源性和外源性Aph-1的蛋白表达水平,且高度特异的蛋白酶体抑制剂乳胞素（Lactacystin）对Aph-1表达的增强效应呈剂量依赖性和时间依赖性;而非蛋白酶体蛋白酶抑制剂ALLM和溶酶体酶抑制剂对Aph-1的蛋白表达无影响;Pulsechase结果显示,蛋白酶体抑制剂可增强细胞内新合成Aph-1的表达水平,其增强作用是通过阻止35S-Aph-1的蛋白降解实现;免疫荧光双标结果显示,Aph-1与泛素在细胞内共存.结论 神经细胞内Aph-1的蛋白降解由蛋白酶体途径介导,与溶酶体途径无关;Aph-1在降解之前经泛素化修饰.

Objectives To investigate whether degradation of anterior pharynx decfective-1（Aph-1） goes through proteasomal pathway or lysosomal pathway.Methods Various methods such as cell culture,Western blotting,pulse-chase metabolic labeling technique,double immunofluoresecnt staining,combined with proteasomal and lysosomal inhibition were used to check Aph-1 expression level in stable Aph-1-transfected or non-transfected neuronal（SH-SY5Y）cell line.Results Using Western blotting,treating the neuronal cells with proteasome specific inhibitors significantly increased the expression of both endogenous and exogenous Aph-1.The effect of the proteasome inhibitors on Aph-1 expression was dose-and time-dependent Lysosomal pathway was not involved in Aph-1 degradation. Pulse-chase metabolic labeling experiment showed that the turnover of newly-synthesized radiolabeled Aph-1 protein was blocked by Lactacystin.Double immunofluorescent staining revealed colocalization of Aph-1 and ubiquitin in the same cells.Conclusion Degradation of Aph-1 protein is mediated by proteasomal pathway in neuronal cells,and is not related to lysosomal pathway.Aph-1 protein is ubiquitinated before degradation.