突变型α-核突触蛋白的自噬性降解途径及可能机制

目的 观察突变型α-核突触蛋白对PC12细胞增殖的影响和可能的降解途径,探讨其在帕金森病发病机制中的作用.方法 对转染了α-核突触蛋白(A30P)的PC12细胞进行药物干预,检测细胞的增殖活性,并采用透射电镜观察细胞超微结构改变以及自噬的特征性改变,同时检测α-核突触蛋白的表达和超氧化物歧化酶(SOD)的水平.结果 (1)Western Blot法检测α-核突触蛋白的表达:A30P+渥曼青霉素组(A30P+W组)、A30P+1-甲基4-苯基吡啶组(A30P+MPP+组)较A30P组明显增高,以A30P+W组最为明显;而A30P+雷帕霉素组(A30P+R组)条带较A30P组减低(P＜0.01);(2)不同时间点细胞培养液中SOD水平(U/ml)的测定:用MPP+处理转染了突变型α-核突触蛋白的PC12细胞后,培养液中SOD水平(A30P+MPP+组:3 h:97.49±13.8;12 h:102.7±12.7:24 h:101.5±11.8;48 h:104.3±12.4)较A30P组在各时间点显著下调(t=3.7721,P=0.0017);A30P+R组在给药12 h以后,培养液中SOD水平逐渐升高,其中在24 h(121.2±13.0)、48 h(124.3±14.1)和72 h(127.7±13.7)时与A30P+W组比较差异有统计学意义(t=2.9746,P=0.0083);突变型α-核突触蛋白激活了自噬途径,并介导了MPP+的毒性作用,自噬抑制剂渥曼青霉素可通过抑制自噬而加剧α-核突触蛋白积聚,导致细胞死亡;而自噬诱导剂雷帕霉素则可以通过诱导自噬的发生而促进α-核突触蛋白的降解和细胞生长.结论 α-核突触蛋白的异常积聚导致PC12细胞的自噬性细胞死亡,促进自噬有助于突变型α-核突触蛋白降解,对细胞具有保护作用.

Autophagic pathway and probable mechanism in degradation of mutant α-synuclein in PC12 cells

Objective To observe the effect of mutant α-synuclein(A30P)in autophagic programmed cell death by transfected PC12 cells and explore its probable role and pathway in PD.Methods The definite PC12 cells which were transfected mutant α-synuclein(A30P)were constructed at first and MPP+,Rapamycin and Wortmanin were administrated to transfected PC12 cells with mutant α-synuclein. Not only the proliferative activity of cells was detected with MTT method but also the ultrastructttre changes of cells and expression of α-synuclein in different circumstance were observed by transmission electron microscopy(TEM),Western Blot and the level of SOD.Results (1)The expression of α-synuclein in groups A30P+Wortmannin and A30P+MPP+was higher than that in group A30P(P＜0.01), particularly.there was more significant expression of α-synuclein in group A30P+Wortmannin.The expression of α-synuclein in group A30P+Rapamycin was weaker than that in group A30P(P＜0.01); (2)The results showed that the SOD level(group A30P+MPP+:3 h:97.49±13.8;12 h:102.7±12.7; 24 h:101.5±11.8;48 h:104.3±12.4)was significantly decreased at various time points after MPP+ treatment compared that of group A30P(t=3.7721,P=0.0017).SOD level gradually increased in A30P +Rapamycin 12 h and showed significant difference at 24 h(121.2±13.0),48 h(124.3±14.1)and 72 h(127.7±13.7)after drug treatment compared with that in group A30P+Wortmannin(t:2.9746, P=0.0083);(3)Mutant α-synuclein(A30P)leading to PC12 cells death by means of autophagy involved α-synuclein accumulation,membrane lipid oxidation,and loss of plasma membrane integrity.Mutant α- synuclein(A30P)mediated the toxicity of MPP+.Rapamycin,an inducer of autophagy,reduced the aggregation of α-synuclein in transfected cells.Meanwhile,Wortmanin,an inhibitor of autophagy,promoted the aggregation of α-synuclein in transfected cells and induced cells to die.Conclusions The abnormal aggregation of α-synuclein induces autophagic programmed cell death in PC12 cells and mutant α-synuclein (A30P)mediates the toxicity of MPP+.Meanwhile,Rapamycin may reduce the aggregation of α-synuclein in transfeeted cells by activation of autophagic pathway.