Alzheimer样磷酸酯酶缺陷导致神经细丝异常磷酸化和聚积

Alzheimer-like Protein Phosphatase Deficiency Leads to Abnormal Phosphorylation and Accumulation of Neurofilaments

目的研究Alzheimer病(AD)样蛋白磷酸酯酶缺陷与神经细丝异常的关系,探讨神经细丝在AD发病中的作用。方法用蛋白磷酸酯酶抑制剂冈田酸(OA)处理人成神经瘤细胞(SY5Y)后,用倒置显微镜,免疫组化,生物化学等技术观察细胞形态,神经细丝的表达、磷酸化和细胞定位以及细胞毒性作用。结果未经处理的SY5Y细胞中被SMI32识别的非磷酸化神经细丝在细胞体和突起中均被检测,但在胞体中的含量特别丰富;被SMI34识别的磷酸化神经细丝则主要在细胞的表层和突起部分被检测。用OA处理后,非磷酸化神经细丝的显色反应随OA浓度增加而显著减弱;而磷酸化神经细丝的显色则随OA浓度增加而明显增强,并由轴丘向胞体聚积。免疫印迹结果显示:OA处理使SMI34显色呈剂量依赖性增高。OA在引起神经细丝异常改变的同时,对细胞产生剂量依赖性毒性作用:15nmol/LOA使SY5Y细胞光泽度降低,数目减少,轴突长度缩短,细胞活性降低;当OA浓度增加至30nmol/L时,上述细胞毒性作用增强,并出现大量无光泽,无突起的圆形细胞;当OA浓度达45nmol/L时,全部细胞均漂浮死亡。结论蛋白磷酸酯酶缺陷导致神经细丝的异常磷酸化和聚积,这一过程很可能参与AD神经原纤维变性。

Objective To explore the effect of Alzheimer-like protein phosphatase deficiency on neurofilam ent phosphorylation.Methods Cell culture,light microscopy,immunocytochemistry and biochemistry techni -ques were used to make a phosphatase deficient cell model,to detect cell morphology,neurofilament phosphorylation and distribution,cell viability and activity.Results Non-phosphorylated neurofilament recognized by SMI32was detected both in cell body and cell processes,it was extremely enriched in cell bodies;Phosphorylated neurofilament bound to SMI34was mainly determined in cell processes and cell surface.After treatment with okadaic acid (OA),non-phosphorylation-dependent antibodies SMI32staining was significantly decreased in the cell body,whereas phosphorylated neurofilament rea-cted with SMI34was strikingly increased in immunocytochemistry and Western blot,and prominently acc umulated to the same cell location.Accompanied with hyperphosphorylation and accumulation of neu ro filament,dose dependent cell toxicity was observed by okadaic acid treatment.Conclusion Defi-ciency in protein phosphatase induces in neuroblastome cell line,neurofilament phosphorylation and acc umulation,which is involved in Alzheimer neurofibrillary degeneration.