胰岛素信号通路磷脂酰肌醇-3激酶/丝氨酸苏氨酸蛋白激酶对海马神经元β-淀粉样前体蛋白裂解酶1表达的影响

目的 通过胰岛素和磷脂酰肌醇-3激酶(PDK)抑制剂渥曼青霉素(wortmannin,WORT)对PI3K/丝氨酸苏氨酸蛋白激酶(PDK/Akt)信号通路的激活和抑制作用,观察PI3K/Akt信号通路对海马神经元B-淀粉样前体蛋白裂解酶1(BACE1)表达的影响.方法 40只SD大鼠随机分为空白对照组、假手术组、胰岛素组和WORT组(每组10只),海马立体定向注射胰岛素和PI3K抑制剂WORT.免疫组织化学和Western blot法检测PI3K/Akt信号传导相关蛋白以及BACE1的表达水平.结果 注射胰岛素的海马PI3K信号通路下游信号分子较对照组:Akt表达增加(0.952±0.060与0.835±0.029,t=4.9150,P=0.0001),Akt set473位点磷酸化(pAkt)水平上调(0.800±0.075与0.657±0.025,t=4.5598,P=0.0002),糖原合成激酶-3α(GSK-3α)磷酸化水平降低(0.604±0.062与0.726±0. 041,t=3.5871,P=0.0018),而成熟的BACE1及其裂解产物β分泌酶C末端(β-CTF)表达下调.WORT组的PI3K下游信号分子Akt、pAkt表达明显被抑制,磷酸化GSK-3α表达增加,同时成熟的BACE1(1.004±0.096)和β-CTF(1.031±0.048)的表达较对照组(分别0.498±0.064,0.786±0.101)上调(分别t=11.5980,P=0.0000;t=4.2194,P=0.0004).结论 胰岛素信号通路PI3K/AKt可以调节BACE1的表达和活性并参与阿尔茨海默病的发病机制.

Effects of phosphatidylinositol-3 kinase/serine threonine kinase pathway on expression of beta-site amyloid precursor protein cleaving enzyme-1 in the hippocampus neurons

Objective To investigate the effect of phosphatidylinesitol-3 kinase/serine threonine kinase (PI3K/Akt) signaling pathway on expression of beta-site amyloid precursor protein cleaving enzyme-1 (BACE1) in the hippocampus neurons of rat brain. Methods Forty SD rats were randomly divided into 4 groups: blank control group, sham-operated group, insulin group and wortmannin group. Insulin or the specific inhibitor of PI3K, wortmannin was injected into hippocampus neurons to activate or inhibit the signaling pathway in insulin group or wortmannin group, respectively. Immunoprecipitation and Western blot were used to analyze the proteins levels of PI3K/Akt and BACE1. Results In insulin treatment group,among the proteins downstream of signaling pathway, expression of Akt increased (0. 952±0.060 vs 0.835±0.029,t=4.9150, P=0.0001), phospho-Akt set473 increased (0.800±0.075 vs 0.657± 0.025,t=4.5598, P=0.0002), phospho-GSK-3α decreased (0.604±0.062 vs 0.726±0.041, t= 3.5871, P=0.0018 ), and the expression of mature BACE1 and β-CTF significantly decreased. In wortmannin group, the expression of Akt and phospho-Akt ser473 were inhibited; phospho-GSK-3α increased ; mature BACEI (1.004±0.096) and β-CTF (1.031±0.048) increased (t=11.5980, P= 0.0000 and t =4.2194, P =0.0004, respectively). Conclusions PI3K/Akt signaling pathway might effect the expression of BACE1, in which impaired signaling pathway may cause the amyloid precursor protein to be easily processed by BACE1, and thus involves the pathology of Alzheimer' s disease.