PI3K/Akt调控内质网应激对GRP78的诱导

PI3K/Akt regulates endoplasmic reticulum stress-mediated GRP78 induction

目的:研究内质网应激条件下PI3K/Akt信号通路对HEK293细胞中葡萄糖调节蛋白78(GRP78)表达水平的调控作用。方法:采用PI3K抑制剂LY294002、Akt1失活型突变载体Akt1(K179M)及Akt siRNAs阻断内质网应激介导的Akt活化,采用Akt激活型突变载体Myr-Akt过度激活内质网应激介导的Akt活化,并利用RT-PCR和Western blotting技术分析内质网应激条件下PI3K/Akt信号途径对HEK293细胞中GRP78表达水平的调控作用。结果:LY294002、Akt1(K179M)及Akt1 siRNA均明显抑制了内质网应激对GRP78的诱导。Myr-Akt1明显促进内质网应激对GRP78的诱导。Myr-Akt2/3及Akt2/3 siRNA对GRP78的诱导均无影响。PI3K/Akt信号通路阻断或过度激活对GRP78 mRNA水平的诱导无影响,但是对GRP78的降解有显著影响。结论:HEK293细胞中,PI3K/Akt通过蛋白稳定性调节促进内质网应激对GRP78的诱导。

AIM：To investigate the effect of PI3K/Akt pathway on endoplasmic reticulum（ER）stress-mediated glucose-regulated protein 78（GRP78）induction in human embryonic kidney 293 cells（HEK293）cells.METHODS： PI3K inhibitor LY294002,dominant negative kinase-dead mutant vector for HA-Akt（K179M）and Aktl siRNAs were used to block the PI3K/Akt pathway under ER stress.Constitutively active expression vectors for Akt（myr-HA-Akt） were used to up-regulate Akt activity under ER stress.The effects of PI3K/Akt on ER stress-mediated GRP78 induction in HEK293 cells were determined by Western blotting and RT-PCR.RESULTS：GRP78 induction was inhibited by LY294002,Akt1（K179M）and Akt1 siRNA,but was increased by myr-Akt1 in dithiothreitol-and thapsigargin-treated HEK293 cells.However,both myr-Akt2/3 and Akt2/3 siRNA had no effect on GRP78 induction in HEK293 cells under ER stress.Furthermore,the PI3K/Akt pathway didn＇t regulated GRP78mRNA induction but increased GRP78 protein stability.CONCLUSION：PI3K/Akt promotes GRP78 accumulation through increasing the stability of GRP78 protein in HEK293 cells under ER stress.