GRP75 overexpression inhibits apoptosis induced by glucose deprivation via Raf/Mek/Erk1/2 signaling pathway / 生理学报

ABSTRACT

The purpose of the present study is to investigate whether glucose-regulated protein 75 (GRP75) overexpression inhibits apoptosis induced by glucose deprivation through Raf/Mek/Erk1/2 signaling pathway. After pretreatment with Mek-specific inhibitor U0126, GRP75 overexpressing PC12 cells were incubated in glucose-free DMEM medium for indicated time (6, 12 and 24 h). And DMSO-treated GRP75 overexpressing PC12 cells were applied as control. Western blot was used to determine the expression and phosphorylation level of Erk1/2. MTT assay was used to measure cell viability. Hoechst 33258 staining and flow cytometry using propidium iodide (PI) staining was used to analysis apoptosis. Immunofluorescence with antibody against cytochrome c (Cyt c) was used to detect Cyt c release from mitochondrion. The results showed U0126 prevented the activation of Erk1/2 maintained by GRP75, but the total Erk1/2 expression was not affected. U0126-treated group showed lower cell viability and higher apoptotic rate compared with control group. Immunofluorescence indicated the delay in release of Cyt c was blocked by U0126. These results suggest U0126 prevents protective effect of GRP75 on PC12 cells by inhibiting Erk1/2 phosphorylation, which certifies that GRP75 can inhibit the mitochondria-dependent apoptotic pathway through Raf/Mek/Erk1/2 signaling cascade.