γ-突触核蛋白通过调控自噬对结肠癌细胞起保护作用

γ-Synuclein protects colon cancer cells through autophagy regulation

目的:研究γ-突触核蛋白(γ-synuclein)对内质网应激诱导的结肠癌细胞自噬和凋亡的影响及其细胞保护作用。方法:针对稳定表达γ-synuclein siRNA的人结肠癌HCT116细胞和空载体HCT116细胞,通过基因表达谱芯片分析γ-synuclein下游差异基因,找到可能的自噬及凋亡相关分子。用毒胡萝卜素(thapsigargin,TG)模拟内质网应激,采用Western blot检测γ-synuclein蛋白、自噬相关蛋白[微管相关蛋白1轻链3(microtubule-associated protein 1 light chain 3,LC3)、beclin-1、自噬相关蛋白5(autophagy-related protein 5,ATG5)和ATG7]及凋亡相关蛋白{多腺苷二磷酸核糖聚合酶[poly(ADP-ribose)polymerase,PARP]、pro-caspase-3和pro-caspase-9}的表达,CCK-8法检测细胞活力,荧光显微镜观察吖啶橙染色的酸性囊泡细胞器和绿色荧光蛋白标记的LC3,检测人结肠癌HCT116和SW480细胞自噬、凋亡及活力的变化。分别采用γ-synuclein siRNA、细胞外信号调节激酶(extracellular signal-regulated kinase,ERK)抑制剂PD98059、c-Jun氨基末端激酶(c-Jun N-terminal kinase,JNK)抑制剂SP600125和JNK激活剂anisomycin预处理,Western blot检测γ-synuclein及ERK和JNK信号通路相关蛋白表达,检测伴随的HCT116细胞自噬和凋亡的变化,研究γ-synuclein通过调控相关信号通路对细胞自噬的影响及其细胞保护作用。结果:TG模拟内质网应激诱导的结肠癌细胞自噬主要发生在早期(0~24 h),细胞凋亡主要发生在晚期(36~48 h)。内质网应激上调γ-synuclein的表达,并伴有自噬的增强。γ-synuclein早期(0~24 h)通过激活ERK和JNK通路促进自噬,晚期(36~48 h)通过抑制JNK通路抑制凋亡,从而起到保护细胞的作用。γ-synuclein可能在内质网应激诱导的细胞自噬和凋亡之间的过渡发挥一定的作用。结论:在内质网应激环境下,γ-synuclein通过调控ERK和JNK信号通路来促进自噬、抑制凋亡,发挥针对结肠癌细胞的保护作用,这为抗肿瘤治疗提供了一个潜在的思路。

AIM:To investigate the effects ofγ-synuclein on autophagy and apoptosis of colon cancer cells induced by endoplasmic reticulum stress,as well as the protective effect on the cells.METHODS:Gene expression profile chip analysis was performed to compare the cDNA expression profiles between human colon cancer HCT116 cells withγ-synuclein knockdown and HCT116 cells with control siRNA,and to identify potential molecules related to autophagy and apoptosis.In colon cancer cell lines,the functional effects ofγ-synuclein on autophagy and apoptosis induced by thapsigargin(TG),an endoplasmic reticulum stress-inducing agent,were systematically explored by conducting immunofluorescence staining,Western blot,CCK-8 assay,flow cytometry,and transmission electron microscopy.Western blot was used to detect the expression ofγ-synuclein protein,autophagy-related proteins[microtubule-associated protein 1 light chain 3(LC3),beclin-1,autophagy-related protein 5(ATG5)and ATG7],and apoptosis-related proteins[poly(ADP-ribose)polymerase(PARP),pro-caspase-3,and pro-caspase-9].To further analyze the mechanism ofγ-synuclein in regulating autophagy and apoptosis,extracellular signal-regulated kinase(ERK)inhibitor PD98059,ERK inhibitor SP600125 and c-Jun N-terminal kinase(JNK)activator anisomycin were applied separately to test HCT116 cells transfected withγ-synuclein siRNA.Subsequently,autophagy proteins,apoptosis proteins,and ERK and JNK pathway-related proteins were detected by Western blot.RESULTS:The TG-induced autophagy of colon cancer cells mainly occurred at the early stage(0~24 h),and apoptosis mainly occurred at the late stage(36~48 h).Endoplasmic reticulum stress up-regulated the expression ofγ-synuclein in colon cancer cells,which was associated with enhanced autophagy.γ-Synuclein promoted autophagy by activating ERK and JNK pathways at the early stage(0~24 h),and inhibited apoptosis by blocking JNK pathways at the late stage(24~48 h)to protect HCT116 cells.In our model,γ-synuclein was observed to play a critical role in the transition from endoplasmic reticulum stress-induced autophagy to apoptosis.CONCLUSION:In the context of endoplasmic reticulum stress,γ-synuclein promotes autophagy and inhibits apoptosis by regulating ERK and JNK signaling pathways,thus protecting colon cancer cells.This provides a potential idea for anti-tumor therapy.