巨自噬与分子伴侣介导的自噬在饥饿诱导的Raji细胞中相继顺序被激活

The sequential switch from macroautophagy to chaperone-mediated autophagy in Raji cells induced by starvation

目的 研究巨自噬与分子伴侣介导的自噬在饥饿诱导的Raji细胞中出现的先后顺序及其机制。方法用激光共聚焦显微镜和荧光显微镜观察MDC荧光染色后,Raji细胞内自噬体的形成情况;Western blot检测细胞LC3Ⅰ/Ⅱ、 Beclin-1、Hsc70及Lamp-2a等蛋白的表达水平。结果在饥饿诱导的Raji细胞中,巨自噬与分子伴侣介导的自噬是相继顺序,而非同步被激活,巨自噬活性在饥饿诱导的最初几小时快速升高并达到峰值,然后随着饥饿时间的延长逐渐下降,而与巨自噬活性下降相伴随的是分子伴侣介导的自噬活性逐渐增加。结论肿瘤细胞在饥饿诱导的不同阶段通过不同的自噬方式应对压力刺激,巨自噬与分子伴侣介导的自噬之间此消彼长、协调补充的关系更有助于肿瘤细胞适应内外环境的变化,维持自身的生长与增殖。

Aim To research the cross-talk and conversion between macroautophagy and chaperone-mediated autophagy(CMA) in cultured Burkitt lymphoma Raji cells induced by starvation.Methods The autophagic vacuoles were observed by fluorescence microscopy and confocal laser-scanning microscopy with monodansylcadaverine staining.The expression of autophagy associated-proteins were determined by Western blot.Results Both macroautophagy and CMA were activated sequentially instead of simultaneously in starvation-induced Raji cells, and macroautophagy was quickly activated and peaked during the first hours of nutrition deprivation, and then gradually decreased to near baseline.With starvation persisted, CMA progressively increased along with the decline of macroautophagy.Conclusions Macroautophagy and CMA are maximally activated during different stages of starvation.Activation of these two pathways is often sequential.The sequential switch from macroautophagy to CMA might be conducive to the adaption of cancer cells to miscellaneous intracellular or extracellular changes, maintaining their own growth and proliferation.