Xie Kun, Tian Ling, Guo Xinyu, Li Kang, Li Jianping, Deng Xiaojuan, Li Qingrong, Xia Qingyou, Zhong Yangjin, Huang Zhijun, Liu Jiping, Li Sheng, Yang Wanying, Cao Yang
a Guangdong Provincial Key Laboratory of Agro-animal Genomics and Molecular Breeding/Guangdong Provincial Sericulture and Mulberry Engineering Research Center, College of Animal Science, South China Agricultural University , Guangzhou , China.
b Key Laboratory of Crops with High Quality and Efficient Cultivation and Security Control, Yunnan Higher Education Institutions, College of Life Science and Technology, HongHe University , Mengzi , Yunnan , China.
Autophagy. 2016;12(2):381-96. doi: 10.1080/15548627.2015.1134079.
Autophagy and apoptosis, which could be induced by common stimuli, play crucial roles in development and disease. The functional relationship between autophagy and apoptosis is complex, due to the dual effects of autophagy. In the Bombyx Bm-12 cells, 20-hydroxyecdysone (20E) treatment or starvation-induced cell death, with autophagy preceding apoptosis. In response to 20E or starvation, BmATG8 was rapidly cleaved and conjugated with PE to form BmATG8-PE; subsequently, BmATG5 and BmATG6 were cleaved into BmATG5-tN and BmATG6-C, respectively. Reduction of expression of BmAtg5 or BmAtg6 by RNAi decreased the proportion of cells undergoing both autophagy and apoptosis after 20E treatment or starvation. Overexpression of BmAtg5 or BmAtg6 induced autophagy but not apoptosis in the absence of the stimuli, but promoted both autophagy and apoptosis induced by 20E or starvation. Notably, overexpression of cleavage site-deleted BmAtg5 or BmAtg6 increased autophagy but not apoptosis induced by 20E or starvation, whereas overexpression of BmAtg5-tN and BmAtg6-C was able to directly trigger apoptosis or promote the induced apoptosis. In conclusion, being cleaved into BmATG5-tN and BmATG6-C, BmATG5 and BmATG6 mediate apoptosis following autophagy induced by 20E or starvation in Bombyx Bm-12 cells, reflecting that autophagy precedes apoptosis in the midgut during Bombyx metamorphosis.
自噬和凋亡可由常见刺激诱导，在发育和疾病中发挥关键作用。由于自噬的双重作用，自噬与凋亡之间的功能关系较为复杂。在家蚕Bm - 12细胞中，20 - 羟基蜕皮激素（20E）处理或饥饿诱导细胞死亡，自噬先于凋亡发生。响应20E或饥饿时，BmATG8迅速被切割并与磷脂酰乙醇胺（PE）结合形成BmATG8 - PE；随后，BmATG5和BmATG6分别被切割成BmATG5 - tN和BmATG6 - C。通过RNA干扰降低BmAtg5或BmAtg6的表达，会降低20E处理或饥饿后同时发生自噬和凋亡的细胞比例。在无刺激的情况下，过表达BmAtg5或BmAtg6会诱导自噬但不诱导凋亡，但会促进20E或饥饿诱导的自噬和凋亡。值得注意的是，过表达缺失切割位点的BmAtg5或BmAtg6会增加20E或饥饿诱导的自噬但不诱导凋亡，而过表达BmATG5 - tN和BmATG6 - C能够直接触发凋亡或促进诱导的凋亡。总之，在家蚕Bm - 12细胞中，BmATG5和BmATG6被切割成BmATG5 - tN和BmATG6 - C后，介导20E或饥饿诱导的自噬后的凋亡过程，这反映在家蚕变态过程中中肠自噬先于凋亡发生。
