The invasion of tobacco mosaic virus RNA induces endoplasmic reticulum stress-related autophagy in HeLa cells

Li, Li; Wang, Li; Xiao, Ruijing; Zhu, Guoguo; Li, Yan; Liu, Changxuan; Yang, Ru; Tang, Zhiqing; Li, Jie; Huang, Wei; Chen, Lang; Zheng, Xiaoling; He, Yuling; Tan, Jinquan

Initially, the EM analysis suggested that the autophagosomal membrane might originate from the ER membrane at the ultrastructural level. As shown in Figure 6 (B), most of the ER membranes in TMV-RNA-transfected cells were in a state of expansion, and numerous vacuoles, including nascent vacuoles and typical autophagosomes with a double-membrane vacuolar structure containing visible cytoplasmic contents, appeared around the expanded ER. The nascent vacuoles appeared to be produced from the ends of ER membranes (arrowheads), and they expanded to resemble swollen fingers in some pictures. Such structures might be transported to form autophagosomes. Some images also demonstrated that the ER membrane expanded to resemble forks extending towards the anterior vacuole ( Figures 6B-b, 6B d and 6B-g), suggesting that partial ER membranes might be used to form phagophores, structures that will fuse with a nascent vacuole. Neither autophagic vacuoles nor the expansion of the ER was found in cells not transfected with TMV-RNA ( Figure 6B-a) . Taken together, there are a series of interesting events that are occurring; the distal end of the ER membrane expanded like swollen fingers or forks, which might indicate that the cells were stimulated by the TMV-RNA and induced into a state of ERS. This phenomenon of ER membrane expansion was not found in cells not transfected with TMV-RNA ( Figure 6B-a) .