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

We found that TMV-RNA triggered autophagy in HeLa cells as evidenced by the appearance of autophagic vacuoles, the conversion of LC3-I into LC3-II, the up-regulated expression of Beclin1 and the accumulation of TMV protein on autophagosomal membranes. We presumed that autophagy was triggered to regulate the innate immune response to the TMV-RNA in HeLa cells because no studies to date have been performed to indicate that TMV can invade human cells. An immunological memory against TMV may not exist in human innate immune cells. It is reported that there are two pathways that detect viral infection in cells; one is an exogenous pathway in which virally-derived ssRNA is detected by TLR7 (Toll-like receptor 7) in endosomes after degradation of the viral envelope and capsid proteins by host-cell enzymes. The other pathway is an endogenous pathway in which autophagy serves a function analogous to endocytosis, transferring viral RNA from the cytoplasm to intracellular compartments containing TLR7 [36, 37] . This latter pathway might be the transport pathway used for the detection of TMV-RNA in HeLa cells.