Laboratory of Allergy and Clinical Immunology, Department of Immunology, Institute of Allergy and Immune-related Diseases, Centre for Medical Research, Wuhan University School of Medicine, Wuhan, People's Republic of China.
Biosci Rep. 2012 Apr 1;32(2):171-86. doi: 10.1042/BSR20110069.
The ability of human cells to defend against viruses originating from distant species has long been ignored. Owing to the pressure of natural evolution and human exploration, some of these viruses may be able to invade human beings. If their 'fresh' host had no defences, the viruses could cause a serious pandemic, as seen with HIV, SARS (severe acute respiratory syndrome) and avian influenza virus that originated from chimpanzees, the common palm civet and birds, respectively. It is unknown whether the human immune system could tolerate invasion with a plant virus. To model such an alien virus invasion, we chose TMV (tobacco mosaic virus) and used human epithelial carcinoma cells (HeLa cells) as its 'fresh' host. We established a reliable system for transfecting TMV-RNA into HeLa cells and found that TMV-RNA triggered autophagy in HeLa cells as shown by the appearance of autophagic vacuoles, the conversion of LC3-I (light chain protein 3-I) to LC3-II, the up-regulated expression of Beclin1 and the accumulation of TMV protein on autophagosomal membranes. We observed suspected TMV virions in HeLa cells by TEM (transmission electron microscopy). Furthermore, we found that TMV-RNA was translated into CP (coat protein) in the ER (endoplasmic reticulum) and that TMV-positive RNA translocated from the cytoplasm to the nucleolus. Finally, we detected greatly increased expression of GRP78 (78 kDa glucose-regulated protein), a typical marker of ERS (ER stress) and found that the formation of autophagosomes was closely related to the expanded ER membrane. Taken together, our data indicate that HeLa cells used ERS and ERS-related autophagy to defend against TMV-RNA.
人类细胞抵御来自远缘物种病毒的能力长期以来一直被忽视。由于自然进化和人类探索的压力，其中一些病毒可能能够侵入人类。如果它们的“新鲜”宿主没有防御能力，这些病毒可能会引发严重的大流行，就像艾滋病毒、严重急性呼吸综合征（SARS）和禽流感病毒分别来自黑猩猩、普通果子狸和鸟类一样。目前尚不清楚人类免疫系统是否能够耐受植物病毒的入侵。为了模拟这种外来病毒的入侵，我们选择了 TMV（烟草花叶病毒），并将人上皮癌细胞（HeLa 细胞）作为其“新鲜”宿主。我们建立了一种可靠的转染 TMV-RNA 进入 HeLa 细胞的系统，并发现 TMV-RNA 触发了 HeLa 细胞中的自噬，表现为自噬小体的出现、LC3-I（轻链蛋白 3-I）向 LC3-II 的转化、Beclin1 的上调表达和 TMV 蛋白在自噬体膜上的积累。我们通过 TEM（透射电子显微镜）观察到 HeLa 细胞中的疑似 TMV 病毒粒子。此外，我们发现 TMV-RNA 在 ER（内质网）中被翻译为 CP（外壳蛋白），并且 TMV 阳性 RNA 从细胞质易位到核仁。最后，我们检测到 GRP78（78 kDa 葡萄糖调节蛋白）的表达显著增加，这是 ERS（内质网应激）的典型标志物，并且发现自噬体的形成与扩展的 ER 膜密切相关。总之，我们的数据表明 HeLa 细胞利用 ERS 和 ERS 相关的自噬来抵御 TMV-RNA。
