細胞自噬 (autophagy) 是一種在真核細胞中常見的現象，利用與溶酶體 (lysosome) 結合來代謝一些細胞質中的巨分子及老舊胞器 (organelle)。細胞自噬擁有許多生理以及病理上的功能，其中包括了細胞死亡與神經退化性疾病。細胞自噬也在病毒複製方面扮演了重要角色。腸病毒71型 (enterovirus 71；EV71) 是人類腸病毒A種 (human enterovirus A species)，隸屬於小RNA病毒科 (Picornaviridae) 的一員。腸病毒71型感染能夠在肌肉細胞株RD以及神經細胞株SK-N-SH中誘發細胞自噬的現象，藉由偵測自噬體 (autophagosome) 的專一性標記，細胞微管相關蛋白1輕鏈3 (microtubule-associated protein 1 light chain 3；LC3) 的聚集反應，和與自噬體結合的LC3-II蛋白質表現上升來判斷自噬體的形成增加。本研究中，我們探討了引發細胞自噬相關的訊息傳遞路徑。我們發現在受到感染的兩個細胞株中，Erk1/2的磷酸化受到抑制。而藉由抑制劑雷帕黴素 (rapamycin) 處理及西方墨點法 (Western blotting) 偵測，mTOR的總量和磷酸化只有在SK-N-SH細胞株中才會受到抑制。進一步研究證實腸病毒71型在SK-N-SH細胞中所誘發的細胞自噬是經由mTOR/p70S6K訊息傳遞路徑，然而上游的訊息傳導者並不是經由class I PI3K/Akt。未來將利用在感染的細胞中大量表現mTOR蛋白可以幫助我們釐清mTOR在腸病毒71型感染所誘發的細胞自噬現象中所扮演的角色，以及對於病毒複製的影響。綜述之，我們發現Erk1/2在腸病毒71型所誘發的細胞自噬中是普遍的現象，而mTOR/p70S6K在此是有細胞種類專一性的差異。在小鼠感染病毒模式中，我們在小鼠脊椎 (spinal cord) 神經元細胞中以免疫電子顯微鏡的方法觀察到類似自噬體的空泡 (autophagosome-like vesicle) 出現並與病毒共同存在，顯示細胞自噬也會在感染腸病毒71型的小鼠中發生。總結而言，我們最先證實腸病毒71型能誘發細胞自噬在細胞與動物中產生。藉由了解腸病毒71型所誘發的細胞自噬現象的訊息調控機制，以及在感染小鼠中自噬體空泡的形成，能提供我們新的觀念去控制腸病毒71型感染所造成的疾病。

Autophagy is a conserved lysosomal process for turning over macromolecules and organelles in eukaryotic cells. Autophagy has multiple physiological and pathological functions involving in cell death and neurodegenerative diseases. Autophagy also plays an important role in virus replication. Enterovirus 71 (EV71) belonging to the human enterovirus A species within the family Picornaviridae could induce muscle RD cells and neuron SK-N-SH cells undergoing autophagy detected by aggregation of microtubule-associated protein 1 light chain 3 (LC3) and increased protein level of autophagosome-bound LC3-II. In this study, the autophagy-related signaling pathways were examined. We demonstrate that Erk1/2 phosphorylation was inhibited in both of the tested cell lines. The levels of total mTOR and phosphorylated mTOR expression were only inhibited in SK-N-SH cells demonstrated by Western blotting and inhibitor rapamycin. It indicates that EV71 infection-induced autophagy is through mTOR/p70S6K signaling pathway in SK-N-SH cells, however, class I PI3K/Akt was not the upstream transducer. Further verification of the role of mTOR in EV71-induced autophagy and the effect of mTOR on EV71 replication is needed by over-expression of mTOR in the infected cells. Beclin 1, Bcl-2, BNIP3 expression levels were not affected. All together, our data indicate that Erk1/2 is universally involved in EV71-induced autophagy. In contrast, mTOR/p70S6K participating in EV71-induced autophagy is cell-type specific. Interestingly, autophagosome-like vesicles were detected in the neuron cells of mice orally infected with EV71 by immunoelectron microscopy indicating autophagy occured in mice. In conclusion, autophagy is induced by EV71 infection in vitro and in vivo. Further study is underway to clarify that these autophagosome-like vesicles were indeed induced by EV71 infection. Understanding the regulation mechanisms of autophagy induced in EV71 infected cells and the autophagosome-like vesicles formation in mice will provide us new insights to control the pathogenesis of EV71 infection.

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