Flavivirus activates phosphatidylinositol 3-kinase signaling to block caspase-dependent apoptotic cell death at the early stage of virus infection
Flavivirus activates phosphatidylinositol 3-kinase signaling to block caspase-dependent apoptotic cell death at the early stage of virus infection
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DOI：
10.1128/jvi.79.13.8388-8399.2005
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发表时间：
2005-07-01
影响因子：
5.4
通讯作者：
Lin, YL
中科院分区：
文献类型：
--
作者：
Lee, CJ;Liao, CL;Lin, YL
黄病毒如登革病毒（DEN）和日本脑炎病毒（JEV）在人类中具有重要的医学意义。磷脂酰肌醇3-激酶（PI 3 K）及其下游靶点Akt参与了多种细胞功能的调节，如增殖和凋亡。由于JEV和DEN似乎在感染的晚期阶段触发培养细胞的凋亡，我们评估了PI 31 K/Akt信号通路在黄病毒感染细胞中的可能作用。我们发现，Akt磷酸化在JEV和DEN血清型2（DEN-2）感染的神经元N18细胞中以早期、瞬时、PI 3 K和脂筏依赖的方式明显。阻断PI 3 K激活其特异性抑制剂LY 294002或渥曼青霉素大大增强病毒诱导的细胞病变效应（CPE），即使在感染的早期阶段，但对病毒的产生没有影响。通过TUNEL（末端脱氧核苷酸转移酶介导的dUTP-生物素切口末端标记）染色和caspase-3和聚（ADP-核糖）聚合酶（PARP）的裂解，将这种严重CPE表征为凋亡性细胞死亡。在机械上，所涉及的起始物和效应物半胱天冬酶主要是半胱天冬酶-9和半胱天冬酶-6，因为只有泛半胱天冬酶抑制剂和抑制剂优先靶向半胱天冬酶-9和-6，而不是拮抗半胱天冬酶-8、-3或-7的抑制剂减轻病毒感染和PI 3 K阻断后PARP裂解的水平。此外，Bcl-2似乎是PI 3 K/Akt信号传导下游的关键介质，因为Bcl-2的过表达减少了病毒诱导的细胞凋亡，即使当PI 3 K活化被抑制时。总的来说，我们的研究结果表明，由JEV和DEN-2触发的PI 3 K/Akt通路具有抗凋亡作用，以保护感染的细胞免于早期凋亡细胞死亡。
Flaviviruses such as dengue virus (DEN) and Japanese encephalitis virus (JEV) are medically important in humans. The lipid kinase, phosphatidylinositol 3-kinase (PI3K) and its downstream target Akt have been implicated in the regulation of diverse cellular functions such as proliferation, and apoptosis. Since JEV and DEN appear to trigger apoptosis in cultured cells at a rather late stage of infection, we evaluated the possible roles of the PI31K/Akt signaling pathway in flavivirus-infected cells. We found that Akt phosphorylation was noticeable in the JEV- and DEN serotype 2 (DEN-2)-infected neuronal N18 cells in an early, transient, PI3K- and lipid raft-dependent manner. Blocking of PI3K activation by its specific inhibitor LY294002 or wortmannin greatly enhanced virus-induced cytopathic effects (CPEs), even at an early stage of infection, but had no effect on virus production. This severe CPE was characterized as apoptotic cell death as evidenced by TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) staining and cleavage of caspase-3 and poly(ADP-ribose) polymerase (PARP). Mechanically, the initiator and effector caspases involved are mainly caspase-9 and caspase-6, since only a pan-caspase inhibitor and the inhibitors preferentially target caspase-9 and -6, but not the ones antagonizing caspase-8, -3, or -7 alleviated the levels of PARP cleavage after virus infection and PI3K blockage. Furthermore, Bcl-2 appears to be a crucial mediator downstream of PI3K/Akt signaling, since overexpression of Bcl-2 reduced virus-induced apoptosis even when PI3K activation was repressed. Collectively, our results suggest an antiapoptotic role for the PI3K/Akt pathway triggered by JEV and DEN-2 to protect infected cells from early apoptotic cell death.