Saeed Mohammad F, Kolokoltsov Andrey A, Freiberg Alexander N, Holbrook Michael R, Davey Robert A
Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America.
PLoS Pathog. 2008 Aug 29;4(8):e1000141. doi: 10.1371/journal.ppat.1000141.
The phosphoinositide-3 kinase (PI3K) pathway regulates diverse cellular activities related to cell growth, migration, survival, and vesicular trafficking. It is known that Ebola virus requires endocytosis to establish an infection. However, the cellular signals that mediate this uptake were unknown for Ebola virus as well as many other viruses. Here, the involvement of PI3K in Ebola virus entry was studied. A novel and critical role of the PI3K signaling pathway was demonstrated in cell entry of Zaire Ebola virus (ZEBOV). Inhibitors of PI3K and Akt significantly reduced infection by ZEBOV at an early step during the replication cycle. Furthermore, phosphorylation of Akt-1 was induced shortly after exposure of cells to radiation-inactivated ZEBOV, indicating that the virus actively induces the PI3K pathway and that replication was not required for this induction. Subsequent use of pseudotyped Ebola virus and/or Ebola virus-like particles, in a novel virus entry assay, provided evidence that activity of PI3K/Akt is required at the virus entry step. Class 1A PI3Ks appear to play a predominant role in regulating ZEBOV entry, and Rac1 is a key downstream effector in this regulatory cascade. Confocal imaging of fluorescently labeled ZEBOV indicated that inhibition of PI3K, Akt, or Rac1 disrupted normal uptake of virus particles into cells and resulted in aberrant accumulation of virus into a cytosolic compartment that was non-permissive for membrane fusion. We conclude that PI3K-mediated signaling plays an important role in regulating vesicular trafficking of ZEBOV necessary for cell entry. Disruption of this signaling leads to inappropriate trafficking within the cell and a block in steps leading to membrane fusion. These findings extend our current understanding of Ebola virus entry mechanism and may help in devising useful new strategies for treatment of Ebola virus infection.
磷酸肌醇-3激酶（PI3K）信号通路调控着与细胞生长、迁移、存活及囊泡运输相关的多种细胞活动。已知埃博拉病毒需要通过内吞作用来建立感染。然而，介导这种摄取的细胞信号对于埃博拉病毒以及许多其他病毒来说都是未知的。在此，研究了PI3K在埃博拉病毒进入细胞过程中的作用。结果表明PI3K信号通路在扎伊尔埃博拉病毒（ZEBOV）进入细胞过程中发挥着新的关键作用。PI3K和Akt的抑制剂在复制周期的早期阶段显著降低了ZEBOV的感染。此外，细胞暴露于经辐射灭活的ZEBOV后不久，Akt-1就发生了磷酸化，这表明病毒能主动诱导PI3K信号通路，且这种诱导不需要病毒复制。随后，在一种新型病毒进入细胞检测方法中使用假型埃博拉病毒和/或埃博拉病毒样颗粒，提供了证据表明在病毒进入细胞步骤中需要PI3K/Akt的活性。1A类PI3K似乎在调节ZEBOV进入细胞过程中起主要作用，而Rac1是这一调节级联反应中的关键下游效应分子。对荧光标记的ZEBOV进行共聚焦成像显示，抑制PI3K、Akt或Rac1会破坏病毒颗粒正常进入细胞的过程，并导致病毒异常积聚在一个不允许膜融合的胞质区室中。我们得出结论，PI3K介导的信号传导在调节ZEBOV进入细胞所需的囊泡运输中起重要作用。这种信号传导的破坏会导致细胞内运输异常，并阻断导致膜融合的步骤。这些发现扩展了我们目前对埃博拉病毒进入细胞机制的理解，并可能有助于设计出治疗埃博拉病毒感染的有用新策略。
