The 5′ capped, message-sense RNA genome of Chikungunya virus (CHIKV) utilizes the host cell machinery for translation. Translation is regulated by eIF2 alpha at the initiation phase and by eIF4F at cap recognition. Translational suppression by eIF2 alpha phosphorylation occurs as an early event in many alphavirus infections. We observe that in CHIKV-infected HEK293 cells, this occurs as a late event, by which time the viral replication has reached an exponential phase, implying its minimal role in virus restriction. The regulation by eIF4F is mediated through the PI3K-Akt-mTOR, p38 MAPK and RAS-RAF-MEK-ERK pathways. A kinetic analysis revealed that CHIKV infection did not modulate AKT phosphorylation, but caused a significant reduction in p38 MAPK phosphorylation. It caused degradation of phospho-ERK 1/2 by increased autophagy, leaving the PI3K-Akt-mTOR and p38 MAPK pathways for pharmacological targeting. mTOR inhibition resulted in moderate reduction in viral titre, but had no effect on CHIKV E2 protein expression, indicating a minimal role of the mTOR complex in virus replication. Inhibition of p38 MAPK using SB202190 caused a significant reduction in viral titre and CHIKV E2 and nsP3 protein expression. Furthermore, inhibiting the two pathways together did not offer any synergism, indicating that inhibiting the p38 MAPK pathway alone is sufficient to cause restriction of CHIKV replication. Meanwhile, in uninfected cells the fully functional RAS-RAF-MEK-ERK pathway can circumvent the effect of p38 MAPK inhibition on cap-dependent translation. Thus, our results show that host-directed antiviral strategies targeting cellular p38 MAPK are worth exploring against Chikungunya as they could be selective against CHIKV-infected cells with minimal effects on uninfected host cells.

中文翻译：

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靶向帽依赖性翻译以抑制基孔肯雅病毒复制：由于自噬介导的磷酸化 ERK 下调，p38 MAPK 抑制剂对病毒感染细胞的选择性

基孔肯雅病毒 (CHIKV) 的 5' 加帽信息感 RNA 基因组利用宿主细胞机制进行翻译。翻译在起始阶段由 eIF2 α 调节，在帽识别时由 eIF4F 调节。eIF2 α 磷酸化的翻译抑制是许多甲病毒感染的早期事件。我们观察到，在 CHIKV 感染的 HEK293 细胞中，这是一个晚期事件，此时病毒复制已达到指数阶段，这意味着其在病毒限制中的作用最小。eIF4F 的调节是通过 PI3K-Akt-mTOR、p38 MAPK 和 RAS-RAF-MEK-ERK 通路介导的。动力学分析表明，CHIKV 感染不会调节 AKT 磷酸化，但会导致 p38 MAPK 磷酸化显着降低。它通过增加自噬引起磷酸化 ERK 1/2 的降解，将 PI3K-Akt-mTOR 和 p38 MAPK 途径留给药理学靶向。mTOR 抑制导致病毒滴度适度降低，但对 CHIKV E2 蛋白表达没有影响，表明 mTOR 复合物在病毒复制中的作用很小。使用 SB202190 抑制 p38 MAPK 导致病毒滴度和 CHIKV E2 和 nsP3 蛋白表达显着降低。此外，同时抑制这两种途径没有提供任何协同作用，表明单独抑制 p38 MAPK 途径足以限制 CHIKV 复制。同时，在未感染的细胞中，功能齐全的 RAS-RAF-MEK-ERK 通路可以规避 p38 MAPK 抑制对帽依赖性翻译的影响。因此，