The DEAD-box RNA helicase Dhx15 controls glycolysis and arbovirus replication in Aedes aegypti mosquito cells

Aedes aegypti mosquitoes are responsible for the transmission of arthropod-borne (arbo)viruses including dengue and chikungunya virus (CHIKV), but in contrast to human hosts, arbovirus infected mosquitoes are able to efficiently control virus replication to sub-pathological levels. Yet, our knowledge about the molecular interactions of arboviruses with their mosquito hosts is largely incomplete. Here, we aimed to identify and characterize novel host genes that control arbovirus replication in Aedes mosquitoes. RNA binding proteins (RBPs) are well known to regulate immune signaling pathways in all kingdoms of life. We therefore performed a knockdown screen targeting 461 genes encoding predicted RBPs in Aedes aegypti Aag2 cells and identified 15 genes with antiviral activity against a Sindbis reporter virus. Amongst these, three DEAD-box RNA helicases, AAEL004419/Dhx15, AAEL008728 and AAEL004859 also acted as antiviral factors in dengue and CHIKV infections. Here, we explore the mechanism of Dhx15 in regulating an antiviral transcriptional response in mosquitoes by silencing Dhx15 in Aag2 cells followed by deep-sequencing of poly-A enriched RNAs. Dhx15 knockdown in uninfected or CHIKV-infected cells resulted in differential expression of 856 and 372 genes, respectively. Interestingly, amongst the consistently downregulated genes, glycolytic process was the most strongly enriched GO term as the expression of all core enzymes of the glycolytic pathway was reduced, suggesting that Dhx15 regulates glycolytic function. A decrease in lactate production supported the observation that Dhx15 silencing functionally impaired glycolysis. Modified rates of glycolytic metabolism have been implicated in controlling the replication of several classes of viruses and strikingly, infection of Aag2 cells with CHIKV by itself also resulted in the decrease of several glycolysis genes. Our data suggests that Dhx15 regulates replication of CHIKV, and possibly other arboviruses, by controlling glycolysis in mosquito cells.