The Ras/ERK signaling pathway couples antimicrobial peptides to mediate resistance to dengue virus in Aedes mosquitoes

Author summary Aedesmosquitoes are the vectors that can transmit dengue fever and several other severe vector-borne viral diseases in the human population. Insects control and clear viral infections via their innate immune systems. Studies of the genes and molecules in mosquitos that control pathogen infection may provide insights into finding novel targets for controlling the transmission of mosquito-borne diseases. In this study, we used genetic and pharmacological approaches to investigate the role of MAPKs inAedesmosquitoes following DENV2 infection in vitro and in vivo. Activation of the Ras/ERK pathway via insulin treatment and overexpression of Ras significantly decreased the DENV titers, whereas inhibition of the Ras/ERK pathway by either U0126 treatment or by Ras knockdown enhanced DENV infection. We demonstrated that the Ras/ERK signaling couples AMPs to mediate the resistance ofAedesmosquitoes to DENV infection, which reveals a novel antiviral mechanism regulated by multiple innate immune components in mosquitoes. Aedesmosquitoes can transmit dengue and several other severe vector-borne viral diseases, thereby influencing millions of people worldwide. Insects primarily control and clear the viral infections via their innate immune systems. Mitogen-Activated Protein Kinases (MAPKs) and antimicrobial peptides (AMPs) are both evolutionarily conserved components of the innate immune systems. In this study, we investigated the role of MAPKs inAedesmosquitoes following DENV infection by using genetic and pharmacological approaches. We demonstrated that knockdown of ERK, but not of JNK or p38, significantly enhances the viral replication inAedesmosquito cells. The Ras/ERK signaling is activated in both the cells and midguts ofAedesmosquitoes following DENV infection, and thus plays a role in restricting the viral infection, as both genetic and pharmacological activation of the Ras/ERK pathway significantly decreases the viral titers. In contrast, inhibition of the Ras/ERK pathway enhances DENV infection. In addition, we identified a signaling crosstalk between the Ras/ERK pathway and DENV-induced AMPs in which defensin C participates in restricting DENV infection inAedesmosquitoes. Our results reveal that the Ras/ERK signaling pathway couples AMPs to mediate the resistance ofAedesmosquitoes to DENV infection, which provides a new insight into understanding the crosstalk between MAPKs and AMPs in the innate immunity of mosquito vectors during the viral infection.