ABSTRACT
Dengue virus (DENV) and other flaviviruses are prevented from replicating in mosquitoes by
Wolbachia
. To date, several reports have appeared that highlight multiple molecular and cellular pathways involved in the blocking mechanism, which underlines the complicated nature of the mechanism. Here, we developed a hypothesis on whether
Wolbachia
proteins interact with pro-viral host proteins by using a unique approach to study the antiviral mechanism based on
Wolbachia
-host protein-protein interaction. We selected
Wolbachia
surface protein (WSP) for co-immunoprecipitation because of its abundance and possible secretion. We first confirmed WSP’s secretion in mosquito cells and found two host proteins,
Ae. aegypti
serine-threonine kinase (STK) and synaptic vesicle membrane (SVM) protein VAT-1, and one
Wolbachia
protein (
w
GroEL) interacting with WSP. We examined the role of
STK
and
SVM
genes in relation to DENV replication in
Ae. aegypti
mosquitoes and mosquito cell lines with and without
Wolbachia
. In DENV-infected Aag2 cells, the expression of
SVM
and
STK
was significantly increased. However, although these genes were induced in
Wolbachia
-infected Aag2 cells, they were downregulated after DENV infection. Silencing of
STK
, but not
SVM
, reduced DENV replication in Aag2 cells and mosquitoes. Conversely, RNA activation of
STK
, by utilizing promoter induction via short activating oligos, resulted in higher DENV replication in
Wolbachia
-infected and uninfected cell lines. Overall, our findings suggest that
STK
is a pro-viral gene, and
Wolbachia
WSP binds to STK, possibly making it less accessible for DENV replication.
IMPORTANCEWolbachia
is an endosymbiotic bacterium that blocks the replication of arboviruses in transinfected
Aedes aegypti
mosquitoes. In this study, we focused on identifying the potential interaction of
Wolbachia
proteins with the host pro-viral proteins. For this, we embarked on identifying the interacting proteins with a major
Wolbachia
protein, WSP, which is both structural and also secreted into the host cells. An
Ae. aegypti
STK was identified, which is induced in DENV and
Wolbachia
-infected cells. Silencing or induction of the gene led to reduced and increased DENV replication
in vitro
. Consistently, knocking down the gene in mosquitoes resulted in decreased virus replication. We hypothesize that WSP may sequester STK, which is pro-viral, contributing to
Wolbachia
virus blocking.