Inhibition of protein kinase C promotes dengue virus replication

Warobon Noppakunmongkolchai, Teera Poyomtip, Thichakorn Jittawuttipoka, Natthanej Luplertlop, Anavaj Sakuntabhai, Sarin Chimnaronk, Siwanon Jirawatnotai, Rutaiwan Tohtong

Dengue virus (DENV) is a member of the Flaviviridae family, transmitted to human via mosquito. DENV infection is common in tropical areas and occasionally causes life-threatening symptoms. DENV contains a relatively short positive-stranded RNA genome, which encodes ten viral proteins. Thus, the viral life cycle is necessarily rely on or regulated by host factors. In silico analyses in conjunction with in vitro kinase assay were used to study kinases that potentially phosphorylate DENV NS5. Potential kinase was inhibited or activated by a specific inhibitor (or siRNA), or an activator. Results of the inhibition and activation on viral entry/replication and host cell survival were examined. Our in silico analyses indicated that the non-structural protein 5 (NS5), especially the RNA-dependent RNA polymerase (RdRp) domain, contains conserved phosphorylation sites for protein kinase C (PKC). Phosphorylation of NS5 RdRp was further verified by PKC in vitro kinase assay. Inhibitions of PKC by a PKC-specific chemical inhibitor or siRNA suppressed NS5 phosphorylation in vivo, increased viral replication and reduced viability of the DENV-infected cells. In contrary, activation of PKC effectively suppressed intracellular viral number. These results indicated that PKC may act as a restricting mechanism that modulates the DENV replication and represses the viral outburst in the host cells.