An aquatic virus exploits the IL6-STAT3-HSP90 signaling axis to promote viral entry

Viral seasonality in the aquaculture industry is an important scientific issue for decades. While the molecular mechanisms underpinning the temperature-dependent pathogenesis of aquatic viral diseases remain largely unknown. Here we report that temperature-dependent activation of IL6-STAT3 signaling was exploited by grass carp reovirus (GCRV) to promote viral entry via increasing the expression of heat shock protein 90 (HSP90). Deploying GCRV infection as a model system, we discovered that GCRV induces the IL6-STAT3-HSP90 signaling activation to achieve temperature-dependent viral entry. Further biochemical and microscopic analyses revealed that the major capsid protein VP7 of GCRV interacted with HSP90 and relevant membrane-associated proteins to boost viral entry. Accordingly, exogenous expression of either IL6, HSP90, or VP7 in cells increased GCRV entry in a dose-dependent manner. Interestingly, other viruses (e.g., koi herpesvirus, Rhabdovirus carpio, Chinese giant salamander iridovirus) infecting ectothermic vertebrates have evolved a similar mechanism to promote their infection. This work delineates a molecular mechanism by which an aquatic viral pathogen exploits the host temperature-related immune response to promote its entry and replication, instructing us on new ways to develop targeted preventives and therapeutics for aquaculture viral diseases. Author summaryViral seasonality in the aquaculture industry has been an important scientific issue for decades, which is causing billions of economic losses every year worldwide. However, there is a lack of understanding of how temperature influences the pathogenesis of aquatic viruses infecting fish, shellfish, and other ectotherms. Here, deploying aquatic grass carp reovirus (GCRV) as a model system, we demonstrate for the first time that the temperature-dependent IL6-STAT3-HSP90 signaling axis is exploited by GCRV to promote viral entry. We found that HSP90 interacted with viral structural proteins and membrane-associated proteins to enable viral entry. Furthermore, our study indicates other aquatic viruses might evolve a similar mechanism to promote their infection. By elucidating the molecular mechanism of temperature-dependent aquatic viral pathogenesis, our work may help to develop targeted prevention and control strategies against aquatic viral diseases.