Dynasore enhances the formation of mitochondrial antiviral signalling aggregates and endocytosis‐independent NF‐κB activation

Background and Purpose Dynasore has been used extensively as an inhibitor of clathrin‐mediated endocytosis. While studying the role of endocytosis in LPS‐induced signalling events, we discovered that dynasore itself induced activation of NF‐κB, independently of its effects on endocytosis and without involving the Toll‐like receptor 4 signalling pathways. The purpose of this study was to characterize this novel effect and to explore the underlying mechanism of action. Experimental Approach We utilized gel electrophoresis, microscopy, gene knockdown and luciferase‐based promoter activity to evaluate the effect of dynasore on cell signalling pathways and to delineate the mechanisms involved in its effects, Key Results Dynasore activated the NF‐κB and IFN‐β pathways by activating mitochondrial antiviral signalling protein (MAVS). We showed that MAVS is activated by NOX/Rac and forms high molecular weight aggregates, similar to that observed in response to viral infection. We also demonstrated that dynasore‐induced activation of JNK occurs downstream of MAVS and is required for activation of NF‐κB and IFN‐β. Conclusion and Implications These findings demonstrate a novel effect of dynasore on cell signalling. We describe a novel Rac1‐, ROS‐ and MAVS‐mediated signalling cascade through which dynasore dramatically activates NF‐κB, mimicking the viral induction of this key inflammatory signalling pathway. Our results call attention to the need for a broader interpretation of results when dynasore is used in its traditional fashion as an inhibitor of clathrin‐mediated endocytosis. These results suggest the intriguing possibility that dynasore or one of its analogues might be of value as an antiviral therapeutic strategy or vaccine adjuvant.