The assembly of stress granule-like foci during foot-and-mouth disease virus infection is uncoupled from activation of cellular intrinsic antiviral signalling
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Foot-and-mouth disease virus (FMDV) is highly contagious among cloven-hoofed animals and poses a major threat to the livestock industry worldwide. A fundamental gap in knowledge for high consequence viruses such as FMDV is understanding how the virus evolved to evade cellular antiviral responses. FMDV belongs to the Picornaviridae , a family of positive-sense single-stranded RNA viruses. The detection of viral double-stranded viral RNA intermediates during infection can trigger both the assembly of cytoplasmic stress granules (SGs) and the activation of the RIG-I-like receptors (RLR)-mediated innate immune response (IIR). FMDV has been proposed to antagonize these mechanisms, suggesting that both can limit viral replication. In this study, we investigate the dynamic and importance of SG assembly for IIR activation upon dsRNA stimulation or FMDV replication in porcine epithelial kidney cells.
First, we show that the formation of SG following a challenge with poly(I:C), a viral dsRNA mimic, does not modulate the activation of IIR. Our data further reveal transient assembly of SG during FMDV infection followed by virus-induced cleavage of G3BP1, a core SG protein. While SG assembly does not impact viral replication or antiviral response activation, we demonstrate that preventing their disassembly negatively impacts FMDV replication. Overall, our data suggests that while SGs assembly is uncoupled from IIR activation, manipulating their disassembly limits replication and might serve as a potential therapeutic target to prevent FMDV infection.
Importance
Biomolecular condensates, including stress granules, are key regulatory compartments that control fundamental cellular processes. By condensing RNAs and proteins, these structures enable cells to rapidly adapt to stress, such as viral infection. Different biomolecular condensates with specific dynamics or compositions have been described during infection, and many viruses are known to disrupt or highjack their components. Moreover, the cell-autonomous innate immune response is proposed to be regulated by biomolecular condensates. However, the molecular mechanisms underpinning these functions remain unclear and controversial. Here we investigated the interplay between stress granules and the innate response upon the stimulation with a viral dsRNA mimic or foot-and-mouth disease virus infection. We demonstrate that infection triggers the formation of stress granules independently from activation of innate signalling pathways. We also show that stress granules persistence attenuates viral replication posing them as part of the cell’s response that viruses must overcome or subvert to replicate.
