Abstract
The complex interplay between caspase-8 and receptor-interacting protein (RIP) kinase RIP 3 (RIPK3) driving extrinsic apoptosis and necroptosis is not fully understood. Murine cytomegalovirus triggers both apoptosis and necroptosis in infected cells; however, encoded inhibitors of caspase-8 activity (M36) and RIP3 signaling (M45) suppress these antiviral responses. Here, we report that this virus activates caspase-8 in macrophages to trigger apoptosis that gives rise to secondary necroptosis. Infection with double-mutant ΔM36/M45mutRHIM virus reveals a signaling pattern in which caspase- 8 activates caspase-3 to drive apoptosis with subsequent RIP3- dependent activation of mixed lineage kinase domain-like (MLKL) leading to necroptosis. This combined cell death signaling is highly inflammatory, greater than either apoptosis induced by ΔM36 or necroptosis induced by M45mutRHIM virus. IL-6 production by macrophages is dramatically increased during double-mutant virus infection and correlates with faster antiviral responses in the host. Collaboratively, M36 and M45 target caspase-8 and RIP3 pathways together to suppress this proinflammatory cell death. This study reveals the effect of antiviral programmed cell death pathways on inflammation, shows that caspase-8 activation may go hand-inhand with necroptosis in macrophages, and revises current understanding of independent and collaborative functions of M36 and M45 in blocking apoptotic and necroptotic cell death responses.
Original language | English (US) |
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Pages (from-to) | E2786-E2795 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Volume | 114 |
Issue number | 13 |
DOIs | |
State | Published - Mar 28 2017 |
Keywords
- Caspase-8
- Cell death
- Inflammation
- MCMV
- RIP3 kinase
ASJC Scopus subject areas
- General