BID-dependent release of mitochondrial SMAC dampens XIAP-mediated immunity against Shigella.
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ABSTRACT:
SUBMITTER: Andree M
PROVIDER: S-EPMC4282505 | biostudies-literature | 2014 Oct
REPOSITORIES: biostudies-literature
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Project description:Caspase-1 drives a lytic inflammatory cell death named pyroptosis by cleaving the pore-forming cell death executor gasdermin-D (GSDMD). Gsdmd deficiency, however, only delays cell lysis, indicating that caspase-1 controls alternative cell death pathways. Here, we show that in the absence of GSDMD, caspase-1 activates apoptotic initiator and executioner caspases and triggers a rapid progression into secondary necrosis. GSDMD-independent cell death required direct caspase-1-driven truncation of Bid and generation of caspase-3 p19/p12 by either caspase-8 or caspase-9. tBid-induced mitochondrial outer membrane permeabilization was also required to drive SMAC release and relieve inhibitor of apoptosis protein inhibition of caspase-3, thereby allowing caspase-3 auto-processing to the fully active p17/p12 form. Our data reveal that cell lysis in inflammasome-activated Gsdmd-deficient cells is caused by a synergistic effect of rapid caspase-1-driven activation of initiator caspases-8/-9 and Bid cleavage, resulting in an unusually fast activation of caspase-3 and immediate transition into secondary necrosis. This pathway might be advantageous for the host in counteracting pathogen-induced inhibition of GSDMD but also has implications for the use of GSDMD inhibitors in immune therapies for caspase-1-dependent inflammatory disease.
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Project description:The inhibitors of apoptosis (IAP) are important regulators of apoptosis. However, little is known about the capacity of Smac mimetics (IAP inhibitor) to overcome virally associated-lymphoma's (VAL) resistance to apoptosis. Here, we explored the pro-apoptotic effect of a novel Smac mimetic, RMT5265.2HCL (RMT) in VAL cells. RMT improved the sensitivity to apoptosis in EBV- and to some extend in HTLV-1- but not in HHV-8-VAL. Furthermore, we identified that RMT promotes caspase 3 and 9 cleavage by inhibiting XIAP and inducing the mitochondrial efflux of Smac and cytochrome C. This investigation further support exploring the use of Smac inhibitors in VAL.
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Project description:Mitochondrial damage causes mtDNA release to activate type I interferon (IFN-I) response via the cGAS-STING pathway. mtDNA-induced inflammation promotes autoimmune and aging-related degenerative disorders. However, the global picture of inflammation-inducing mitochondrial damages remains obscure. Here we performed a mitochondria-targeted CRISPR-knockout screen for regulators of the IFN-I response. Strikingly, our screen revealed dozens of hits enriched with key regulators of cristae architecture, including phospholipid cardiolipin and protein complexes such as OPA1, MICOS, SAM, MIB, PHB, and the F1Fo-ATP synthase. Disrupting these cristae organizers consistently induced mtDNA release and STING-dependent IFN-I response. Furthermore, robust STING-dependent IFN-I response was induced in vivo by knocking out MTX2, a subunit of the SAM complex whose null-mutations cause progeria in human. Taken together, beyond revealing the central role of cristae architecture to prevent mtDNA release and inflammation, our results mechanistically link mitochondrial cristae disorganization and inflammation, two emerging hallmarks of aging and aging-related degenerative diseases.
2022-10-28 | GSE216499 | GEO