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A Yersinia effector with enhanced inhibitory activity on the NF-?B pathway activates the NLRP3/ASC/caspase-1 inflammasome in macrophages.

ABSTRACT: A type III secretion system (T3SS) in pathogenic Yersinia species functions to translocate Yop effectors, which modulate cytokine production and regulate cell death in macrophages. Distinct pathways of T3SS-dependent cell death and caspase-1 activation occur in Yersinia-infected macrophages. One pathway of cell death and caspase-1 activation in macrophages requires the effector YopJ. YopJ is an acetyltransferase that inactivates MAPK kinases and IKK? to cause TLR4-dependent apoptosis in naïve macrophages. A YopJ isoform in Y. pestis KIM (YopJ(KIM)) has two amino acid substitutions, F177L and K206E, not present in YopJ proteins of Y. pseudotuberculosis and Y. pestis CO92. As compared to other YopJ isoforms, YopJ(KIM) causes increased apoptosis, caspase-1 activation, and secretion of IL-1? in Yersinia-infected macrophages. The molecular basis for increased apoptosis and activation of caspase-1 by YopJ(KIM) in Yersinia-infected macrophages was studied. Site directed mutagenesis showed that the F177L and K206E substitutions in YopJ(KIM) were important for enhanced apoptosis, caspase-1 activation, and IL-1? secretion. As compared to YopJ(CO92), YopJ(KIM) displayed an enhanced capacity to inhibit phosphorylation of I?B-? in macrophages and to bind IKK? in vitro. YopJ(KIM) also showed a moderately increased ability to inhibit phosphorylation of MAPKs. Increased caspase-1 cleavage and IL-1? secretion occurred in IKK?-deficient macrophages infected with Y. pestis expressing YopJ(CO92), confirming that the NF-?B pathway can negatively regulate inflammasome activation. K+ efflux, NLRP3 and ASC were important for secretion of IL-1? in response to Y. pestis KIM infection as shown using macrophages lacking inflammasome components or by the addition of exogenous KCl. These data show that caspase-1 is activated in naïve macrophages in response to infection with a pathogen that inhibits IKK? and MAPK kinases and induces TLR4-dependent apoptosis. This pro-inflammatory form of apoptosis may represent an early innate immune response to highly virulent pathogens such as Y. pestis KIM that have evolved an enhanced ability to inhibit host signaling pathways.

SUBMITTER: Zheng Y

PROVIDER: S-EPMC3080847 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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A Yersinia effector with enhanced inhibitory activity on the NF-κB pathway activates the NLRP3/ASC/caspase-1 inflammasome in macrophages.

Zheng Ying Y Lilo Sarit S Brodsky Igor E IE Zhang Yue Y Medzhitov Ruslan R Marcu Kenneth B KB Bliska James B JB

PLoS pathogens 20110421 4

A type III secretion system (T3SS) in pathogenic Yersinia species functions to translocate Yop effectors, which modulate cytokine production and regulate cell death in macrophages. Distinct pathways of T3SS-dependent cell death and caspase-1 activation occur in Yersinia-infected macrophages. One pathway of cell death and caspase-1 activation in macrophages requires the effector YopJ. YopJ is an acetyltransferase that inactivates MAPK kinases and IKKβ to cause TLR4-dependent apoptosis in naïve ma ...[more]

PMID: 21533069

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Project description:Propofol infusion syndrome (PRIS) is an uncommon life-threatening complication observed most often in patients receiving high-dose propofol. High-dose propofol treatment with a prolonged duration can damage the immune system. However, the associated molecular mechanisms remain unclear. An increasing number of clinical and experimental observations have demonstrated that tissue-resident macrophages play a critical role in immune regulation during anaesthesia and procedural sedation. Since the inflammatory response is essential for mediating propofol-induced cell death and proinflammatory reactions, we hypothesised that propofol overdose induces macrophage pyroptosis through inflammasomes. Using primary cultured bone marrow-derived macrophages, murine macrophage cell lines (RAW264.7, RAW-asc and J774) and a mouse model, we investigated the role of NLRP3 inflammasome activation and secondary pyroptosis in propofol-induced cell death. We found that high-dose propofol strongly cleaved caspase-1 but not caspase-11 and biosynthesis of downstream interleukin (IL)-1β and IL-18. Inhibition of caspase-1 activity blocks IL-1β production. Moreover, NLRP3 deletion moderately suppressed cleaved caspase-1 as well as the proportion of pyroptosis, while levels of AIM2 were increased, triggering a compensatory pathway to pyroptosis in NLRP3-/- macrophages. Here, we show that propofol-induced mitochondrial reactive oxygen species (ROS) can trigger NLRP3 inflammasome activation. Furthermore, apoptosis-associated speck-like protein (ASC) was found to mediate NLRP3 and AIM2 signalling and contribute to propofol-induced macrophage pyroptosis. In addition, our work shows that propofol-induced apoptotic initiator caspase (caspase-9) subsequently cleaved effector caspases (caspase-3 and 7), indicating that both apoptotic and pyroptotic cellular death pathways are activated after propofol exposure. Our studies suggest, for the first time, that propofol-induced pyroptosis might be restricted to macrophage through an NLRP3/ASC/caspase-1 pathway, which provides potential targets for limiting adverse reactions during propofol application. These findings demonstrate that propofol overdose can trigger cell death through caspase-1 activation and offer new insights into the use of anaesthetic drugs.

Project description:Brains of Alzheimer's disease patients are characterized by the presence of amyloid plaques and neurofibrillary tangles, both invariably associated with neuroinflammation. A crucial role for NLRP3-ASC inflammasome [NACHT, LRR and PYD domains-containing protein 3 (NLRP3)-Apoptosis-associated speck-like protein containing a CARD (ASC)] in amyloid-beta (Aβ)-induced microgliosis and Aβ pathology has been unequivocally identified. Aβ aggregates activate NLRP3-ASC inflammasome (Halle et al. in Nat Immunol 9:857-865, 2008) and conversely NLRP3-ASC inflammasome activation exacerbates amyloid pathology in vivo (Heneka et al. in Nature 493:674-678, 2013), including by prion-like ASC-speck cross-seeding (Venegas et al. in Nature 552:355-361, 2017). However, the link between inflammasome activation, as crucial sensor of innate immunity, and Tau remains unexplored. Here, we analyzed whether Tau aggregates acting as prion-like Tau seeds can activate NLRP3-ASC inflammasome. We demonstrate that Tau seeds activate NLRP3-ASC-dependent inflammasome in primary microglia, following microglial uptake and lysosomal sorting of Tau seeds. Next, we analyzed the role of inflammasome activation in prion-like or templated seeding of Tau pathology and found significant inhibition of exogenously seeded Tau pathology by ASC deficiency in Tau transgenic mice. We furthermore demonstrate that chronic intracerebral administration of the NLRP3 inhibitor, MCC950, inhibits exogenously seeded Tau pathology. Finally, ASC deficiency also decreased non-exogenously seeded Tau pathology in Tau transgenic mice. Overall our findings demonstrate that Tau-seeding competent, aggregated Tau activates the ASC inflammasome through the NLRP3-ASC axis, and we demonstrate an exacerbating role of the NLRP3-ASC axis on exogenously and non-exogenously seeded Tau pathology in Tau mice in vivo. The NLRP3-ASC inflammasome, which is an important sensor of innate immunity and intensively explored for its role in health and disease, hence presents as an interesting therapeutic approach to target three crucial pathogenetic processes in AD, including prion-like seeding of Tau pathology, Aβ pathology and neuroinflammation.

Dataset Information

A Yersinia effector with enhanced inhibitory activity on the NF-?B pathway activates the NLRP3/ASC/caspase-1 inflammasome in macrophages.

Publications

A Yersinia effector with enhanced inhibitory activity on the NF-κB pathway activates the NLRP3/ASC/caspase-1 inflammasome in macrophages.

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