Eliminating Legionella by inhibiting BCL-XL to induce macrophage apoptosis

Speir, Mary; Lawlor, Kate E.; Glaser, Stefan; Abraham, Gilu; Chow, Seong Hoong; Vogrin, Adam; Schulze, Keith E.; Schuelein, Ralf; O’Reilly, Lorraine A.; Mason, Kylie D.; Hartland, Elizabeth L.; Lithgow, Trevor; Strasser, Andreas; Lessène, Guillaume; Huang, David C.S.; Vince, James E.; Naderer, Thomas

doi:10.1038/nmicrobiol.2015.34

Cited by 67 publications

(88 citation statements)

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“…Programmed cell death can also act to eliminate pathogen-infected cells, with recent studies highlighting how targeted apoptosis-inducing anticancer compounds can treat viral and intracellular bacterial infections (1,2). On the other hand, the recently characterized caspase-independent necroptotic cell death pathway is dispensable for organism development but, like apoptosis, can be triggered to kill cells harboring pathogenic microbes (3).…”

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confidence: 99%

Active MLKL triggers the NLRP3 inflammasome in a cell-intrinsic manner

Conos

Chen

Nardo

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Necroptosis is a physiological cell suicide mechanism initiated by receptor-interacting protein kinase-3 (RIPK3) phosphorylation of mixed-lineage kinase domain-like protein (MLKL), which results in disruption of the plasma membrane. Necroptotic cell lysis, and resultant release of proinflammatory mediators, is thought to cause inflammation in necroptotic disease models. However, we previously showed that MLKL signaling can also promote inflammation by activating the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome to recruit the adaptor protein apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC) and trigger caspase-1 processing of the proinflammatory cytokine IL-1β. Here, we provide evidence that MLKL-induced activation of NLRP3 requires (i) the death effector four-helical bundle of MLKL, (ii) oligomerization and association of MLKL with cellular membranes, and (iii) a reduction in intracellular potassium concentration. Although genetic or pharmacological targeting of NLRP3 or caspase-1 prevented MLKLinduced IL-1β secretion, they did not prevent necroptotic cell death. Gasdermin D (GSDMD), the pore-forming caspase-1 substrate required for efficient NLRP3-triggered pyroptosis and IL-1β release, was not essential for MLKL-dependent death or IL-1β secretion. Imaging of MLKL-dependent ASC speck formation demonstrated that necroptotic stimuli activate NLRP3 cell-intrinsically, indicating that MLKL-induced NLRP3 inflammasome formation and IL-1β cleavage occur before cell lysis. Furthermore, we show that necroptotic activation of NLRP3, but not necroptotic cell death alone, is necessary for the activation of NF-κB in healthy bystander cells. Collectively, these results demonstrate the potential importance of NLRP3 inflammasome activity as a driving force for inflammation in MLKLdependent diseases.aspase-dependent apoptotic cell death is required for mammalian development and the prevention of autoimmune and neoplastic diseases. Programmed cell death can also act to eliminate pathogen-infected cells, with recent studies highlighting how targeted apoptosis-inducing anticancer compounds can treat viral and intracellular bacterial infections (1, 2). On the other hand, the recently characterized caspase-independent necroptotic cell death pathway is dispensable for organism development but, like apoptosis, can be triggered to kill cells harboring pathogenic microbes (3). A number of studies have also reported how pathological activation of necroptotic signaling may contribute to diverse disease states, such as ischemia-reperfusion injury, atherosclerosis, and liver disease, presumably through cell death and the release of proinflammatory mediators (4).The execution of necroptosis is dependent on receptor interacting serine-threonine protein kinase 3 (RIPK3) phosphorylation of mixed-lineage kinase domain-like protein (MLKL), and MLKL's association with, and disruption of, plasma membrane integrity (5).In the absence of caspase activit...

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mentioning

confidence: 99%

Active MLKL triggers the NLRP3 inflammasome in a cell-intrinsic manner

Conos

Chen

Nardo

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

380

298

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“…46 Interestingly, a recent study showed that BCL-XL-specific BH3 mimetics potently kill Legionella-infected macrophages and thereby protect mice from pathology induced by these bacteria. 47 Should loss of A1 kill Mycobacterium tuberculosis macrophages, it would be of interest to generate A1-specific BH3 mimetics to test for treatment of tuberculosis.…”

Section: Discussionmentioning

confidence: 99%

Characterisation of mice lacking all functional isoforms of the pro-survival BCL-2 family member A1 reveals minor defects in the haematopoietic compartment

et al. 2017

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The pro-survival proteins of the BCL-2 family regulate the survival of all cells, and genetic deletion models for these proteins have revealed which specific BCL-2 family member(s) is/are critical for the survival of particular cell types. A1 is a pro-survival BCL-2-like protein that is expressed predominantly in haematopoietic cells, and here we describe the characterisation of a novel mouse strain that lacks all three functional isoforms of A1 (A1-a, A1-b and A1-d). Surprisingly, complete loss of A1 caused only minor defects, with significant, although relatively small, decreases in γδTCR T cells, antigen-experienced conventional as well as regulatory CD4 T cells and conventional dendritic cells (cDCs). When examining these cell types in tissue culture, only cDC survival was significantly impaired by the loss of A1. Therefore, A1 appears to be a surprisingly redundant pro-survival protein in the haematopoietic system and other tissues, suggesting that its targeting in cancer may be readily tolerated. Cell Death and Differentiation (2017) 24, 534-545; doi:10.1038/cdd.2016.156; published online 13 Janaury 2017The pro-survival proteins of the BCL-2 family prevent apoptosis 1 and studies using gene-targeted mice have revealed which cell types rely on which pro-survival protein for their survival. For example, Bcl-2 −/− mice exhibit thymic and splenic atrophy, a loss of fur pigment and die~30 days post birth from polycystic kidney disease, attributable to excess lymphocyte, melanocyte and renal epithelial cell apoptosis, respectively. 2-4 Bcl-X −/− mice die before E14.5 of embryonic development because of aberrant death of erythroid and neuronal cells. 5 The generation of chimaeric or tissue-specific Bcl-X −/− revealed a critical role for BCL-XL in the survival of developing lymphocytes 5 and platelets. 6,7 Mcl-1 −/− embryos die before implantation (E3.5), 8 but conditional Mcl-1 deletion models have demonstrated an essential role for MCL-1 in the survival of haematopoietic stem cells, lymphocytes, neurons and cardiomyocytes. 9-15 Bcl-W −/− mice have impaired spermatogenesis. 16,17 A1 remains the only pro-survival BCL-2 family member for which a knockout mouse strain has not been developed. A1 was first discovered as a GM-CSF-inducible gene with significant sequence similarity to BCL-2 and MCL-1, 18 and its human homologue BFL-1 was later identified in fetal liver. 19 Overexpression of A1 protected an IL-3-dependent cell line from growth factor deprivation-induced apoptosis, thus demonstrating its pro-survival function. 20 In mice, A1 expression is restricted to the haematopoietic compartment. 18 Human BFL-1 expression is more widespread, but also predominantly haematopoietic. 21 A1 can be upregulated by NF-κB signalling, and it has been proposed that A1/BFL-1 is important for the survival of several activated immune cell subsets through stimulation of antigen or cytokine receptors. [22][23][24][25] Studies of A1 in mice are complicated by the presence of multiple isoforms that are the result of gene duplication ev...

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“…Apoptotic cell death can promote phagocytic clearance of infected cells to limit pathogenic infections, 1, 2 and is required to delete lymphocytes to prevent autoimmune disease. 3 Intrinsic ‘mitochondria-dependent' apoptosis is triggered by cellular stressors (for example, growth factor withdrawal) and is tightly regulated by the pro- and anti-apoptotic members of the BCL-2 protein family (reviewed in Delbridge et al 4 ).…”

Section: Introductionmentioning

confidence: 99%

Caspase‐8: not so silently deadly

2017

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Apoptosis is a caspase-dependent programmed form of cell death, which is commonly believed to be an immunologically silent process, required for mammalian development and maintenance of cellular homoeostasis. In contrast, lytic forms of cell death, such as RIPK3- and MLKL-driven necroptosis, and caspase-1/11-dependent pyroptosis, are postulated to be inflammatory via the release of damage associated molecular patterns (DAMPs). Recently, the function of apoptotic caspase-8 has been extended to the negative regulation of necroptosis, the cleavage of inflammatory interleukin-1β (IL-1β) to its mature bioactive form, either directly or via the NLRP3 inflammasome, and the regulation of cytokine transcriptional responses. In view of these recent advances, human autoinflammatory diseases that are caused by mutations in cell death regulatory machinery are now associated with inappropriate inflammasome activation. In this review, we discuss the emerging crosstalk between cell death and innate immune cell inflammatory signalling, particularly focusing on novel non-apoptotic functions of caspase-8. We also highlight the growing number of autoinflammatory diseases that are associated with enhanced inflammasome function.

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Eliminating Legionella by inhibiting BCL-XL to induce macrophage apoptosis

Cited by 67 publications

References 36 publications

Active MLKL triggers the NLRP3 inflammasome in a cell-intrinsic manner

Active MLKL triggers the NLRP3 inflammasome in a cell-intrinsic manner

Characterisation of mice lacking all functional isoforms of the pro-survival BCL-2 family member A1 reveals minor defects in the haematopoietic compartment

Caspase‐8: not so silently deadly

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