scholarly journals Human caspase-1 autoproteolysis is required for ASC-dependent and -independent inflammasome activation

2019 ◽  
Author(s):  
Daniel P. Ball ◽  
Cornelius Y. Taabazuing ◽  
Andrew R. Griswold ◽  
Elizabeth L. Orth ◽  
Sahana D. Rao ◽  
...  
Keyword(s):  
Pattern Recognition ◽  
Cell Death ◽  
Pattern Recognition Receptors ◽  
Inflammasome Activation ◽  
Adapter Protein ◽  
Large Structure ◽  
Catalytic Subunits ◽  
Caspase 1 ◽  
Human Caspase

AbstractPathogen-related signals induce a number of cytosolic pattern-recognition receptors (PRRs) to form canonical inflammasomes, which activate pro-caspase-1 and trigger pyroptotic cell death. All well-studied PRRs oligomerize with the pro-caspase-1-adapter protein ASC to generate a single large structure in the cytosol, which induces the autoproteolysis and activation of the pro-caspase-1 zymogen. However, several PRRs can also directly interact with pro-caspase-1 without ASC, forming much smaller “ASC-independent” inflammasomes. It is currently thought that pro-caspase-1 autoproteolysis does not occur during, and is not required for, ASC-independent inflammasome activation. Here, we show that the related human PRRs NLRP1 and CARD8 exclusively form ASC-dependent and ASC-independent inflammasomes, respectively, identifying CARD8 as the first PRR that cannot form an ASC-containing signaling platform. Despite their different structures, we discovered that both the NLRP1 and CARD8 inflammasomes require pro-caspase-1 autoproteolysis between the small and large catalytic subunits to induce pyroptosis. Thus, pro-caspase-1 self-cleavage is an obligate regulatory step in the activation of human canonical inflammasomes.

scholarly journals Caspase-1 interdomain linker cleavage is required for pyroptosis

2020 ◽  
Vol 3 (3) ◽  
pp. e202000664 ◽  
Author(s):  
Daniel P Ball ◽  
Cornelius Y Taabazuing ◽  
Andrew R Griswold ◽  
Elizabeth L Orth ◽  
Sahana D Rao ◽  
...  
Keyword(s):  
Pattern Recognition ◽  
Cell Death ◽  
Pattern Recognition Receptors ◽  
Adapter Protein ◽  
Large Structure ◽  
Catalytic Subunits ◽  
Caspase 1 ◽  
Interdomain Linker

Pathogen-related signals induce a number of cytosolic pattern-recognition receptors (PRRs) to form canonical inflammasomes, which activate pro-caspase-1 and trigger pyroptotic cell death. All well-studied inflammasome-forming PRRs oligomerize with the adapter protein ASC (apoptosis-associated speck-like protein containing a CARD) to generate a large structure in the cytosol, which induces the dimerization, autoproteolysis, and activation of the pro-caspase-1 zymogen. However, several PRRs can also directly interact with pro-caspase-1 without ASC, forming smaller “ASC-independent” inflammasomes. It is currently thought that little, if any, pro-caspase-1 autoproteolysis occurs during, and is not required for, ASC-independent inflammasome signaling. Here, we show that the related human PRRs NLRP1 and CARD8 exclusively form ASC-dependent and ASC-independent inflammasomes, respectively, identifying CARD8 as the first canonical inflammasome-forming PRR that does not form an ASC-containing signaling platform. Despite their different structures, we discovered that both the NLRP1 and CARD8 inflammasomes require pro-caspase-1 autoproteolysis between the small and large catalytic subunits to induce pyroptosis. Thus, pro-caspase-1 self-cleavage is a required regulatory step for pyroptosis induced by human canonical inflammasomes.

scholarly journals Human caspase-4 mediates noncanonical inflammasome activation against gram-negative bacterial pathogens

2015 ◽  
Vol 112 (21) ◽  
pp. 6688-6693 ◽  
Author(s):  
Cierra N. Casson ◽  
Janet Yu ◽  
Valeria M. Reyes ◽  
Frances O. Taschuk ◽  
Anjana Yadav ◽  
...  
Keyword(s):  
Cell Death ◽  
Bacterial Pathogens ◽  
Inflammasome Activation ◽  
Gram Negative Bacteria ◽  
Secretion Systems ◽  
Gram Negative ◽  
Human Macrophages ◽  
Caspase 1 ◽  
Inflammatory Caspases ◽  
Human Caspase

Inflammasomes are critical for host defense against bacterial pathogens. In murine macrophages infected by gram-negative bacteria, the canonical inflammasome activates caspase-1 to mediate pyroptotic cell death and release of IL-1 family cytokines. Additionally, a noncanonical inflammasome controlled by caspase-11 induces cell death and IL-1 release. However, humans do not encode caspase-11. Instead, humans encode two putative orthologs: caspase-4 and caspase-5. Whether either ortholog functions similar to caspase-11 is poorly defined. Therefore, we sought to define the inflammatory caspases in primary human macrophages that regulate inflammasome responses to gram-negative bacteria. We find that human macrophages activate inflammasomes specifically in response to diverse gram-negative bacterial pathogens that introduce bacterial products into the host cytosol using specialized secretion systems. In primary human macrophages, IL-1β secretion requires the caspase-1 inflammasome, whereas IL-1α release and cell death are caspase-1–independent. Instead, caspase-4 mediates IL-1α release and cell death. Our findings implicate human caspase-4 as a critical regulator of noncanonical inflammasome activation that initiates defense against bacterial pathogens in primary human macrophages.

scholarly journals Pattern Recognition Receptors and the Host Cell Death Molecular Machinery

2018 ◽  
Vol 9 ◽  
Author(s):  
Gustavo P. Amarante-Mendes ◽  
Sandy Adjemian ◽  
Laura Migliari Branco ◽  
Larissa C. Zanetti ◽  
Ricardo Weinlich ◽  
...  
Keyword(s):  
Pattern Recognition ◽  
Cell Death ◽  
Host Cell ◽  
Pattern Recognition Receptors ◽  
Host Cell Death ◽  
Molecular Machinery

scholarly journals Complementary regulation of caspase-1 and IL-1β reveals additional mechanisms of dampened inflammation in bats

2020 ◽  
Vol 117 (46) ◽  
pp. 28939-28949 ◽  
Author(s):  
Geraldine Goh ◽  
Matae Ahn ◽  
Feng Zhu ◽  
Lim Beng Lee ◽  
Dahai Luo ◽  
...  
Keyword(s):  
Functional Analysis ◽  
Immune Response ◽  
Cell Death ◽  
Diverse Range ◽  
Caspase 1 ◽  
Enzymatic Function ◽  
Zoonotic Viruses ◽  
Cytoplasmic Dna ◽  
Human Caspase ◽  
Complete Genomic

Bats have emerged as unique mammalian vectors harboring a diverse range of highly lethal zoonotic viruses with minimal clinical disease. Despite having sustained complete genomic loss of AIM2, regulation of the downstream inflammasome response in bats is unknown. AIM2 sensing of cytoplasmic DNA triggers ASC aggregation and recruits caspase-1, the central inflammasome effector enzyme, triggering cleavage of cytokines such as IL-1β and inducing GSDMD-mediated pyroptotic cell death. Restoration of AIM2 in bat cells led to intact ASC speck formation, but intriguingly resulted in a lack of caspase-1 or consequent IL-1β activation. We further identified two residues undergoing positive selection pressures inPteropus alectocaspase-1 that abrogate its enzymatic function and are crucial in human caspase-1 activity. Functional analysis of another bat lineage revealed a targeted mechanism for loss ofMyotis davidiiIL-1β cleavage and elucidated an inverse complementary relationship between caspase-1 and IL-1β, resulting in overall diminished signaling across bats of both suborders. Thus we report strategies that additionally undermine downstream inflammasome signaling in bats, limiting an overactive immune response against pathogens while potentially producing an antiinflammatory state resistant to diseases such as atherosclerosis, aging, and neurodegeneration.

scholarly journals Type I interferon signaling is required for activation of the inflammasome during Francisella infection

2007 ◽  
Vol 204 (5) ◽  
pp. 987-994 ◽  
Author(s):  
Thomas Henry ◽  
Anna Brotcke ◽  
David S. Weiss ◽  
Lucinda J. Thompson ◽  
Denise M. Monack
Keyword(s):  
Cell Death ◽  
Type I Interferon ◽  
Infection Type ◽  
Host Responses ◽  
Inflammasome Activation ◽  
Type I ◽  
Type I Ifn ◽  
Caspase 1 ◽  
Dependent Cell

Francisella tularensis is a pathogenic bacterium whose virulence is linked to its ability to replicate within the host cell cytosol. Entry into the macrophage cytosol activates a host-protective multimolecular complex called the inflammasome to release the proinflammatory cytokines interleukin (IL)-1β and -18 and trigger caspase-1–dependent cell death. In this study, we show that cytosolic F. tularensis subspecies novicida (F. novicida) induces a type I interferon (IFN) response that is essential for caspase-1 activation, inflammasome-mediated cell death, and release of IL-1β and -18. Extensive type I IFN–dependent cell death resulting in macrophage depletion occurs in vivo during F. novicida infection. Type I IFN is also necessary for inflammasome activation in response to cytosolic Listeria monocytogenes but not vacuole-localized Salmonella enterica serovar Typhimurium or extracellular adenosine triphosphate. These results show the specific connection between type I IFN signaling and inflammasome activation, which are two sequential events triggered by the recognition of cytosolic bacteria. To our knowledge, this is the first example of the positive regulation of inflammasome activation. This connection underscores the importance of the cytosolic recognition of pathogens and highlights how multiple innate immunity pathways interact before commitment to critical host responses.

scholarly journals Phenothiazine Inhibits Neuroinflammation and Inflammasome Activation Independent of Hypothermia After Ischemic Stroke

2021 ◽  
Author(s):  
Sichao Guo ◽  
Xiaokun Geng ◽  
Hangil Lee ◽  
Yuchuan Ding
Keyword(s):  
Cell Death ◽  
Ischemic Stroke ◽  
Brain Activity ◽  
Ischemia Reperfusion ◽  
Inflammasome Activation ◽  
Mrna Levels ◽  
Sprague Dawley ◽  
Neuroinflammatory Response ◽  
Protein Levels ◽  
Caspase 1

Abstract A depressive or hibernation-like effect of chlorpromazine and promethazine (C + P) on brain activity was reported to induce neuroprotection, with or without induced-hypothermia. However, the underlying mechanisms remain unclear. The current study evaluated the pharmacological function of C + P on the inhibition of neuroinflammatory response and inflammasome activation after ischemia/reperfusion. A total of 72 adult male Sprague-Dawley rats were subjected to 2 h middle cerebral artery occlusion (MCAO) followed by 6 or 24 h reperfusion. At the onset of reperfusion, rats received C + P (8 mg/kg) with temperature control. Brain cell death was detected by measuring CD68 and myeloperoxidase (MPO) levels. Inflammasome activation was measured by mRNA levels of NLRP3, IL-1β, and TXNIP, and protein quantities of NLRP3, IL-1β, TXNIP, cleaved-Caspase-1, and IL-18. Activation of JAK2/STAT3 pathway was detected by the phosphorylation of STAT3 (p-STAT3) and JAK2 (p-JAK2), and the co-localization of p-STAT3 and NLRP3. Activation of the p38 pathway was assessed with the protein levels of p-p38/p38. The mRNA and protein levels of HIF-1α, FoxO1, and p-FoxO1, and the co-localization of p-STAT3 with HIF-1α or FoxO1 were quantitated. As expected, C + P significantly reduced cell death and attenuated the neuroinflammatory response as determined by reduced CD68 and MPO. C + P decreased ischemia-induced inflammasome activation, shown by reduced mRNA and protein expressions of NLRP3, IL-1β, TXNIP, cleaved-Caspase-1, and IL-18. Phosphorylation of JAK2/STAT3 and p38 pathways and the co-localization of p-STAT3 with NLRP3 were also inhibited by C + P. Furthermore, mRNA levels of HIF-1α and FoxO1 were decreased in the C + P group. While C + P inhibited HIF-1α protein expression, it increased FoxO1 phosphorylation, which promoted the exclusion of FoxO1 from the nucleus and inhibited FoxO1 activity. At the same time, C + P reduced the co-localization of p-STAT3 with HIF-1α or FoxO1. In conclusion, C + P treatment conferred neuroprotection in stroke by suppressing neuroinflammation and NLRP3 inflammasome activation. The present study suggests that JAK2/STAT3/p38/HIF-1α/FoxO1 are vital regulators and potential targets for efficacious therapy following ischemic stroke.

scholarly journals Short Exposure to Ethanol Diminishes Caspase-1 and ASC Activation in Human HepG2 Cells In Vitro

2020 ◽  
Vol 21 (9) ◽  
pp. 3196
Author(s):  
Jason-Alexander Hörauf ◽  
Shinwan Kany ◽  
Andrea Janicova ◽  
Baolin Xu ◽  
Teodora Vrdoljak ◽  
...  
Keyword(s):  
Cell Death ◽  
Hepg2 Cells ◽  
Purinergic Receptor ◽  
Short Exposure ◽  
Ros Generation ◽  
Inflammasome Activation ◽  
Ros Production ◽  
Sodium Orthovanadate ◽  
Tyrosine Phosphatases ◽  
Caspase 1

This paper discusses how the assembly of pro-caspase-1 and apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) in macromolecular protein complexes, inflammasomes, activates caspase-1. The present study investigates the molecular mechanisms of inflammasome activation in HepG2 cells and examines how short exposures to ethanol (EtOH) affect inflammasome activation. HepG2 cells were treated with lipopolysaccharide (LPS), ATP or nigericin (NIG) in a two-step model. After LPS priming, ATP or NIG were added. As inhibitors, sodium orthovanadate (general inhibitor of tyrosine phosphatases), AC-YVAD-CMK (caspase-1 inhibitor) or AZ10606120 (purinergic receptor P2X7R inhibitor) were applied after LPS priming. To monitor the inflammasome activation, the caspase-1 activity, ASC speck formation, reactive oxygen species (ROS) production and cell death were analyzed. To elucidate the mechanistical approach of EtOH to the inflammasome assembly, the cells were treated with EtOH either under simultaneous LPS administration or concurrently with ATP or NIG application. The co-stimulation with LPS and ATP induced a significant ASC speck formation, caspase-1 activation, cell death and ROS generation. The inhibition of the ATP-dependent purinoreceptor P2X7 decreased the caspase-1 activation, whereas sodium orthovanadate significantly induced caspase-1. Additional treatment with EtOH reversed the LPS and ATP-induced caspase-1 activation, ASC speck formation and ROS production. The ASC speck formation and caspase-1 induction require a two-step signaling with LPS and ATP in HepG2 cells. Inflammasome activation may depend on P2X7. The molecular pathway of an acute effect of EtOH on inflammasomes may involve a reduction in ROS generation, which in turn may increase the activity of tyrosine phosphatases.

Inhibitory pattern recognition receptors

2021 ◽  
Vol 219 (1) ◽  
Author(s):  
Matevž Rumpret ◽  
Helen J. von Richthofen ◽  
Victor Peperzak ◽  
Linde Meyaard
Keyword(s):  
Pattern Recognition ◽  
Cell Death ◽  
Immune System ◽  
Immune Responses ◽  
Pattern Recognition Receptors ◽  
Inhibitory Receptors ◽  
Danger Signals ◽  
Molecular Pattern ◽  
Molecular Patterns ◽  
Damage Associated Molecular Patterns

Pathogen- and damage-associated molecular patterns are sensed by the immune system’s pattern recognition receptors (PRRs) upon contact with a microbe or damaged tissue. In situations such as contact with commensals or during physiological cell death, the immune system should not respond to these patterns. Hence, immune responses need to be context dependent, but it is not clear how context for molecular pattern recognition is provided. We discuss inhibitory receptors as potential counterparts to activating pattern recognition receptors. We propose a group of inhibitory pattern recognition receptors (iPRRs) that recognize endogenous and microbial patterns associated with danger, homeostasis, or both. We propose that recognition of molecular patterns by iPRRs provides context, helps mediate tolerance to microbes, and helps balance responses to danger signals.

scholarly journals New insights in caspase-11 functions in noncanonical inflammasome signalling

Inflammasome ◽  
2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Mélanie Bodnar ◽  
Virginie Petrilli
Keyword(s):  
Cell Death ◽  
Inflammatory Cell ◽  
Protein Complexes ◽  
Inflammasome Activation ◽  
Gram Negative Bacteria ◽  
Nucleotide Binding Domain ◽  
Gram Negative ◽  
Caspase 1 ◽  
Nlrp3 Inflammasome Activation ◽  
Dependent Pathway

AbstractInflammasomes are multi-protein complexes that play a crucial role in innate immunity. They are assembled by cytosolic sensors of the Nucleotide-binding domain and Leucine-rich repeat containing Receptor (NLR) and PYrin and HIN (PYHIN) domain-containing protein families upon sensing various pathogens and danger signals. Inflammasome formation culminates in caspase-1 activation, which causes the cleavage of pro-IL-1β and pro- IL-18 into active cytokines; this eventually results in the induction of an inflammatory cell death called pyroptosis. Recent data using Gram-negative bacteria suggests a role for caspase-11 not only in NLRP3 inflammasome activation but also in a caspase-1- and inflammasome-independent cell death. This novel caspase-11-dependent pathway is critical to control infection by Gram-negative bacteria and has been named the noncanonical inflammasome.

scholarly journals Heterologous Expression and Auto-Activation of Human Pro-Inflammatory Caspase-1 in Saccharomyces cerevisiae and Comparison to Caspase-8

2021 ◽  
Vol 12 ◽  
Author(s):  
Marta Valenti ◽  
María Molina ◽  
Víctor J. Cid
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Death ◽  
Heterologous Expression ◽  
Cysteine Proteases ◽  
Intrinsic Activity ◽  
Caspase 8 ◽  
Caspase 1 ◽  
Death Effector ◽  
Human Caspase

Caspases are a family of cysteine proteases that play an essential role in inflammation, apoptosis, cell death, and development. Here we delve into the effects caused by heterologous expression of human caspase-1 in the yeast Saccharomyces cerevisiae and compare them to those of caspase-8. Overexpression of both caspases in the heterologous model led to their activation and caused mitochondrial hyperpolarization, damage to different organelles, and cell death. All these effects were dependent on their protease activity, and caspase-8 was more aggressive than caspase-1. Growth arrest could be at least partially explained by dysfunction of the actin cytoskeleton as a consequence of the processing of the yeast Bni1 formin, which we identify here as a likely direct substrate of both caspases. Through the modulation of the GAL1 promoter by using different galactose:glucose ratios in the culture medium, we have established a scenario in which caspase-1 is sufficiently expressed to become activated while yeast growth is not impaired. Finally, we used the yeast model to explore the role of death-fold domains (DD) of both caspases in their activity. Peculiarly, the DDs of either caspase showed an opposite involvement in its intrinsic activity, as the deletion of the caspase activation and recruitment domain (CARD) of caspase-1 enhanced its activity, whereas the deletion of the death effector domain (DED) of caspase-8 diminished it. We show that caspase-1 is able to efficiently process its target gasdermin D (GSDMD) when co-expressed in yeast. In sum, we propose that S. cerevisiae provides a manageable tool to explore caspase-1 activity and structure–function relationships.

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