# Inflammasome
An inflammasome is a multiprotein complex in the innate immune system that activates inflammatory caspases, most prominently caspase-1, in response to pathogens and cellular danger signals. Once assembled, the complex processes the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18 into their mature forms and triggers a lytic, inflammatory form of cell death called pyroptosis. The complex was named and first described in 2002 by Fabio Martinon, Kimberly Burns, and [Jürg Tschopp](https://www.edgepedia.org/jurg-tschopp) at the University of Lausanne, who identified a caspase-activating platform containing caspase-1, caspase-5, the adaptor Pycard/Asc, and NALP1.[1](https://pubmed.ncbi.nlm.nih.gov/12191486/)
| Key fact | Detail |
|---|---|
| Discovery | Named in 2002 by Martinon, Burns, and Tschopp; the original complex comprised caspase-1, caspase-5, Pycard/Asc, and NALP1[1](https://pubmed.ncbi.nlm.nih.gov/12191486/) |
| Core architecture | An upstream sensor protein, the adaptor ASC, and the effector caspase-1[2](https://www.nature.com/articles/s41392-023-01687-y) |
| Canonical sensors | NLRP1, NLRP3, NLRC4, AIM2, and pyrin, all capable of activating caspase-1[3](https://www.nature.com/articles/s41392-021-00650-z) |
| Noncanonical pathway | Human caspase-4 and caspase-5, and murine caspase-11, directly bind intracellular LPS lipid A without a receptor or ASC[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10232970/) |
| Execution of pyroptosis | Caspase-1/4/5/11 cleave gasdermin D, whose N-terminal fragment forms pores in the plasma membrane[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC8844060/) |
| Cytokine output | Caspase-1 cleaves pro-IL-1β and pro-IL-18 into active forms; caspase-4/5/11 cannot process pro-IL-1β[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10232970/) |
| Disease links | Dysregulated activation contributes to diabetes, cancer, cardiovascular and neurodegenerative disorders, gout, and atherosclerosis[2](https://www.nature.com/articles/s41392-023-01687-y) • [6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10560975/) |
## Structure and assembly
Each canonical inflammasome has three functional components: a sensor molecule that recognizes the activating signal, the adaptor protein ASC (apoptosis-associated speck-like protein), and the effector pro-caspase-1.[2](https://www.nature.com/articles/s41392-023-01687-y) After binding its ligand, most inflammasome sensors recruit ASC via homotypic PYD–PYD interactions; ASC then oligomerizes and uses its caspase activation and recruitment domain (CARD) to recruit pro-caspase-1, although NLRP1 and NLRC4 can recruit caspase-1 directly through CARD–CARD interactions.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC8463274/) • [2](https://www.nature.com/articles/s41392-023-01687-y) Activated inflammasome-forming receptors oligomerize into multi-subunit wheel-shaped assemblies, as shown by cryo-electron microscopy of the NAIP–NLRC4 complex.[8](https://www.nature.com/articles/nri.2016.58)
Assembly is tightly controlled. Inflammasome activation can also produce a second caspase-1-activating structure, the ASC speck or pyroptosome, whose formation is regulated by complex mechanisms.[9](https://pubmed.ncbi.nlm.nih.gov/24579701/) The adaptor ASC must become linearly ubiquitinated and phosphorylated for inflammasome assembly to occur.[10](https://pubmed.ncbi.nlm.nih.gov/26121197/) NLRP3 assembly additionally requires NEK7, a serine and threonine kinase involved in mitotic cell cycle progression.[11](https://www.nature.com/articles/s41421-020-0167-x)
## Canonical inflammasomes
The NLRP1, NLRP3, NLRC4, and AIM2 inflammasomes are termed canonical because all of them activate caspase-1.[3](https://www.nature.com/articles/s41392-021-00650-z) Their sensors fall into structural families: NOD-like receptors (NLRs) with a leucine-rich repeat domain (NLRC4, NLRP1, NLRP3, NLRP6), AIM2-like receptors with a HIN200 DNA-binding domain, and RIG-I-like receptors.[12](https://www.frontiersin.org/articles/10.3389/fcell.2023.1218807/pdf)
**NLRP3** is the most widely studied inflammasome. It responds indirectly to a broad range of stimuli, including products of damaged cells such as ATP, crystalline substances, and nucleic acids, as well as pathogen-derived molecules, and it participates in immune responses against bacterial, viral, fungal, and parasitic infections.[3](https://www.nature.com/articles/s41392-021-00650-z) • [6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10560975/) Unlike NLRP1, NLRP3 lacks a [CARD domain](https://www.edgepedia.org/card-domain) and must recruit pro-caspase-1 through ASC.[3](https://www.nature.com/articles/s41392-021-00650-z)
**NLRC4** responds mainly to bacterial flagellin and components of the bacterial type III secretion system. It contains a CARD domain and can directly recruit pro-caspase-1, but its ligand specificity is determined by NAIP proteins, which are receptors for bacterial ligands. Mice have four NAIPs: NAIP1 binds the needle protein, NAIP2 detects rod proteins, and NAIP5/6 interact with flagellin. Humans have a single NAIP, which interacts with the needle protein CprI.[3](https://www.nature.com/articles/s41392-021-00650-z)
**AIM2** binds cytosolic double-stranded DNA directly and sequence-independently, sensing DNA from bacteria and viruses as well as damaged, mislocalized host DNA; a minimum DNA length of 80 base pairs is required for activation. Because AIM2 lacks a CARD domain it recruits ASC, and it can recognize self-DNA, which may contribute to systemic lupus erythematosus, though more direct evidence is required.[3](https://www.nature.com/articles/s41392-021-00650-z) • [13](https://www.nature.com/articles/s41423-025-01354-y.pdf)
## Noncanonical inflammasome
The noncanonical inflammasome is an abridged complex with no dedicated receptor or adaptor: the inflammatory caspases themselves act as the sensors. In rodents this is caspase-11; in humans, caspase-4 and caspase-5. The CARD domain of pro-caspase-11 (pro-caspase-4/5 in humans) directly binds the lipid A of lipopolysaccharide (LPS) released by [Gram-negative bacteria](https://www.edgepedia.org/gram-negative-bacteria), triggering conformational change, oligomerization, and autoproteolysis, without involvement of the membrane LPS receptor TLR4.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10232970/) • [3](https://www.nature.com/articles/s41392-021-00650-z) Caspase-11-deficient mice resist a lethal dose of injected LPS.[3](https://www.nature.com/articles/s41392-021-00650-z)
The noncanonical pathway crosstalks with the canonical one: caspase-11 can indirectly activate the NLRP3 inflammasome, leading to cleavage of pro-IL-1β and pro-IL-18.[3](https://www.nature.com/articles/s41392-021-00650-z) Substrate use differs between species: caspase-4 cleaves IL-18 and the 43 kDa TAR DNA-binding protein (TDP-43), whereas caspase-11 does not, implying different outcomes of noncanonical activation in humans versus rodents; caspase-4/5/11 are unable to process pro-IL-1β directly.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC8844060/) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10232970/) A proteomic study using a degenerate monoclonal antibody library found the caspase-4 cleavage motif in over 300 proteins, including spliceosome components.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC8844060/)
## Pyroptosis and gasdermin D
Activation of caspase-1 through the canonical pathway, or of caspase-4/5/11 through the noncanonical pathway, triggers pyroptosis, a lytic form of programmed cell death characterized by cell swelling, loss of membrane integrity, and release of cellular contents.[14](https://pmc.ncbi.nlm.nih.gov/articles/PMC5890894/) The effector is gasdermin D (GSDMD): inflammatory caspases cleave it between its N-terminal and C-terminal domains, releasing the inhibitory C-terminal fragment. The freed N-terminal domain (GSDMD-NT) migrates to the plasma membrane and assembles large pore complexes, causing lysis.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC8844060/) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10232970/)
During pyroptosis, GSDMD pores and membrane rupture release cytokines, damage-associated molecular patterns (DAMPs), and alarmins that amplify local and systemic inflammation, and they destroy the replicative environment for intracellular bacteria.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC8844060/) • [15](https://pmc.ncbi.nlm.nih.gov/articles/PMC10699704/) GSDMD-NT also binds mitochondrial cardiolipin, forming mitochondrial pores that release mitochondrial ROS and mitochondrial DNA and cause mitochondrial dysfunction.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10232970/) GSDMD pores are subject to cellular repair: calcium influx through the pores activates ESCRT-I and ESCRT-III proteins.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC8844060/) The gasdermin family is conserved in vertebrates, with four paralogous genes in humans (GSDMA, GSDMB, GSDMC, GSDMD), while mice lack Gsdmb.[14](https://pmc.ncbi.nlm.nih.gov/articles/PMC5890894/)
## Role in disease
Inflammasomes defend against infection, but excessive or dysregulated activation drives pathology. Aberrant inflammasome activity contributes to diabetes, cancer, and several cardiovascular and neurodegenerative disorders.[2](https://www.nature.com/articles/s41392-023-01687-y) In sterile inflammatory conditions, including crystal deposition disorders, neurodegenerative diseases, depression, atherosclerosis, insulin resistance, inflammatory bowel disease, and cancer, inflammasome roles are diverse.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10560975/) In neurodegenerative disorders such as Alzheimer's disease and [Parkinson's disease](https://www.edgepedia.org/parkinsons-disease), protein aggregates including amyloid-β and α-synuclein, together with mitochondrial dysfunction, induce inflammasome activation and aggravate neuroinflammation.[16](https://www.nature.com/articles/s41423-025-01284-9.pdf) [The NLRP3 inflammasome](https://www.edgepedia.org/the-nlrp3-inflammasome) in particular is implicated in inflammation-driven diseases including COVID-19, Alzheimer's disease, and gout.[17](https://www.sciencedirect.com/science/article/pii/S0165614725000732)
## Therapeutic targeting
Inflammasome blockade is an active area of drug development. Glyburide, a small molecule already used to treat type 2 diabetes, was the first compound identified to inhibit NLRP3-dependent, but not NLRC4- or NLRP1-dependent, IL-1β production. The direct NLRP3 inhibitor MCC950 reduces IL-1β production and attenuates severity in experimental autoimmune encephalomyelitis, a model of multiple sclerosis, although its mechanism is not fully understood.[18](https://pmc.ncbi.nlm.nih.gov/articles/PMC4519035/) MCC950 later showed off-target effects.[17](https://www.sciencedirect.com/science/article/pii/S0165614725000732) Multiple NLRP3 inhibitors are in clinical trials: VTX-2735, an orally administered NLRP3 inhibitor from Ventyx Biosciences, passed a phase 1 trial in 2022 and entered a phase 2 study in cryopyrin-associated periodic syndrome, a condition caused by NLRP3 gene mutation.[19](https://www.nature.com/articles/s12276-024-01261-8) IL-1-blocking agents are already in clinical use.[20](https://wjpr.s3.ap-south-1.amazonaws.com/article_issue/1f7ad3ac1edd65d785e3686414037374.pdf) A recurring challenge is off-target effect, which in clinical trials has led to fatal infection.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10560975/)
## References
1. [Martinon F, Burns K, Tschopp J (2002). The inflammasome: a molecular platform triggering activation of inflammatory caspases and processing of proIL-beta. Molecular Cell.](https://pubmed.ncbi.nlm.nih.gov/12191486/)
2. [Yao J, Sterling K, Wang Z, Zhang Y, Song W (2024). The role of inflammasomes in human diseases and their potential as therapeutic targets. Signal Transduction and Targeted Therapy.](https://www.nature.com/articles/s41392-023-01687-y)
3. [Inflammasomes as therapeutic targets in human diseases. Signal Transduction and Targeted Therapy (2021).](https://www.nature.com/articles/s41392-021-00650-z)
4. [Gasdermin D-mediated pyroptosis: mechanisms, diseases, and inhibitors. PMC (2023).](https://pmc.ncbi.nlm.nih.gov/articles/PMC10232970/)
5. [Mechanisms and Consequences of Noncanonical Inflammasome-Mediated Pyroptosis. PMC (2022).](https://pmc.ncbi.nlm.nih.gov/articles/PMC8844060/)
6. [Inflammasome: structure, biological functions, and therapeutic targets. PMC (2023).](https://pmc.ncbi.nlm.nih.gov/articles/PMC10560975/)
7. [Gasdermin D in pyroptosis. PMC (2021).](https://pmc.ncbi.nlm.nih.gov/articles/PMC8463274/)
8. [Inflammasomes: mechanism of assembly, regulation and signalling. Nature Reviews Immunology (2016).](https://www.nature.com/articles/nri.2016.58)
9. [The inflammasome and its regulation. PubMed (2014).](https://pubmed.ncbi.nlm.nih.gov/24579701/)
10. [Inflammasomes: mechanism of action, role in disease, and therapeutics. PubMed (2015).](https://pubmed.ncbi.nlm.nih.gov/26121197/)
11. [Inflammasome activation and regulation: toward a better understanding of complex mechanisms. Cell Discovery (2020).](https://www.nature.com/articles/s41421-020-0167-x)
12. [Pyroptosis and gasdermins in metabolic dysfunction-associated steatohepatitis. Frontiers in Cell and Developmental Biology (2023).](https://www.frontiersin.org/articles/10.3389/fcell.2023.1218807/pdf)
13. [Molecular mechanisms and regulation of inflammasome activation and signaling. Cellular & Molecular Immunology (2025).](https://www.nature.com/articles/s41423-025-01354-y.pdf)
14. [Mechanisms governing inflammasome activation, assembly and pyroptosis induction. PMC (2018).](https://pmc.ncbi.nlm.nih.gov/articles/PMC5890894/)
15. [The noncanonical inflammasome in health and disease. PMC (2023).](https://pmc.ncbi.nlm.nih.gov/articles/PMC10699704/)
16. [Updated insights into the molecular networks for NLRP3 inflammasome activation. Cellular & Molecular Immunology (2024).](https://www.nature.com/articles/s41423-025-01284-9.pdf)
17. [Targeting the NLRP3 inflammasome for inflammatory disease therapy. ScienceDirect (2025).](https://www.sciencedirect.com/science/article/pii/S0165614725000732)
18. [Inflammasomes: Mechanism of Action, Role in Disease, and Therapeutics. PMC (2015).](https://pmc.ncbi.nlm.nih.gov/articles/PMC4519035/)
19. [NLRP3 inflammasome: a key player in the pathogenesis of life-style disorders. Experimental & Molecular Medicine (2024).](https://www.nature.com/articles/s12276-024-01261-8)
20. [World Journal of Pharmaceutical Research (2025).](https://wjpr.s3.ap-south-1.amazonaws.com/article_issue/1f7ad3ac1edd65d785e3686414037374.pdf)
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*Topic: Encyclopedia › Life and health › Biological foundations › Biochemistry and metabolism › Enzyme classes and activities › Proteolytic and peptidase enzymes › Proteases by catalytic mechanism › Cysteine proteases › Caspases and apoptotic proteolysis › Inflammatory caspases*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license