NLRP3 and beyond: inflammasomes as central cellular hub and emerging therapeutic target in inflammation and disease

Abstract

The NLRP3 inflammasome is a key cytosolic sensor in the innate immune system, activated by diverse danger signals such as metabolic stress, infections, and structural cellular disruptions. Its activation leads to the maturation of IL-1β and IL-18 and induces pyroptosis through gasdermin D cleavage. Multiple regulatory mechanisms modulate NLRP3 activation, including BRCC3-mediated deubiquitination, lysine carbamylation, intracellular trafficking to the microtubule-organizing center, and endolysosomal localization via PI4P. Dysregulation of these checkpoints contributes to inflammatory, neurodegenerative, hepatic, metabolic, and infectious diseases. Beyond pathogen defense, inflammasomes influence tissue regeneration, cell death pathways, and sterile inflammation, highlighting their role as integrative immune hubs. Alternative inflammatory pathways involving gasdermin E and caspase-8/3 enable persistent cytokine release in the absence of gasdermin D, revealing redundant effector arms within the inflammasome network. Structural triggers such as potassium efflux and intracellular transport disruptions lower the threshold for inflammasome assembly, while hypoxic conditions link its activation to immunometabolic imbalance. Aggresome-like mechanisms further reflect a convergence between proteostasis and inflammation. While NLRP3 remains the most extensively characterized, other inflammasomes-including NLRP1 in epithelial ribotoxic stress, CARD8 in HIV-1 protease sensing, and AIM2/IFI16 in viral and DNA sensing-highlight the diversity of inflammasome signaling in tissue- and pathogen-specific contexts. Small molecules such as MCC950, thiolutin, HDAC6 inhibitors, and CuET have demonstrated efficacy in preclinical models by selectively modulating inflammasome components or their regulatory pathways. Novel strategies such as carbamylation-mediated suppression and disruption of endocytic dynamics offer additional therapeutic entry points. A deeper understanding of inflammasome biology is essential for advancing precision immunotherapy in inflammatory and infectious diseases.

Keywords: NLRP3; caspase 1; inflammasome; interleukin-1 beta (IL-1β); pattern recognition receptors (PRRs); programmed cell death; pyroptosis.

Figure 1

Molecular Regulation of NLRP3. The activation of NLRP3 is tightly controlled by multiple intracellular mechanisms. (A) Post-translational modifications: In the resting state, NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3) is polyubiquitinated, preventing its activation. The deubiquitinase BRCC3, part of the BRISC (BRCC36 isopeptidase complex), removes ubiquitin chains and enables NLRP3 to oligomerize with ASC (apoptosis-associated speck-like protein containing a CARD) and pro-caspase-1. Thiolutin (THL) inhibits BRCC3, blocking NLRP3 activation. (B) Deubiquitination regulates cell death pathways: USP9X and USP13 stabilize the anti-apoptotic protein MCL-1, while USP15 promotes apoptosis via procaspase-3 (CASP3); CYLD promotes necroptosis through activation of RIPK3 and MLKL; GPX4 and SLC7A11 prevent ferroptosis by maintaining glutathione (GSH)-dependent redox balance; BRCC3 and ABRO1 promote NLRP3-dependent pyroptosis, while USP5, CYLD, and TNFAIP3 inhibit it. (C) Intracellular trafficking: NLRP3 is trafficked from the trans-Golgi network (TGN) to the microtubule-organizing center (MTOC) along microtubules via dynein and HDAC6 (histone deacetylase 6), which recognizes ubiquitinated cargo and facilitates inflammasome assembly. (D) Aggresome dynamics: Misfolded proteins such as CFTR (cystic fibrosis transmembrane conductance regulator) and PS1 (presenilin-1), resistant to proteasomal degradation, accumulate and are transported to the MTOC, forming perinuclear aggresomes surrounded by vimentin filaments. These structures are cleared by selective autophagy (aggrephagy) to preserve proteostasis.

Figure 2

Emerging Mechanisms of Inflammasome Activation. (A) Endocytic trafficking dysfunction: Under disrupted endocytic trafficking, NLRP3 is recruited to endolysosomes marked by LAMP1 (lysosomal-associated membrane protein 1), where it colocalizes with PI4P (phosphatidylinositol-4-phosphate), remaining in a primed but inactive state. (B) Potassium efflux Potassium (K⁺) efflux triggered by stimuli such as ATP, uric acid crystals, or bacterial toxins induces NLRP3 activation by lowering intracellular K⁺, promoting ATP binding to the NACHT domain and oligomerization of NLRP3 with ASC and pro-caspase-1. This leads to IL-1β and IL-18 release and gasdermin D (GSDMD)-mediated pyroptosis. (C) Ribotoxic stress in NLRP1 activation: In epithelial tissues, UVB radiation and ribotoxins induce ribosome collisions sensed by the kinase ZAKα (sterile alpha motif and leucine zipper-containing kinase alpha), which triggers NLRP1 inflammasome assembly, activation of caspase-1, and pyroptosis. (D) Immunometabolism and Hypoxia: In metabolic stress conditions (e.g., glucose deprivation or hypoxia), inhibition of HMG-CoA reductase reduces GGPP (geranylgeranyl pyrophosphate) synthesis, causing Rac1 retention in the cytosol and binding to IQGAP1, which activates NLRP3 and drives IL-1β release and pyroptosis.