A Review on Structural Insights into NLRP3 and NEK7: Domain Architecture, Subcellular Localization, and Their Interaction in Inflammasome Assembly and Signaling.

The NLRP3 inflammasome plays an important role in the innate immune system that mediates caspase-1 activation and the subsequent secretion of the pro inflammatory cytokines IL-1β and IL-18 in response to microbial infections and cellular stress. Aberrant activation of the NLRP3 inflammasome has been implicated in a range of inflammatory and metabolic disorders, including cryopyrin-associated periodic syndromes (CAPS), Alzheimer's disease, type 2 diabetes, and atherosclerosis. NLRP3 activation can be triggered by diverse stimuli and involves multiple cellular events, such as ionic flux, mitochondrial dysfunction, reactive oxygen species (ROS) generation, and lysosomal damage. A critical regulator of NLRP3 activation is NEK7, a serine/threonine kinase also known for its role in mitotic spindle formation and cytokinesis. Structurally, NEK7 exhibits a partially assembled regulatory spine (R-spine), consistent with an inactive kinase state. However, a mutant form of NEK7 engineered to stabilize the R-spine retains catalytic activity and has been crystallized in complex with compound 51- an ATP-competitive, small-molecule chemical inhibitor that targets both NEK2 and NEK7. Interestingly, wild-type NEK7 crystallized in both apo form and with compound 51 showed variable R-spine conformations, while NEK7 displayed a uniform, partially stacked R-spine configuration. Despite the structural similarity in compound 51 binding between NEK2 and NEK7, subtle differences in ligand orientation reveal potential avenues for designing isoform-selective inhibitors. In this review, we comprehensively examine the structural domains and subcellular localizations of NLRP3 and NEK7, and highlight how their interaction promotes inflammasome assembly. I also discuss recent insights from cryo-electron microscopy (cryo-EM), X-ray crystallography, and molecular modeling studies that illuminate the conformational dynamics of the NLRP3-NEK7 complex. Additionally, we explore the crosstalk between the STING pathway and inflammasome signaling, and address key unanswered questions that may guide future research into therapeutic modulation of these essential protein-protein interactions.