Structural basis for the oligomerization-facilitated NLRP3 activation

Area of Science:

• Molecular Biology
• Structural Biology
• Immunology

Background:

• The NACHT-, leucine-rich-repeat-, and pyrin domain-containing protein 3 (NLRP3) is a key sensor in innate immunity.
• NLRP3 inflammasomes are implicated in various inflammation-driven human diseases.
• The precise mechanism of NLRP3 activation, particularly its intermediate states, remains poorly understood.

Purpose of the Study:

• To elucidate the structural basis of NLRP3 activation.
• To investigate the role of oligomerization in NLRP3 function.
• To understand the interaction between NLRP3 and its regulator NEK7.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to determine the structure of NLRP3.
• Site-directed mutagenesis was employed to probe the function of specific interfaces.
• Biochemical assays were performed to study NEK7/NLRP3 interactions.

Main Results:

• The cryo-EM structure revealed NLRP3 forming an open octamer with a ~90° hinge rotation at the NACHT domain.
• Mutations at the open octamer interfaces impaired IL-1β signaling, confirming their role in activation.
• The centrosomal kinase NEK7 was shown to disrupt large NLRP3 oligomers, forming monomers/dimers as a prerequisite for inflammasome assembly.

Conclusions:

• NLRP3 activation involves a cooperative, oligomeric mechanism.
• The open octameric state is a critical intermediate in NLRP3 inflammasome assembly.
• NEK7 plays a crucial role in initiating the NLRP3 activation cascade by destabilizing higher-order oligomers.