AMBRA1 allosterically activates NLRP3 by releasing its autoinhibition.

Nod-like receptor family pyrin domain-containing 3 (NLRP3) is activated by many stimuli, and its dysfunction is involved in various inflammatory diseases. Activation of NLRP3 is thought to happen via a multistep process involving phase separation, conformational opening and oligomerization. However, how NLRP3 is released from its autorepressed conformation remains elusive. Here we report that activating molecule in Beclin1-regulated autophagy protein 1 (AMBRA1), previously known for its role in autophagy, bound NLRP3 to scaffold and allosterically activate NLRP3. AMBRA1 engaged the leucine-rich repeat and helical domain 2 subdomains of NLRP3 through its β-propeller domain and destabilized the closed, inactive conformation of NLRP3, facilitating adenosine triphosphate binding and transition of NLRP3 to the active state. AMBRA1 deficiency in monocytes or macrophages impaired NLRP3 activation and reduced inflammatory responses in mouse models of endotoxic shock, colitis and sepsis. Nanobodies blocking the interaction between AMBRA1 and NLRP3 inhibited NLRP3 activation, underscoring the therapeutic potential of targeting this interaction. Our study revealed the role of AMBRA1 in NLRP3 inflammasome assembly and activation, offering potential pharmacological targets for related diseases.