PMID: 26449474
Authors:
Zhang L, Chen S, Ruan J, Wu J, Tong AB, Yin Q, Li Y, David L, Lu A, Wang WL, Marks C, Ouyang Q, Zhang X, Mao Y, Wu H
Title:
Cryo-EM structure of the activated NAIP2-NLRC4 inflammasome reveals nucleated polymerization.
Journal:
Science. 2015 Oct 8. pii: aac5789.
Abstract:
The NLR family apoptosis inhibitory proteins (NAIPs) bind conserved bacterial ligands, like the bacterial rod protein PrgJ, and recruit the NLR family CARD-containing protein 4 (NLRC4) as the inflammasome adapter to activate innate immunity. Here we show that the PrgJ-NAIP2-NLRC4 inflammasome is assembled into multisubunit disk-like structures through a unidirectional ATPase polymerization, primed with a single PrgJ-activated NAIP2 per disk. Cryo-electron microscopy (cryo-EM) reconstruction at a subnanometer resolution revealed a ~90 degrees hinge rotation accompanying NLRC4 activation. Unlike in the related, heptameric Apaf-1 apoptosome in which each subunit needs to be conformationally activated by its ligand before assembly, a single PrgJ-activated NAIP2 initiates NLRC4 polymerization in a domino-like reaction to promote the disk assembly. These insights reveal the mechanism of signal amplification in NAIP/NLRC4 inflammasomes.