Nek7 is an essential mediator of NLRP3 activation downstream of potassium efflux

Inflammasomes are intracellular protein complexes that drive the activation of inflammatory caspases. The NLRP3 inflammasome has been implicated in the pathogenesis of several acquired inflammatory diseases as well as Cryopyrin-associated periodic fever syndromes (CAPS) caused by inherited NLRP3 mutations. Despite extensive investigation, the molecular mechanism leading to NLRP3 activation remains unknown. We have identified Nek7 as an NLRP3-binding protein that acts downstream of potassium efflux to regulate NLRP3 oligomerization and activation. In the absence of Nek7, caspase-1 activation and IL-1β release were abrogated in response to signals that activate NLRP3, but not NLRC4 or AIM2 inflammasome. NLRP3 associated with the catalytic domain of Nek7, but the catalytic activity of Nek7 was dispensable for activation of the NLRP3 inflammasome. Activated macrophages formed a high-molecular-mass NLRP3-Nek7 complex, which along with ASC oligomerization and ASC speck formation were abrogated in the absence of Nek7. Nek7 was required for macrophages harboring the CAPS-associated NLRP3 R258W activating mutation to activate caspase-1. Mouse chimeras reconstituted with wild-type, Nek7 −/− or Nlrp3 −/− hematopoietic cells revealed that Nek7 was required for NLRP3 inflammasome activation in vivo. Our studies demonstrate that Nek7 is an essential protein that acts downstream of potassium efflux to mediate NLRP3 inflammasome assembly and activation.