Journal Article

NEK7 is an essential mediator of NLRP3 activation downstream of potassium efflux

Yang, Dahai, Motro, Benny, Núñez, Gabriel, Zeng, Melody Y., He, Yuan

2016

Overview

NEK7, a member of the NIMA-related kinase family, is identified as a regulator of NLRP3 inflammasome oligomerization and activation; NEK7 functions downstream of potassium efflux in a manner that is independent of its kinase activity. NEK7 mediates NLRP3 inflammasome activation The NLRP3 inflammasome, a critical component of the innate immune system, has been linked to multiple acquired and inherited diseases. However, the molecular mechanism that leads to NLRP3 oligomerization and activation remains elusive. Here Gabriel Núñez and colleagues identify a member of the family of NIM related kinases (NEK7) as a regulator of NLRP3 inflammasome oligomerization and activation. NEK7 functions downstream of potassium efflux in a manner that is independent of its kinase activity. Inflammasomes are intracellular protein complexes that drive the activation of inflammatory caspases 1 . So far, four inflammasomes involving NLRP1, NLRP3, NLRC4 and AIM2 have been described that recruit the common adaptor protein ASC to activate caspase-1, leading to the secretion of mature IL-1β and IL-18 proteins 2 , 3 . The NLRP3 inflammasome has been implicated in the pathogenesis of several acquired inflammatory diseases 4 , 5 as well as cryopyrin-associated periodic fever syndromes (CAPS) caused by inherited NLRP3 mutations 6 , 7 . Potassium efflux is a common step that is essential for NLRP3 inflammasome activation induced by many stimuli 8 , 9 . Despite extensive investigation, the molecular mechanism leading to NLRP3 activation in response to potassium efflux remains unknown. Here we report the identification of NEK7, a member of the family of mammalian NIMA-related kinases (NEK proteins) 10 , 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 inflammasomes. NLRP3-activating stimuli promoted the NLRP3–NEK7 interaction in a process that was dependent on potassium efflux. NLRP3 associated with the catalytic domain of NEK7, but the catalytic activity of NEK7 was shown to be 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, was abrogated in the absence of NEK7. NEK7 was required for macrophages containing the CAPS-associated NLRP3(R258W) activating mutation to activate caspase-1. Mouse chimaeras reconstituted with wild-type, Nek7 −/− or Nlrp3 −/− haematopoietic cells showed that NEK7 was required for NLRP3 inflammasome activation in vivo . These studies demonstrate that NEK7 is an essential protein that acts downstream of potassium efflux to mediate NLRP3 inflammasome assembly and activation.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/250 / 631/250/262/2106/2517 / Analysis / Animals / Apoptosis Regulatory Proteins - deficiency / Apoptosis Regulatory Proteins - genetics / Apoptosis Regulatory Proteins - metabolism / Biocatalysis / CARD Signaling Adaptor Proteins / Carrier Proteins - chemistry / Carrier Proteins - genetics / Carrier Proteins - metabolism / Caspase 1 - metabolism / Catalytic Domain / Cells, Cultured / Cryopyrin-Associated Periodic Syndromes - genetics / Enzyme Activation / Gene mutations / HEK293 Cells / Humanities and Social Sciences / Humans / Inflammasomes - chemistry / Inflammasomes - metabolism / Inflammation / Influence / Interleukin-1beta - secretion / Interleukins / letter / Macrophages - metabolism / Mice / Mice, Inbred C57BL / multidisciplinary / Mutation / NIMA-Related Kinases / NLR Family, Pyrin Domain-Containing 3 Protein / Potassium / Potassium - metabolism / Potassium acetate / Protein Binding / Protein Multimerization / Protein-Serine-Threonine Kinases - chemistry / Protein-Serine-Threonine Kinases - deficiency / Protein-Serine-Threonine Kinases - genetics / Protein-Serine-Threonine Kinases - metabolism / Proteins / Rodents / Salmonella / Science / Signal transduction