A Single Amino Acid Residue Defines the Difference in NLRP3 Inflammasome Activation between NEK7 and NEK6

The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a critical component of the innate immune system that is activated by microbial infections and cellular stress signals. The molecular mechanism of NLRP3 inflammasome activation remains not fully understood. As an NLRP3-interacting partner, NEK7 has emerged as a critical mediator for NLRP3 inflammasome activation. In contrast to NEK7, NEK6, the closely related member of the NEK family, does not support NLRP3 inflammasome activation. In this study, we show that the mouse NEK7 catalytic domain, which shares high sequence identity with the counterpart of NEK6, mediates its interaction with NLRP3 and inflammasome activation in mouse macrophages. Within their catalytic domains, a single amino acid residue at a corresponding position (R121^NEK7, Q132^NEK6) differentiates their function in NLRP3 inflammasome activation. Surprisingly, substitution of the glutamine residue to an arginine residue at position 132 confers NEK6 the ability of NLRP3 binding and inflammasome activation in mouse macrophages. Furthermore, our results suggest a structural pocket surrounding the residue R121 of NEK7 that is essential for NLRP3 binding and inflammasome activation.