Identification and Validation of PKR as a Direct Target for the Novel Sulfonamide-Substituted Tetrahydroquinoline Nonselective Inhibitor of the NLRP3 Inflammasome

The NLRP3 inflammasome is a critical component of the
innate immune
system. The persistent abnormal activation of the NLRP3 inflammasome
is implicated in numerous human diseases. Herein, sulfonamide-substituted
tetrahydroquinoline derivative S-9 was identified as
the most promising NLRP3 inhibitor, without obvious cytotoxicity. In vitro, S-9 inhibited the priming and activation
stages of the NLRP3 inflammasome. Incidentally, we also observed that S-9 had inhibitory effects on the NLRC4 and AIM2 inflammasomes.
To elucidate the multiple anti-inflammatory activities of S-9, photoaffinity probe P-2, which contained a photoaffinity
label and a functional handle, was developed for target identification
by chemical proteomics. We identified PKR as a novel target of S-9 in addition to NLRP3 by target fishing. Furthermore, S-9 exhibited a significant anti-neuroinflammatory effect in vivo. In summary, our findings show that S-9 is a promising lead compound targeting both PKR and NLRP3 that could
emerge as a molecular tool for treating inflammasome-related diseases.