Oxidized thioredoxin-1 restrains the NLRP1 inflammasome [mBMDM]

The danger signals that activate the NLRP1 inflammasome have yet to be firmly established. NLRP1 undergoes autoproteolysis to generate N-terminal (NT) and C-terminal (CT) fragment, which importantly, is a necessary step for its check-point regulation by the DPP9 ternary complex and the mechanistic activation of NLRP1 through functional degradation. Here, we report an added layer of regulatory complexity to NLRP1 activity, in the form of a repressive interaction that NLRP1 forms with the oxidized, but not reduced, form of thioredoxin-1 (TRX1). Loss of TRX1 destabilizes the NT fragment of NLRP1 and promotes enhanced inflammasome activation. The TRX1 interaction occurs through the NACHT-LRR of NLRP1 and requires nucleotide binding in its ATPase domain. In addition, we found that several patient-derived and ATPase-inactivating mutations in the NACHT-LRR region hyperactive the inflammasome by destabilize protein folding and are also shown to abrogate TRX1 binding. Thus, NLRP1 appears to detect intracellular reductive stress through a decrease in the fraction of intracellular oxidized TRX1, which enhances protein disorder, leading to inflammasome signaling. These findings link the cellular redox environment to NLRP1-mediated innate immunity. Overall design: Total RNA content from wild-type and Txn1 KO C57BL/6J mouse BMDMs is analyzed by RNASeq. Experiment was performed in triplicate, and the differential gene expression analysis was used to determine the impact of TRX1 protein loss on the expression of NLRP1 inflammasome genes.