Functional and Evolutionary Analyses Identify Proteolysis as a General Mechanism for NLRP1 Inflammasome Activation
(A) The amino acid sequence of the first 244 residues of NLRP1AB6 was aligned to NLRP1B129 and NLRP1BB6. The arrow above the alignment indicates the LF-cleavage site in NLRP1B129. (B) 293T cells were transfected for 36h with 200ng empty vector (V) or plasmids pcDNA3.1-HA-NLRP1B129 or -NLRP1AB6-MYC (CMV promoter) along with 200ng mCASP1 and 200ng mIL-1β expression vectors. Cells were treated overnight with anthrax lethal toxin (LeTx, 1μg/ml) 24h post-transfection, and then lysates were analyzed by immunoblotting (IB) with the indicated antibodies. (C) 293T cells were transfected for 36h with plasmids encoding 400ng GFP-HA-NLRP1B129 or GFP-HA-NLRP1AB6 (under the control of the LTR promoter in pMSCV) or with mutants engineered to contain an N-terminal TEV protease site. Cells were also co-transfected with 100ng empty vector (V) or plasmids encoding TEV-protease (pTEV) or lethal factor protease (pLF), plus 300ng empty pMSCV. (D) To assess IL-1β cleavage, cells were transfected as in C, but with 8ng of GFP-HA-NLRP1B and co-transfected with vectors encoding 200ng mCASP1 and 200ng mIL-1β. For panels B-D, data shown are representative of at least three similar experiments.