A TAK1-Driven NLRP1 Inflammasome Pathway Revealed by Phosphatase-Targeting Environmental Toxins

Abstract Human NLRP1 is highly sensitive to phosphorylation-dependent activation, indicating a need for tight phosphatase control to prevent excessive inflammasome activity. In this study, we identified the phosphatases PP1 and PP2A as negative regulators of the NLRP1 inflammasome in human keratinocytes. Accordingly, exposure to the environmental toxins Dinophysistoxin, Okadaic acid, and Cantharidin, which inhibit PP1 and PP2A, triggered NLRP1 inflammasome activation. Notably, this toxin-induced activation process relied on hyperactivation of the MAP3 kinase TAK1. Mechanistically, both TAK1 and its downstream effectors p38 kinases phosphorylated and activated the NLRP1 inflammasome. Further studies underscored that TAK1 also contributed to the NLRP1 inflammasome activation during double-stranded RNA stimulation and viral infection. Finally, human native skins exposed to environmental toxins underlined the role of the PP1/PP2A-regulated TAK1/p38 axis in the development of skin dermatitis. Thus, these findings reveal a novel pathway of phosphorylation-driven NLRP1 activation and expand our understanding of its regulation in epithelial immunity. One Sentence Summary PP1/PP2A phosphatases restrict TAK1-driven NLRP1 inflammasome response. Graphical abstract Schematic representation of the phosphorylation-driven hNLRP1 inflammasome response upon exposure to environmental toxins and to dsRNA/viral infection.