TY - JOUR T1 - DPP9 directly sequesters the NLRP1 C-terminus to repress inflammasome activation JF - bioRxiv DO - 10.1101/2020.08.14.246132 SP - 2020.08.14.246132 AU - L. Robert Hollingsworth AU - Humayun Sharif AU - Andrew R. Griswold AU - Pietro Fontana AU - Julian Mintseris AU - Kevin B. Dagbay AU - Joao A. Paulo AU - Steven P. Gygi AU - Daniel A. Bachovchin AU - Hao Wu Y1 - 2020/01/01 UR - http://biorxiv.org/content/early/2020/08/17/2020.08.14.246132.abstract N2 - NLRP1 is a cytosolic inflammasome sensor that mediates activation of caspase-1, which in turn induces cytokine maturation and pyroptotic cell death1-6. Gain-of-function NLPR1 mutations cause skin inflammatory diseases including carcinoma, keratosis, and papillomatosis7-14. NLRP1 contains a unique function-to-find domain (FIIND) that autoproteolyzes into noncovalently associated subdomains15-18. Proteasomal degradation of the autoinhibitory N-terminal fragment (NT) activates NLRP1 by releasing the inflammatory C-terminal fragment (CT)19,20. Cytosolic dipeptidyl peptidases 8 and 9 (DPP8/9) interact with NLRP1, and small-molecule DPP8/9 inhibitors activate NLRP1 by poorly characterized mechanisms11,19,21. Here, we report cryo-EM structures of the human NLRP1-DPP9 complex, alone and in complex with the DPP8/9 inhibitor Val-boroPro (VbP). Surprisingly, the NLRP1-DPP9 complex is a ternary complex comprised of DPP9, one intact FIIND of a non-degraded full-length NLRP1 (NLRP1-FL) and one NLRP1-CT freed by NT degradation. The N-terminus of the NLRP1-CT unfolds and inserts into the DPP9 active site but is not cleaved by DPP9, and this binding is disrupted by VbP. Structure-based mutagenesis reveals that the binding of NLRP1-CT to DPP9 requires NLRP1-FL and vice versa, and inflammasome activation by ectopic NLRP1-CT expression is rescued by co-expressing autoproteolysis-deficient NLRP1-FL. Collectively, these data indicate that DPP9 functions as a “bomb-diffuser” to prevent NLRP1-CTs from inducing inflammation during homeostatic protein turnover.Competing Interest StatementH.W. is a co-founder of Ventus Therapeutics. The other authors declare no competing financial interests. ER -