Interaction between NLRP11, CASP4, and LPS in the context of the innate immune response to bacterial pathogens 3660

Description Macrophages initiate innate immune responses using pattern recognition receptors to detect pathogen-associated molecules, such as lipopolysaccharide (LPS). When cytosolic LPS (cLPS) is recognized, it activates caspase (CASP)-4/5 in humans, triggering inflammasome formation, pyroptotic cell death, and cytokine release. We identified NLRP11 as a primate-specific pattern recognition receptor for cLPS that functions in the CASP4 pathway. It is required for human macrophage cLPS-induced cell death after gram-negative pathogen infection or LPS electroporation and the activation of CASP4 and gasdermin D. This study investigates the interaction between NLRP11, CASP4 and LPS to elucidate cLPS signaling, CASP4 inflammasome assembly and their innate immunity role. NLRP11 was found to interact with LPS and CASP4 at a stoichiometry of 7:1 (CASP4:NLRP11), independently of the ASC adaptor, which is critical for the NLRP3-CASP1 inflammasome. The CASP4 p19 domain, particularly residue D174, was required for CASP4-NLRP11 binding. Moreover, NLRP11 enhanced LPS binding to CASP4, suggesting its role in licensing LPS recognition. Mutational analysis of CASP4 CARD domain residues K19, KVR53-55 and QEK62-64 disrupted CASP4-LPS binding, regardless of NLRP11 presence, and did not affect NLRP11-CASP4 interaction, showing that NLRP11 binds LPS independently of CASP4. NLRP11 reshapes our understanding of innate immunity by enhancing LPS-CASP4 binding and acting as a key receptor in the CASP4 inflammasome. Funding Sources Supported by NIH R01 AI081724 (MBG); NIH R01 AI173030 (MBG); the Fund for Medical Discovery (FMD) Research Fellowship Awards (ECOR, Massachusetts General Hospital) (MLGM). Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)