Potentiation of caspase-1 activation by the P2X7 receptor is dependent on TLR signals and requires NF-kappaB-driven protein synthesis

• Published in: The Journal of immunology (1950) 2005-12, Vol.175 (11), p.7611-7622
• Main Authors: Kahlenberg, J Michelle, Lundberg, Kathleen C, Kertesy, Sylvia B, Qu, Yan, Dubyak, George R
• Format: Article
• Language: English
• Subjects: Animals; Blotting, Western; Caspase 1 - metabolism; Cells, Cultured; Electrophoresis, Polyacrylamide Gel; Enzyme Activation - immunology; Enzyme-Linked Immunosorbent Assay; I-kappa B Kinase - immunology; I-kappa B Kinase - metabolism; Interleukin-1 - immunology; Interleukin-1 - metabolism; Lipopolysaccharides - immunology; Macrophage Activation - immunology; Macrophages - immunology; Macrophages - metabolism; MAP Kinase Kinase 4 - immunology; MAP Kinase Kinase 4 - metabolism; Mice; NF-kappa B - immunology; NF-kappa B - metabolism; Receptors, Purinergic P2 - immunology; Receptors, Purinergic P2 - metabolism; Receptors, Purinergic P2X7; Signal Transduction - immunology; Toll-Like Receptors - immunology; Toll-Like Receptors - metabolism
• ISSN: 0022-1767

The proinflammatory cytokines IL-1beta and IL-18 are inactive until cleaved by the enzyme caspase-1. Stimulation of the P2X7 receptor (P2X7R), an ATP-gated ion channel, triggers rapid activation of caspase-1. In this study we demonstrate that pretreatment of primary and Bac1 murine macrophages with TLR agonists is required for caspase-1 activation by P2X7R but it is not required for activation of the receptor itself. Caspase-1 activation by nigericin, a K+/H+ ionophore, similarly requires LPS priming. This priming by LPS is dependent on protein synthesis, given that cyclohexamide blocks the ability of LPS to prime macrophages for activation of caspase-1 by the P2X7R. This protein synthesis is likely mediated by NF-kappaB, as pretreatment of cells with the proteasome inhibitor MG132, or the IkappaB kinase inhibitor Bay 11-7085 before LPS stimulation blocks the ability of LPS to potentiate the activation of caspase-1 by the P2X7R. Thus, caspase-1 regulation in macrophages requires inflammatory stimuli that signal through the TLRs to up-regulate gene products required for activation of the caspase-1 processing machinery in response to K+-releasing stimuli such as ATP.