Potentiation of Caspase-1 Activation by the P2X7 Receptor Is Dependent on TLR Signals and Requires NF-κB-Driven Protein Synthesis

• Published in: Journal of Immunology Vol. 175; no. 11; pp. 7611 - 7622
• Main Authors: Kahlenberg, J. Michelle, Lundberg, Kathleen C., Kertesy, Sylvia B., Qu, Yan, Dubyak, George R.
• Format: Journal Article
• Language: English
• Published: 01.12.2005
• ISSN: 0022-1767; 1550-6606; 1365-2567
• DOI: 10.4049/jimmunol.175.11.7611

Abstract The proinflammatory cytokines IL-1β 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-κB, as pretreatment of cells with the proteasome inhibitor MG132, or the IκB 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.