Potentiation of caspase-1 activation by the P2X7 receptor is dependent on TLR signals and requires NF-kappaB-driven protein synthesis.
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.
Kahlenberg
J Michelle
JM
Department of Pathology, Case School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Lundberg
Kathleen C
KC
Kertesy
Sylvia B
SB
Qu
Yan
Y
Dubyak
George R
GR
D000818:Animals; D015153:Blotting, Western; D020170:Caspase 1 / Q000378:metabolism*; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D051550:I-kappa B Kinase / Q000276:immunology / Q000378:metabolism; D007375:Interleukin-1 / Q000276:immunology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology; D048670:MAP Kinase Kinase 4 / Q000276:immunology / Q000378:metabolism; D008262:Macrophage Activation / Q000276:immunology; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000276:immunology / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D015398:Signal Transduction / Q000276:immunology; D051193:Toll-Like Receptors / Q000276:immunology / Q000378:metabolism*
D007375:Interleukin-1; D008070:Lipopolysaccharides; D016328:NF-kappa B; C546469:P2rx7 protein, mouse; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D051193:Toll-Like Receptors; D051550:I-kappa B Kinase; D048670:MAP Kinase Kinase 4; D020170:Caspase 1