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. 2009 Aug;157(8):1318–1329. doi: 10.1111/j.1476-5381.2009.00331.x

Figure 1.

Figure 1

IL-1 family members as released mediators. IL-1α and β, the two best characterized IL-1 family agonists, are translated in the cytoplasm as 31 kD pro-forms. Pro-IL-1α and β are then proteolytically cleaved by calpain and caspase-1, respectively, to produce the mature proteins. Caspase-1 is activated by recruitment to multimeric inflammasomes, enhancing caspase-1 autoproteolysis. Pro-IL-1α, mature IL-1α and mature IL-1β can all be released from cells and bind to transmembrane IL-1RI (RI) on IL-1-responsive cells. This leads to the recruitment of IL-1RAcP (AcP) to IL-1RI. A multi-protein complex is recruited to the cytoplasmic domain of the receptor dimer, leading to the activation of NFκB and mitogen-activated protein kinases, and to changes in gene expression and RNA stability. IL-1RA, the best developed anti-IL-1 therapeutic agent, acts as a competitive antagonist, binding IL-1RI but failing to recruit IL-1RAcP and activate signal transduction. IL-1, interleukin-1; IL-1RA, IL-1 receptor antagonist; IL-1RI, type I IL-1 receptor; IL-1RAcP, IL-1 receptor accessory protein; NFκB, nuclear factor κB.