349870 Increase in Cytosolic Ca^(2+) Contributes to NLRP3 Inflammasome Activation in Response to Bacterial Pore Toxins and Lysosomal Destabilization

Monday, November 4, 2013
Grand Ballroom B (Hilton)
Louis Graham Rucker, Vanderbilt University, Nashville, TN

Abstract: Inflammasomes are multi-protein signaling complexes consisting of a member of the NOD-like receptor (NLR) and are defined by the NLR protein that they contain. The NLR protein recruits the inflammasome-adaptor protein ASC, which in turn interacts with caspase-1 leading to its activation. The cytokine precursor pro-interleukin 1β (pro-IL-1β) is proteolytically cleaved by the activated caspase-1. This cleavage allows for the release of the biologically active form IL-1β, an important mediator of pro-inflammatory and antimicrobial responses. IL-1β signaling has a protective role in atherosclerosis by promoting vessel remodeling and enhancing features of plaque stability. The cytokine is also responsible for the induction of fever by directly stimulating the hypothalamus leading to an increase in body temperature. The NLRP3 inflammasome, an essential component of the innate immune system, is activated by an unknown mechanism; however its dependence on the efflux of cytosolic  into the extracellular space has been demonstrated. We hypothesize that cytosolic [Ca2+] modulates NLRP3 inflammasome activation. We show that stimulation of cells with NLRP3 activators nigericin, a specific ionophore; ATP, a influx agent; and the soluble peptide LLME cause plasma membrane disruption resulting in an increase in cytosolic [Ca2+]. Furthermore, incubation of cells with the chelator bapta prior to stimulation by NLRP3 activators, results in inflammasome activation, but a reduction in cytosolic [Ca2+] influx. The ability of 1 mM thapsigargin to induce noncononical endoplasmic reticulum stress was suppressed by the absence of extracellular. Together our findings further emphasize the importance of cations to inflammasome activation

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