The pyroptosome: a supramolecular assembly of ASC dimers mediating inflammatory cell death via caspase-1 activation
The pyroptosome: a supramolecular assembly of ASC dimers mediating inflammatory cell death via caspase-1 activation
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DOI：
10.1038/sj.cdd.4402194
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发表时间：
2007-09-01
影响因子：
12.4
通讯作者：
Alnemri, E. S.
中科院分区：
文献类型：
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作者：
Fernandes-Alnemri, T.;Wu, J.;Alnemri, E. S.
上睑下垂是一种依赖caspase-1的炎性细胞死亡形式。接头蛋白ASC直接与caspase-1结合，对caspase-1在多种刺激下的激活起关键作用。为了阐明ASC激活caspase-1的机制及其在巨噬细胞松弛中的确切作用，我们对稳定表达ASC-GFP融合蛋白的人THP-1巨噬细胞进行了时间推移共聚焦生物成像分析。我们发现，用几种促炎刺激刺激这些细胞，会触发ASC的一个大的超分子组装，在这里被称为焦胞体。在每个受刺激的细胞中只形成一个不同的焦胞体，它迅速招募并激活caspase-1，导致下垂和细胞内促炎细胞因子的释放。焦胞体主要由寡聚化的ASC二聚体组成。ASC的二聚化是由亚生理浓度的钾驱动的，因为在亚生理浓度的钾存在下，纯化的重组ASC在体外孵育会诱导一个功能性的热核小体的组装。此外，用耗钾剂刺激THP-1细胞的钾外排会诱导火胞体的形成，而增加培养液中的钾浓度或药物抑制这种外排会抑制其组装。我们的结果证实巨噬细胞的下垂是由一种独特的焦小体介导的，与炎性小体不同。
Pyroptosis is a caspase-1-dependent inflammatory form of cell death. The adapter protein ASC binds directly to caspase-1 and is critical for caspase-1 activation in response to a broad range of stimuli. To elucidate the mechanism of activation of caspase-1 by ASC and its exact role in macrophage pyroptosis, we performed time-lapse confocal bioimaging analysis on human THP-1 macrophages stably expressing an ASC-GFP fusion protein. We show that stimulation of these cells with several proinflammatory stimuli trigger the formation of a large supramolecular assembly of ASC, termed here pyroptosome. Only one distinct pyroptosome in each stimulated cell is formed, which rapidly recruits and activates caspase-1 resulting in pyroptosis and the release of the intracellular proinflammatory cytokines. The pyroptosome is largely composed of oligomerized ASC dimers. Dimerization of ASC is driven by subphysiological concentrations of potassium as in vitro incubation of purified recombinant ASC in the presence of subphysiological concentrations of potassium induces the assembly of a functional pyroptosome. Furthermore, stimulation of potassium efflux in THP-1 cells with potassium-depleting agents induces formation of the pyroptosome, while increasing potassium concentrations in the culture medium or pharmacological inhibition of this efflux inhibits its assembly. Our results establish that macrophage pyroptosis is mediated by a unique pyroptosome, distinct from the inflammasome.