Inhibitory effects of chloride on the activation of caspase-1, IL-1β secretion, and cytolysis by the P2X7 receptor
Inhibitory effects of chloride on the activation of caspase-1, IL-1β secretion, and cytolysis by the P2X7 receptor
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DOI：
10.4049/jimmunol.175.11.7623
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发表时间：
2005-12-01
影响因子：
4.4
通讯作者：
Dubyak, GR
中科院分区：
文献类型：
--
作者：
Verhoef, PA;Kertesy, SB;Dubyak, GR
P2 X7受体（P2 X7 R）是一种ATP门控阳离子通道，可激活caspase-1，导致IL-1 β成熟和分泌。由于先前的研究表明细胞外Cl-对P2 X7 R通道的ATP门控产生负变构效应，我们测试了Cl-是否减弱鼠和人巨噬细胞中的P2 X7 R->半胱天冬酶-1-> IL-1 β信号级联。在Bac 1小鼠巨噬细胞中，用葡萄糖酸盐取代细胞外Cl-使ATP诱导的IL-1 β加工和分泌的速率和程度增加10倍，同时使ATP的EC 50降低5倍。用葡萄糖酸盐替代Cl-也增加了ATP作为原代小鼠骨髓源性巨噬细胞和THP-1人单核细胞/巨噬细胞中成熟IL-1 β分泌诱导剂的效力。我们的观察结果与Cl-在三个水平上的作用一致：1）Cl-的负变构效应，它限制了ATP门控P2 X7 R介导的阳离子通量的能力，而阳离子通量触发caspase-1的激活; 2）Cl-通过P2 X7 R诱导的非选择性孔在细胞内积聚，从而抑制caspase-1介导的IL-1 β的加工;和3）Cl-取代对未加工的pro-IL-1 β的溶细胞释放的促进作用，其发生在P2 X7 R的持续激活中。这种细胞溶解被细胞保护剂甘氨酸抑制，允许P2 X7 R调节的成熟IL-1 β分泌从IL-1 β原的溶解释放中解离。这些结果表明，在生理条件下，P2 X7 R保持在构象约束状态，限制通道门控和耦合的受体的信号转导途径，调节半胱天冬酶-1。
The P2X7 receptor (P2X7R) is an ATP-gated cation channel that activates caspase-1 leading to the maturation and secretion of IL-1 beta. Because previous studies indicated that extracellular Cl- exerts a negative allosteric effect on ATP-gating of P2X7R channels, we tested whether Cl- attenuates the P2X7R -> caspase-1 -> IL-1 beta signaling cascade in murine and human macrophages. In Bac1 murine macrophages, substitution of extracellular Cl- with gluconate produced a 10-fold increase in the rate and extent of ATP-induced IL-1 beta processing and secretion, while reducing the EC50 for ATP by 5-fold. Replacement of Cl- with gluconate also increased the potency of ATP as an inducer of mature IL-1 beta secretion in primary mouse bone marrow-derived macrophages and in THP-1 human monocytes/macrophages. Our observations were consistent with actions of Cl- at three levels: 1) a negative allosteric effect of Cl-, which limits the ability of ATP to gate the P2X7R-mediated cation fluxes that trigger caspase-1 activation; 2) an intracellular accumulation of Cl- via nonselective pores induced by P2X7R with consequential repression of caspase-1-mediated processing of IL-1 beta; and 3) a facilitative effect of Cl- substitution on the cytolytic release of unprocessed pro-IL-1 beta that occurs with,sustained activation of P2X7R. This cytolysis was repressed by the cytoprotectant glycine, permitting dissociation of P2X7R-regulated secretion of mature IL-1 beta from the lytic release of pro-IL-1 beta. These results suggest that under physiological conditions P2X7R are maintained in a conformationally restrained state that limits channel gating and coupling of the receptor to signaling pathways that regulate caspase-1.