Potentiation of Fcepsilon receptor I-activated Ca(2+) current (I(CRAC)) by cholera toxin: possible mediation by ADP ribosylation factor.
Potentiation of Fcepsilon receptor I-activated Ca(2+) current (I(CRAC)) by cholera toxin: possible mediation by ADP ribosylation factor.
复制标题
霍乱毒素对Fcepsilon受体I激活的Ca(2)电流(I(CRAC))的增强：可能由ADP核糖基化因子介导。
DOI：
10.1083/jcb.148.1.137
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
Zhang,L
中科院分区：
文献类型：
--
作者：
McCloskey,MA;Zhang,L
抗原诱发的细胞外Ca2+内流进入肥大细胞可能通过储存操作的Ca2+通道发生，称为钙释放激活钙（CRAC）通道。在大鼠嗜碱性白血病细胞系（RBL-2H3）的肥大细胞中，霍乱毒素（CT）通过camp非依赖性手段增强了45ca2 +的抗原驱动摄取。在这里，我们在生理温度下使用穿孔膜片钳记录来测试霍乱毒素或其底物Gs是否直接调节CRAC通道的活性。霍乱毒素显著放大（2至4倍）Ca2+释放激活Ca2+电流（ICRAC）引起的抗原的次优浓度，没有自身诱导ICRAC，这种增强不模仿cAMP升高。相比之下，霍乱毒素不影响通过thapsigargin（一种细胞器Ca2+泵抑制剂）或通过低Ca2+移液管溶液的细胞内透析诱导icracp。因此，CRAC通道的活性不受霍乱毒素或Gsα的直接控制。也不是由于磷酸肌肽水解或钙释放的增强而增强icracd。由于Gs和霍乱毒素的A亚基结合ADP核糖基化因子（ARF）并能调节其活性，我们测试了抗原诱发的icracc对brefeldin A的敏感性，brefeldin A是ARF依赖性功能的抑制剂，包括囊泡运输。Brefeldin A阻断了抗原诱导的icrac增强，但不抑制Gsα的ADP核糖基化，但对次优抗原和thapsigargin诱导的icrac没有影响。这些数据提供了新的证据，表明CRAC通道是fceε受体i触发Ca2+内流的主要途径，并提示ARF可能调节ICRACby抗原的诱导。
Antigen-evoked influx of extracellular Ca2+into mast cells may occur via store-operated Ca2+channels called calcium release–activated calcium (CRAC) channels. In mast cells of the rat basophilic leukemia cell line (RBL-2H3), cholera toxin (CT) potentiates antigen-driven uptake of45Ca2+through cAMP-independent means. Here, we have used perforated patch clamp recording at physiological temperature to test whether cholera toxin or its substrate, Gs, directly modulates the activity of CRAC channels. Cholera toxin dramatically amplified (two- to fourfold) the Ca2+release–activated Ca2+current (ICRAC) elicited by suboptimal concentrations of antigen, without itself inducing ICRAC, and this enhancement was not mimicked by cAMP elevation. In contrast, cholera toxin did not affect the induction of ICRACby thapsigargin, an inhibitor of organelle Ca2+pumps, or by intracellular dialysis with low Ca2+pipette solutions. Thus, the activity of CRAC channels is not directly controlled by cholera toxin or Gsα. Nor was the potentiation of ICRACdue to enhancement of phosphoinositide hydrolysis or calcium release. Because Gs and the A subunit of cholera toxin bind to ADP ribosylation factor (ARF) and could modulate its activity, we tested the sensitivity of antigen-evoked ICRACto brefeldin A, an inhibitor of ARF-dependent functions, including vesicle transport. Brefeldin A blocked the enhancement of antigen-evoked ICRACwithout inhibiting ADP ribosylation of Gsα, but it did not affect ICRACinduced by suboptimal antigen or by thapsigargin. These data provide new evidence that CRAC channels are a major route for Fcε receptor I–triggered Ca2+influx, and they suggest that ARF may modulate the induction of ICRACby antigen.