Fast calcium-dependent inactivation of calcium release-activated calcium current (CRAC) in RBL-1 cells
Fast calcium-dependent inactivation of calcium release-activated calcium current (CRAC) in RBL-1 cells
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DOI：
10.1007/s002329900493
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发表时间：
1999-03-01
影响因子：
2.4
通讯作者：
Parekh, AB
中科院分区：
文献类型：
--
作者：
Fierro, L;Parekh, AB
使用大鼠嗜碱性白血病 (RBL-1) 细胞的全细胞膜片钳记录研究了 Ca2+ 释放激活的 Ca2+ 电流 (I-CRAC) 的快速失活。从 0 mV 的保持电势开始应用超极化电压阶跃表明，在比 -40 mV 更负的阶跃中，I-CRAC 的幅度在数十毫秒内下降。这种快速失活主要依赖于 Ca2+，因为首先，当记录移液器中包含 BAPTA 而不是 EGTA 时，可以更有效地抑制这种快速失活；其次，用 Sr2+ 代替外部 Ca2+ 会导致更少的失活。 BAPTA 存在下的失活恢复速度比 EGTA 更快。快速失活的程度与全细胞 I-CRAC 幅度无关，这与失活是由于 Ca2+ 离子仅渗透到其所渗透的通道上而引起的局部反馈抑制引起的概念相一致。 Ca2+从储存中的释放不影响快速失活，FC epsilon RI 受体刺激也不影响。目前的钳记录显示，在刺激 FC epsilon RI 受体后，大多数 RBL 细胞的膜电位接近 -90 mV。因此，快速失活可能会影响生理条件下 Ca2+ 通过 CRAC 通道流入的程度，并且似乎是限制 Ca2+ 增加的重要负反馈过程。
Fast inactivation of the Ca2+ release-activated Ca2+ current (I-CRAC) was studied using whole cell patch-clamp recordings in rat basophilic leukemia (RBL-1) cells. Application of hyperpolarizing voltage steps from the holding potential of 0 mV revealed that I-CRAC declined in amplitude over tens of milliseconds during steps more negative than -40 mV. This fast inactivation was predominantly Ca2+-dependent because first, it could be more effectively suppressed when BAPTA was included in the recording pipette instead of EGTA and second, replacing external Ca2+ with Sr2+ resulted in less inactivation. Recovery from inactivation was faster in the presence of BAPTA than EGTA. The extent of fast inactivation was independent of the whole cell I-CRAC amplitude, compatible with the notion that the inactivation arose from a local feedback inhibition by permeating Ca2+ ions only on the channel it permeated. Ca2+ release from stores did not affect fast inactivation, nor did FC epsilon RI receptor stimulation. Current clamp recordings showed that the majority of RBL cells had a membrane potential close to -90 mV following stimulation of FC epsilon RI receptors. Hence fast inactivation is likely to impact on the extent of Ca2+ influx through CRAC channels under physiological conditions and appears to be an important negative feedback process that limits Ca2+ increases.