Funnel-web spider venom and a toxin fraction block calcium current expressed from rat brain mRNA in Xenopus oocytes.
Funnel-web spider venom and a toxin fraction block calcium current expressed from rat brain mRNA in Xenopus oocytes.
复制标题
漏斗网蜘蛛毒液和毒素成分可阻断爪蟾卵母细胞中大鼠脑 mRNA 表达的钙电流。
DOI：
10.1073/pnas.87.12.4538
复制
发表时间：
1990
影响因子：
11.1
通讯作者：
Llinás,R
中科院分区：
文献类型：
--
作者：
Lin,JW;Rudy,B;Llinás,R
将大鼠脑 mRNA 注射到非洲爪蟾卵母细胞中已被证明可诱导对二氢吡啶和 omega-芋螺毒素不敏感的钙电流 (ICa)。我们研究了漏斗网蜘蛛毒液对该表达的 ICa 的两个方面的影响：(i) 钙激活的氯电流 [ICl(Ca)] 和 (ii) 钡离子通过钙通道 (IBa) 携带的电流。在存在 1.8 mM 细胞外钙的情况下，ICl(Ca) 尾电流从 -80 mV 的保持电位变为可在 -30 至 -40 mV 之间检测到，并在 0 至 +10 mV 之间达到最大幅度。总蜘蛛毒液部分（83％）并可逆地阻断钙激活的氯化物电流，而不改变其电压敏感性。毒液中的色谱毒素成分也阻断了该电流（64%）。毒液对 INa 和 IK 的影响很小。在高钡溶液中对钙通道介导的内向电流进行了直接研究。 IBa 具有较高的激活阈值（-30 至 -20 mV），并在约 +20 mV 时达到其最大幅度。总毒液或部分纯化的色谱毒性部分可部分且可逆地阻断IBa，而不改变其电流-电压特性。此外，总毒液阻断的程度取决于细胞外钡的浓度。在 60 mM Ba2+ 中，仅 35% 的 IBa 被阻断，而在 40 mM Ba2+ 中，阻断率分别增加至 65% 和 71%。基于这些结果，我们提出爪蟾卵母细胞中大鼠脑 mRNA 表达的钙通道与最近发现的 P 型通道相似。
Injection of rat brain mRNA into Xenopus oocytes has been shown to induce a calcium current (ICa) that is insensitive to dihydropyridine and omega-conotoxin. We examined the effect of funnel-web spider venom on two aspects of this expressed ICa: (i) the calcium-activated chloride current [ICl(Ca)] and (ii) the currents carried by barium ions through calcium channels (IBa). In the presence of 1.8 mM extracellular calcium, ICl(Ca) tail current became detectable between -30 and -40 mV from a holding potential of -80 mV and reached a maximal amplitude between 0 and +10 mV. Total spider venom partially (83%) and reversibly blocked the calcium-activated chloride current without changing its voltage sensitivity. A chromatographic toxin fraction from the venom also blocked this current (64%). The venom had a minimal effect on INa and IK. Direct investigation of inward current mediated by calcium channels was carried out in high-barium solution. IBa had a higher threshold of activation (-30 to -20 mV) and reached its maximal amplitude at about +20 mV. Total venom or a partly purified chromatographic toxic fraction blocked IBa partially and reversibly without changing its current-voltage characteristics. Furthermore, the extent of the total venom block depended on the concentration of extracellular barium. Only 35% of the IBa was blocked in 60 mM Ba2+, whereas the block increased to 65% and 71%, respectively, for 40 and 20 mM Ba2+. On the basis of these results, we propose that the calcium channels expressed from rat brain mRNA in Xenopus oocytes is similar to the recently discovered P-type channels.