Characterisation of the effects of robustoxin, the lethal neurotoxin from the Sydney funnel-web spider Atrax robustus, on sodium channel activation and inactivation
Characterisation of the effects of robustoxin, the lethal neurotoxin from the Sydney funnel-web spider Atrax robustus, on sodium channel activation and inactivation
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DOI：
10.1007/s004240050612
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发表时间：
1998-04
期刊：
影响因子：
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通讯作者：
G. Nicholson;Robyn Walsh;M. Little;M. Tyler
中科院分区：
文献类型：
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作者：
G. Nicholson;Robyn Walsh;M. Little;M. Tyler
本研究采用全细胞膜片钳技术研究了从雄性悉尼漏斗网蜘蛛（Atrax robustus）毒液中分离纯化的robustoxin（Robustoxin-Ar 1）对大鼠背根神经节细胞河豚毒素抗性（TTX-R）和河豚毒素敏感性（TTX-S）钠通道门控的作用。与漏斗网蜘蛛毒素versutoxin（δ-Hv 1）相似，robustoxin对TTX-R钠电流无影响，但对TTX-S钠电流有明显影响。粗壮毒素的主要作用是浓度依赖性地减缓或消除TTX-S钠电流失活。在所有测试电位下，这种稳态电流在长期去极化期间都得到维持。Robustoxin（30 nM）还导致稳态钠通道失活（h∞）的电压中点发生13 mV超极化偏移，导致在-80 mV保持电位下的峰电流降低。此外，在通常抑制所有TTX-S钠通道（去极化程度高于-40 mV）的前脉冲电位下，存在稳态或非失活组分（最大钠电流的18%）。此外，当通道在激活后恢复到静息状态时，robustoxin使钠通道的再引发动力学显著增加。钠电流恢复率的增加似乎可以解释高刺激频率下对峰值钠电流振幅的使用依赖性影响。最后，30 nM的robustoxin引起的通道的电压依赖性的11 mV的超极化位移，但没有显着修改尾电流动力学。这些行动表明，robustoxin抑制TTX-S钠通道的开放状态到失活状态的转换，从而允许钠电流的一部分保持在膜电位，在该失活通常是完全的。鉴于最近将漏斗网蜘蛛毒素重新分类为α-毒素，因此robustoxin应该被称为δ-α-毒素-Ar 1，以反映这种对钠通道失活的主要作用。这些结果进一步支持了漏斗网蜘蛛毒素与神经毒素受体位点3相互作用以类似于α-蝎毒素和海葵毒素的方式减缓通道失活的假设。
The present study investigates the actions of robustoxin (atracotoxin-Ar1) purified from the venom of the male Sydney funnel-web spiderAtrax robustuson sodium channel gating.Using whole-cell patch-clamp techniques the study assessed the actions of robustoxin on tetrodotoxin-resistant (TTX-R) and tetrodotoxin-sensitive (TTX-S) sodium currents in rat dorsal root ganglion cells. Similar to the closely related funnel-web spider toxin versutoxin (δ-atracotoxin-Hv1) fromHadronyche versuta, robustoxin had no effect on TTX-R sodium currents but exerted potent effects on TTX-S sodium currents. The main action of robustoxin was a concentration-dependent slowing or removal of TTX-S sodium current inactivation. This steady-state current was maintained during long-lasting depolarisations at all test potentials. Robustoxin (30 nM) also caused a 13-mV hyperpolarising shift in the voltage midpoint of steady-state sodium channel inactivation (h∞) leading to a reduced peak current at a holding potential of –80 mV. Moreover there was a steady-state or non-inactivating component present (18% of maximal sodium current) at prepulse potentials that normally inactivate all TTX-S sodium channels (more depolarised than –40 mV). In addition robustoxin produced a significant increase in the repriming kinetics of the sodium channel when channels returned to the resting state following activation. This increase in the rate of recovery of sodium current appears to explain the use-dependent effects on peak sodium current amplitude at high stimulation frequencies. Finally 30 nM robustoxin caused an 11-mV hyperpolarising shift in the voltage dependence of the channel but did not markedly modify tail current kinetics. These actions suggest that robustoxin inhibits conversion of the open state to the inactivated state of TTX-S sodium channels, thus allowing a fraction of the sodium current to remain at membrane potentials at which inactivation is normally complete. Given the recent reclassification of funnel-web spider toxins as atracotoxins, robustoxin should henceforth be known as δ-atracotoxin-Ar1 to reflect this main action on sodium channel inactivation. These present results further support the hypothesis that funnel-web spider toxins interact with neurotoxin receptor site 3 to slow channel inactivation in a manner similar to that of α-scorpion and sea anemone toxins.