Modulation of cloned skeletal muscle sodium channels by the scorpion toxins Lqh II, Lqh III, and LqhαIT
Modulation of cloned skeletal muscle sodium channels by the scorpion toxins Lqh II, Lqh III, and LqhαIT
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DOI：
10.1007/s004240050959
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发表时间：
2000-02-01
影响因子：
4.5
通讯作者：
Heinemann, SH
中科院分区：
文献类型：
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作者：
Chen, HJ;Gordon, D;Heinemann, SH
来自Leiurus quinquestriatus hebraeus的蝎α-毒素Lqh II、Lqh III和Lqh α IT是典型的α-毒素的代表，其特异于哺乳动物（Lqh II）或昆虫（Lqh α IT），以及作用于哺乳动物和昆虫的α-样毒素（Lqh III）。为了比较研究这些毒素对哺乳动物钠通道的影响，我们在HEK 293细胞中稳定表达大鼠骨骼肌钠通道α亚基（μ I），并在全细胞膜片钳模式下测量Na+电流。α-和α-样毒素强烈减缓通道失活，在1.4 nM（Lqh II）、5.4 nM（Lqh III）和0.5 nM（Lqh α IT）下具有半数最大效应。所有毒素均加速了快速灭活的恢复，效力顺序为：Lqh II > Lqh α IT > Lqh III。失活和失活恢复的电压依赖性降低，而激活的阈值仅略微偏移一致至10 mV，而不改变斜率因子，表明受损失活与激活解偶联。毒素诱导的峰值内向电流的增加，这是占了增加的最大开放通道的概率。虽然所有三种毒素诱导类似的修改的通道特性，其动力学的协会和解离是非常不同的。在-140 mV和-80 mV之间，毒素结合不是电压依赖性的。在100 nM毒素中，缔合时间常数为：1.3 s（Lqh II）、20 s（Lqh III）和3.8 s（Lqh alpha IT）。在正电压下，毒素从通道解离;在+100 mV下，解离时间常数分别为30、321和135 ms。与缔合相反，解离是电压依赖性的，对于所有三种毒素，具有约12 mV/e倍变化的相似斜率。这些毒素的缔合和解离动力学的强烈差异可以将它们鉴定为不同蝎α毒素亚组的成员。
The scorpion alpha-toxins Lqh II, Lqh III, and Lqh alpha IT from Leiurus quinquestriatus hebraeus are representatives of typical alpha-toxins, specific for either mammals (Lqh II) or insects (Lqh alpha IT), and alpha-like toxins (Lqh III) which act on both mammals and insects. For a comparative study of the effects of these toxins on mammalian sodium channels we stably expressed rat skeletal muscle sodium channel alpha subunits (mu I) in HEK 293 cells and measured Na+ currents in the whole-cell patch-clamp mode. The alpha- and alpha-like toxins strongly slowed down channel inactivation with a half-maximal effect at 1.4 nM (Lqh II), 5.4 nM (Lqh III), and 0.5 nM (Lqh alpha IT). The recovery from fast inactivation was accelerated by all toxins with the potency sequence: Lqh II > Lqh alpha IT > Lqh III. The voltage dependence of inactivation and recovery from inactivation were reduced while the threshold for activation was only slightly shifted by congruent to 10 mV without altering the slope factors, suggesting uncoupling of the impaired inactivation from the activation. The toxins induced an increase in peak inward current, which was accounted for by an increased maximal open-channel probability. Although all three toxins induced similar modifications of the channel properties, their kinetics of association and dissociation were very different. Between -140 and -80 mV toxin association was not voltage dependent. In 100 nM toxin the association time constants were: 1.3 s (Lqh II), 20 s (Lqh III), and 3.8 s (Lqh alpha IT). At positive voltages the toxin dissociated from the channel; at +100 mV the dissociation time constants were 30, 321, and 135 ms, respectively. In contrast to the association, dissociation was voltage dependent with a similar slope of about 12 mV per e-fold change for all three toxins. The strong differences in the association and dissociation kinetics of these toxins may identify them as members of different scorpion alpha-toxin subgroups.