Contribution of sialic acid to the voltage dependence of sodium channel gating - A possible electrostatic mechanism
Contribution of sialic acid to the voltage dependence of sodium channel gating - A possible electrostatic mechanism
复制标题
DOI：
10.1085/jgp.109.3.327
复制
发表时间：
1997-03-01
影响因子：
3.8
通讯作者：
Levinson, SR
中科院分区：
文献类型：
--
作者：
Bennett, E;Urcan, MS;Levinson, SR
利用稳定转染rSkM 1的中国仓鼠卵巢（CHO）细胞研究了唾液酸在大鼠骨骼肌钠通道（rSkM 1）电压依赖性门控中的潜在作用。在酶（神经氨酸酶）去除表达rSkM 1的细胞中的唾液酸后，通过在唾液酸化缺陷细胞系（lec 2）中表达rSkM 1，观察到通道门控的电压依赖性的变化。在每种减少唾液酸化的条件下，通道的稳态半激活电压（V-a）与对照通道相比去极化增加10 mV相似。通道激活和失活的时间常数的电压依赖性也在相同的方向和类似的幅度移动。此外，从rSkM 1序列中重组删除可能的糖基化位点导致突变通道，其门控电压比野生型通道高10 mV。因此，减少通道唾液酸化的三种独立方法对通道门控的电压依赖性显示出非常相似的效果。最后，减少唾液酸化条件下的通道的稳态激活电压对外部钙的影响比在控制条件下测量的那些敏感得多，这表明唾液酸直接有助于负表面电位。这些结果是一致的静电机制，外部，带负电荷的唾液酸残基rSkM 1改变通道门控元件感测的电场。
A potential role for sialic acid in the voltage-dependent gating of rat skeletal muscle sodium channels (rSkM1) was investigated using Chinese hamster ovary (CHO) cells stably transfected with rSkM1. Changes in the voltage dependence of channel gating were observed after enzymatic (neuraminidase) removal of sialic acid from cells expressing rSkM1 and through the expression of rSkM1 in a sialylation-deficient cell line (lec2). The steady-state half-activation voltages (V-a) of channels under each condition of reduced sialylation were similar to 10 mV more depolarized than control channels. The voltage dependence of the time constants of channel activation and inactivation were also shifted in the same direction and by a similar magnitude. In addition, recombinant deletion of likely glycosylation sites from the rSkM1 sequence resulted in mutant channels that gated at voltages up to 10 mV more positive than wild-type channels. Thus three independent means of reducing channel sialylation show very similar effects on the voltage dependence of channel gating. Finally, steady-state activation voltages for channels subjected to reduced sialylation conditions were much less sensitive to the effects of external calcium than those measured under control conditions, indicating that sialic acid directly contributes to the negative surface potential. These results are consistent with an electrostatic mechanism by which external, negatively charged sialic acid residues on rSkM1 alter the electric field sensed by channel gating elements.