Tryptophan substitution of a putative D4S6 gating hinge alters slow inactivation in cardiac sodium channels.
Tryptophan substitution of a putative D4S6 gating hinge alters slow inactivation in cardiac sodium channels.
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DOI：
10.1529/biophysj.105.059352
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发表时间：
2005-06
影响因子：
3.4
通讯作者：
Sho‐Ya Wang;Corinna Russell;G. Wang
中科院分区：
文献类型：
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作者：
Sho‐Ya Wang;Corinna Russell;G. Wang
电压门控Na（+）通道在去极化期间显示快速激活门控（打开）以及快速和缓慢失活门控（关闭）。我们用A（丙氨酸）、D（天冬氨酸）、K（赖氨酸）、L（亮氨酸）、P（脯氨酸）和W（色氨酸）取代了残基S1759（丝氨酸），即人心脏hNav1.5 Na（+）通道的推定D4 S6门控铰链。在A-、D-、K-和W-取代的突变Na（+）通道中观察到激活和稳态快速失活的门控参数的显著变化。在L-取代的突变体中没有发生门控移位，而P-取代的突变体没有产生足够的Na（+）电流。野生型、A-、D-和L-取代的突变型Na（+）通道在-180至0 mV范围内的10 s条件脉冲下几乎没有或没有缓慢失活。出乎意料的是，W-和K-取代的突变Na（+）通道在-100 mV左右显示出显著的最大缓慢失活（分别约为85%和约70%）。然而，缓慢失活的幅度从-70 mV逐渐逆转至0 mV。这种回归在失活缺陷型hNav1.5-S1759 W/L409 C/A410 W Na（+）通道中最小化，表明细胞内快速失活门导致这种逆转。我们的数据表明hNav1.5-S1759残基在缓慢失活中起关键作用。S1759参与慢失活和快，慢失活之间的拮抗作用的可能机制进行了讨论。
Voltage-gated Na(+) channels display rapid activation gating (opening) as well as fast and slow inactivation gating (closing) during depolarization. We substituted residue S1759 (serine), a putative D4S6 gating hinge of human cardiac hNav1.5 Na(+) channels with A (alanine), D (aspartate), K (lysine), L (leucine), P (proline), and W (tryptophan). Significant shifts in gating parameters for activation and steady-state fast inactivation were observed in A-, D-, K-, and W-substituted mutant Na(+) channels. No gating shifts occurred in the L-substituted mutant, whereas the P-substituted mutant did not yield sufficient Na(+) currents. Wild-type, A-, D-, and L-substituted mutant Na(+) channels showed little or no slow inactivation with a 10-s conditioning pulse ranging from -180 to 0 mV. Unexpectedly, W- and K-substituted mutant Na(+) channels displayed profound maximal slow inactivation around -100 mV ( approximately 85% and approximately 70%, respectively). However, slow inactivation was progressively reversed in magnitude from -70 to 0 mV. This regression was minimized in inactivation-deficient hNav1.5-S1759W/L409C/A410W Na(+) channels, indicating that the intracellular fast-inactivation gate caused such a reversal. Our data suggest that the hNav1.5-S1759 residue plays a critical role in slow inactivation. Possible mechanisms for S1759 involvement in slow inactivation and for antagonism between fast and slow inactivation are discussed.