Impaired slow inactivation due to a polymorphism and substitutions of Ser-906 in the II-III loop of the human Nav1.4 channel
Impaired slow inactivation due to a polymorphism and substitutions of Ser-906 in the II-III loop of the human Nav1.4 channel
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DOI：
10.1007/s00424-003-1137-5
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发表时间：
2003-10-01
影响因子：
4.5
通讯作者：
Mitrovic, N
中科院分区：
文献类型：
--
作者：
Kuzmenkin, A;Jurkat-Rott, K;Mitrovic, N
连接钠通道α-亚基的结构域II和III的环对通道门控没有重大影响。最近，各种钠通道亚型的II-III环突变已被报道引起通道病，表明该区域的功能重要性。在骨骼肌亚型Na（v）1.4的II-III环中，我们发现在5%的钙代谢障碍性周期性麻痹患者和4%的健康人中，906位的丝氨酸-苏氨酸取代。为了研究这个位置对于通道门控是否重要，我们通过全细胞膜片钳实验表征了906处的以下氨基酸：Gln、Ser、Thr、Cys、Pro、瓦尔，根据其疏水性排序。所有取代主要影响慢失活。例如，Gln使稳态慢失活曲线右移+13 mV，进入慢失活的速度比Ser慢6倍，导致慢失活状态不稳定;相反，瓦尔，在疏水性谱的另一端，使稳态缓慢失活曲线移动-6 mV，并使从缓慢失活状态的恢复速度慢于Ser的三倍，导致缓慢失活的增强。从缓慢失活状态的恢复也被Pro、Cys和Thr减慢。我们的研究结果表明：（1）良性多态性影响通道功能，（2）II-III环对缓慢失活很重要，（3）对缓慢失活的影响可能取决于906位残基的疏水性。
The loop connecting domains II and III of the sodium channel alpha-subunit is not known to have a major effect on channel gating. Recently mutations in the II-III loop of various sodium channel isoforms have been reported to cause channelopathies suggesting the functional importance of this region. In the II-III loop of the skeletal muscle isoform Na(v)1.4, we found a Ser-to-Thr substitution at position 906 in 5% of patients with dyskalemic periodic paralysis but also in 4% of healthy human individuals. To investigate whether this position is important for channel gating, we characterized the following amino acids at 906 by whole-cell patch-clamp experiments: Gln, Ser, Thr, Cys, Pro, Val, ordered according to their hydrophobicity. All substitutions mainly affected slow inactivation. For example, Gln caused a +13-mV right-shift of the steady-state slow inactivation curve, and entry into slow inactivation was 6 times slower compared with Ser, leading to a destabilization of the slow inactivated state; in contrast, Val, at the other end of the hydrophobicity spectrum, shifted the steady-state slow inactivation curve by -6 mV and slowed the recovery from the slow inactivated state threefold compared with Ser, resulting in an enhancement of slow inactivation. Recovery from the slow inactivated state was also slowed by Pro, Cys and Thr. Our results suggest that (1) a benign polymorphism affects channel function, (2) the II-III loop is important for slow inactivation, and (3) the effects on slow inactivation may depend on the hydrophobicity of the residue at position 906.