Gating Properties of Mutant Sodium Channels and Responses to Sodium Current Inhibitors Predict Mexiletine-Sensitive Mutations of Long QT Syndrome 3
Gating Properties of Mutant Sodium Channels and Responses to Sodium Current Inhibitors Predict Mexiletine-Sensitive Mutations of Long QT Syndrome 3
复制标题
突变钠通道的门控特性和对钠电流抑制剂的反应预测长 QT 综合征 3 的美西律敏感突变
DOI：
10.3389/fphar.2020.01182
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发表时间：
2020-08-04
影响因子：
5.6
通讯作者：
Wu, Lin
中科院分区：
文献类型：
--
作者：
Li, Gang;Woltz, Ryan L.;Wu, Lin
长QT综合征3 （LQT3）是由scn5突变引起的。晚期钠电流（lateI(Na)）抑制剂是治疗LQT3患者的电流特异性抑制剂，但美西汀（MEX）敏感（N1325S和R1623Q）和不敏感（M1652R）突变的机制仍有待阐明。方法对LQT3致病突变患者在静脉注射利多卡因后口服MEX治疗。使用全细胞膜片钳技术和分子重塑来确定对MEX敏感性的机制。结果N1325S和R1623Q钠通道突变LQT患者静脉给予利多卡因后口服MEX可缩短QTc间期，消除心律失常，心电图完全正常化。在HEK293细胞中，M1652R通道的稳态失活曲线相对于WT通道右移5.6 mV。与WT通道相比，R1623Q突变使稳态失活曲线左移15.2 mV， N1325S突变对稳态失活无影响（n = 5 ~ 13，P< 0.05）。与WT相比，这三个突变通道的窗口电流范围都扩大了。三个突变都增加了晚ei (Na)，其中M1652R通道的增幅最大（n = 9-15，P< 0.05）。MEX引起了稳态失活的超极化转移，并延迟了所有三个突变通道的恢复。与M1652R突变体通道相比，N1325S和R1623Q突变体通道对晚ei （Na）的抑制程度更大。突变通过变构机制改变Na(v)1.5的构象，改变Na(v)1.5对MEX的敏感性，使其更或更不有利于MEX的结合。LateI（Na）抑制剂在N1325S和R1623Q中抑制LateI（Na）的程度大于M1652R突变（n = 4 ~ 7，P< 0.05）。结论N1325S、R1623Q和M1652R突变与晚期ei （Na）的可变增加有关，而这种增加被MEX逆转。M1652R突变改变Na(v)1.5的构象，破坏影响MEX结合的通道失活，对应于对MEX的不良反应。在表达突变通道的细胞中，利多卡因试验、分子模型和药物筛选有助于预测晚期ei （Na）抑制剂的有效性。
Background Long QT syndrome 3 (LQT3) is caused bySCN5Amutations. Late sodium current (lateI(Na)) inhibitors are current-specific to treat patients with LQT3, but the mechanisms underlying mexiletine (MEX) -sensitive (N1325S and R1623Q) and -insensitive (M1652R) mutations remains to be elucidated. Methods LQT3 patients with causative mutations were treated with oral MEX following i.v. lidocaine. Whole-cell patch-clamp techniques and molecular remodeling were used to determine the mechanisms underlying the sensitivity to MEX. Results Intravenous administration of lidocaine followed by MEX orally in LQT patients with N1325S and R1623Q sodium channel mutation shortened QTc interval, abolished arrhythmias, and completely normalized the ECG. In HEK293 cells, the steady-state inactivation curves of the M1652R channels were rightward shifted by 5.6 mV relative to the WT channel. In contrast, the R1623Q mutation caused a leftward shift of the steady-state inactivation curve by 15.2 mV compared with WT channel, and N1325S mutation did not affect steady-state inactivation (n = 5-13,P< 0.05). The extent of the window current was expanded in all three mutant channels compared with WT. All three mutations increased lateI(Na)with the greatest amplitude in the M1652R channel (n = 9-15,P< 0.05). MEX caused a hyperpolarizing shift of the steady-state inactivation and delayed the recovery of all three mutant channels. Furthermore, it suppressed lateI(Na)in N1325S and R1623Q to a greater extent compared to that of M1652R mutant channel. Mutations altered the sensitivity of Na(v)1.5 to MEX through allosteric mechanisms by changing the conformation of Na(v)1.5 to become more or less favorable for MEX binding. LateI(Na)inhibitors suppressed lateI(Na)in N1325S and R1623Q to a greater extent than that in the M1652R mutation (n = 4-7,P< 0.05). Conclusion The N1325S, R1623Q, and M1652R mutations are associated with a variable augmentation of lateI(Na), which was reversed by MEX. M1652R mutation changes the conformation of Na(v)1.5 that disrupt the inactivation of channel affecting MEX binding, corresponding to the poor response to MEX. The lidocaine test, molecular modeling, and drugs screening in cells expressing mutant channels are useful for predicting the effectiveness of lateI(Na)inhibitors.