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Abstract：
Background : Mutations in SCN5A that decrease Na current underlie arrhythmia syndromes such as the Brugada syndrome (BrS). SCN5A in humans has two splice variants, one lacking a glutamine at position 1077 (Q1077del) and one containing Q1077. We investigated the effect of splice variant background on loss-of-function and rescue for R1512W, a mutation reported to cause BrS. Methods and results : We made the mutation in both variants and expressed them in HEK-293 cells for voltage-clamp study. After 24 hours of transfection, the current expression level of R1512W was reduced by ~50% in both Q1077del and Q1077 compared to the wild-type (WT) channel, respectively. The activation and inactivation midpoint were not different between WT and mutant channels in both splice variant backgrounds. However, slower time constants of recovery and enhanced intermediate inactivation were observed for R1512W/Q1077 compared with WT-Q1077, while the recovery and intermediate inactivation parameters of R1512W/Q1077del were similar to WT-Q1077del. Furthermore, both mexiletine and the common polymorphism H558R restored peak sodium current (INa) amplitude of the mutant channel by increasing the cell surface expression of SCN5A. Conclusion : These findings provide further evidence that the splice variant affects the molecular phenotype with implications for the clinical phenotype, and they provide insight into the expression defect mechanisms and potential treatment in BrS.
摘要：
背景：SCN5A中降低Na电流的突变是心律失常综合征的基础，例如Brugada综合征（BrS）。人类的SCN5A有两个剪接变体，一个在1077位缺乏谷氨酰胺(Q1077del),一个含有Q1077。我们研究了剪接变体背景对R1512W功能丧失和挽救的影响，据报道导致BrS的突变。方法和结果：我们在两种变体中进行了突变，并在HEK-293细胞中表达，用于电压钳研究。转染24小时后，与野生型（WT）通道相比，Q1077del和Q1077中R1512W的当前表达水平降低了约50％，分别。在两种剪接变体背景下，WT和突变体通道之间的激活和失活中点没有差异。然而,与WT-Q1077相比，R1512W/Q1077的恢复时间常数较慢，中间失活增强，而R1512W/Q1077del的恢复和中间失活参数与WT-Q1077del相似。此外，美西律和常见多态性H558R均通过增加SCN5A的细胞表面表达来恢复突变通道的钠电流（INa）峰值。结论：这些发现提供了进一步的证据，即剪接变体影响分子表型，并暗示临床表型。它们提供了对BrS表达缺陷机制和潜在治疗的见解。
