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 (I _Na) 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.

 抽象的

背景：SCN5A 突变导致 Na 电流减少，是 Brugada 综合征 (BrS) 等心律失常综合征的基础。人类的SCN5A有两种剪接变体，一种在 1077 位 (Q1077del) 缺乏谷氨酰胺，另一种含有 Q1077。我们研究了剪接变异背景对 R1512W 功能丧失和挽救的影响，据报道，R1512W 是一种导致 BrS 的突变。方法和结果：我们对两种变体进行了突变，并在 HEK-293 细胞中表达它们以进行电压钳研究。转染 24 小时后，与野生型 (WT) 通道相比，Q1077del 和 Q1077 中 R1512W 的当前表达水平分别降低了约 50%。在两种剪接变体背景下，WT 通道和突变体通道的激活和失活中点没有差异。然而，与 WT-Q1077 相比，R1512W/Q1077 观察到较慢的恢复时间常数和增强的中间灭活，而 R1512W/Q1077del 的恢复和中间灭活参数与 WT-Q1077del 相似。此外，美西律和常见的多态性 H558R 都通过增加 SCN5A 的细胞表面表达来恢复突变通道的峰值钠电流 ( I _Na ) 幅度。结论：这些发现提供了进一步的证据，证明剪接变异影响分子表型，对临床表型有影响，并且它们提供了对 BrS 表达缺陷机制和潜在治疗的见解。