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Abstract：
Genetic variants in SCN5A gene were identified in patients with various arrhythmogenic conditions including Brugada syndrome. Despite significant progress of last decades in studying the molecular mechanism of arrhythmia-associated SCN5A mutations, the understanding of relationship between genetics, electrophysiological consequences and clinical phenotype is lacking. We have found a novel genetic variant Y739D in the SCN5A-encoded sodium channel Nav1.5 of a male patient with Brugada syndrome (BrS). The objective of the study was to characterize the biophysical properties of Nav1.5-Y739D and provide possible explanation of the phenotype observed in the patient. The WT and Y739D channels were heterologously expressed in the HEK-293T cells and the whole-cell sodium currents were recorded. Substitution Y739D reduced the sodium current density by 47 ± 2% at -20 mV, positively shifted voltage-dependent activation, accelerated both fast and slow inactivation, and decelerated recovery from the slow inactivation. The Y739D loss-of-function phenotype likely causes the BrS manifestation. In the hNav1.5 homology models, which are based on the cryo-EM structure of rat Nav1.5 channel, Y739 in the extracellular loop IIS1-S2 forms H-bonds with K1381 and E1435 and pi-cation contacts with K1397 (all in loop IIIS5-P1). In contrast, Y739D accepts H-bonds from K1397 and Y1434. Substantially different contacts of Y739 and Y739D with loop IIIS5-P1 would differently transmit allosteric signals from VSD-II to the fast-inactivation gate at the N-end of helix IIIS5 and slow-inactivation gate at the C-end of helix IIIP1. This may underlie the atomic mechanism of the Y739D channel dysfunction.
摘要：
在包括Brugada综合征在内的各种心律失常患者中鉴定出SCN5A基因的遗传变异。尽管过去几十年在研究心律失常相关SCN5A突变的分子机制方面取得了重大进展，对遗传学之间关系的理解，电生理后果和临床表型缺乏。我们在Brugada综合征（BrS）男性患者的SCN5A编码的钠通道Nav1.5中发现了一种新的遗传变异体Y739D。该研究的目的是表征Nav1.5-Y739D的生物物理特性，并提供在患者中观察到的表型的可能解释。WT和Y739D通道在HEK-293T细胞中异源表达,并记录全细胞钠电流。替代Y739D在-20mV时将钠电流密度降低了47±2%，正移位的电压依赖性激活，加速了快速和缓慢的失活，并从缓慢失活中减速恢复。Y739D功能丧失表型可能导致BrS表现。在hNav1.5同源性模型中,基于大鼠Nav1.5通道的低温EM结构，细胞外环IIS1-S2中的Y739与K1381和E1435形成H-键,并且π-阳离子与K1397接触(全部在环IIIS5-P1中)。相比之下,Y739D接受K1397和Y1434的H债券。Y739和Y739D与环IIIS5-P1的实质上不同的接触将不同地将变构信号从VSD-II传输到螺旋IIIS5的N端的快速失活栅极和螺旋IIIP1的C端的慢速失活栅极。这可能是Y739D通道功能障碍的原子机制的基础。
