A dual mechanism for I(Ks) current reduction by the pathogenic mutation KCNQ1-S277L.
A dual mechanism for I(Ks) current reduction by the pathogenic mutation KCNQ1-S277L.
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DOI：
10.1111/j.1540-8159.2011.03190.x
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发表时间：
2011-12
期刊：
影响因子：
--
通讯作者：
McDonald TV
中科院分区：
文献类型：
--
作者：
Chen J;Weber M;Um SY;Walsh CA;Tang Y;McDonald TV
遗传性长QT综合征的特征是心室复极延长，可能由KCNQ 1基因突变引起，该基因编码携带IKs电流的心脏钾通道复合体的α亚基（β亚基由KCNE 1编码）。在这项研究中，我们的特点是一个有害的变体，KCNQ 1-S277 L，发现在一个病人谁提出了心脏性猝死的可卡因使用的存在。通过全细胞膜片钳、共聚焦成像、表面生物素化测定和计算机建模分析KCNQ 1-S277 L突变。同源突变体KCNQ 1-S277 L通道不能携带电流，无论是单独或与KCNE 1。当与WT KCNQ 1以50/50的比例共表达时，电流密度以显性负性方式降低，剩余电流主要为野生型。KCNQ 1电流和IKs电流的激活率没有变化，电压依赖性激活的变化很小。免疫荧光共聚焦成像显示突变体KCNQ 1-S277 L的表面表达减少，这通过表面生物素化得到生物化学证实，显示突变体表面表达减少44%。与KCNQ 1-WT共表达相比，KCNQ 1-S277 L与人ether-a-go-go相关基因（HERG）的表达对HERG蛋白或电流密度没有显著影响。KCNQ 1-S277 L突变导致生物物理缺陷，导致KCNQ 1和IKs电流密度的显性负性降低，以及导致表面表达降低的运输缺陷，两者均不影响HERG/IKr。先证者的KCNQ 1-S277 L突变导致通道缺陷，损害复极储备，从而增强药物阻断IKr电流的药物敏感性。
The hereditary long QT syndrome is characterized by prolonged ventricular repolarization that can be caused by mutations to the KCNQ1 gene, which encodes the α subunits of the cardiac potassium channel complex that carries the IKs current (the β subunits are encoded by KCNE1). In this study, we characterized a deleterious variant, KCNQ1-S277L, found in a patient who presented with sudden cardiac death in the presence of cocaine use. The KCNQ1-S277L mutation was analyzed via whole-cell patch clamp, confocal imaging, surface biotinylation assays, and computer modeling. Homomeric mutant KCNQ1-S277L channels were unable to carry current, either alone or with KCNE1. When co-expressed in a 50/50 ratio with WT KCNQ1, current density was reduced in a dominant-negative manner, with the residual current predominantly wild type. There was no change in the activation rate and minimal changes to voltage-dependent activation for both KCNQ1 current and IKs current. Immunofluorescence confocal imaging revealed reduced surface expression of mutant KCNQ1-S277L, which was biochemically confirmed by surface biotinylation showing a 44% decrease in mutant surface expression. Expression of KCNQ1-S277L with human ether-a-go-go-related gene (HERG) did not significantly affect HERG protein or current density compared to KCNQ1-WT co-expression. The KCNQ1-S277L mutation causes biophysical defects that result in dominant-negative reduction in KCNQ1 and IKs current density, and a trafficking defect that results in reduced surface expression, both without affecting HERG/IKr. KCNQ1-S277L mutation in the proband resulted in defective channels that compromised repolarization reserve, thereby enhancing the arrhythmic susceptibility to pharmacological blockage of IKr current.
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