HCN4中与窦性心动过缓相关的A414G功能缺失突变的功能特征

IF 0.5 Q4 CARDIAC & CARDIOVASCULAR SYSTEMS Cardiogenetics Pub Date : 2023-08-04 DOI:10.3390/cardiogenetics13030012
A. Verkerk, R. Wilders
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引用次数: 0

摘要

在编码HCN4蛋白的HCN4基因中携带杂合A414G突变的患者表现出中度至重度心动过缓。HCN4亚基的四聚体组成窦房结中的离子通道,携带超极化激活的“有趣”电流(If),也称为“起搏器电流”。If在窦房结起搏器的活动中起着重要的调节作用。为了评估A414G突变导致窦性心动过缓的机制,我们首先对中国仓鼠卵巢(CHO)细胞中表达的野生型(WT)和杂合突变HCN4通道进行了电压钳测量。这些实验是在生理温度下使用两性霉素穿孔膜片钳技术进行的。接下来,我们将实验观察到的CHO细胞HCN4电流的突变诱导变化应用于Fabbri及其同事开发的单个人类窦房结细胞模型的If。杂合突变体HCN4电流的半最大激活电压V1/2比野生型HCN4的电流负19.9mV(p<0.001)。此外,杂合突变体HCC4电流(去)激活时间常数的电压依赖性显示出与野生型HCN3电流相比的−11.9mV偏移(p<001)。完全激活的电流密度、激活曲线的斜率因子和逆转电位不受杂合A414G突变的显著影响。在人类窦房结计算机模型中,周期长度显著增加,几乎完全是由于稳态激活的电压依赖性的变化,而这种增加在迷走神经张力下更为显著。将被动心房负荷引入模型窦房结细胞进一步降低了跳动速率,表明窦房结和心房之间的相互作用使窦房结的心动过缓更加明显。总之,实验确定的A414G诱导的If变化可以解释携带A414G HCN4基因突变的患者临床观察到的窦性心动过缓。
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Functional Characterization of the A414G Loss-of-Function Mutation in HCN4 Associated with Sinus Bradycardia
Patients carrying the heterozygous A414G mutation in the HCN4 gene, which encodes the HCN4 protein, demonstrate moderate to severe bradycardia of the heart. Tetramers of HCN4 subunits compose the ion channels in the sinus node that carry the hyperpolarization-activated ‘funny’ current (If), also named the ‘pacemaker current’. If plays an essential modulating role in sinus node pacemaker activity. To assess the mechanism by which the A414G mutation results in sinus bradycardia, we first performed voltage clamp measurements on wild-type (WT) and heterozygous mutant HCN4 channels expressed in Chinese hamster ovary (CHO) cells. These experiments were performed at physiological temperature using the amphotericin-perforated patch-clamp technique. Next, we applied the experimentally observed mutation-induced changes in the HCN4 current of the CHO cells to If of the single human sinus node cell model developed by Fabbri and coworkers. The half-maximal activation voltage V1/2 of the heterozygous mutant HCN4 current was 19.9 mV more negative than that of the WT HCN4 current (p < 0.001). In addition, the voltage dependence of the heterozygous mutant HCN4 current (de)activation time constant showed a −11.9 mV shift (p < 0.001) compared to the WT HCN4 current. The fully-activated current density, the slope factor of the activation curve, and the reversal potential were not significantly affected by the heterozygous A414G mutation. In the human sinus node computer model, the cycle length was substantially increased, almost entirely due to the shift in the voltage dependence of steady-state activation, and this increase was more prominent under vagal tone. The introduction of a passive atrial load into the model sinus node cell further reduced the beating rate, demonstrating that the bradycardia of the sinus node was even more pronounced by interactions between the sinus node and atria. In conclusion, the experimentally identified A414G-induced changes in If can explain the clinically observed sinus bradycardia in patients carrying the A414G HCN4 gene mutation.
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来源期刊
Cardiogenetics
Cardiogenetics CARDIAC & CARDIOVASCULAR SYSTEMS-
自引率
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发文量
26
审稿时长
11 weeks
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