Novel molecular mechanism involving α1D (Cav1.3) L-type calcium channel in autoimmune-associated sinus bradycardia
Novel molecular mechanism involving α1D (Cav1.3) L-type calcium channel in autoimmune-associated sinus bradycardia
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DOI：
10.1161/circulationaha.104.517326
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发表时间：
2005-06-14
期刊：
影响因子：
37.8
通讯作者：
Boutjdir, M
中科院分区：
文献类型：
--
作者：
Qu, YX;Baroudi, G;Boutjdir, M
背景-先天性心脏传导阻滞（CHB）是一种自身免疫性疾病，影响抗Ro/La抗体（IgG阳性）母亲所生的胎儿/婴儿。虽然CHB的标志是完全性房室传导阻滞，但最近在CHB动物模型中报告了窦性心动过缓。有趣的是，敲除小鼠神经内分泌α（1D）Ca通道导致显著的窦性心动过缓和房室传导阻滞，这是一种与CHB相似的表型。在这里，我们测试的假设，α（1D）钙通道是一个新的目标为阳性IgG.Methods和结果-逆转录-聚合酶链反应，共聚焦间接免疫染色，和Western印迹数据建立了表达的α（1D）钙通道在人胎心。在异源表达系统（tsA 201细胞和非洲爪蟾卵母细胞）中表征了阳性IgG对α 1D Ca电流（ICa-L）的影响，因为α（1D）特异性调节剂不可用。α（1D）ICa-L在负电位（-60和-50 mV之间）下激活。阳性IgG在两种表达系统中均抑制α（1D）ICa-L。这种抑制被钙通道激活剂Bay K8644所拯救。阴性IgG和变性阳性IgG对α（1D）ICa-L无影响。Western blot结果表明，阳性IgG可直接与α（1D）Ca通道蛋白结合。结论：首次证实了人胎心α（1D）Ca通道的表达，阳性IgG对α（1D）ICa-L的抑制作用，以及阳性IgG与α（1D）Ca通道蛋白的直接交叉反应。考虑到α（1D）ICa-L在起搏器舒张期去极化内的电压下激活，α（1D）ICa-L的抑制可能部分解释了自身免疫相关的窦性心动过缓。此外，Bay K8644对α 1D ICa-L抑制的拯救为CHB管理中药物治疗方法的开发开辟了新的方向。
Background - Congenital heart block ( CHB) is an autoimmune disease that affects fetuses/infants born to mothers with anti-Ro/La antibodies (positive IgG). Although the hallmark of CHB is complete atrioventricular block, sinus bradycardia has been reported recently in animal models of CHB. Interestingly, knockout of the neuroendocrine alpha(1D) Ca channel in mice results in significant sinus bradycardia and atrioventricular block, a phenotype reminiscent to that seen in CHB. Here, we tested the hypothesis that the alpha(1D) Ca channel is a novel target for positive IgG.Methods and Results - Reverse transcription - polymerase chain reaction, confocal indirect immunostaining, and Western blot data established the expression of the alpha(1D) Ca channel in the human fetal heart. The effect of positive IgG on alpha 1D Ca current ( ICa-L) was characterized in heterologous expression systems ( tsA201 cells and Xenopus oocytes) because of the unavailability of alpha(1D)-specific modulators. alpha(1D) ICa-L activated at negative potentials ( between -60 and -50 mV). Positive IgG inhibited alpha(1D) ICa-L in both expression systems. This inhibition was rescued by a Ca channel activator, Bay K8644. No effect on alpha(1D) ICa-L was observed with negative IgG and denatured positive IgG. Western blot data showed that positive IgG binds directly to alpha(1D) Ca channel protein.Conclusions - The data are the first to demonstrate (1) expression of the alpha(1D) Ca channel in human fetal heart, ( 2) inhibition of alpha(1D) ICa-L by positive IgG, and (3) direct cross-reactivity of positive IgG with the alpha(1D) Ca channel protein. Given that alpha(1D) ICa-L activates at voltages within the pacemaker's diastolic depolarization, inhibition of alpha(1D) ICa-L in part may account for autoimmune-associated sinus bradycardia. In addition, Bay K8644 rescue of alpha 1D ICa-L inhibition opens new directions in the development of pharmacotherapeutic approaches in the management of CHB.