Congenital heart block maternal sera autoantibodies target an extracellular epitope on the α1G T-type calcium channel in human fetal hearts.
Congenital heart block maternal sera autoantibodies target an extracellular epitope on the α1G T-type calcium channel in human fetal hearts.
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DOI：
10.1371/journal.pone.0072668
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Hamilton RM
中科院分区：
文献类型：
--
作者：
Strandberg LS;Cui X;Rath A;Liu J;Silverman ED;Liu X;Siragam V;Ackerley C;Su BB;Yan JY;Capecchi M;Biavati L;Accorroni A;Yuen W;Quattrone F;Lung K;Jaeggi ET;Backx PH;Deber CM;Hamilton RM
先天性心脏传导阻滞（CHB）是一种与抗Ro/SSA和抗La/SSB母体自身抗体相关的经胎盘获得性自身免疫性疾病，其主要特征是胎儿心脏的房室（AV）传导阻滞。本研究旨在探讨T型钙通道亚单位α 1G是否可能是CHB母血清自身抗体的胎儿靶点。我们证明了人胎儿心脏房室结与心尖（妊娠18 - 22.6周）T型钙通道CACNA1G（α 1G基因）的差异mRNA表达。使用人胎儿心脏（妊娠20 - 22周），我们的免疫沉淀（IP）、蛋白质印迹分析和免疫荧光（IF）染色结果结合在一起，证明了心肌细胞表面α 1G表位的可及性以及CHB影响妊娠的母体血清对α 1G蛋白的反应性。通过ELISA，我们证明CHB母体血清对α 1G的反应性显著高于对照组，反应性表位定位于命名为p305的肽（对应于α 1G重复序列I中连接跨膜片段S5-S6的细胞外环的aa305 - 319）。CHB感染孕妇的母体血清对α 1H通道的同源区（7/15个氨基酸保守）的反应也较弱。单细胞膜片钳电生理实验也证实了CHB母亲血清对小鼠窦房结（SAN）细胞T型电流的影响。总之，这些结果表明CHB母体血清抗体容易靶向人胎儿心肌细胞中α 1G T型钙通道的细胞外表位。CHB母体血清也显示对α 1H的反应性，表明自身抗体可以靶向多个胎儿靶点。
Congenital heart block (CHB) is a transplacentally acquired autoimmune disease associated with anti-Ro/SSA and anti-La/SSB maternal autoantibodies and is characterized primarily by atrioventricular (AV) block of the fetal heart. This study aims to investigate whether the T-type calcium channel subunit α1G may be a fetal target of maternal sera autoantibodies in CHB. We demonstrate differential mRNA expression of the T-type calcium channel CACNA1G (α1G gene) in the AV junction of human fetal hearts compared to the apex (18–22.6 weeks gestation). Using human fetal hearts (20–22 wks gestation), our immunoprecipitation (IP), Western blot analysis and immunofluorescence (IF) staining results, taken together, demonstrate accessibility of the α1G epitope on the surfaces of cardiomyocytes as well as reactivity of maternal serum from CHB affected pregnancies to the α1G protein. By ELISA we demonstrated maternal sera reactivity to α1G was significantly higher in CHB maternal sera compared to controls, and reactivity was epitope mapped to a peptide designated as p305 (corresponding to aa305–319 of the extracellular loop linking transmembrane segments S5–S6 in α1G repeat I). Maternal sera from CHB affected pregnancies also reacted more weakly to the homologous region (7/15 amino acids conserved) of the α1H channel. Electrophysiology experiments with single-cell patch-clamp also demonstrated effects of CHB maternal sera on T-type current in mouse sinoatrial node (SAN) cells. Taken together, these results indicate that CHB maternal sera antibodies readily target an extracellular epitope of α1G T-type calcium channels in human fetal cardiomyocytes. CHB maternal sera also show reactivity for α1H suggesting that autoantibodies can target multiple fetal targets.
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