Targeted disruption of Na+/Ca2+ exchanger gene leads to cardiomyocyte apoptosis and defects in heartbeat
Targeted disruption of Na+/Ca2+ exchanger gene leads to cardiomyocyte apoptosis and defects in heartbeat
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DOI：
10.1074/jbc.m004035200
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发表时间：
2000-11-24
影响因子：
4.8
通讯作者：
Komuro, I
中科院分区：
文献类型：
--
作者：
Wakimoto, K;Kobayashi, K;Komuro, I
Ca2+在兴奋期间通过电压依赖性Ca2+通道进入心肌细胞，在松弛期间主要由Na+/Ca2+交换器（NCX1）从肌细胞中挤出。洋地黄治疗和缺血/再灌注后肌细胞内Ca2+浓度的增加也被认为是Na+/Ca2+交换机制的反向模式的结果。然而，由于缺乏特异性抑制剂，NCX1的确切作用仍不清楚。我们通过基因靶向产生ncx1缺陷小鼠，以确定该交换剂的体内功能。纯合子ncx1缺陷小鼠在胚胎第9天至第10天死亡。心脏停止跳动，心肌细胞凋亡。在零突变心脏中没有检测到Na+/Ca2+交换活性的正向模式或反向模式。在杂合小鼠的心脏、肾脏、主动脉和平滑肌细胞中，Na+依赖性Ca2+交换活性和NCX1蛋白含量下降了50%以上，并且在Na+无溶液中，杂合小鼠的主动脉环张力发育明显受损。这些发现表明，NCX1是胚胎中心跳和心肌细胞存活所必需的，并在心脏和主动脉中Na+依赖性Ca2+处理中起关键作用。
Ca2+, which enters cardiac myocytes through voltage dependent Ca2+ channels during excitation, is extruded from myocytes primarily by the Na+/Ca2+ exchanger (NCX1) during relaxation. The increase in intracellular Ca2+ concentration in myocytes by digitalis treatment and after ischemia/reperfusion is also thought to result from the reverse mode of the Na+/Ca2+ exchange mechanism. However, the precise roles of the NCX1 are still unclear because of the lack of its specific inhibitors. We generated Ncx1-deficient mice by gene targeting to determine the in vivo function of the exchanger. Homozygous Ncx1-deficient mice died between embryonic days 9 and 10. Their hearts did not beat, and cardiac myocytes showed apoptosis. No forward mode or reverse mode of the Na+/Ca2+ exchange activity was detected in null mutant hearts. The Na+-dependent Ca2+ exchange activity as well as protein content of NCX1 were decreased by similar to 50% in the heart, kidney, aorta, and smooth muscle cells of the heterozygous mice, and tension development of the aortic ring in Na+-free solution was markedly impaired in heterozygous mice. These findings suggest that NCX1 is required for heartbeats and survival of cardiac myocytes in embryos and plays critical roles in Na+-dependent Ca2+ handling in the heart and aorta.