BIN1 减少， Cav1.2 转运受损，见于人类衰竭心肌细胞。
BIN1 is reduced and Cav1.2 trafficking is impaired in human failing cardiomyocytes.
机构信息
Cardiovascular Research Institute, University of California, San Francisco, CA, USA.
出版信息
Heart Rhythm. 2012 May;9(5):812-20. doi: 10.1016/j.hrthm.2011.11.055. Epub 2011 Dec 2.
BACKGROUND
Heart failure is a growing epidemic, and a typical aspect of heart failure pathophysiology is altered calcium transients. Normal cardiac calcium transients are initiated by Cav1.2 channels at cardiac T tubules. Bridging integrator 1 (BIN1) is a membrane scaffolding protein that causes Cav1.2 to traffic to T tubules in healthy hearts. The mechanisms of Cav1.2 trafficking in heart failure are not known.
OBJECTIVE
To study BIN1 expression and its effect on Cav1.2 trafficking in failing hearts.
METHODS
Intact myocardium and freshly isolated cardiomyocytes from nonfailing and end-stage failing human hearts were used to study BIN1 expression and Cav1.2 localization. To confirm Cav1.2 surface expression dependence on BIN1, patch-clamp recordings were performed of Cav1.2 current in cell lines with and without trafficking-competent BIN1. Also, in adult mouse cardiomyocytes, surface Cav1.2 and calcium transients were studied after small hairpin RNA-mediated knockdown of BIN1. For a functional readout in intact heart, calcium transients and cardiac contractility were analyzed in a zebrafish model with morpholino-mediated knockdown of BIN1.
RESULTS
BIN1 expression is significantly decreased in failing cardiomyocytes at both mRNA (30% down) and protein (36% down) levels. Peripheral Cav1.2 is reduced to 42% by imaging, and a biochemical T-tubule fraction of Cav1.2 is reduced to 68%. The total calcium current is reduced to 41% in a cell line expressing a nontrafficking BIN1 mutant. In mouse cardiomyocytes, BIN1 knockdown decreases surface Cav1.2 and impairs calcium transients. In zebrafish hearts, BIN1 knockdown causes a 75% reduction in calcium transients and severe ventricular contractile dysfunction.
CONCLUSIONS
The data indicate that BIN1 is significantly reduced in human heart failure, and this reduction impairs Cav1.2 trafficking, calcium transients, and contractility.
背景
心力衰竭是一种日益严重的流行病，心力衰竭病理生理学的一个典型方面是钙瞬变改变。正常的心脏钙瞬变是由心肌 T 管上的 Cav1.2 通道启动的。桥连整合蛋白 1（BIN1）是一种膜支架蛋白，可使 Cav1.2 在健康心脏中向 T 管转运。心力衰竭中 Cav1.2 转运的机制尚不清楚。
目的
研究 BIN1 的表达及其对心力衰竭时 Cav1.2 转运的影响。
方法
使用来自非衰竭和终末期衰竭人心肌的完整心肌和新鲜分离的心肌细胞来研究 BIN1 的表达和 Cav1.2 的定位。为了确认 Cav1.2 表面表达对 BIN1 的依赖性，在具有和不具有转运能力的 BIN1 的细胞系中进行 Cav1.2 电流的膜片钳记录。此外，在成年小鼠心肌细胞中，在用短发夹 RNA 敲低 BIN1 后，研究了表面 Cav1.2 和钙瞬变。为了在完整心脏中进行功能检测，在 BIN1 功能丧失的斑马鱼模型中分析了钙瞬变和心脏收缩性。
结果
BIN1 的表达在衰竭的心肌细胞中，无论是在 mRNA（下调 30%）还是在蛋白质水平（下调 36%）均显著降低。通过成像将外周 Cav1.2 减少到 42%，并且生化 T 管 Cav1.2 分数减少到 68%。表达非转运 BIN1 突变体的细胞系中，总钙电流减少到 41%。在小鼠心肌细胞中，BIN1 敲低减少了表面 Cav1.2 并损害了钙瞬变。在斑马鱼心脏中，BIN1 敲低导致钙瞬变减少 75%和严重的心室收缩功能障碍。
结论
数据表明，BIN1 在人类心力衰竭中显著减少，这种减少会损害 Cav1.2 的转运、钙瞬变和收缩性。
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