Cardiac-specific overexpression of phospholamban alters calcium kinetics and resultant cardiomyocyte mechanics in transgenic mice
Cardiac-specific overexpression of phospholamban alters calcium kinetics and resultant cardiomyocyte mechanics in transgenic mice
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DOI：
10.1172/jci118446
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发表时间：
1996-01-15
影响因子：
15.9
通讯作者：
Kranias, EG
中科院分区：
文献类型：
--
作者：
Kadambi, VJ;Ponniah, S;Kranias, EG
Phospholamban 是心脏肌浆网 (SR) Ca2+-ATP 酶活性的调节剂，也是心脏基础收缩力的重要调节剂。为了确定所有SR Ca2+-ATP酶是否在体内受到受磷蛋白的调节，产生了转基因小鼠，其在心脏特异性α-肌球蛋白重链启动子的驱动下在心脏中过度表达受磷蛋白。定量免疫印迹显示，与野生型同窝心脏相比，转基因心脏中的受磷蛋白水平增加了一倍。转基因小鼠没有表现出表型改变，心脏/体重、心/肺重量和心肌细胞大小也没有变化。与野生型（100%）心肌细胞相比，来自转基因小鼠的分离的卸载心肌细胞表现出缩短分数（63%）减少以及缩短率（64%）和再延长率（55%）降低。转基因心肌细胞收缩参数的降低反映了 Ca2+ 信号幅度的降低 (83%) 和 Ca2+ 信号衰减时间的延长 (131%)，这与与野生型 (100%) 心肌细胞相比，SR Ca2+-ATPase 对 Ca2+ (56%) 的表观亲和力降低有关。使用 M 模式和脉冲波多普勒超声心动图对左心室收缩功能的体内分析显示，与野生型 (100%) 小鼠相比，转基因小鼠的缩短分数 (79%) 和圆周缩短的归一化平均速度 (67%) 降低。转基因心肌细胞收缩参数和Ca2+动力学的差异以及转基因小鼠左心室收缩功能的降低在异丙肾上腺素刺激后消失。这些发现表明，天然 SR 中的一部分 Ca2+-ATP 酶不受受磷蛋白的调节。额外受磷蛋白分子的表达导致： (a) SR Ca2+ 转运的抑制； (b) 心室肌细胞收缩期 Ca2+ 水平和收缩参数降低； (c)体内基础左心室收缩功能的抑制。
Phospholamban is the regulator of the cardiac sarcoplasmic reticulum (SR) Ca2+-ATPase activity and an important modulator of basal contractility in the heart. To determine whether all the SR Ca2+-ATPase enzymes are subject to regulation by phospholamban in vivo, transgenic mice were generated which overexpressed phospholamban in the heart, driven by the cardiac-specific alpha-myosin heavy chain promoter. Quantitative immunoblotting revealed a twofold increase in the phospholamban protein levels in transgenic hearts compared to wild type littermate hearts. The transgenic mice showed no phenotypic alterations and no changes in heart/body weight, heart/lung weight, and cardiomyocyte size. Isolated unloaded cardiac myocytes from transgenic mice exhibited diminished shortening fraction (63%) and decreased rates of shortening (64%) and relengthening (55%) compared to wild type (100%) cardiomyocytes. The decreases in contractile parameters of transgenic cardiomyocytes reflected decreases in the amplitude (83%) of the Ca2+ signal and prolongation (131%) in the time for decay of the Ca2+ signal, which was associated with a decrease in the apparent affinity of the SR Ca2+-ATPase for Ca2+ (56%), compared to wild type (100%) cardiomyocytes. In vivo analysis of left ventricular systolic function using M mode and pulsed-wave Doppler echocardiography revealed decreases in fractional shortening (79%) and the normalized mean velocity of circumferential shortening (67%) in transgenic mice compared to wild type (100%) mice. The differences in contractile parameters and Ca2+ kinetics in transgenic cardiomyocytes and the depressed left ventricular systolic function in transgenic mice were abolished upon isoproterenol stimulation. These findings indicate that a fraction of the Ca2+-ATPases in native SR is not under regulation by phospholamban. Expression of additional phospholamban molecules results in: (a) inhibition of SR Ca2+ transport; (b) decreases in systolic Ca2+ levels and contractile parameters in ventricular myocytes; and (c) depression of basal left ventricular systolic function in vivo.