Overexpression of the rat sarcoplasmic reticulum Ca2+ ATPase gene in the heart of transgenic mice accelerates calcium transients and cardiac relaxation
Overexpression of the rat sarcoplasmic reticulum Ca2+ ATPase gene in the heart of transgenic mice accelerates calcium transients and cardiac relaxation
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DOI：
10.1172/jci119544
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发表时间：
1997-07-15
影响因子：
15.9
通讯作者：
Dillmann, WH
中科院分区：
文献类型：
--
作者：
He, HP;Giordano, FJ;Dillmann, WH
肌浆网钙ATPase(SERCA2)在心脏松弛过程中起着降低胞浆钙水平的主导作用，其活性的降低与甲状腺功能低下和衰竭心脏的舒张期延迟有关。为了确定SERCA2基因表达增加引起的收缩变化，我们建立了过表达大鼠SERCA2基因的转基因小鼠，对一个杂合子转基因小鼠系(CJ5)的鉴定表明，与对照小鼠相比，SERCA2mRNA和蛋白的量分别增加了2.6倍和1.2倍。SERCA2蛋白的相对合成速率增加了82%，参与钙调节的兰尼定受体和钙调素等基因的mRNA水平没有变化，但磷蛋白和钠/钙交换蛋白的mRNA水平分别增加了1.4倍和1.8倍，而磷蛋白或钠/钙交换蛋白的增加并没有引起蛋白水平的变化。功能分析表明，SERCA2转基因小鼠乳头肌细胞内钙下降(t(1/2))和再增快(t(1/2))分别加快了23%和22%，心肌细胞缩短速度也明显加快，SERCA2转基因小鼠乳头肌达到静息后半峰值的时间明显缩短。此外，体内测量的心功能显示，SERCA2转基因小鼠的收缩和松弛速度显著加快，两组应用异丙肾上腺素后均进一步增强。从另一个纯合子SERCA2转基因小鼠(CJ2)分离的心肌细胞的收缩性能也得到了类似的结果，我们的发现首次表明，增加SERCA2的表达在体内是可行的，并导致钙瞬变、心肌收缩和松弛增强，这可能具有进一步的治疗意义。
The Ca2+ ATPase of the sarcoplasmic reticulum (SERCA2) plays a dominant role in lowering cytoplasmic calcium levels during cardiac relaxation and reduction of its activity has been linked to delayed diastolic relaxation in hypothyroid and failing hearts, To determine the contractile alterations resulting from increased SERCA2 expression, we generated transgenic mice overexpressing a rat SERCA2 transgene, Characterization of a heterozygous transgenic mouse line (CJ5) showed that the amount of SERCA2 mRNA and protein increased 2.6-fold and 1.2-fold, respectively, relative to control mice. Determination of the relative synthesis rate of SERCA2 protein showed an 82% increase, The mRNA levels of some of the other genes involved in calcium handling, such as the ryanodine receptor and calsequestrin, remained unchanged, but the mRNA levels of phospholamban and Na+/Ca2+ exchanger increased 1.4-fold and 1.8-fold, respectively, The increase in phospholamban or Na+/Ca2+ exchanger mRNAs did not, however, result in changes in protein levels, Functional analysis of calcium handling and contractile parameters in isolated cardiac myocytes indicated that the intracellular calcium decline (t(1/2)) and myocyte relengthening (t(1/2)) were accelerated by 23 and 22%, respectively, In addition, the rate of myocyte shortening was also significantly faster, In isolated papillary muscle from SERCA2 transgenic mice, the time to half maximum postrest potentiation was significantly shorter than in negative littermates. Furthermore, cardiac function measured in vivo, demonstrated significantly accelerated contraction and relaxation in SERCA2 transgenic mice that were further augmented in both groups with isoproterenol administration. Similar results were obtained for the contractile performance of myocytes isolated from a separate line (CJ2) of homozygous SERCA2 transgenic mice, Our findings suggest, for the first time, that increased SERCA2 expression is feasible in vivo and results in enhanced calcium transients, myocardial contractility, and relaxation that may have further therapeutic implications.