Phospholamban ablation rescues sarcoplasmic reticulum Ca(2+) handling but exacerbates cardiac dysfunction in CaMKIIdelta(C) transgenic mice.
Phospholamban ablation rescues sarcoplasmic reticulum Ca(2+) handling but exacerbates cardiac dysfunction in CaMKIIdelta(C) transgenic mice.
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DOI：
10.1161/circresaha.109.207423
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发表时间：
2010-02-05
影响因子：
20.1
通讯作者：
Brown JH
中科院分区：
文献类型：
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作者：
Zhang T;Guo T;Mishra S;Dalton ND;Kranias EG;Peterson KL;Bers DM;Brown JH
我们先前的研究表明，表达钙/钙调蛋白依赖的蛋白激酶IIδC(CaMKII-TG)的转基因小鼠会出现扩张型心肌病，与兰尼定受体(RyR2)磷酸化增加、肌浆网(SR)钙泄漏增加和肌浆网(SR)钙负荷降低相关。我们推测，磷蛋白(PLN)消融可以恢复SR的钙负荷，并防止CaMKII-TG中出现的心室收缩、扩张和死亡率下降。我们的目的是建立缺乏PLN的CaMKII-TG小鼠，确定心脏CaMKIIδC表达的不良适应效应是否得到纠正，并建立这些变化的机制基础。将CaMKII-Tg与PLN基因敲除(PLN-KO)小鼠杂交，得到KO/Tg小鼠。比较野生型(WT)、CaMKII-TG、PLN-KO和KO/TG的心肌细胞。在KO/TG中，CaMKII-TG中出现的肌浆网钙负荷下降和抽动钙瞬变在KO/TG中正常化。令人惊讶的是，心力衰竭的表型恶化，表现为左心室扩张增加，心功能下降，细胞凋亡增加，死亡率增加。在KO/TG心肌细胞中，肌浆网钙离子火花和漏电流显著增加，这可能是由于恢复的肌浆网钙负荷和RyR2磷酸化的共同作用。KO/TG与WT或CaMKII-TG小鼠相比，心肌细胞线粒体Ca~(2+)负荷增加，这依赖于SR Ca~(2+)火花的升高。KO/TG培养的心肌细胞存活率较低，但可通过抑制肌浆网钙释放和线粒体钙负荷而改善。在CaMKII和RyR2磷酸化升高的情况下，使心肌细胞SR钙负荷正常化会导致SR Ca~(2+)泄漏和线粒体Ca~(2+)升高，从而加剧细胞死亡、心力衰竭和死亡率。
We previously showed that transgenic mice expressing Ca2+/calmodulin-dependent protein kinase II δC (CaMKII-TG) develop dilated cardiomyopathy associated with increased ryanodine receptors (RyR2) phosphorylation, enhanced sarcoplasmic reticulum (SR) Ca2+ leak and lowering of SR Ca2+ load. We hypothesized that phospholamban (PLN) ablation would restore SR Ca2+ load and prevent the decreased ventricular contractility, dilation and mortality seen in CaMKII-TG. Our objective was to generate CaMKII-TG mice lacking PLN, determine if the maladaptive effects of cardiac CaMKIIδC expression were corrected and establish the mechanistic basis for these changes. CaMKII-TG were crossed with PLN knockout (PLN-KO) mice to generate KO/TG mice. Myocytes from wild type (WT), CaMKII-TG, PLN-KO and KO/TG were compared. The decreased SR Ca2+ load and twitch Ca2+ transients seen in CaMKII-TG were normalized in KO/TG. Surprisingly the heart failure phenotype was exacerbated as indicated by increased left ventricular dilation, decreased ventricular function, increased apoptosis and greater mortality. In KO/TG myocytes SR Ca2+ sparks and leak were significantly increased, presumably due to the combined effects of restored SR Ca2+ load and RyR2 phosphorylation. Mitochondrial Ca2+ loading was increased in cardiomyocytes from KO/TG vs. WT or CaMKII-TG mice and this was dependent upon elevated SR Ca2+ sparks. Cardiomyocytes from KO/TG showed poor viability, improved by inhibiting SR Ca2+ release and mitochondrial Ca2+ loading. Normalizing cardiomyocyte SR Ca2+ loading in the face of elevated CaMKII and RyR2 phosphorylation leads to enhanced SR Ca2+ leak and mitochondrial Ca2+ elevation, associated with exacerbated cell death, heart failure and mortality.