Disrupted junctional membrane complexes and hyperactive ryanodine receptors after acute junctophilin knockdown in mice.
Disrupted junctional membrane complexes and hyperactive ryanodine receptors after acute junctophilin knockdown in mice.
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DOI：
10.1161/circulationaha.110.006437
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发表时间：
2011-03-08
期刊：
影响因子：
37.8
通讯作者：
Wehrens XH
中科院分区：
文献类型：
--
作者：
van Oort RJ;Garbino A;Wang W;Dixit SS;Landstrom AP;Gaur N;De Almeida AC;Skapura DG;Rudy Y;Burns AR;Ackerman MJ;Wehrens XH
横纹肌兴奋-收缩偶联需要连接膜复合体（JMCs）内肌浆网（SR）上质膜电压激活的Ca 2+通道和Ca 2+释放通道的适当通信。尽管先前的研究揭示了JMC的损失和胚胎致死性的种系junctophilin-2（JPH 2）基因敲除小鼠，它仍然不清楚是否JPH 2在JMC的形成和Ca 2+诱导的Ca 2+释放过程中发挥重要作用的心脏。我们最近的工作证明了肥厚型心肌病患者JPH 2的功能缺失突变。为了阐明JPH 2在心脏中的作用，我们开发了一种新的方法，使用RNA干扰有条件地降低JPH 2蛋白水平。心脏特异性JPH 2敲低导致心脏收缩力受损，从而导致心力衰竭和死亡率增加。JPH 2缺乏导致兴奋-收缩耦合增益的损失，由JMC数量的减少和质膜-SR距离的可变性增加而沉淀。JPH 2的缺失对Ca 2+释放通道的失活有深远的影响，表明JPH 2在调节心肌细胞内Ca 2+释放通道中具有新的功能作用。因此，我们的心脏特异性shRNA介导的junctophilin-2敲低的新方法揭示了junctophilin在心脏细胞内Ca 2+释放中的关键作用。
Excitation-contraction coupling in striated muscle requires proper communication of plasmalemmal voltage-activated Ca2+ channels and Ca2+ release channels on sarcoplasmic reticulum (SR) within junctional membrane complexes (JMCs). Whereas previous studies revealed a loss of JMCs and embryonic lethality in germ-line junctophilin-2 (JPH2) knockout mice, it has remained unclear whether JPH2 plays an essential role in JMC formation and the Ca2+-induced Ca2+ release process in the heart. Our recent work demonstrated loss-of-function mutations in JPH2 in patients with hypertrophic cardiomyopathy. To elucidate the role of JPH2 in the heart, we developed a novel approach to conditionally reduce JPH2 protein levels using RNA interference. Cardiac-specific JPH2 knockdown resulted in impaired cardiac contractility, which caused heart failure and increased mortality. JPH2 deficiency resulted in loss of excitation-contraction coupling gain, precipitated by a reduction in the number of JMCs and increased variability in the plasmalemma-SR distance. Loss of JPH2 had profound effects on Ca2+ release channel inactivation, suggesting a novel functional role for JPH2 in regulating intracellular Ca2+ release channels in cardiac myocytes. Thus, our novel approach of cardiac-specific shRNA-mediated knockdown of junctophilin-2 has uncovered a critical role for junctophilin in intracellular Ca2+ release in the heart.