Junctophilin-2 expression silencing causes cardiocyte hypertrophy and abnormal intracellular calcium-handling.
Junctophilin-2 expression silencing causes cardiocyte hypertrophy and abnormal intracellular calcium-handling.
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DOI：
10.1161/circheartfailure.110.958694
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发表时间：
2011-03
期刊：
影响因子：
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通讯作者：
Ackerman MJ
中科院分区：
文献类型：
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作者：
Landstrom AP;Kellen CA;Dixit SS;van Oort RJ;Garbino A;Weisleder N;Ma J;Wehrens XH;Ackerman MJ
嗜连接蛋白-2（JPH 2）是心肌细胞膜连接复合体中表达的一种蛋白质，是心肌细胞内钙信号传导所必需的。最近，在心肌肥厚模型中JPH 2表达的下调与质膜L型Ca 2+通道和肌浆网ryanodine受体之间的偶联缺陷有关。然而，目前尚不清楚肥厚型心肌病（HCM）患者的JPH 2表达是否改变。此外，JPH 2表达下调对细胞内Ca 2+处理的影响目前知之甚少。我们试图确定在HCM患者中是否注意到JPH 2表达的丧失，以及表达沉默是否可能以促肥大的方式干扰Ca 2+处理。与表面上健康的创伤性死亡受害者相比，从HCM患者中获得的快速冷冻人心脏组织中JPH 2表达减少。通过针对鼠JPH 2 mRNA的小干扰RNA探针（shJPH 2）部分沉默HL-1细胞中JPH 2的表达，导致心肌细胞肥大和已知心脏肥大标志物的表达增加。虽然主要的Ca 2+处理蛋白的表达水平不变，shJPH 2细胞表现出抑制的最大Ca 2+瞬时振幅，这是不敏感的LTCC激活与JPH 2敲低。此外，观察到咖啡因触发的SR储存Ca 2+水平降低，总Ca 2+储存可能增加。自发的Ca 2+振荡引起在一个较高的细胞外[Ca 2 +]和频率降低JPH 2敲低细胞。我们的研究结果表明，HCM患者的JPH 2水平降低。JPH 2表达减少导致兴奋-收缩偶联增益减少以及Ca 2+稳态改变，这可能与促肥大重塑相关。
Junctophilin-2 (JPH2), a protein expressed in the junctional membrane complex, is necessary for proper intracellular calcium (Ca2+) signaling in cardiac myocytes. Down-regulation of JPH2 expression in a model of cardiac hypertrophy was recently associated with defective coupling between plasmalemmal L-type Ca2+ channels and sarcoplasmic reticular ryanodine receptors. However, it remains unclear whether JPH2 expression is altered in patients with hypertrophic cardiomyopathy (HCM). In addition, the effects of down-regulation of JPH2 expression on intracellular Ca2+-handling are presently poorly understood. We sought to determine whether loss of JPH2 expression is noted among patients with HCM and whether expression silencing might perturb Ca2+-handling in a pro-hypertrophic manner. JPH2 expression was reduced in flash frozen human cardiac tissue procured from patients with HCM compared to ostensibly healthy traumatic death victims. Partial silencing of JPH2 expression in HL-1 cells by a small interfering RNA probe targeted to murine JPH2 mRNA (shJPH2) resulted in myocyte hypertrophy and increased expression of known markers of cardiac hypertrophy. While expression levels of major Ca2+-handling proteins were unchanged, shJPH2 cells demonstrated depressed maximal Ca2+ transient amplitudes that were insensitive to LTCC activation with JPH2 knock-down. Further, reduced caffeine-triggered SR store Ca2+ levels were observed with potentially increased total Ca2+ stores. Spontaneous Ca2+ oscillations were elicited at a higher extracellular [Ca2+] and with decreased frequency in JPH2 knock-down cells. Our results show that JPH2 levels are reduced in patients with HCM. Reduced JPH2 expression results in reduced excitation-contraction coupling gain as well as altered Ca2+ homeostasis which may be associated with pro-hypertrophic remodeling.