Functional consequences of stably expressing a mutant calsequestrin (CASQ2D307H) in the CASQ2 null background.
Functional consequences of stably expressing a mutant calsequestrin (CASQ2D307H) in the CASQ2 null background.
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在 CASQ2 无效背景中稳定表达突变型 calsequestrin (CASQ2D307H) 的功能后果。
DOI：
10.1152/ajpheart.00578.2011
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
Periasamy,Muthu
中科院分区：
文献类型：
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作者：
Kalyanasundaram,Anuradha;Viatchenko-Karpinski,Serge;Belevych,AndriyE;Lacombe,VeroniqueA;Hwang,HyunSeok;Knollmann,BjörnC;Gyorke,Sandor;Periasamy,Muthu
钙螯合蛋白（CASQ 2）在心肌肌浆网（SR）钙（Ca 2+）转运中的作用受到了广泛关注，因为CASQ 2的点突变被报道可导致室性心律失常。在本研究中，我们严格评估了在CASQ 2敲除小鼠中表达CASQ 2D 307 H突变蛋白的功能后果。我们最近报道了突变体CASQ 2D 307 H蛋白可以在CASQ 2无效心脏中稳定表达，并且其适当地靶向连接SR（Kalyanasundaram A，Bal NC，Franzini-Armstrong C，Knollmann BC，Periasamy M.J Biol Chem 285：3076-3083，2010）。在这项研究中，我们发现在CASQ 2无效背景中引入CASQ 2D 307 H蛋白部分恢复了在CASQ 2无效小鼠中降低的三醇溶蛋白1水平。尽管两倍的表达（相对于野生型CASQ 2），突变体蛋白未能增加SR Ca 2+负荷。我们还发现，在CASQ 2 null和CASQ 2D 307 H细胞中，Ca 2+瞬变衰减较慢。CASQ 2D 307 H心肌细胞在节律性起搏和异丙肾上腺素刺激下，表现出与CASQ 2缺失心肌细胞相似的自发性Ca ~（2+）波;然而，CASQ 2D 307 H心肌细胞中Ca ~（2+）循环的稳定性增加。在异丙肾上腺素的存在下，在CASQ 2D 307 H心肌细胞中的Ca 2 +-瞬时振幅显着降低，可能表明在高Ca 2+浓度下的Ca 2+缓冲能力和从突变体CASQ 2释放的固有缺陷。我们还在CASQ 2D 307 H小鼠中观察到多态性室性心动过速，尽管比CASQ 2缺失小鼠少。提示CASQ 2D 307 H点突变可能影响Ca 2+缓冲能力和Ca 2+释放。我们认为，CASQ 2D 307和triadin 1之间的不良相互作用可能会影响ryanodine受体2的稳定性，从而增加对延迟后去极化和触发性心律失常活动的敏感性。
The role of calsequestrin (CASQ2) in cardiac sarcoplasmic reticulum (SR) calcium (Ca2+) transport has gained significant attention since point mutations in CASQ2 were reported to cause ventricular arrhythmia. In the present study, we have critically evaluated the functional consequences of expressing the CASQ2D307Hmutant protein in the CASQ2 null mouse. We recently reported that the mutant CASQ2D307Hprotein can be stably expressed in CASQ2 null hearts, and it targets appropriately to the junctional SR (Kalyanasundaram A, Bal NC, Franzini-Armstrong C, Knollmann BC, Periasamy M.J Biol Chem285: 3076–3083, 2010). In this study, we found that introduction of CASQ2D307Hprotein in the CASQ2 null background partially restored triadin 1 levels, which were decreased in the CASQ2 null mice. Despite twofold expression (relative to wild-type CASQ2), the mutant protein failed to increase SR Ca2+load. We also found that the Ca2+transient decays slower in the CASQ2 null and CASQ2D307Hcells. CASQ2D307Hmyocytes, when rhythmically paced and challenged with isoproterenol, exhibit spontaneous Ca2+waves similar to CASQ2 null myocytes; however, the stability of Ca2+cycling was increased in the CASQ2D307Hmyocytes. In the presence of isoproterenol, Ca2+-transient amplitude in CASQ2D307Hmyocytes was significantly decreased, possibly indicating an inherent defect in Ca2+buffering capacity and release from the mutant CASQ2 at high Ca2+concentrations. We also observed polymorphic ventricular tachycardia in the CASQ2D307Hmice, although lesser than in the CASQ2 null mice. These data suggest that CASQ2D307Hpoint mutation may affect Ca2+buffering capacity and Ca2+release. We propose that poor interaction between CASQ2D307Hand triadin 1 could affect ryanodine receptor 2 stability, thereby increasing susceptibility to delayed afterdepolarizations and triggered arrhythmic activity.