Cardiac-specific overexpression of sarcolipin inhibits sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA2a) activity and impairs cardiac function in mice
Cardiac-specific overexpression of sarcolipin inhibits sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA2a) activity and impairs cardiac function in mice
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DOI：
10.1073/pnas.0402596101
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发表时间：
2004-06-22
影响因子：
11.1
通讯作者：
MacLennan, DH
中科院分区：
文献类型：
--
作者：
Asahi, M;Otsu, K;MacLennan, DH
Sarcolipin（SLN）通过直接结合抑制心脏肌（内）质网Ca 2 + ATP酶（SERCA 2a），并且如果其通过受磷蛋白（PLN）结合则是超抑制性的。为了确定SLN在心脏中的过表达是否会损害心脏功能，用心脏特异性过表达的NF-SLN（SLN在其N末端用FLAG表位标记）产生转基因（TG）小鼠。NF-SLN表达水平（NF-SLN/PLN表达比率）相当于当在HEK-293细胞中与PLN和SERCA 2a共表达时诱导深度超抑制的水平。在TG心脏中，与非TG同窝对照心脏相比，SERCA 2a对Ca 2+的表观亲和力降低。侵入性血流动力学和超声心动图分析显示TG小鼠心肌收缩力受损和心室肥大。基础PLN磷酸化减少。在离体乳头肌进行等长张力，Ca 2+瞬变和峰值张力的峰值幅度降低，而衰减时间的Ca 2+瞬变和紧张的松弛时间增加在TG小鼠。异丙肾上腺素在很大程度上恢复了乳头肌的收缩力，并刺激PLN磷酸化到野生型水平在完整的心脏。在TG心脏中未观察到SERCA 2a、PLN、ryanodine受体和钙螯合蛋白表达的代偿性变化。免疫共沉淀表明过表达的NF-SLN与SERCA 2a和PLN结合，形成三元复合物。这些数据表明，NF-SLN过表达通过在PLN磷酸化不存在的情况下稳定SERCA 2a-PLN相互作用和通过抑制PLN磷酸化来抑制SERCA 2a。抑制SERCA 2a会损害收缩性和钙循环，但对β-肾上腺素能激动剂的反应性可能会阻止心力衰竭的进展。
Sarcolipin (SLN) inhibits the cardiac sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA2a) by direct binding and is superinhibitory if it binds through phospholamban (PLN). To determine whether overexpression of SLN in the heart might impair cardiac function, transgenic (TG) mice were generated with cardiac-specific overexpression of NF-SLN (SLN tagged at its N terminus with the FLAG epitope). The level of NF-SLN expression (the NF-SLN/PLN expression ratio) was equivalent to that which induces profound superinhibition when coexpressed with PLN and SERCA2a in HEK-293 cells. In TG hearts, the apparent affinity of SERCA2a for Ca2+ was decreased compared with non-TG littermate control hearts. Invasive hemodynamic and echocardiographic analyses revealed impaired cardiac contractility and ventricular hypertrophy in TG mice. Basal PLN phosphorylation was reduced. In isolated papillary muscle subjected to isometric tension, peak amplitudes of Ca2+ transients and peak tensions were reduced, whereas decay times of Ca2+ transients and relaxation times of tension were increased in TG mice. Isoproterenol largely restored contractility in papillary muscle and stimulated PLN phosphorylation to wild-type levels in intact hearts. No compensatory changes in expression of SERCA2a, PLN, ryanodine receptor, and calsequestrin were observed in TG hearts. Coimmunoprecipitation indicated that overexpressed NF-SLN was bound to both SERCA2a and PLN, forming a ternary complex. These data suggest that NF-SLN overexpression inhibits SERCA2a through stabilization of SERCA2a-PLN interaction in the absence of PLN phosphorylation and through the inhibition of PLN phosphorylation. Inhibition of SERCA2a impairs contractility and calcium cycling, but responsiveness to beta-adrenergic agonists may prevent progression to heart failure.