Overexpression of SERCA2b in the heart leads to an increase in sarcoplasmic reticulum calcium transport function and increased cardiac contractility
Overexpression of SERCA2b in the heart leads to an increase in sarcoplasmic reticulum calcium transport function and increased cardiac contractility
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DOI：
10.1074/jbc.m001783200
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发表时间：
2000-08-11
影响因子：
4.8
通讯作者：
Periasamy, M
中科院分区：
文献类型：
--
作者：
Greene, AL;Lalli, MJ;Periasamy, M
肌浆网钙ATP酶SERCA 2b是由SERCA 2基因编码的替代同种型。SERCA 2b广泛表达，与SERCA 2a相比具有更高的Ca 2+亲和力。我们制作了在心脏中过表达大鼠SERCA 2b cDNA的转基因小鼠。在转基因心脏中，SERCA 2b mRNA水平比内源性SERCA 2b mRNA高约20倍。心脏中SERCA 2b蛋白增加8-10倍，而SERCA 2a mRNA/蛋白水平保持不变。共聚焦显微镜显示SERCA 2b优先定位于SR的T-小管周围，而SERCA 2a亚型在SR膜中横向和纵向分布。钙依赖性钙摄取测量显示，与野生型对照小鼠（0.269 +/-0.012 mu M，p < 0.01）相比，SERCA 2b转基因小鼠（0.199 +/-0.011 mu M）中Ca 2+摄取的最大速度没有改变，但对Ca 2+的表观泵亲和力（K-0.5）增加。工作执行心脏准备表明，SERCA 2b转基因心脏比野生型心脏具有更高的收缩和舒张速率，更短的峰值压力时间和半松弛时间。这些数据表明SERCA 2b与心肌细胞肌浆网内的亚隔室相关。SERCA 2b的过表达导致SR钙转运功能的增加和心脏收缩力的增加，表明SERCA 2b在调节心脏的搏动到搏动收缩中起高度特异性的作用。
The sarcoplasmic reticulum calcium ATPase SERCA2b is an alternate isoform encoded by the SERCA2 gene. SERCA2b is expressed ubiquitously and has a higher Ca2+ affinity compared with SERCA2 a. We made transgenic mice that overexpress the rat SERCA2b cDNA in the heart. SERCA2b mRNA level was approximately similar to 20-fold higher than endogenous SERCA2b mRNA in transgenic hearts. SERCA2b protein was increased 8-10-fold in the heart, whereas SERCA2a mRNA/protein level remained unchanged. Confocal microscopy showed that SERCA2b is localized preferentially around the T-tubules of the SR, whereas SERCA2a isoform is distributed both transversely and longitudinally in the SR membrane. Calcium-dependent calcium uptake measurements showed that the maximal velocity of Ca2+ uptake was not changed, but the apparent pump affinity for Ca2+ (K-0.5) was increased in SERCA2b transgenic mice (0.199 +/- 0.011 mu M) compared with wild-type control mice (0.269 +/- 0.012 mu M, p < 0.01). Work-performing heart preparations showed that SERCA2b transgenic hearts had a higher rates of contraction and relaxation, shorter time to peak pressure and half-time for relaxation than wild-type hearts. These data show that SERCA2b is associated in a subcompartment within the sarcoplasmic reticulum of cardiac myocytes. Overexpression of SERCA2b leads to an increase in SR calcium transport function and increased cardiac contractility, suggesting that SERCA2b plays a highly specialized role in regulating the beat-to-beat contraction of the heart.