Relationship of calcium transients to calcium currents and charge movements in myotubes expressing skeletal and cardiac dihydropyridine receptors.
Relationship of calcium transients to calcium currents and charge movements in myotubes expressing skeletal and cardiac dihydropyridine receptors.
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DOI：
10.1085/jgp.103.1.125
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发表时间：
1994-01
期刊：
影响因子：
--
通讯作者：
Beam KG
中科院分区：
文献类型：
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作者：
García J;Tanabe T;Beam KG
在骨骼肌和心肌中，二氢吡啶 (DHP) 受体是兴奋-收缩 (e-c) 耦合的关键元件。然而，这些肌肉的钙释放机制完全不同。在心肌中，DHP 受体充当快速激活的钙通道，钙通过该通道流入会诱导肌浆网 (SR) 释放钙。相比之下，在骨骼肌中，DHP 受体充当电压传感器和缓慢激活的钙通道。在这种情况下，电压传感器控制 SR 钙的释放。先前已经证明，用编码骨骼肌 DHP 受体的 cDNA (pCAC6) 注射发育不良肌管可恢复慢钙电流和骨骼型 e-c 耦合，而无需外部钙的进入 (Tanabe, Beam, Powell, and Numa. 1988. Nature. 336:134-139)。此外，注射编码心脏 DHP 受体的 cDNA (pCARD1) 会产生快速激活的钙电流和心脏型 e-c 耦合，这确实需要钙进入 (Tanabe, Mikami, Numa, and Beam. 1990. Nature. 344:451-453)。在本文中，我们研究了培养的正常骨骼肌细胞中电荷运动、钙瞬变和钙电流的电压依赖性以及它们之间的关系。此外，我们将pCAC6或pCARD1注射到发育不良肌管的细胞核中，研究恢复事件之间的关系，并将其与正常细胞的恢复事件进行比较。用全细胞膜片钳技术记录电荷运动和钙电流。使用通过贴片移液管引入的 Fluo-3 测量钙瞬变。表达 pCAC6 的基因缺陷肌管中的电荷运动、钙瞬变和钙电流的动力学和电压依赖性在质量上与正常肌管中引起的类似：钙瞬变表现出对电压的 S 形依赖性，并且在添加 0.5 mM Cd2+ + 0.1 mM La3+ 后仍然存在。相反，表达 pCARD1 的基因缺陷肌管中的钙瞬变遵循钙电流的幅度，因此表现出对电压的钟形依赖性。此外，瞬态的上升速率比注射 pCAC6 的肌管慢，并且通过添加 Cd2+ + La3+ 完全消除。
In both skeletal and cardiac muscle, the dihydropyridine (DHP) receptor is a critical element in excitation-contraction (e-c) coupling. However, the mechanism for calcium release is completely different in these muscles. In cardiac muscle the DHP receptor functions as a rapidly-activated calcium channel and the influx of calcium through this channel induces calcium release from the sarcoplasmic reticulum (SR). In contrast, in skeletal muscle the DHP receptor functions as a voltage sensor and as a slowly-activating calcium channel; in this case, the voltage sensor controls SR calcium release. It has been previously demonstrated that injection of dysgenic myotubes with cDNA (pCAC6) encoding the skeletal muscle DHP receptor restores the slow calcium current and skeletal type e-c coupling that does not require entry of external calcium (Tanabe, Beam, Powell, and Numa. 1988. Nature. 336:134-139). Furthermore, injection of cDNA (pCARD1) encoding the cardiac DHP receptor produces rapidly activating calcium current and cardiac type e-c coupling that does require calcium entry (Tanabe, Mikami, Numa, and Beam. 1990. Nature. 344:451-453). In this paper, we have studied the voltage dependence of, and the relationship between, charge movement, calcium transients, and calcium current in normal skeletal muscle cells in culture. In addition, we injected pCAC6 or pCARD1 into the nuclei of dysgenic myotubes and studied the relationship between the restored events and compared them with those of the normal cells. Charge movement and calcium currents were recorded with the whole cell patch-clamp technique. Calcium transients were measured with Fluo-3 introduced through the patch pipette. The kinetics and voltage dependence of the charge movement, calcium transients, and calcium current in dysgenic myotubes expressing pCAC6 were qualitatively similar to the ones elicited in normal myotubes: the calcium transient displayed a sigmoidal dependence on voltage and was still present after the addition of 0.5 mM Cd2+ + 0.1 mM La3+. In contrast, the calcium transient in dysgenic myotubes expressing pCARD1 followed the amplitude of the calcium current and thus showed a bell shaped dependence on voltage. In addition, the transient had a slower rate of rise than in pCAC6-injected myotubes and was abolished completely by the addition of Cd2+ + La3+.