‡Department of Physiology, University of Bern, Bern, Switzerland.
Biochem J. 2013 Oct 15;455(2):169-77. doi: 10.1042/BJ20130698.
Excitation-contraction coupling is the physiological mechanism occurring in muscle cells whereby an electrical signal sensed by the dihydropyridine receptor located on the transverse tubules is transformed into a chemical gradient (Ca2+ increase) by activation of the ryanodine receptor located on the sarcoplasmic reticulum membrane. In the present study, we characterized for the first time the excitation-contraction coupling machinery of an immortalized human skeletal muscle cell line. Intracellular Ca2+ measurements showed a normal response to pharmacological activation of the ryanodine receptor, whereas 3D-SIM (super-resolution structured illumination microscopy) revealed a low level of structural organization of ryanodine receptors and dihydropyridine receptors. Interestingly, the expression levels of several transcripts of proteins involved in Ca2+ homoeostasis and differentiation indicate that the cell line has a phenotype closer to that of slow-twitch than fast-twitch muscles. These results point to the potential application of such human muscle-derived cell lines to the study of neuromuscular disorders; in addition, they may serve as a platform for the development of therapeutic strategies aimed at correcting defects in Ca2+ homoeostasis due to mutations in genes involved in Ca2+ regulation.
兴奋-收缩偶联是发生在肌肉细胞中的生理机制，通过横管上的二氢吡啶受体感知电信号，激活肌浆网上的兰尼碱受体，将其转化为化学梯度（Ca2+增加）。在本研究中，我们首次对永生化的人骨骼肌细胞系的兴奋-收缩偶联机制进行了表征。细胞内 Ca2+测量显示对兰尼碱受体的药理学激活有正常反应，而 3D-SIM（超分辨率结构照明显微镜）显示兰尼碱受体和二氢吡啶受体的结构组织水平较低。有趣的是，参与 Ca2+动态平衡和分化的几种蛋白的转录本的表达水平表明，该细胞系的表型更接近慢肌而非快肌。这些结果表明，这种源自人肌肉的细胞系可能适用于研究神经肌肉疾病；此外，它们可以作为一个平台，用于开发治疗策略，旨在纠正由于涉及 Ca2+调节的基因突变导致的 Ca2+动态平衡缺陷。
