Murayama Takashi, Ogawa Haruo, Kurebayashi Nagomi, Ohno Seiko, Horie Minoru, Sakurai Takashi
Department of Cellular and Molecular Pharmacology, Juntendo University Graduate School of Medicine, Tokyo, 113-8421, Japan.
Institute for Quantitative Biosciences, The University of Tokyo, Tokyo, 113-0032, Japan.
Commun Biol. 2018 Jul 23;1:98. doi: 10.1038/s42003-018-0103-x. eCollection 2018.
Ryanodine receptors (RyRs) are Ca release channels in the sarcoplasmic reticulum of skeletal and cardiac muscles and are essential for muscle contraction. Mutations in genes encoding RyRs cause various muscle and arrhythmogenic heart diseases. Although RyR channels are activated by Ca, the actual mechanism of Ca binding remains largely unknown. Here, we report the molecular basis of Ca binding to RyRs for channel activation and discuss its implications in disease states. RyR1 and RyR2 carrying mutations in putative Ca and caffeine-binding sites were functionally analysed. The results were interpreted with respect to recent near-atomic resolution RyR1 structures in various ligand states. We demonstrate that a tryptophan residue in the caffeine-binding site controls the structure of the Ca-binding site to regulate the Ca sensitivity. Our results reveal the initial step of RyR channel activation by Ca and explain the molecular mechanism of Ca sensitization by caffeine and disease-causing mutations.
兰尼碱受体（RyRs）是骨骼肌和心肌肌浆网中的钙释放通道，对肌肉收缩至关重要。编码RyRs的基因突变会导致各种肌肉疾病和致心律失常性心脏病。尽管RyR通道由钙激活，但其钙结合的实际机制仍 largely 未知。在此，我们报告了钙结合至 RyRs 以激活通道的分子基础，并讨论其在疾病状态中的意义。对在假定的钙和咖啡因结合位点携带突变的 RyR1 和 RyR2 进行了功能分析。根据最近在各种配体状态下的近原子分辨率 RyR1 结构对结果进行了解释。我们证明咖啡因结合位点中的一个色氨酸残基控制钙结合位点的结构以调节钙敏感性。我们的结果揭示了钙激活 RyR 通道的初始步骤，并解释了咖啡因和致病突变导致钙敏化的分子机制。
