Department of Physiology and Cellular Biophysics, Vagelos College of Physicians and Surgeons of Columbia University, New York, NY, 10032, USA.
Department of Anesthesiology, Vagelos College of Physicians and Surgeons of Columbia University, New York, NY, 10032, USA.
Acta Neuropathol Commun. 2021 Nov 22;9(1):186. doi: 10.1186/s40478-021-01287-3.
The type 1 ryanodine receptor (RyR1) is an intracellular calcium (Ca) release channel on the sarcoplasmic/endoplasmic reticulum that is required for skeletal muscle contraction. RyR1 channel activity is modulated by ligands, including the activators Ca and ATP. Patients with inherited mutations in RyR1 may exhibit muscle weakness as part of a heterogeneous, complex disorder known as RYR1-related myopathy (RYR1-RM) or more recently termed RYR1-related disorders (RYR1-RD). Guided by high-resolution structures of skeletal muscle RyR1, obtained using cryogenic electron microscopy, we introduced mutations into putative Ca and ATP binding sites and studied the function of the resulting mutant channels. These mutations confirmed the functional significance of the Ca and ATP binding sites identified by structural studies based on the effects on channel regulation. Under normal conditions, Ca activates RyR1 at low concentrations (µM) and inhibits it at high concentrations (mM). Mutations in the Ca-binding site impaired both activating and inhibitory regulation of the channel, suggesting a single site for both high and low affinity Ca-dependent regulation of RyR1 function. Mutation of residues that interact with the adenine ring of ATP abrogated ATP binding to the channel, whereas mutating residues that interact with the triphosphate tail only affected the degree of activation. In addition, patients with mutations at the Ca or ATP binding sites suffer from muscle weakness, therefore impaired RyR1 channel regulation by either Ca or ATP may contribute to the pathophysiology of RYR1-RM in some patients.
1 型兰尼碱受体 (RyR1) 是肌浆/内质网的细胞内钙 (Ca) 释放通道，是骨骼肌收缩所必需的。RyR1 通道的活性受配体调节，包括激动剂 Ca 和 ATP。RyR1 遗传性突变的患者可能表现为肌肉无力，这是一种称为 RyR1 相关肌病 (RYR1-RM) 的异质、复杂疾病的一部分，或者最近被称为 RyR1 相关疾病 (RYR1-RD)。在使用低温电子显微镜获得的骨骼肌 RyR1 高分辨率结构的指导下，我们将突变引入到假定的 Ca 和 ATP 结合位点，并研究了产生的突变通道的功能。这些突变证实了基于结构研究确定的 Ca 和 ATP 结合位点的功能意义，这些结构研究基于对通道调节的影响。在正常情况下，Ca 在低浓度 (µM) 下激活 RyR1，在高浓度 (mM) 下抑制它。Ca 结合位点的突变破坏了通道的激活和抑制调节，表明 Ca 依赖性调节 RyR1 功能的高亲和性和低亲和性的单一结合位点。与 ATP 的腺嘌呤环相互作用的残基的突变消除了 ATP 与通道的结合，而与三磷酸尾相互作用的残基的突变仅影响激活程度。此外，Ca 或 ATP 结合位点的突变患者会出现肌肉无力，因此 Ca 或 ATP 对 RyR1 通道调节的损害可能导致某些患者的 RYR1-RM 的病理生理学。
