School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
School of Biosciences, Faculty of Science, The University of Sheffield, Sheffield S10 2TN, UK.
Open Biol. 2023 May;13(5):230045. doi: 10.1098/rsob.230045. Epub 2023 May 24.
Rapid release of calcium from internal stores via ryanodine receptors (RyRs) is one of the fastest types of cytoplasmic second messenger signalling in excitable cells. In the heart, rapid summation of the elementary events of calcium release, 'calcium sparks', determine the contraction of the myocardium. We adapted a correlative super-resolution microscopy protocol to correlate sub-plasmalemmal spontaneous calcium sparks in rat right ventricular myocytes with the local nanoscale RyR2 positions. This revealed a steep relationship between the integral of a calcium spark and the sum of the local RyR2s. Segmentation of recurring spark sites showed evidence of repeated and triggered saltatory activation of multiple local RyR2 clusters. In myocytes taken from failing right ventricles, RyR2 clusters themselves showed a dissipated morphology and fragmented (smaller) clusters. They also featured greater heterogeneity in both the spark properties and the relationship between the integral of the calcium spark and the local ensemble of RyR2s. While fragmented (smaller) RyR2 clusters were rarely observed directly underlying the larger sparks or the recurring spark sites, local interrogation of the channel-to-channel distances confirmed a clear link between the positions of each calcium spark and the tight, non-random clustering of the local RyR2 in both healthy and failing ventricles.
Ryanodine 受体（RyRs）介导的细胞内钙库快速释放是可兴奋细胞中最快的细胞质第二信使信号转导方式之一。在心脏中，钙释放的基本事件（“钙火花”）的快速总和决定了心肌的收缩。我们采用了一种相关的超分辨率显微镜方案，将大鼠右心室心肌细胞的亚质膜自发性钙火花与局部纳米尺度 RyR2 位置相关联。这表明钙火花的积分与局部 RyR2 的总和之间存在陡峭的关系。反复发作的火花部位的分割显示出多个局部 RyR2 簇的重复和触发跳跃式激活的证据。在取自衰竭右心室的心肌细胞中，RyR2 簇本身表现出消散的形态和碎片化（较小）的簇。它们还表现出火花特性和钙火花积分与局部 RyR2 集合之间关系的更大异质性。虽然在较大火花或反复发作的火花部位下方很少直接观察到碎片化（较小）的 RyR2 簇，但对通道-通道距离的局部询问证实了每个钙火花的位置与局部 RyR2 的紧密、非随机聚集之间存在明确联系在健康和衰竭的心室中。
