Cardiomyocyte ryanodine receptor clusters expand and coalesce after application of isoproterenol.

David R L Scriven, Anne Berit Johnsen, Parisa Asghari, Keng C Chou, Edwin D W Moore

The Journal of general physiology 2023 Nov 06

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Earlier work has shown that ventricular ryanodine receptors (RyR2) within a clus ter rearrange on phosphorylation as well as with a number of other stimuli. Using dSTORM, we investigated the effects of 300 nmol/liter isoproterenol on RyR2 clusters. In rat ventricular cardiomyocytes, there was a symmetrical enlargement of RyR2 cluster areas, a decrease in the edge-to-edge nearest neighbor distance, and distribution changes that suggested movement to increase the cluster areas by coalescence. The surface area covered by the phosphorylated clusters was significantly greater than in the control cells, as was the cluster density. This latter change was accompanied by a decreased cluster fragmentation, implying that new tetramers were brought into the sarcoplasmic reticulum. We propose a possible mechanism to explain these changes. We also visualized individual RyR2 tetramers and confirmed our earlier electron-tomographic finding that the tetramers are in a disorganized but non-random array occupying about half of the cluster area. Multiclusters, cluster groups defined by the maximum distance between their members, were analyzed for various distances. At 100 nm, the areas occupied by the multiclusters just exceeded those of the single clusters, and more than half of the multiclusters had only a single subcluster that could initiate a spark. Phosphorylation increased the size of the multiclusters, markedly so for distances >100 nm. There was no relationship between the number of subclusters in a group and the area covered by it. We conclude that isoproterenol induces rapid, significant, changes in the molecular architecture of excitation-contraction coupling. © 2023 Crown copyright. The government of Australia, Canada, or the UK ("the Crown") owns the copyright interests of authors who are government employees. The Crown Copyright is not transferable.

Citation

David R L Scriven, Anne Berit Johnsen, Parisa Asghari, Keng C Chou, Edwin D W Moore. Cardiomyocyte ryanodine receptor clusters expand and coalesce after application of isoproterenol. The Journal of general physiology. 2023 Nov 06;155(11)