Nanoscale analysis of XXXX receptor clusters in dyadic couplings of @entity35 cardiac myocytes.

@entity35 @entity48744 @entity8452 @entity37541 @entity460 @entity141
UNASSIGNED: The contractile properties of cardiac myocytes depend on the @entity460 ( @entity141 ) released by clusters of @entity8452 receptors (RyRs) throughout the myoplasm. Accurate quantification of the spatial distribution of RyRs has previously been challenging due to the comparatively low resolution in optical microscopy. We have combined single-molecule localisation microscopy (SMLM) in a super-resolution modality known as dSTORM with immunofluorescence staining of tissue sections of @entity35 ventricles to resolve a wide, near-exponential size distribution of @entity48744 clusters that lined on average ~57% of the perimeter of each myofibril. The average size of internal couplons is ~63 RyRs (nearly 4 times larger than that of peripheral couplons) and the largest clusters contain many hundreds of RyRs. Similar to previous observations in peripheral couplons, we observe many clusters with one or few receptors; however >= 80% of the total RyRs were detected in clusters containing >= 100 receptors. ~56% of all clusters were within an edge-to-edge distance sufficiently close to co-activate via @entity141 -induced @entity141 release (100nm) and were grouped into 'superclusters'. The co-location of superclusters with the same or adjacent t-tubular connections in dual-colour super-resolution images suggested that member sub-clusters may be exposed to similar local luminal @entity141 levels. Dual-colour dSTORM revealed high co-localisation between the cardiac junctional protein @entity37541 ( @entity37541 ) and @entity48744 clusters that confirmed that the majority of the @entity48744 clusters observed are dyadic. The increased sensitivity of super-resolution images revealed approximately twice as many @entity48744 clusters (2.2clusters/ m(3)) compared to previous confocal measurements. We show that, in general, the differences of previous confocal estimates are largely attributable to the limited spatial resolution of diffraction-limited imaging. The new data can be used to inform the construction of detailed mechanistic models of cardiac @entity141 signalling.
