Cardiac expression of ryanodine receptor subtype 3; a strategic component in the intracellular Ca2+ release system of Purkinje fibers in large mammalian heart

Increased spontaneous Ca2+activity in Cardiac Purkinje cells after myocardial infarction; A consequence of a dramatic shift of SERCA isoforms as potential adaptation to acute ischemia?

“…But, the shifted relationship was detected in both peripheral and central regions of Pcells. It is unlikely that, within 48Hrs, the same alteration affects simultaneously the Ca 2+ release threshold of the different Ca 2+ release channels (RyR2, RyR3) previously reported in those subcellular regions of Pcell 18,22 . Alternatively and consistent with an upward shift of Ca 2+ event rate-pCa relationship, an acceleration of Ca 2+ recycling by the SR can increase the opening frequency of a constant number of SR-Ca 2+ channels.…”

“…1) and the typical plateau of CWWs reported in normal Pcells 18 was absent in the majority of selected MI Pcells (see supplement Fig.2S ). In contrast to the large CWWs, Ca 2+ wavelets are small and localized Ca 2+ transients ( Fig.1B .a) propagating over short distances in peripheral regions of Pcells 18,22 . In MI Pcells, the decay duration of wavelets was significantly reduced by 25% while their amplitude was 50% larger compared to normal Pcells ( Fig.1B .a, Tab.…”

“…Emitted fluorescence was simultaneously collected at 586 nm. Ca 2+ dependent fluorescence of Fluo-4 was captured by line scanning confocal microscopy (LSCM) at 333 scans/sec or 2-dimensional spinning disk confocal microscopy (2DCM) at 30 frames per second (fps) as described elsewhere 18,20,22,26 . The relative free-Ca 2+ concentration ([Ca 2+ ]) was given by the pixel-to-pixel ratio F/Fo, where F and Fo were the instantaneous fluorescence intensity and basal fluorescence intensity, respectively.…”

“…SR-Ca 2+ -release function was assessed in Pcells of canine heart 48Hrs post MI through the analysis of typical Ca 2+ transients previously identified in Pcells 18,22 . The SR-Ca 2+ -uptake system was examined by determining the density distribution of SERCA pumps and regulatory protein phospholamban (PLB).…”

Glucocorticoid Receptor ablation promotes cardiac regeneration by hampering cardiomyocyte terminal differentiation

“…Intriguingly, our data point at proteins of the I band and/or Z-disk, where the first step of sarcomere disassembly in proliferating cardiomyocytes has been previously reported 32 . Among downregulated I band genes in GR-cKO we observed PDLIM5 (PDZ and LIM domain protein 5, also known as Enigma Homolog -ENH), which plays a key role in Z-line structure 40 ; PGM1 (Phosphoglucomutase 1), an enzyme that is involved in energy metabolism, whose reduction lead to increased flow of glucose into glycolysis 41 , and may localize at the Z disk in stress conditions 42 ; ANK2 (Ankyrin-B), which is involved in calcium handling 43 ; RYR3 (Ryanodine Receptor type 3), which is mainly involved in calcium cycling in purkinje fibers 44,45 ;…”