Functional Consequence of Protein Kinase A-dependent Phosphorylation of the Cardiac Ryanodine Receptor SENSITIZATION OF STORE OVERLOAD-INDUCED Ca2+ RELEASE

摘要: The phosphorylation of the cardiac Ca2+-release channel (ryanodine receptor, RyR2) by protein kinase A (PKA) has been extensively characterized, but its functional consequence remains poorly defined and controversial. We have previously shown that RyR2 is phosphorylated PKA at two major sites, serine 2030 2808, which Ser-2030 site responding to β-adrenergic stimulation. Here we investigated effect on properties single channels spontaneous Ca2+ release during sarcoplasmic reticulum overload, a process referred as store overload-induced (SOICR). found activated in presence, not absence, luminal Ca2+. On other hand, had no marked sensitivity activation cytosolic Importantly, S2030A mutation, mutations Ser-2808, diminished RyR2. Furthermore, phosphomimetic S2030D, potentiated response enhanced propensity for SOICR HEK293 cells. In intact rat ventricular myocytes, isoproterenol reduced amplitude increased frequency SOICR. Confocal line-scanning fluorescence microscopy further revealed rate propagation velocity waves, despite wave resting Collectively, our data indicate PKA-dependent enhances reduces threshold this largely mediated Ser-2030.