Structural Insights into Recognition of Ryanodine Receptors by PKA

Ryanodine Receptors (RyRs) are large intracellular channels that control the release of Ca2+ from the SR or ER. They are targets for a multitude of regulatory events, including the phosphorylation by kinases like PKA and CaMKII. Here we provide direct crystallographic insights into the recognition of RyR2, the cardiac isoform, by PKA. We found an extensive and unusual binding interface that is the target for several disease-associated mutations. Calorimetry and enzyme kinetic assays show that RyR2 is a better substrate than RyR1. Either phosphorylation or phosphomimetics at nearby target sites drastically change the affinity and activity of PKA towards the RyR2 phosphorylation substrate. Structures show that the PKA-RYR2 interface is highly dynamic and subject to change depending on the phosphorylation status. Our results directly suggest an interplay between CaMKII and PKA for recognizing their target sites in RyR2