RYR2 and atrial fibrillation: Using the same mouse model, we performed a similar RyR2 AP-MS and identified serine 2367 on RyR2 as a novel kinase substrate of SPEG and showed in another mouse model that ablation of this phosphorylation site led to inappropriate RyR2 activity in atrial myocytes and increased susceptibility for atrial fibrillation [9].