RYR2 and atrial fibrillation: During AF with reduced LVEF in pigs, phosphorylation of RyR2 by PKA at Ser2808 was significantly reduced by 62% (n = 5; P = 0.040), whereas total RyR2 protein (n = 5; P = 0.50) and CaMKIIδ phosphorylation at Ser2814 (n = 5; P = 0.82) was not different between AF and SR animal groups (Fig. 5A-D).