RYR2 and atrial fibrillation: Remodeling of the PP1 interactome (Figure 1iii), involving inhomogeneous changes of protein phosphorylation levels across different subcellular components (e.g., hyperphosphorylation of RyR2 and hypophosphorylation of L-type Ca2+ channel), could be one of the main causes of subcellular heterogeneity in protein phosphorylation associated with AF pathogenesis [27].