Figure 1. Cardiac atrial signaling “hubs” regulate local calcium signaling.

(A) Schematic of the atrial myocyte TT and AT networks and the SR. In this issue, Brandenburg et al. have described an atrial “super hub” (inset), which harbors a unique signaling platform with CRUs and regulatory proteins. RyR2 clusters are differentially regulated at TT and AT domains, potentially due to a distinct constituency of regulatory macromolecular complexes. (B) Schematic showing the distribution of hyperphosphorylated (red) and unphosphorylated (blue) CRUs in association with ATs and TTs at baseline, following β-AR stimulation, and in atrial hypertrophy.