Oxidized CaMKII: a "heart stopper" for the sinus node?

Each normal heart beat is triggered by an electrical impulse emitted from a group of specialized cardiomyocytes that together form the sinoatrial node (SAN). In this issue of the JCI, Swaminathan and colleagues demonstrate a new molecular mechanism that can disrupt the normal beating of the heart: angiotensin II - typically found in increased levels in heart failure and hypertension - oxidizes and activates Ca2+/calmodulin-dependent kinase II via NADPH oxidase activation, causing SAN cell death. The loss of SAN cells produces an electrical imbalance termed the "source-sink mismatch," which may contribute to the SAN dysfunction that affects millions of people later in life and complicates a number of heart diseases.