Strategic Positioning and Biased Activity of the Mitochondrial Calcium Uniporter in Cardiac Muscle.

Control of myocardial energetics by Ca signal propagation to the mitochondrial matrix includes local Ca delivery from sarcoplasmic reticulum (SR) ryanodine receptors (RyR2) to the inner mitochondrial membrane (IMM) Ca uniporter (mtCU). mtCU activity in cardiac mitochondria is relatively low, whereas the IMM surface is large, due to extensive cristae folding. Hence, stochastically distributed mtCU may not suffice to support local Ca transfer.