FIGURE 1.

The scheme of mitochondrion and its interaction with other subcellular systems in cardiomyocyte. The major function of mitochondrion is to produce ATP, which occurs at complex V (a.k.a. F0F1 ATPase) using the electrochemical gradient generated by electron transport chain (complex I to IV). A byproduct of ATP production is superoxide (O₂^.-), which is probably generated at complex I and complex III. ATP is translocated to cytosol via ANT and hydrolyzed to support excitation-contraction and energy-sensitive ion transporters (indicated by green dashed lines). O₂^.- can freely diffuse to cytosol and form ROS, which can modify a variety of redox sensitive ion transporters (indicated by red dashed lines). Altogether, mitochondrial dysfunction-associated ATP depletion and ROS accumulation can significantly affect cellular action potentials and ion homeostasis. ROS, reactive oxygen species; CaMKII, Ca²⁺/calmodulin-dependent protein kinase II; SR, sarcoplasmic reticulum; TCA, tricarboxylic acid; ANT, adenine nucleotide translocator; mCU, mitochondrial Ca²⁺ uniporter; mNCE, mitochondrial Na⁺/Ca²⁺ exchanger; I–V, complex I to complex V.