Fig. 1

Regulation of mitochondrial functions by mitochondrial Ca²⁺. Mitochondrial Ca²⁺ activates three dehydrogenases in the mitochondrial matrix: pyruvate dehydrogenase (PDHC), oxoglutarate dehydrogenase (OGDH), and isocitrate dehydrogenase (ICDH). ROS production is stimulated by increased mitochondrial Ca²⁺, possibly via increased NADH production. F1-Fo ATP synthase is activated by mitochondrial Ca²⁺, although this is still controversial. This regulatory activity contributes to energy homeostasis. PTP opening is activated by a large increase of mitochondrial Ca²⁺, resulting in the release of a variety of compounds from mitochondria, for example cytochrome c (cytc), pro-caspase, and Ca²⁺, leading to apoptosis or necrosis. CS citrate synthase, ACO aconitase, SCS succinyl-CoA synthase, SDH succinate dehydrogenase, FH fumarate hydratase, MDH malate dehydrogenase, SN F1-Fo ATP synthase, RR ruthenium red, MUni mitochondrial Ca²⁺ uniporter, mRyR mitochondrial RyR, mNCX mitochondrial Na⁺–Ca²⁺ exchanger, mHCX mitochondrial H⁺–Ca²⁺ exchanger