Mitochondrial respiratory chain complexes I, II, and IV (MRC I/II/IV)

Mitochondrial respiratory complexes I, II, and IV are critical multi-subunit protein assemblies located within the inner mitochondrial membrane that facilitate the electron transport chain (ETC) [1, 6]. Complex I (NADH:ubiquinone oxidoreductase) and Complex II (succinate dehydrogenase) serve as the primary entry points for electrons from NADH and succinate, respectively, while Complex IV (cytochrome c oxidase) is the terminal enzyme that reduces molecular oxygen to water [5, 8, 12]. These complexes work in concert to generate a proton motive force that drives ATP synthesis through oxidative phosphorylation [1, 7]. In therapeutic development, these complexes are targeted to exploit the metabolic vulnerabilities of cancer cells or to mitigate the effects of mitochondrial dysfunction in neurodegenerative and metabolic diseases [2, 3, 10]. For example, drugs like metformin and elesclomol interact with these complexes to modulate energy metabolism and induce oxidative stress in malignant tissues [2, 11, 13]. Conversely, dysfunction or unintended inhibition of these complexes is a hallmark of various pathologies, including Parkinson's disease and mitochondrial myopathies [8, 14, 25]. Their inhibition can lead to severe adverse effects, such as lactic acidosis and increased production of reactive oxygen species (ROS), which are significant considerations in drug safety and toxicology [4, 11, 16]. Monitoring biomarkers like the oxygen consumption rate and ATP levels is essential for evaluating the efficacy and safety of drugs targeting these mitochondrial components [4, 16, 18].

Other names

Electron transport chain complexes I, II, and IVETC complexes I, II, and IVNADH:ubiquinone oxidoreductase (I), Succinate dehydrogenase (II), and Cytochrome c oxidase (IV)Mitochondrial complexes I, II, and IVNADH dehydrogenase (I), Succinate-CoQ reductase (II), and Cytochrome oxidase (IV)

Inhibition of electron transfer within the respiratory chain, leading to the disruption of the mitochondrial proton gradient, decreased ATP production, and increased generation of reactive oxygen species (ROS) [1, 4, 11].