Mitochondria are physiologically maintained at close to 50 °C

• Published in: PLoS biology 2018-01, Vol.16 (1), p.e2003992-e2003992
• Main Authors: Chrétien, Dominique, Bénit, Paule, Ha, Hyung-Ho, Keipert, Susanne, El-Khoury, Riyad, Chang, Young-Tae, Jastroch, Martin, Jacobs, Howard T, Rustin, Pierre, Rak, Malgorzata
• Format: Article
• Language: English
• Subjects: Alternative oxidase; Biology and Life Sciences; Cellular Biology; Data collection; Dehydrogenases; Deoxyribonucleic acid; Diabetes; Diderot, Denis (1713-1784); DNA; Electron transport; Environmental conditions; Environmental health; Enzymes; Fibroblasts; Fibroblasts - physiology; Fluorescence; Fluorescent Dyes; Fluorescent proteins; Heat; HEK293 Cells; Hot Temperature; Humans; Laboratories; Life Sciences; Mammals; Medicine and Health Sciences; Metabolism; Metabolites; Methods; Mitochondria; Mitochondria - physiology; Mitochondrial DNA; Mitochondrial Membranes - physiology; Mitochondrial Proteins - metabolism; Oxidation; Oxidoreductases - metabolism; Physical Sciences; Physiological aspects; Plant Proteins - metabolism; Primary Cell Culture; Properties; Proteins; Short Reports; Skin; Substrates; Temperature; Temperature effects; Thermal properties; Thermogenesis - physiology; Uncoupling protein 1; Uncoupling Protein 1 - metabolism
• ISSN: 1545-7885; 1544-9173; 1545-7885
• DOI: 10.1371/journal.pbio.2003992

In endothermic species, heat released as a product of metabolism ensures stable internal temperature throughout the organism, despite varying environmental conditions. Mitochondria are major actors in this thermogenic process. Part of the energy released by the oxidation of respiratory substrates drives ATP synthesis and metabolite transport, but a substantial proportion is released as heat. Using a temperature-sensitive fluorescent probe targeted to mitochondria, we measured mitochondrial temperature in situ under different physiological conditions. At a constant external temperature of 38 °C, mitochondria were more than 10 °C warmer when the respiratory chain (RC) was fully functional, both in human embryonic kidney (HEK) 293 cells and primary skin fibroblasts. This differential was abolished in cells depleted of mitochondrial DNA or treated with respiratory inhibitors but preserved or enhanced by expressing thermogenic enzymes, such as the alternative oxidase or the uncoupling protein 1. The activity of various RC enzymes was maximal at or slightly above 50 °C. In view of their potential consequences, these observations need to be further validated and explored by independent methods. Our study prompts a critical re-examination of the literature on mitochondria.