The biology of mitochondrial uncoupling proteins.
Uncoupling proteins (UCPs) are mitochondrial transporters present in the inner membrane of mitochondria. They are found in all mammals and in plants. They belong to the family of anion mitochondrial carriers including adenine nucleotide transporters. The term "uncoupling protein" was originally used for UCP1, which is uniquely present in mitochondria of brown adipocytes, the thermogenic cells that maintain body temperature in small rodents. In these cells, UCP1 acts as a proton carrier activated by free fatty acids and creates a shunt between complexes of the respiratory chain and ATP synthase. Activation of UCP1 enhances respiration, and the uncoupling process results in a futile cycle and dissipation of oxidation energy as heat. UCP2 is ubiquitous and highly expressed in the lymphoid system, macrophages, and pancreatic islets. UCP3 is mainly expressed in skeletal muscles. In comparison to the established uncoupling and thermogenic activities of UCP1, UCP2 and UCP3 appear to be involved in the limitation of free radical levels in cells rather than in physiological uncoupling and thermogenesis. Moreover, UCP2 is a regulator of insulin secretion and UCP3 is involved in fatty acid metabolism.
Rousset
Sophie
S
Centre National de la Recherche Scientifique, Unité Propre de Recherche 9078, Faculté de Médecine and Institut de Recherches Necker-Enfants Malades (IRNEM), Paris, France.
Alves-Guerra
Marie-Clotilde
MC
Mozo
Julien
J
Miroux
Bruno
B
Cassard-Doulcier
Anne-Marie
AM
Bouillaud
Frédéric
F
Ricquier
Daniel
D
D000818:Animals; D002352:Carrier Proteins / Q000502:physiology*; D006801:Humans; D007425:Intracellular Membranes / Q000502:physiology; D007473:Ion Channels; D008565:Membrane Proteins / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000502:physiology; D024101:Mitochondrial Proteins / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D000071256:Uncoupling Protein 1; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3
D002352:Carrier Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species; C000604371:UCP1 protein, human; C000604389:UCP2 protein, human; C000604392:UCP3 protein, human; D000071256:Uncoupling Protein 1; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3