title: Mitochondrial UCPs: new insights into regulation and impact.
abstract: Uncoupling proteins (UCPs) are mitochondrial inner membrane proteins sustaining an inducible proton conductance. They weaken the proton electrochemical gradient built up by the mitochondrial respiratory chain. Brown fat UCP1 sustains a free fatty acid (FA)-induced purine nucleotide (PN)-inhibited proton conductance. Inhibition of the proton conductance by PN has been considered as a diagnostic of UCP activity. However, conflicting results have been obtained in isolated mitochondria for UCP homologues (i.e., UCP2, UCP3, plant UCP, and protist UCP) where the FFA-activated proton conductance is poorly sensitive to PN under resting respiration conditions. Our recent work clearly indicates that the membranous coenzyme Q, through its redox state, represents a regulator of the inhibition by PN of FFA-activated UCP1 homologues under phosphorylating respiration conditions. Several physiological roles of UCPs have been suggested, including a control of the cellular energy balance as well as the preventive action against oxidative stress. In this paper, we discuss new information emerging from comparative proteomics about the impact of UCPs on mitochondrial physiology, when recombinant UCP1 is expressed in yeast and when UCP2 is over-expressed in hepatic mitochondria during steatosis.
authors.affiliation: Laboratory of Bioenergetics, Department of Life Sciences, Institute of Chemistry B6c, University of Liège, Sart Tilman, B-4000 Liege, Belgium. f.sluse@ulg.ac.be
authors.forename: Francis E
authors.initials: FE
authors.lastname: Sluse
authors.forename: Wieslawa
authors.initials: W
authors.lastname: Jarmuszkiewicz
authors.forename: Rachel
authors.initials: R
authors.lastname: Navet
authors.forename: Pierre
authors.initials: P
authors.lastname: Douette
authors.forename: Gregory
authors.initials: G
authors.lastname: Mathy
authors.forename: Claudine M
authors.initials: CM
authors.lastname: Sluse-Goffart
mesh_terms: D002001:Adipose Tissue, Brown / Q000502:physiology; D000818:Animals; D002352:Carrier Proteins / Q000502:physiology*; D019069:Cell Respiration / Q000502:physiology; D004734:Energy Metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005234:Fatty Liver / Q000378:metabolism; D007473:Ion Channels; D008565:Membrane Proteins / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000502:physiology*; D008930:Mitochondria, Liver / Q000502:physiology*; D024101:Mitochondrial Proteins / Q000502:physiology*; D010085:Oxidative Phosphorylation; D018384:Oxidative Stress; D010101:Oxygen Consumption; D020543:Proteome / Q000378:metabolism; D014451:Ubiquinone / Q000378:metabolism; D000071256:Uncoupling Protein 1; D000071246:Uncoupling Protein 2
chemical_list: D002352:Carrier Proteins; D005230:Fatty Acids, Nonesterified; D007473:Ion Channels; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D020543:Proteome; D000071256:Uncoupling Protein 1; D000071246:Uncoupling Protein 2; D014451:Ubiquinone