  Mitochondrial uncoupling proteins: new insights from functional and proteomic studies.; Sluse, Francis  in Free Radical Biology & Medicine (2006), 40 Mitochondria are the major sites of ATP synthesis through oxidative phosphorylation, a process that is weakened by proton leak. Uncoupling proteins are mitochondrial membrane proteins specialized in ... [more ▼] Mitochondria are the major sites of ATP synthesis through oxidative phosphorylation, a process that is weakened by proton leak. Uncoupling proteins are mitochondrial membrane proteins specialized in inducible proton conductance. They dissipate the proton electrochemical gradient established by the respiratory chain at the expense of reducing substrates. Several physiological roles have been suggested for uncoupling proteins, including roles in the control of the cellular energy balance and in preventive action against oxidative stress. This review focuses on new leads emerging from comparative proteomics about the involvement of uncoupling protein in the mitochondrial physiology. A brief overview on uncoupling proteins and on proteomics applied to mitochondria is also presented herein. [less ▲] Detailed reference viewed: 10 (4 ULg)Proton leak induced by reactive oxygen species produced during in vitro anoxia/reoxygenation in rat skeletal muscle mitochondria.; ; et al in Journal of Bioenergetics & Biomembranes (2006), 38 Superoxide anion generation and the impairment of oxidative phosphorylation yield were studied in rat skeletal muscle mitochondria submitted to anoxia/reoxygenation in vitro. Production of superoxide ... [more ▼] Superoxide anion generation and the impairment of oxidative phosphorylation yield were studied in rat skeletal muscle mitochondria submitted to anoxia/reoxygenation in vitro. Production of superoxide anion was detected after several cycles of anoxia/reoxygenation. Concomitantly, a decrease of state 3 respiration and phosphorylation yield (ADP/O) were observed. The latter resulted from a proton leak. The presence of palmitic acid during anoxia/reoxygenation cycles led to a dose-dependent inhibition of superoxide anion production together with a partial protection of the ADP/O ratio measured after anoxia/reoxygenation. The ADP/O decrease was shown to be due to a permeability transition pore-sustained proton leak, as it was suppressed by cyclosporine A. The permeability transition pore activation was induced during anoxia/reoxygenation by superoxide anion, as it was cancelled by the spin trap (POBN), which scavenges superoxide anion and by palmitic acid, which induces mitochondrial uncoupling. It can be proposed that the palmitic acid-induced proton leak cancels the production of superoxide anion by mitochondria during anoxia/reoxygenation and therefore prevents the occurrence of the superoxide anion-induced permeability transition pore-mediated proton leak after anoxia/reoxygenation [less ▲] Detailed reference viewed: 24 (9 ULg)Regulation of uncoupling protein activity in phosphorylating potato tuber mitochondria.; ; et al in FEBS Letters (2005), 579 In isolated potato tuber mitochondria, palmitic acid (PA) can induce a H+ leak inhibited by GTP in the phosphorylating (state 3) respiration but not in the resting (state 4) respiration. The PA-induced H ... [more ▼] In isolated potato tuber mitochondria, palmitic acid (PA) can induce a H+ leak inhibited by GTP in the phosphorylating (state 3) respiration but not in the resting (state 4) respiration. The PA-induced H+ leak is constant when state 3 respiration is decreased by an inhibition of the succinate uptake with n-butyl malonate (nBM). We show that the efficiency of inhibition by GTP is decreased when state 3 respiration is progressively inhibited by antimycin A (AA) and is restored following subsequent addition of nBM. We propose that in phosphorylating potato tuber mitochondria, the redox state of ubiquinone, which can antagonistically be varied with AA and nBM, modulates inhibition of the PA-activated UCP-sustained H+ leak by GTP. [less ▲] Detailed reference viewed: 14 (3 ULg)Escherichia coli fusion carrier proteins act as solubilizing agents for recombinant uncoupling protein 1 through interactions with GroEL.; ; et al in Biochemical and Biophysical Research Communications (2005), 333 Fusing recombinant proteins to highly soluble partners is frequently used to prevent aggregation of recombinant proteins in Escherichia coli. Moreover, co-overexpression of prokaryotic chaperones can ... [more ▼] Fusing recombinant proteins to highly soluble partners is frequently used to prevent aggregation of recombinant proteins in Escherichia coli. Moreover, co-overexpression of prokaryotic chaperones can increase the amount of properly folded recombinant proteins. To understand the solubility enhancement of fusion proteins, we designed two recombinant proteins composed of uncoupling protein 1 (UCP1), a mitochondrial membrane protein, in fusion with MBP or NusA. We were able to express soluble forms of MBP-UCP1 and NusA-UCP1 despite the high hydrophobicity of UCP1. Furthermore, the yield of soluble fusion proteins depended on co-overexpression of GroEL that catalyzes folding of polypeptides. MBP-UCP1 was expressed in the form of a non-covalent complex with GroEL. MBP-UCP1/GroEL was purified and characterized by dynamic light scattering, gel filtration, and electron microscopy. Our findings suggest that MBP and NusA act as solubilizing agents by forcing the recombinant protein to pass through the bacterial chaperone pathway in the context of fusion protein. [less ▲] Detailed reference viewed: 10 (6 ULg)Mitochondrial respiratory chain complex patterns from Acanthamoeba castellanii and Lycopersicon esculentum: comparative analysis by BN-PAGE and evidence of protein-protein interaction between alternative oxidase and complex III.; ; et al in Journal of Bioenergetics & Biomembranes (2004), 36(5), 471-479 We have previously shown that a kinetic interplay exists between the cytochrome pathway and the alternative oxidase in mitochondria from amoeba Acanthamoeba castellanii . Native interaction analyses using ... [more ▼] We have previously shown that a kinetic interplay exists between the cytochrome pathway and the alternative oxidase in mitochondria from amoeba Acanthamoeba castellanii . Native interaction analyses using blue native gel electrophoresis coupled to denaturating electrophoresis and immunodetection have indicated associations between alternative oxidase and oxidative phosphorylation complexes in both amoeba and tomato mitochondria. These associations are dependent on the expression level of alternative oxidase according to the physiological state in both organisms. Alternative oxidase associates broadly with large complexes of the respiratory chain when it is expressed in large amount, i.e., in ripe tomato and exponentially growing amoeba. On the contrary, alternative oxidase interacts specifically with complex III even if expression of the oxidase is low, i.e., in green tomato and stationary phase amoeba. This specific interaction represents a higher level of regulation driven by protein-protein interactions leading to a direct kinetic interplay between the cytochrome pathway and alternative oxidase in both plant and amoeba mitochondria. [less ▲] Detailed reference viewed: 10 (3 ULg)Redox state of endogenous coenzyme q modulates the inhibition of linoleic acid-induced uncoupling by guanosine triphosphate in isolated skeletal muscle mitochondria.; ; et al in Journal of Bioenergetics & Biomembranes (2004), 36 The skeletal muscle mitochondria contain two isoforms of uncoupling protein, UCP2 and mainly UCP3, which had been shown to be activated by free fatty acids and inhibited by purine nucleotides in ... [more ▼] The skeletal muscle mitochondria contain two isoforms of uncoupling protein, UCP2 and mainly UCP3, which had been shown to be activated by free fatty acids and inhibited by purine nucleotides in reconstituted systems. On the contrary in isolated mitochondria, the protonophoretic action of muscle UCPs had failed to be demonstrated in the absence of superoxide production. We showed here for the first time that muscle UCPs were activated in state 3 respiration by linoleic acid and dissipated energy from oxidative phosphorylation by decreasing the ADP/O ratio. The efficiency of UCPs in mitochondrial uncoupling increased when the state 3 respiratory rate decreased. The inhibition of the linoleic acid-induced uncoupling by a purine nucleotide (GTP), was not observed in state 4 respiration, in uninhibited state 3 respiration, as well as in state 3 respiration inhibited by complex III inhibitors. On the contrary, the progressive inhibition of state 3 respiration by n -butyl malonate, which inhibits the uptake of succinate, led to a full inhibitory effect of GTP. Therefore, as the inhibitory effect of GTP was observed only when the reduced state of coenzyme Q was decreased, we propose that the coenzyme Q redox state could be a metabolic sensor that modulates the purine nucleotide inhibition of FFA-activated UCPs in muscle mitochondria. [less ▲] Detailed reference viewed: 14 (3 ULg) |
||
