Hydroperoxy fatty acid cycling mediated by mitochondrial uncoupling protein UCP2.
Functional activation of mitochondrial uncoupling protein-2 (UCP2) is proposed to decrease reactive oxygen species production. Skulachev and Goglia (Skulachev, V. P., and Goglia, F. (2003) FASEB J. 17, 1585-1591) hypothesized that hydroperoxy fatty acid anions are translocated by UCPs but cannot flip-flop across the membrane. We found that the second aspect is otherwise; the addition of synthesized linoleic acid hydroperoxides (LAOOH, a mix of four isomers) caused a fast flip-flop-dependent acidification of liposomes, comparable with the linoleic acid (LA)-dependent acidification. Using Escherichia coli-expressed UCP2 reconstituted into liposomes we found that LAOOH induced purine nucleotide-sensitive H(+) uniport in UCP2-proteoliposomes with higher affinity than LA (K(m) values 97 microM for LAOOH and 275 microM for LA). In UCP2-proteoliposomes LAOOH also induced purine nucleotide-sensitive K(+) influx balanced by anionic charge transfer, indicating that LAOOH was also transported as an anion with higher affinity than linoleate anion, the K(m) values being 90 and 350 microM, respectively. These data suggest that hydroperoxy fatty acids are transported via UCP2 by a fatty acid cycling mechanism. This may alternatively explain the observed activation of UCP2 by the externally generated superoxide. The ability of LAOOH to induce UCP2-mediated H(+) uniport points to the essential role of superoxide reaction products, such as hydroperoxyl radical, hydroxyl radical, or peroxynitrite, initiating lipoperoxidation, the released products of which support the UCP2-mediated uncoupling and promote the feedback down-regulation of mitochondrial reactive oxygen species production.
Jaburek
Martin
M
Department of Membrane Transport Biophysics, No.75, Institute of Physiology, Academy of Sciences of the Czech Republic, Vídenská 1083, 14220 Prague 4, Czech Republic.
Miyamoto
Sayuri
S
Di Mascio
Paolo
P
Garlid
Keith D
KD
Jezek
Petr
P
D000838:Anions; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D015536:Down-Regulation; D004926:Escherichia coli / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D017665:Hydroxyl Radical; D007473:Ion Channels; D007700:Kinetics; D019787:Linoleic Acid / Q000737:chemistry; D008041:Linoleic Acids / Q000737:chemistry; D008054:Lipid Peroxides / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D008956:Models, Chemical; D030421:Peroxynitrous Acid; D010957:Plasmids / Q000378:metabolism; D011188:Potassium / Q000737:chemistry; D021381:Protein Transport; D011522:Protons; D011687:Purines / Q000737:chemistry; D017382:Reactive Oxygen Species; D013997:Time Factors; D000071246:Uncoupling Protein 2
D000838:Anions; D018076:DNA, Complementary; D005227:Fatty Acids; D007473:Ion Channels; D008041:Linoleic Acids; D008054:Lipid Peroxides; D008081:Liposomes; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D011522:Protons; D011687:Purines; D017382:Reactive Oxygen Species; C000604389:UCP2 protein, human; D000071246:Uncoupling Protein 2; D030421:Peroxynitrous Acid; C008285:linoleic acid hydroperoxide; D017665:Hydroxyl Radical; D019787:Linoleic Acid; D011188:Potassium