The basal proton conductance of skeletal muscle mitochondria from transgenic mice overexpressing or lacking uncoupling protein-3.

TitleThe basal proton conductance of skeletal muscle mitochondria from transgenic mice overexpressing or lacking uncoupling protein-3.
Publication TypeJournal Article
Year of Publication2002
AuthorsCadenas, S, Echtay, KS, Harper, JA, Jekabsons, MB, Buckingham, JA, Grau, E, Abuin, A, Chapman, H, Clapham, JC, Brand, MD
JournalJ Biol Chem
Volume277
Issue4
Pagination2773-8
Date Published2002 Jan 25
ISSN0021-9258
KeywordsAnimals, Blotting, Western, Body Weight, Carrier Proteins, Humans, Ion Channels, Kinetics, Mice, Mice, Knockout, Mice, Transgenic, Mitochondria, Mitochondrial Proteins, Muscle, Skeletal, Oxygen, Oxygen Consumption, Phosphorylation, Protein Binding, Protons, Succinic Acid, Superoxides, Uncoupling Protein 3
Abstract

The ability of native uncoupling protein-3 (UCP3) to uncouple mitochondrial oxidative phosphorylation is controversial. We measured the expression level of UCP3 and the proton conductance of skeletal muscle mitochondria isolated from transgenic mice overexpressing human UCP3 (UCP3-tg) and from UCP3 knockout (UCP3-KO) mice. The concentration of UCP3 in UCP3-tg mitochondria was approximately 3 microg/mg protein, approximately 20-fold higher than the wild type value. UCP3-tg mitochondria had increased nonphosphorylating respiration rates, decreased respiratory control, and approximately 4-fold increased proton conductance compared with the wild type. However, this increased uncoupling in UCP3-tg mitochondria was not caused by native function of UCP3 because it was not proportional to the increase in UCP3 concentration and was neither activated by superoxide nor inhibited by GDP. UCP3 was undetectable in mitochondria from UCP3-KO mice. Nevertheless, UCP3-KO mitochondria had unchanged respiration rates, respiratory control ratios, and proton conductance compared with the wild type under a variety of assay conditions. We conclude that uncoupling in UCP3-tg mice is an artifact of transgenic expression, and that UCP3 does not catalyze the basal proton conductance of skeletal muscle mitochondria in the absence of activators such as superoxide.

DOI10.1074/jbc.M109736200
Alternate JournalJ. Biol. Chem.
Citation Key10.1074/jbc.M109736200
PubMed ID11707458