Carboxyatractyloside effects on brown-fat mitochondria imply that the adenine nucleotide translocator isoforms ANT1 and ANT2 may be responsible for basal and fatty-acid-induced uncoupling respectively.
In brown-fat mitochondria, fatty acids induce thermogenic uncoupling through activation of UCP1 (uncoupling protein 1). However, even in brown-fat mitochondria from UCP1-/- mice, fatty-acid-induced uncoupling exists. In the present investigation, we used the inhibitor CAtr (carboxyatractyloside) to examine the involvement of the ANT (adenine nucleotide translocator) in the mediation of this UCP1-independent fatty-acid-induced uncoupling in brown-fat mitochondria. We found that the contribution of ANT to fatty-acid-induced uncoupling in UCP1-/- brown-fat mitochondria was minimal (whereas it was responsible for nearly half the fatty-acid-induced uncoupling in liver mitochondria). As compared with liver mitochondria, brown-fat mitochondria exhibit a relatively high (UCP1-independent) basal respiration ('proton leak'). Unexpectedly, a large fraction of this high basal respiration was sensitive to CAtr, whereas in liver mitochondria, basal respiration was CAtr-insensitive. Total ANT protein levels were similar in brown-fat mitochondria from wild-type mice and in liver mitochondria, but the level was increased in brown-fat mitochondria from UCP1-/- mice. However, in liver, only Ant2 mRNA was found, whereas in brown adipose tissue, Ant1 and Ant2 mRNA levels were equal. The data are therefore compatible with a tentative model in which the ANT2 isoform mediates fatty-acid-induced uncoupling, whereas the ANT1 isoform may mediate a significant part of the high basal proton leak in brown-fat mitochondria.
Shabalina
Irina G
IG
The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, SE-106 91 Stockholm, Sweden.
Kramarova
Tatiana V
TV
Nedergaard
Jan
J
Cannon
Barbara
B
D033741:Adenine Nucleotide Translocator 1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D033742:Adenine Nucleotide Translocator 2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002001:Adipose Tissue, Brown / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001278:Atractyloside / Q000031:analogs & derivatives* / Q000494:pharmacology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D019069:Cell Respiration / Q000187:drug effects; D003433:Crosses, Genetic; D005227:Fatty Acids / Q000378:metabolism / Q000494:pharmacology*; D006153:Guanosine Diphosphate / Q000494:pharmacology; D007473:Ion Channels / Q000172:deficiency / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000172:deficiency / Q000235:genetics; D008954:Models, Biological; D019301:Oleic Acid / Q000494:pharmacology; D009928:Organ Specificity; D010101:Oxygen Consumption / Q000187:drug effects; D010168:Palmitates / Q000494:pharmacology; D011522:Protons; D019289:Pyruvic Acid / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D022722:Thermogenesis / Q000187:drug effects / Q000502:physiology; D014475:Uncoupling Agents / Q000494:pharmacology*; D000071256:Uncoupling Protein 1
D033741:Adenine Nucleotide Translocator 1; D033742:Adenine Nucleotide Translocator 2; D005227:Fatty Acids; D007473:Ion Channels; D024101:Mitochondrial Proteins; D010168:Palmitates; D011522:Protons; D012333:RNA, Messenger; C000604372:Ucp1 protein, mouse; D014475:Uncoupling Agents; D000071256:Uncoupling Protein 1; D006153:Guanosine Diphosphate; D001278:Atractyloside; D019301:Oleic Acid; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D019289:Pyruvic Acid; C003853:carboxyatractyloside