期刊
BIOCHEMICAL JOURNAL
卷 399, 期 -, 页码 405-414出版社
PORTLAND PRESS LTD
DOI: 10.1042/BJ20060706
关键词
ATP/ADP-carrier isoform; basal proton leak; brown adipose tissue; fatty-acid-induced uncoupling; liver mitochondrion; uncoupling protein 1 (UCP1)
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 nueleotide 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-insensifive. 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.
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