THE EXPRESSION OF SUBUNIT-C CORRELATES WITH AND THUS MAY LIMIT THE BIOSYNTHESIS OF THE MITOCHONDRIAL F0F1-ATPASE IN BROWN ADIPOSE-TISSUE

A low content of mitochondrial ATPase in brown adipose tissue (BAT) has previously been found to contrast with high levels of the transcripts of the beta-subunit of the F-1 part of the ATPase and of the transcripts of the mitochondrial encoded subunits (Houstek, J., Tvrdik, P., Pavelka, S., and Baudysova, M. (1991) FEES Lett. 294, 191-194). To delineate which subunit limits the synthesis of the ATPase complex, we have studied the expression of the nuclear genes encoding subunits alpha, beta, and gamma of the catalytic F-1 part and the b, c, d, and OSCP subunits of the F-0 part of the ATPase. In comparison with other tissues of mice, high levels of transcripts of alpha-F-1, beta-F-1, gamma-F-1, b-F-0, d-F-0, and OSCP were found in BAT. The only genes expressed at a low level in BAT were those of the c-F-0 subunit. The levels of c-F, transcripts were 4-70-fold lower in BAT than in other tissues. An analogous expression pattern of the ATPase genes was found in BAT of adult rat and hamster, In BAT of newborn lamb, which, in contrast to other mammals, has a high content of mitochondrial ATPase, correspondingly high levels of c-F-0 mRNA were found, Expression of the c-F-0 genes also correlated well with the ontogenic development of EAT in the hamster, being high during the first postnatal week when mitochondria are nonthermogenic and contain a relatively high amount of ATPase, but low on subsequent days when ATPase content decreases, as the thermogenic function develops. It is suggested that expression of the c-P-0 genes and subsequent synthesis of the hydrophobic subunit c of the membrane-intrinsic F-0 part of the enzyme may control the biosynthesis of the ATPase complex in BAT. An analogous regulatory role of the c-F-0 subunit could be postulated in other tissues.