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) ha s previously been found to contrast with high levels of the transcript s of the beta-subunit of the F-1 part of the ATPase and of the transcr ipts of the mitochondrial encoded subunits (Houstek, J., Tvrdik, P., P avelka, S., and Baudysova, M. (1991) FEES Lett. 294, 191-194). To deli neate which subunit limits the synthesis of the ATPase complex, we hav e 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 s ubunits of the F-0 part of the ATPase. In comparison with other tissue s 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 a dult rat and hamster, In BAT of newborn lamb, which, in contrast to ot her mammals, has a high content of mitochondrial ATPase, corresponding ly 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 ham ster, being high during the first postnatal week when mitochondria are nonthermogenic and contain a relatively high amount of ATPase, but lo w 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 subun it could be postulated in other tissues.