Evidence that CTP:choline-phosphate cytidylyltransferase is regulated at a pretranslational level in rat liver after partial hepatectomy.
Regulation of CTP:choline-phosphate cytidylyltransferase activity was studied in regenerating rat liver. The formation of phosphatidylcholine from [14C]choline in hepatocytes isolated from regenerating liver at 22 h after surgery was increased 1.9-fold when compared with hepatocytes from sham-operated animals. This effect was accompanied by a 1.4-fold increase in cytosolic cytidylyltransferase activity as well as by a 1.5-fold increase in the amount of immunoreactive cytidylyltransferase protein, and a 1.7-fold increase in [35S]methionine incorporation into cytidylyltransferase protein. Northern blot analysis of cytidylyltransferase mRNA showed two signals at 1.5 and 5.0 kb. Partial hepatectomy caused a significant 2-3-fold increase in the 1.5-kb and 5.0-kb messengers at 12 h after surgery. During the next 10 h after partial hepatectomy cytidylyltransferase mRNA levels slightly decreased, although they were still elevated in comparison with sham-operated rats 20-22 h after surgery. In contrast to the elevated cytidylyltransferase mRNA levels, the amount of acetyl-CoA carboxylase mRNA did not increase between 12 and 22 h after surgery, which is in line with the unchanged activity of this enzyme. In conclusion, our data demonstrate that in regenerating liver phosphatidylcholine biosynthesis and cytidylyltransferase activity are regulated at a pretranslational level.
Laboratory of Veterinary Biochemistry, Utrecht University, The Netherlands.
M
M
Houweling
L B
LB
Tijburg
W J
WJ
Vaartjes
J J
JJ
Batenburg
G B
GB
Kalmar
R B
RB
Cornell
L M
LM
Van Golde
D000818:Animals; D019916:Choline-Phosphate Cytidylyltransferase; D003600:Cytosol / Q000201:enzymology; D005786:Gene Expression Regulation; D006498:Hepatectomy; D007527:Isoenzymes / Q000302:isolation & purification; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D009713:Nucleotidyltransferases / Q000096:biosynthesis* / Q000302:isolation & purification; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D007527:Isoenzymes; D010713:Phosphatidylcholines; D012333:RNA, Messenger; D009713:Nucleotidyltransferases; D019916:Choline-Phosphate Cytidylyltransferase