Activities | Families | Sequences | Fold types | References | Help
B6db references: 94179292

type Journal Article
authors Uchida, C.; Funai, T.; Oda, T.; Ohbayashi, K.; Ichiyama, A.
title Regulation by glucagon of serine: pyruvate/alanine: glyoxylate aminotransferase gene expression in cultured rat hepatocytes
journal J Biol Chem
ui 94179292
year (1994)
volume 269
number 12
pages 8849-56.
keywords 8-Bromo Cyclic Adenosine Monophosphate/pharmacology
abstract The effects of glucagon on serine: pyruvate/alanine: glyoxylate aminotransferase (SPT/AGT) gene expression were studied in primary cultured rat hepatocytes. When hepatocytes had been precultured for 16- 18 h under serum- and hormone-free conditions, the addition of glucagon caused (after a lag period of about 2 h) a remarkable increase in the cellular level of SPT/AGT mRNA by 4 h in a time- and dose-dependent manner. The induced mRNA was that for mitochondrial SPT/AGT, as judged by ribonuclease protection analysis. A nuclear run-on assay revealed that activation of transcription is responsible for the increase in mitochondrial SPT/AGT mRNA and that the maximal rate of transcription occurs 1.5 h after glucagon addition. The effect of glucagon was mimicked by 8-bromo-cAMP and suppressed by N-[2-(p- bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide, an inhibitor of cAMP-dependent protein kinase (protein kinase A), while both 12-O- tetradecanoylphorbol-13-acetate and A23187 were without effect in elevating the SPT/AGT mRNA level, suggesting that the cAMP/protein kinase A system is involved in the regulation of SPT/AGT gene expression. In hepatocytes precultured for 16-18 h under serum- and hormone-free conditions, the glucagon-induced transcription was severely inhibited by cycloheximide. When the preculture was for 2 h, on the other hand, the activation of transcription by glucagon was more rapid, and the inhibition by cycloheximide was less than that observed with cells precultured for 16-18 h, suggesting that a short-lived protein factor is involved in the hormonal regulation. The glucagon- induced expression of the SPT/AGT gene was also turned off by dexamethasone.
last changed 2002/11/12 16:17

B6db references