Expression of asparagine synthetase mRNA through asparagine independent signal transduction pathway that might involve protein kinase C in BALB3T3 cells.
Basal level of asparagine synthetase mRNA in BALB3T3 cells was elevated when the cells were shifted from medium containing a high concentration (3.3 mM) of asparagine to one lacking asparagine. We then studied whether the expression of asparagine synthetase mRNA is also mediated through other asparagine-independent signaling pathways. BALB3T3 cells grown to near confluence were quiesced by serum-starvation, and various agents were then added to the culture to examine the enzyme activity and mRNA level of asparagine synthetase. 12-O-tetradecanoylphorbol-13-acetate (TPA), a direct activator of protein kinase C (PKC), elevated dose and time dependently the level of asparagine synthetase mRNA even in Eagle's minimum essential medium with alpha modification (MEM alpha) that contains protein-constituting 20 amino acids and is supplemented with 3.3 mM asparagine. Staurosporine and H-7, PKC inhibitors, strongly blocked the fetal bovine serum-dependent accumulation of asparagine synthetase mRNA. TPA could also enhance the activity of asparagine synthetase within 24 h at concentrations of more than 10 nM. These results suggest that expression of asparagine synthetase gene can be induced both through a pathway that involves PKC and through a pathway the origin of which is a reduced concentration of asparagine in BALB3T3 cells.
Chiyo
T
T
Second Department of Biochemistry, Showa University School of Medicine, Tokyo, Japan.
Hongo
S
S
Takeda
M
M
D016475:3T3 Cells; D000818:Animals; D001216:Asparagine / Q000494:pharmacology*; D001217:Aspartate-Ammonia Ligase / Q000235:genetics* / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D051379:Mice; D011493:Protein Kinase C / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism
D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D001216:Asparagine; D003513:Cycloheximide; D011493:Protein Kinase C; D001217:Aspartate-Ammonia Ligase; D013755:Tetradecanoylphorbol Acetate