Induction of rat liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase mRNA by refeeding and insulin.
The effects of fasting/refeeding and untreated or insulin-treated diabetes on the bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase and its mRNA in rat liver were determined. Both enzymatic activities fell to 20% of control values with fasting or streptozotocin-induced diabetes and were coordinately restored to normal within 48 h of refeeding or 24 h of insulin administration. These alterations in enzymatic activities were always mirrored by corresponding changes in amount of enzyme as determined by phosphoenzyme formation and immunoblotting. In contrast, mRNA for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase did not decrease during starvation or in diabetes, but there was a 3-6-fold increase upon refeeding a high carbohydrate diet to starved rats or insulin treatment of diabetic rats. The decrease of the enzyme in starved or diabetic rats without associated changes in mRNA levels suggests a decrease in the rate of mRNA translation, an increase in enzyme degradation, or both. The rise in enzyme amount and mRNA for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase with refeeding and insulin treatment suggests an insulin-dependent stimulation of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase gene expression. Northern blots of RNA from heart, brain, kidney, and skeletal muscle probed with restriction fragments of a full-length cDNA from liver showed that only skeletal muscle contained an RNA species that hybridized to any of the probes. Skeletal muscle mRNA for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase was 2.0 kilobase pairs but in contrast to the liver message (2.2 kilobase pairs) was not regulated by refeeding.
Colosia
A D
AD
Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232.
Marker
A J
AJ
Lange
A J
AJ
el-Maghrabi
M R
MR
Granner
D K
DK
Tauler
A
A
Pilkis
J
J
Pilkis
S J
SJ
D000818:Animals; D001483:Base Sequence; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology; D004790:Enzyme Induction; D005502:Food; D005941:Glucokinase / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases / Q000096:biosynthesis*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000032:analysis*; D013217:Starvation / Q000201:enzymology
D007328:Insulin; D012333:RNA, Messenger; D017853:Phosphotransferases (Alcohol Group Acceptor); D025481:Phosphofructokinase-2; D005941:Glucokinase; D010744:Phosphoric Monoester Hydrolases