TY - JOUR
T1 - Respective roles of glucose, fructose, and insulin in the regulation of the liver-specific pyruvate kinase gene promoter
AU - Doiron, Bruno
AU - Cuif, Marie Hélène
AU - Kahn, Axel
AU - Diaz-Guerra, Maria Jose M.
PY - 1994/4/8
Y1 - 1994/4/8
N2 - The L-type pyruvate kinase (L-PK) is a key enzyme of the glycolytic pathway mainly expressed in the liver. Rat liver contains a regulatory protein that inhibits glucokinase (GK) activity. The effect of this protein is greatly reinforced by the fructose 6-phosphate and antagonized by the fructose 1-phosphate (Van Schaftingen, E. (1989) Eur. J. Biochem. 179, 179- 184). In hepatocytes, fructose in low concentrations is phosphorylated into fructose 1-phosphate, and therefore is able to activate GK in the absence of insulin via the regulatory protein in the liver. In primary culture of rat hepatocytes, 0.2 mM fructose in the presence of 20 or 40 mM glucose stimulated the activity of the L-PK gene promoter fused with the chloramphenicol acetyltransferase reporter gene, regardless of the addition of insulin, through the glucose/insulin response element. A constitutive GK expression vector co-transfected with the L-PK/chloramphenicol acetyltransferase construct is also able to confer an insulin-independent glucose responsiveness in hepatocytes. Thus, the insulin effect on glucose- dependent activation of the L-PK promoter is, under these experimental conditions, to permit glucose phosphorylation through the stimulation of the GK synthesis. In the presence of glucose, the L-PK promoter can also be activated by a post-translational GK activation, mediated by a low concentration of fructose acting via the regulatory protein of glucokinase.
AB - The L-type pyruvate kinase (L-PK) is a key enzyme of the glycolytic pathway mainly expressed in the liver. Rat liver contains a regulatory protein that inhibits glucokinase (GK) activity. The effect of this protein is greatly reinforced by the fructose 6-phosphate and antagonized by the fructose 1-phosphate (Van Schaftingen, E. (1989) Eur. J. Biochem. 179, 179- 184). In hepatocytes, fructose in low concentrations is phosphorylated into fructose 1-phosphate, and therefore is able to activate GK in the absence of insulin via the regulatory protein in the liver. In primary culture of rat hepatocytes, 0.2 mM fructose in the presence of 20 or 40 mM glucose stimulated the activity of the L-PK gene promoter fused with the chloramphenicol acetyltransferase reporter gene, regardless of the addition of insulin, through the glucose/insulin response element. A constitutive GK expression vector co-transfected with the L-PK/chloramphenicol acetyltransferase construct is also able to confer an insulin-independent glucose responsiveness in hepatocytes. Thus, the insulin effect on glucose- dependent activation of the L-PK promoter is, under these experimental conditions, to permit glucose phosphorylation through the stimulation of the GK synthesis. In the presence of glucose, the L-PK promoter can also be activated by a post-translational GK activation, mediated by a low concentration of fructose acting via the regulatory protein of glucokinase.
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M3 - Article
C2 - 8144600
AN - SCOPUS:0028206043
VL - 269
SP - 10213
EP - 10216
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 14
ER -